The Geology and Petrology of 

Mauna Kea "\foleano, Hawaii— 

A Study *r of ' ' PostsMeld ' " "" ' ' ' ' " ' Volcanism ' ' ' - " •"* " ' *" "- '

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The Geology and Petrology of 

Mauna Kea Volcano, Hawaii— 

A Study of Postshield Volcanism

By Edward W. Wolfe, William S. Wise, and G. Brent Dalrymple

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1557

A detailed investigation of the growth and 

magmatic history of a Hawaiian volcano 

in its postshield stage

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1997
U.S DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S GEOLOGICAL SURVEY 

GORDON P. EATON, Director

For sale by U.S. Geological Survey, Information Services 

Box 25286, Federal Center, Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government.

Published in the Western Region, Menlo Park, Calif. 

Manuscript approved for publication July 13, 1994.

Text edited by George A. Havach 

Illustrations edited by Taryn A. Lindquist

Library of Congress Cataloging-in-Publication Data

The geology and petrology of Mauna Kea volcano, Hawaii: A study of postshield volcanism / by Edward 

W. Wolfe, William S. Wise, and G. Brent Dalrymple

p. cm. -- (U.S. Geological Survey professional paper ; 1557)

Includes bibliographical references.

Supt. of Docs, no.: I 19.16:1557

1. Geology-Hawaii—Mauna Kea. 2. Rocks, Igneous-Hawaii—Mauna Kea. I.

Wise, William S., 1933- . II. Dalrymple, G. Brent. III. Title. IV. Series. 

QE523.M37W65 1997

559.69'l-dc21 97-18869

CIP
CONTENTS

Abstract........................................................................................................................ 1

Introduction.................................................................................................................. 2

Previous major contributions............................................................................... 2

Current work........................................................................................................ 6

Acknowledgments................................................................................................ 6

Geologic setting................................................................................................... 6

Compositional data set......................................................................................... 16

Major rock classes and petrographic groups........................................................ 17

Stratigraphic overview......................................................................................... 18

Previous Stratigraphic nomenclature............................................................ 18

Changes in Stratigraphic definitions and nomenclature............................... 20

Geochronology............................................................................................................. 21

Stratigraphy.................................................................................................................. 25

Hamakua Volcanics.............................................................................................. 25

General statement......................................................................................... 25

Hamakua Volcanics (undivided).................................................................. 27

Definition and occurrence.................................................................... 27

Previous work...................................................................................... 30

Geologic observations.......................................................................... 30

Age....................................................................................................... 30

Hopukani Springs Volcanic Member........................................................... 31

Definition and occurrence.................................................................... 31

Previous work...................................................................................... 31

Geologic observations.......................................................................... 31

Age....................................................................................................... 32

Pohakuloa Glacial Member.......................................................................... 32

Definition and occurrence.................................................................... 32

Previous work...................................................................................... 32

Geologic observations.......................................................................... 33

Age....................................................................................................... 34

Liloe Spring Volcanic Member.................................................................... 34

Definition and occurrence.................................................................... 34

Previous work...................................................................................... 34

Geologic observations.......................................................................... 36

Lithology...................................................................................... 36

Lava-flow characteristics............................................................. 37

Hyaloclastitetuff.......................................................................... 37

Ice-contact fabric ......................................................................... 38

Vents............................................................................................. 38

Dikes............................................................................................ 38

Inferred near-summit vents.......................................................... 40

Age....................................................................................................... 40

Waihu Glacial Member................................................................................ 40

Definition and occurrence.................................................................... 40

Previous work...................................................................................... 40

Geologic observations.......................................................................... 40

Age....................................................................................................... 42

III
IV CONTENTS

Laupahoehoe Volcanics ....................................................................................... 42

General statement........................................................................................ 42

Benmoreite flows and cinder cones..................................................... 43

Hawaiite-mugearite.............................................................................. 43

Lithology...................................................................................... 43

Lava flows.................................................................................... 43

Vent deposits................................................................................ 47

Distribution of cinder cones................................................. 47

Pit craters..................................................................................... 49

Older volcanic rocks member...................................................................... 49

Definition and occurrence.................................................................... 49

Previous work...................................................................................... 49

Geologic observations.......................................................................... 50

Modification of flow and cinder-cone surfaces ........................... 50

Puu Waiau, Puu Poliahu, and related flows ................................. 50

Ice-contact features...................................................................... 52

Flow from Puu Poepoe ................................................................ 52

Age....................................................................................................... 53

Makanaka Glacial Member.......................................................................... 53

Definition and occurrence.................................................................... 53

Previous work...................................................................................... 53

Geologic observations.......................................................................... 54

Age....................................................................................................... 56

Younger volcanic rocks member.................................................................. 56

Definition and occurrence.................................................................... 56

Previous work...................................................................................... 56

Geologic observations.......................................................................... 56

Age....................................................................................................... 58

Laupahoehoe air-fall deposits...................................................................... 58

Definition and occurrence.................................................................... 58

Previous work...................................................................................... 58

Geologic observations.......................................................................... 58

Age....................................................................................................... 59

Alluvial, colluvial, and eolian deposits................................................................ 59

Slope deposits.............................................................................................. 59

Definition and occurrence.................................................................... 59

Previous work...................................................................................... 59

Geologic observations.......................................................................... 60

Age and origin ..................................................................................... 64

Eolian deposits............................................................................................. 67

Loess............................................................................................................ 67

Alluvium and colluvium .............................................................................. 68

Petrology...................................................................................................................... 68

Introduction.......................................................................................................... 68

Characteristics of postshield lavas............................................................... 68

Development of petrogenetic concepts........................................................ 68

Isotopic compositions.................................................................................. 69

Scope of this petrologic study...................................................................... 69

Hamakua Volcanics.............................................................................................. 70

Compositional groups.................................................................................. 70

Alteration of basalts..................................................................................... 70

Mineral compositions .................................................................................. 70

Primary magmas and picrites....................................................................... 74

Alkali, transitional, and tholeiitic basalts..................................................... 74

Picrites and ankaramites .............................................................................. 79
CONTENTS V

Evolved alkali and transitional basalts......................................................... 81

Introduction.......................................................................................... 81

High-Ti basalts..................................................................................... 83

Basalts of theLiloe Spring Volcanic Member..................................... 85

Plagioclase-rich basalts........................................................................ 93

Basalts of the Hopukani Springs Volcanic Member ............................ 93

Basalt from Kanoa............................................................................... 96

Laupahoehoe Volcanics........................................................................................ 96

Introduction.................................................................................................. 96

Previous investigations ................................................................................ 97

Petrography.................................................................................................. 100

Composition................................................................................................. 104

Origin of the most mafic hawaiite ............................................................... 105

Fractionation within the hawaiitic suite....................................................... 108

Mafic and ultramafic xenoliths .................................................................... 110

Origin of Laupahoehoe hawaiitic lavas ....................................................... 112

Development of Mauna Kea Volcano—an interpretative summary ............................ 114

Introduction.......................................................................................................... 114

Preshield stage ..................................................................................................... 115

Shield stage.......................................................................................................... 115

Postshield stage.................................................................................................... 121

Basaltic substage.......................................................................................... 121

Hawaiitic substage....................................................................................... 125

Glaciation..................................................................................................... 126

References cited........................................................................................................... 126
VI CONTENTS

PLATES

1. Geologic map of the lower northwest flank of Mauna Kea Volcano, Hawaii

2. Geologic map of the south flank and summit of Mauna Kea Volcano, Hawaii

3. Map of Mauna Kea Volcano, Hawaii, showing the locations and radiometric ages of analyzed and dated samples from 

the south flank and summit

4. Map of Mauna Kea Volcano, Hawaii, showing the locations and radiometric ages of analyzed and dated samples from 

areas other than the south flank and summit

FIGURES

1. Maps showing location, topography, bathymetry, and geographic features of Mauna Kea Volcano................... 3

2. Index map of north half of the Island of Hawaii, showing locations of U.S. Geological Survey 7.5-minute

quadrangle maps that cover area of Mauna Kea lavas......................................................................................... 15

3. Cross section through northeast flank of Mauna Kea, illustrating relations between shield and postshield

lavas...................................................................................................................................................................... 16

4. Plot of volume versus time for Mauna Kea, illustrating three stages of growth of the volcano.......................... 17

5. Plot of Na2O+K2O versus SiO2 contents for all analyzed Mauna Kea lavas ....................................................... 17

6. Plot of differentiation index versus anorthite content in normative plagioclase for all analyzed Mauna

Kea lavas.............................................................................................................................................................. 18

7. Correlation diagram comparing stratigraphic terminology for Mauna Kea used by previous workers with

that used in this report.......................................................................................................................................... 19

8. Correlation diagram showing time-stratigraphic and rock-stratigraphic units and isotopic ages as reported

by Porter (1979a-d) for Mauna Kea..................................................................................................................... 20

9. Diagrammatic cross section through summit and upper north and south flanks of Mauna Kea, illustrating

spatial relations among stratigraphic units ........................................................................................................... 21

10. Correlation diagram of stratigraphic units and summary of isotopic ages of Mauna Kea lavas.......................... 26

11. Schematic columnar diagram summarizing K-Ar ages for lavas of the Liloe Spring and Hopukani Springs

Volcanic Members of the Hamakua Volcanics..................................................................................................... 27

12. Geologic map of Mauna Kea, showing generalized distribution of the Hamakua Volcanics .............................. 28

13. Stratigraphic sections of the Hamakua Volcanics exposed in Kaawalii, Laupahoehoe, and Maulua Gulches .... 29 

14-21. Photographs showing:

14. Members of the Hamakua Volcanics exposed in west wall of Waikahalulu Gulch .................................... 31

15. Basalt cinder cone of the Hopukani Springs Volcanic Member, overlain by the Pohakuloa Glacial

Member of the Hamakua Volcanics ............................................................................................................ 32

16. Diamict and gravel of the Pohakuloa Glacial Member of the Hamakua Volcanics.................................... 33

17. Type section of the Liloe Spring Volcanic Member of the Hamakua Volcanics......................................... 35

18. Supplementary type section of the Liloe Spring Volcanic Member of the Hamakua Volcanics................. 36

19. South-summit region of Mauna Kea........................................................................................................... 39

20. End moraines of the Waihu Glacial Member of the Hamakua Volcanics and Makanaka Glacial

Member of the Laupahoehoe Volcanics on south flank of Mauna Kea ...................................................... 41

21. Diamict (till) of the Waihu Glacial Member of the Hamakua Volcanics .................................................... 42

22. Geologic map of Mauna Kea, showing generalized distribution of the Laupahoehoe Volcanics........................ 44

23-27. Photographs showing:

23. Cinder cones and lava flows of older volcanic rocks member of the Laupahoehoe Volcanics on upper

west flank of Mauna Kea ............................................................................................................................ 45

24. Puu Lehu and nearby lava flows and cinder cones of the Laupahoehoe Volcanics on upper northeast

flank of Mauna Kea..................................................................................................................................... 46

25. Blanket of air-fall tephra partly surrounding and mantling Puu Kanakaleonui.......................................... 48

26. Eroded surface of lava flow of older volcanic rocks member of the Laupahoehoe Volcanics ................... 51

27. Poorly consolidated till in lateral moraine of the Makanaka Glacial Member of the Laupahoehoe

Volcanics..................................................................................................................................................... 54
CONTENTS VII

28. Geologic map of part of upper north flank of Mauna Kea, showing relations among intertill lava flows

and older and younger tills of the Makanaka Glacial Member............................................................................ 55

29-34. Photographs showing:

29. Reference section of slope deposits exposed in west wall of aqueduct gulch ............................................ 61

30. Bedded, dark pebbly sand in slope deposits exposed in west wall of aqueduct gulch................................ 63

31. Diamict overlying eolian sand in slope deposits......................................................................................... 63

32. Basaltic rubble and reworked ashy deposits separating lava flows of the Hamakua and Laupahoehoe

Volcanics in west wall of small gulch ......................................................................................................... 64

33. Slope deposits overlying outwash of the Waihu Glacial Member of the Hamakua Volcanics in west

wall of aqueduct gulch ................................................................................................................................ 65

34. Outwash of the Waihu Glacial Member of the Hamakua Volcanics and overlying slope deposits in

west wall of aqueduct gulch........................................................................................................................ 66

35. Plots of isotopic compositions of postshield lavas............................................................................................... 69

36. SiO2 -variation diagrams for lavas of the Hamakua Volcanics, Hilo Ridge, and Kilauea Volcano....................... 71

37. Plots of K2O/P2O5 versus MgO contents and Na2O+K2O versus SiO2 contents for lavas of the Hamakua

Volcanics and Hilo Ridge ..................................................................................................................................... 72

38. Plot of CaO versus MgO contents in sample IP-20............................................................................................. 75

39. MgO-variation diagrams for basaltic rocks of the Hamakua Volcanics............................................................... 76

40^12. Phase diagrams for selected samples of basalt of the Hamakua Volcanics, illustrating:

40. Relation to 30-kbar phase boundaries and progressive changes in normative-mineral components.......... 78

41. Relation to liquid paths along 1-bar phase boundaries................................................................................ 80

42. Inferred melting paths of garnet peridotite.................................................................................................. 82

43. Geologic map of Mauna Kea, showing generalized distribution of ankaramite and picrite lava flows of the

Hamakua Volcanics.............................................................................................................................................. 84

44. Photomicrographs of Mauna Kea lavas and xenoliths......................................................................................... 86

45. Plot of CaO versus MgO contents in ankaramites and picrites of the Hamakua Volcanics................................. 88

46. Phase diagram for selected samples of picrite and ankaramite............................................................................ 89

47. Geologic map of Mauna Kea, showing generalized distribution of high-Ti basalt lava flows ............................ 90

48. Plots of CaO versus MgO contents and A12O3 versus SiO2 contents, comparing high-Ti basalts with other

basalts of the Hamakua Volcanics ........................................................................................................................ 92

49. Phase diagram for selected samples of high-Ti basalt.......................................................................................... 94

50. Polybaric phase diagram for selected samples of high-Ti basalt of the Hamakua Volcanics............................... 95

51. Phase diagram showing liquidus boundaries in the system diopside-anorthite-forsterite.................................... 95

52. Geologic map of Mauna Kea, showing generalized distribution of basalts of the Liloe Spring Volcanic

Member of the Hamakua Volcanics...................................................................................................................... 98

53. Plots comparing CaO versus MgO contents and A12O3 versus SiO2 contents in basalts of the Liloe Spring

Volcanic Member with those in other basalts of the Hamakua Volcanics............................................................ 99

54. Phase diagram for selected samples of basalt of the Liloe Spring Volcanic Member of the Hamakua

Volcanics............................................................................................................................................................... 101

55. Geologic map of Mauna Kea, showing generalized distribution of plagioclase-rich basalts of the Hamakua

Volcanics............................................................................................................................................................... 102

56. Plot of A12O3 versus SiO2 contents of plagioclase-rich basalts in comparison with other basalts of the

Hamakua Volcanics.............................................................................................................................................. 103

57. Phase diagram for selected samples of basalt of the Hopukani Springs Volcanic Member of the Hamakua

Volcanics............................................................................................................................................................... 107

58. MgO-variation diagrams for lavas of the Laupahoehoe Volcanics ...................................................................... Ill

59. Polybaric phase diagram for lavas of the Laupahoehoe Volcanics ...................................................................... 112

60. Phase diagram for selected samples of lavas of the Laupahoehoe Volcanics ...................................................... 113

61. Plot of Sr versus P2O5 contents in lavas of the Hamakua and Laupahoehoe Volcanics....................................... 114

62. Phase diagram showing liquidus boundaries in diopside-anorthite-forsterite system.......................................... 114

63. Schematic diagram illustrating fractionation of hawaiitic lavas of the Laupahoehoe Volcanics......................... 116

64. Schematic diagrams illustrating growth of Mauna Kea in relation to adjacent volcanoes ................................. 119

65. Topographic strip maps and profiles of summits and upper flanks of Mauna Kea and Mauna Loa

Volcanoes.............................................................................................................................................................. 122
VIII CONTENTS

TABLES

1. Chemical analyses and normative ne, ol, hy, and q in Mauna Kea lavas................................................................... 7

2. Petrographic nomenclature for lavas of theHamakua Volcanics............................................................................... 18

3. Summary of postshield stratigraphic units of Mauna Kea......................................................................................... 22

4. Analytical data for newly reported whole-rock K-Ar ages on Mauna Kea lavas ...................................................... 23

5. Other K-Ar ages on Mauna Kea lavas........................................................................................................................ 24

6. Radiocarbon ages on charcoal from beneath Mauna Kea lava flows......................................................................... 25

7. Reference section of slope deposits............................................................................................................................ 62

8. Representative electron-microprobe analyses of minerals in basalts of the Hamakua Volcanics.............................. 73

9. Chemical compositions of basaltic magma, adjusted by addition of olivine to be in equilibrium with olivine

phenocrysts and mantle olivine.................................................................................................................................. 75

10. Mass-balance calculations testing the relation by crystal fractionation among the basalts plotted in figure 40........ 81

11. Major-oxide and normative-mineral compositions of typical ankaramites and picrites of the Hamakua

Volcanics and Hilo Ridge........................................................................................................................................... 85

12. Major-oxide and normative-mineral compositions of high-Ti basalts of the Hamakua Volcanics............................ 91

13. Mass-balance calculations testing the derivation of high-Ti basalts.......................................................................... 96

14. Major-oxide and normative-mineral compositions of representative lavas of the Liloe Spring Volcanic

Member and of a similar flow from the northwest flank of Mauna Kea.................................................................... 97

15. Mass-balance calculations illustrating the origin of some basalts of the Liloe Spring Volcanic Member................ 100

16. Major-oxide and normative-mineral compositions and phenocryst modes of representative plagioclase-rich

basalts and porphyritic basalt..................................................................................................................................... 104

17. Mass-balance calculations to derive the compositions of plagioclase-rich basalts and porphyritic basalt................ 105

18. Major-oxide and normative-mineral compositions of representative basalts of the Hopukani Springs Volcanic

Member...................................................................................................................................................................... 106

19. Major-oxide and normative-mineral compositions of basalt from Kanoa and nepheline basanite of the Honolulu

Volcanics, Oahu.......................................................................................................................................................... 108

20. Electron-microprobe analyses of representative minerals in hawaiitic lavas of the Laupahoehoe Volcanics, and

compositions of minerals used in mass-balance calculations .................................................................................... 109

21. Major-oxide and normative-mineral compositions of representative lavas of the Laupahoehoe Volcanics............. 110

22. Mass-balance calculations to derive the compositions of the most mafic hawaiites of the Laupahoehoe

Volcanics..................................................................................................................................................................... 115

23. Mass-balance calculations illustrating fractionation in hawaiitic lavas of the Laupahoehoe Volcanics.................... 117
The Geology and Petrology of Mauna Kea Volcano, HawaiiA Study of Postshield Volcanism

By Edward W. Wolfe, William S. Wise, 1 and G. Brent Dalrymple

ABSTRACT

The subaerially exposed lavas of Mauna Kea form a 

cap that conceals the underlying tholeiitic basalts of the volcano's shield stage. Our geologic mapping shows that this 

postshield cap consists of older basaltic lavas overlain by 

younger hawaiitic lavas. Thus, the postshield eruptive stage 

consisted of basaltic and hawaiitic substages. Lavas of the 

basaltic substage compose the Hamakua Volcanics, which 

were erupted between approximately 250 and 70-65 ka, 

whereas those of the hawaiitic substage compose the Laupahoehoe Volcanics, which were erupted between approximately 65 and 4 ka.

Hamakua lavas were erupted both from fissure vents 

near the summit and from point-source vents marked by 

cinder cones that are scattered over the flanks of Mauna 

Kea. Lithologic distinctions and an intercalated glacial 

deposit permit stratigraphic subdivision of the Hamakua 

Volcanics on the upper flanks of the volcano. Lower and 

upper volcanic units, herein named the Hopukani Springs 

and Liloe Spring Volcanic Members, are separated by the 

Pohakuloa Glacial Member. A younger glacial deposit, the 

Waihu Glacial Member, occurs as a lens enclosed, at least in 

part, within the Liloe Spring Volcanic Member. No consistent criteria exist for stratigraphic subdivision of the 

Hamakua lavas exposed on the lower slopes.

Laupahoehoe lavas issued from numerous point-source 

vents, most of which are marked by scoria cones mainly on 

the upper flanks and summit of the volcano. Air-fall ash and 

lapilli from the Laupahoehoe eruptions mantle much of the 

upper slopes, forming scattered tephra blankets and ash 

dunes. Reworked ash is the dominant component of local 

slope deposits.

A final glaciation of Mauna Kea's summit occurred 

between approximately 40 and 13 ka. Till and outwash 

deposited at that time compose the Makanaka Glacial

1 Department of Geological Sciences, University of California, Santa 

Barbara, CA 93106.

Member of the Laupahoehoe Volcanics. Laupahoehoe eruptions occurred before, during, and after the Makanaka glacial episode.

The Hamakua Volcanics consist of alkali basalt, transitional basalt, and, among the oldest lavas, rare tholeiitic 

basalt. Evolved basalts are common, apparently derived by 

crystal fractionation of olivine-controlled parental magma 

in reservoirs within the volcano, mostly at shallow levels. 

Petrologic considerations suggest that these parental magmas originated from partial melting of peridotite at approximately 30-kbar pressure and that the degree of silica 

saturation reflects the degree of partial melting: Alkali 

basalt originates from a lesser degree of partial melting, and 

tholeiitic basalt from a greater degree. Alkali basalt is common on the lower flanks of the volcano but rare on the upper 

flanks, a difference suggesting that the degree of partial 

melting decreased outward from beneath the center of the 

volcano during Hamakua time.

A distinct compositional gap separates the Hamakua 

and Laupahoehoe lavas. The Laupahoehoe lavas consist 

mostly of felsic hawaiite to mugearite but include some 

benmoreite. They are aphyric to somewhat plagioclase phyric and, unlike the underlying basaltic lavas, commonly 

contain xenoliths of gabbro, peridotite, or pyroxenite. We 

interpret these hawaiitic magmas as derived from fractionation of basaltic magma in reservoirs below the base of the 

crust. Little or no additional fractionation occurred during 

ascent.

The estimated total volume of Mauna Kea is more than 

30,000 km3 . Shield-stage lavas represent the bulk of the volcano; the volume of postshield lavas is less than 1,000 km3 . 

The transition from the shield to the postshield stage 

occurred before approximately 250 to 200 ka, and we estimate that Mauna Kea volcanism began about 1 Ma. 

Decreasing magma supply provides a context for the magmatic and volcanic evolution of the volcano. The decreasing 

supply was accompanied by changing lava composition, 

from tholeiitic basalt that dominated the shield stage, 

through transitional and alkali basalt that dominated the 

postshield basaltic substage, to hawaiitic lava of the postshield hawaiitic substage.
GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

INTRODUCTION

Mauna Kea and Mauna Loa, both volcanoes that rise 

more than 4,000 m above sea level, dominate the landscape 

of the Island of Hawaii (fig. 1). Offshore soundings led 

early students of the Hawaiian volcanoes (Dana, 1890) to 

realize that these volcanoes were built on a sea floor 5 km 

deep and are each, therefore, at least 9 km high. Recent seismic-refraction studies, however (summarized by Moore, 

1987), have shown that as these piles of lava accumulated, 

they depressed the sea floor by as much as another 6 km 

(fig. 1). Thus, the summits of Mauna Kea and Mauna Loa 

are approximately 15 km above the down warped substrate, 

and the volume of each volcano exceeds 32,000 km3 , representing enormous outpourings of magma from localized 

sources.

Evidence from volcanoes of differing ages suggests 

that an idealized Hawaiian volcano evolves through a 

sequence of four eruptive stages—preshield, shield, postshield, and rejuvenated (Clague and Dalrymple, 1987, 

1989)—distinguished on the bases of lava composition, 

eruptive rate and style, and stage of development. No 

preshield lavas are exposed on the Hawaiian islands. However, dredge samples from the active Loihi Seamount 

include alkalic basalt and basanite, which led Moore and 

others (1982) to conclude that Loihi Seamount and, possibly, all Hawaiian volcanoes initially erupt alkalic basalt. 

Loihi Seamount represents the preshield stage. The shield 

stage is marked by rapid eruption of tholeiitic basalt. 

Kilauea and Mauna Loa are vigorously active shield-stage 

volcanoes; their lavas consist, with rare exception, of tholeiitic basalt, which contains a relatively low concentration of 

alkalis and, relative to postshield-stage basalt, a relatively 

high concentration of SiO2 (Wolfe and Morris, 1996). We 

infer that the shield-stage lavas of Mauna Kea are composed 

predominantly of tholeiitic basalt similar to that of Kilauea 

and Mauna Loa. Postshield volcanism is characterized by 

relatively slow eruption of alkalic and transitional basalt. 

Hualalai, Mauna Kea, and Kohala are all capped by postshield lavas, which are more alkalic than the shield-stage 

basalt (Wolfe and Morris, 1996). The rejuvenated stage, 

during which small amounts of SiO2-poor lava are erupted, 

occurs after as much as a few million years of volcanic quiescence; no volcanoes of the Island of Hawaii have reached 

this stage.

R.A. Daly, the first petrologist to study the rocks of 

Mauna Kea (Daly, 1911), realized that the lavas erupted 

near the summit are distinctly andesitic (we use the term 

"hawaiitic"; see subsection below entitled "Major Rock 

Classes and Petrographic Groups"), compositionally more 

evolved than those of Mauna Loa or the lower flanks of 

Mauna Kea. All subsequent petrologic investigations of the 

two volcanoes have concluded that although Mauna Loa is 

still actively building a shield of tholeiitic basalt with summit and rift-zone eruptions, Mauna Kea had evolved to a

later stage with its own characteristic eruptive style and 

more alkalic lava compositions. On the basis of their reconnaissance mapping, Stearns and Macdonald (1946) 

described this postshield activity of Mauna Kea, and it 

became the type example of the "postcaldera stage" of 

Hawaiian volcanoes (Stearns, 1946).

Postshield lavas cover the entire subaerial surface of 

Mauna Kea. Recent detailed geologic mapping of these 

postshield lavas and intercalated sedimentary deposits, and 

new K-Ar and 14C radiometric data on selected lava flows, 

provide a new stratigraphic framework for refinement of 

our ideas concerning the volcanic and petrologic evolution 

of the volcano. This report presents a detailed analysis of 

the geologic and magmatic evolution of Mauna Kea Volcano during its postshield stage, which had begun by about 

250-200 ka, and an interpretative synthesis of the development of the volcano from its inception to the present.

PREVIOUS MAJOR CONTRIBUTIONS

Previous studies of the geology of Mauna Kea focused 

primarily on two aspects: the composition and petrology of 

the lavas, and the glacial deposits and their interrelations 

with the lavas. We mention briefly here only the major contributions to our geologic understanding of Mauna Kea and 

elaborate further elsewhere in this report.

R.A. Daly set the stage for subsequent study of Mauna 

Kea by recognizing that the summit has been glaciated 

(Daly, 1910) and that the volcano is basaltic on its lower 

flanks and consists of "andesite" and "trachydolerite" (both 

hawaiitic in our terminology) on its upper flanks and summit (Daly, 1911). He attributed this apparent stratification to 

"gravitative differentiation." Daly's analyses of two samples 

of hawaiite from the upper slopes provided the first compositional data from Mauna Kea. Washington (1923) described 

and analyzed an additional nine Mauna Kea rocks, including both basalt and hawaiite. These 11 analyses constituted 

the entire compositional data set for Mauna Kea when 

Stearns and Macdonald (1946) published their classic volume on the geology of the Island of Hawaii.

Gregory and Wentworth (1937) published an excellent 

description of the glacial features of the most recent glacial 

episode; they pointed out that some postglacial volcanic 

activity had occurred. Wentworth and Powers (1941) recognized that several separate glacial episodes have occurred 

on Mauna Kea and that the various glacial deposits are 

interleaved with volcanic rocks. Stearns (1945) clarified the 

aerial distribution of these glacial deposits. He concluded, 

however, that only the youngest, his Makanaka Drift, is a 

glacial deposit; he viewed the other deposits as volcanic 

explosion breccias or fanglomerates.

Macdonald (1945, 1949) and Stearns and Macdonald 

(1946) established the fundamental volcanic framework for 

Mauna Kea. Their geologic map (Stearns and Macdonald,
INTRODUCTION

160° 159° 158° 157° 156^ 155° 154°

22°

21 c

20C

19C

100 KILOMETERS

Figure 1. Location, topography, bathymetry, and geographic 

features of Mauna Kea Volcano. A, Generalized topography and 

bathymetry of southeastern part of the Hawaiian Ridge (Mark and 

Moore, 1987). Individual volcanoes are identified for those islands 

composed of more than one shield volcano. Extinct Mahukona 

Volcano (Clague and Moore, 1991) and youthful Loihi Volcano 

are identified on submarine flanks of the Island of Hawaii. 

B, Topography and bathymetry of Island of Hawaii, showing areal 

extent of Mauna Kea Volcano, locations of nearby volcanoes, and 

contour of surface of oceanic crust beneath volcanoes. Topography 

modified from U.S. Geological Survey, 1:250,000, Hawaii, 1975; 

contour interval, 1,000 ft. Bathymetry modified from Chase and 

others (1980); contour interval, 300 m. Dashed lines represent

1946), showing the distribution of their Hamakua and 

Laupahoehoe Volcanic Series, is a major milestone in the 

study of Mauna Kea geology. Subsequently, Macdonald and 

Katsura (1964) and Macdonald (1968) significantly amplified the compositional data set for Mauna Kea and definitively characterized the compositional evolution of 

Hawaiian volcanoes.

100-m contours; hachures point into closed depressions. Structurecontour values calculated by subtracting thickness of crust (5 km; 

Hill and Zucca, 1987) from structure-contour values for base of 

crust (in kilometers below sea level) from Moore (1987); in addition, 7-km contour is shifted northwestward to avoid its near-coincidence with surface of oceanic crust on sea floor adjacent to steep 

flanks of volcanic pile at a depth of approximately 5 km. A-A' 

marks position of cross section shown in figure 3. C, Geographic 

features of Mauna Kea discussed in text. Topographic contours 

from U.S. Geological Survey, Hawaii County, Sheets 1 and 2, 

1980; 4,000-m contour omitted, ag, the aqueduct gulch; HS, Hopukani Springs; HSS, Humuula Sheep Station; LS, Liloe Spring; WS, 

Waihu Spring. j

S.C. Porter reexamined the glacial deposits and their 

relations to the volcanic rocks. He presented compelling 

evidence that the explosion breccias and fanglomerates of 

Stearns (1945) are, in fact, glacial deposits. Porter was the 

first to recognize subglacially erupted lavas on Mauna Kea. 

He emphasized the importance of the various glacial deposits as markers for subdividing the volcanic rocks, and he
GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

156° 155° 154°

20C

19°

B

EXPLANATION

Subaerially exposed lavas of Mauna Kea Volcano

Inferred areal extent of lavas of Mauna Kea Volcano 

that are either below sea level or beneath lavas 

of Hualalai, Mauna Loa, or Kilauea Volcanoes

Rift zone of Mauna Kea Volcano 

Present-day shoreline of Island of Hawaii

Inferred shoreline of Mauna Kea Volcano at end of 

its shield stage

9 ""••""I Structure contour (in kilometers below sea level) of 

surface of oceanic crust beneath Island of 

Hawaii

25 MILES

25 KILOMETERS

Figure 1. Continued.
INTRODUCTION

§ 

U
GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

also was the first to use isotopic dating to relate the 

sequence to global glacial events. Porter's studies resulted 

in a geologic map of the upper parts of Mauna Kea (Porter, 

1979a) and a series of published reports treating various 

aspects of the geology (Porter, 1971, 1972a, b, 1973, 1975, 

1979a-d, 1987; Porter and others, 1977).

CURRENT WORK

This report is the culmination of detailed mapping of 

the entire volcano by Wolfe and Wise (see pis. 1, 2; figs. 12, 

22; Wolfe and Morris, 1996), new K-Ar dating by Dalrymple, and assembly of a comprehensive set of major-oxide 

analyses (table 1) of samples tied to the mapping (see pis. 3, 

4). These three components together constitute a powerful 

data set for evaluating the growth of the volcano in its postshield stage; we examine the volcanic and magmatic record 

with well-understood stratigraphic and chronologic constraints.

Wise began his new work on Mauna Kea in 1981, 

spending a total of 8 months during summer field seasons 

through 1987. During that period, his effort was focused on 

mapping and sampling the Hamakua Volcanics of the lower 

flanks to study the petrology of the Hamakua lavas. In addition, he mapped the geology of the southwest and upper 

west flanks in fall 1987. Wolfe began mapping on the upper 

south and east flanks and in the summit area in 1986, working there intermittently through 1987. Dairymple began collecting and dating samples closely tied to the mapping in 

1985; that effort continued throughout the remaining period 

of our study.

Preparation of this report has been a mutual effort in 

which Wise took the lead in petrologic analysis and in 

discussion of the Hamakua Volcanics of the lower flanks, 

Wolfe focused primarily on geologic evaluation of the upper 

flanks and summit, and Dalrymple was responsible for discussion of the K-Ar dating.

ACKNOWLEDGMENTS

M.A. Kuntz mapped much of the geology of the 

Umikoa and Makahalau quadrangles, both of which are on 

the upper north flank of Mauna Kea (fig. 2). Meyer Rubin 

determined 14C ages on charcoal samples from beneath several lava flows of the younger volcanic rocks member of the 

Laupahoehoe Volcanics. B.D. Turrin collected samples of 

and determined K-Ar ages on several lava flows of the 

Hamakua Volcanics and the older volcanic rocks member of 

the Laupahoehoe Volcanics. J.C. Dohrenwend gave useful 

counsel on surficial processes and deposits during the early 

stages of our mapping on the upper flanks of the volcano, 

and provided results of a morphometric reconnaissance of 

Mauna Kea's cinder cones. T.E.C. Keith graciously analyzed alteration minerals in samples from Puu Waiau and

Puu Poliahu. F.A. Frey supplied major- and trace-element 

analyses of selected Mauna Kea lavas. K.J. Murata provided 

important major-element analyses, notes, and thin sections 

for lavas he had examined along the lower northeast flank 

of Mauna Kea. Cartographer Jean Morris was an indispensable colleague in preparation of the map illustrations.

We also thank the managements of the Parker Ranch, 

the Hamakua Sugar Co., and the Hilo Coast Processing Co. 

and personnel of the Hawaii Division of Forestry for their 

helpful cooperation in permitting access to ranchland, plantations, and forestland not normally open to the public.

Finally, we thank M.A. Mangan and W.E. Scott for 

their helpful reviews.

GEOLOGIC SETTING

The subaerial and submarine contours of the upper surface of the volcano indicate that most of the mass of Mauna 

Kea lies to the east of the present summit and that the shield 

apparently had a shape and orientation similar to those of 

the present-day Kilauea (fig. 1). The central conduit system 

for Mauna Kea's shield was probably beneath the present 

summit area, and the only major rift zone extended eastward, where it formed Hilo Ridge. The older Mahukona and 

Kohala shields and the largely concurrent Hualalai shield 

buttressed the growing Mauna Kea shield from northwest to 

southwest, inhibiting the development of a rift zone extending westerly. Conversely, because of the assumed younger 

age of Mauna Loa, we show Mauna Kea extending beneath 

the adjacent Mauna Loa shield. Eruptive activity of Mauna 

Kea was partly contemporaneous with that at Kohala, Hualalai, and Mauna Loa, and the volcano boundaries are 

undoubtedly complex. Field evidence indicates that lavas of 

Mauna Kea are intercalated with those of all three of its subaerial neighbors.

Cross sections of volcanoes during their shield stages 

have a characteristic shape (Moore and Fiske, 1969): Fluid, 

subaerial flows originating from summit or rift-zone vents 

slope gently, whereas the submarine slopes, composed of 

submarine flows and clastic debris fans that form where 

subaerial flows reached the shoreline, slope more steeply. 

The average subaerial slope from the shoreline of Kilauea 

and Mauna Loa up to about 2,000-m elevation is about 4°, 

whereas below sea level this slope increases abruptly to an 

average of 13° at 500-m depth (Mark and Moore, 1987). 

Moore and Fiske (1969) showed that the break in slope at 

the shoreline is a feature only of shield-stage volcanoes, on 

which upward growth at the shoreline is sufficiently rapid to 

keep pace with the subsidence that records isostatic adjustment of the growing volcanic mass (Moore, 1987). Postshield lavas apparently are insufficiently fluid or 

voluminous to consistently reach the shoreline and maintain 

the slope break at sea level. Thus, continuing subsidence 

during the postshield stage progressively submerges the
Table 1. Chemical analyses and normative ne, ol, hy, and q in Mauna Kea lavas

[Major-oxide compositions and partial Cross, Iddings, Pirsson, and Washington (CIPW) norms in weight percent; nd, not determined. Norms were computed fr

weight after removal of normative calcite and partitioning of Fe to FeO and Fe2O3 in the ratio 88:12. Units: h, undivided Hamakua Volcanics; hh, Hopukani Spr

canics; hi, Liloe Spring Volcanic Member of the Hamakua Volcanics; lo, older volcanic rocks member of the Laupahoehoe Volcanics; ly, younger volcanic ro

Rock types (see table 2 and fig. 5): ank, ankaramite; ben, benmoreite; bs, phenocryst-poor basalt; gm, mechanically separated sample of groundmass; h/m, haw

picrite; plbs, plagioclase basalt; ppbs, porphyritic basalt. Most sample localities are grouped by quadrangle identifier (for example, GQ-18; see pis. 3 and 4 

locality-numbering system); most others are traverses (for example, La-7) along stratigraphic sections exposed in gulches (Ki, Kaawalii; La, Laupahoehoe; Ma

for locations of traverses); the remaining samples (for example, Er-21; not plotted) were dredged from Hilo Ridge. Suffix "G" identifies mechanically separ

sample with otherwise-identical sample-locality number, do, ditto. The data of this table are available as a digital electronic file (Wolfe, 1997)]

Remarks: a, Dredged from Hilo Ridge (D.L. Peck, unpub. data, 1965). Collection depths: Er-20, 1,650 m; Er-21, 2,740 m; Er-22, 3,200 m. Classical chemical analyses; analy

Colo. 

b, X-ray-fluorescence analyses. H2O specifically determined only for those samples analyzed for CO2 ; otherwise, H2O content is loss on ignition. Analysts: A.J. Bartel

U.S. Geological Survey, Denver, Colo.

c, X-ray-fluorescence analyses. H2O content is loss on ignition. Analysts: R. Johnson and J. Evans, U.S. Geological Survey, Reston, Va. 

d, X-ray-fluorescence analyses; analyst, F.A. Prey, Massachusetts Institute of Technology, Cambridge, Mass, 

e, Collected by K.J. Murata (unpub. data, 1961-66). Classical chemical analyses; analysts: P. Buschman, E.S. Daniels, E.L. Munson, D.F. Powers, and R.T. Okamura, U

Sample 

Locality Unit 

No.

Er-20

Er-21

Er-22

GP-36

GP-37

GQ-9

GQ-11

GQ-18

GQ-19

GQ-21

GQ-22

GQ-23

GR-12

GR-13

GR-14

GR-15

GR-16

GR-17

GR-18

GR-19

GR-20

GR-21

GR-22

GR-23

GR-24

GR-25

GR-26

GR-27

GR-28

GR-29

GR-30

GR-31

GR-32

GR-33

GR-34

GR-35

GR-36

GR-37

GR-38

GR-39

__

--

--

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

ly

ly

lo

lo

lo

lo

lo

lo

lo

lo

ly

lo

lo

lo

lo

ly

lo

lo

lo

ly

lo

lo

ly

lo

lo

Feature

Flow

dododoCone

doFlow

Cone

doFlow

doCone

doFlow

Cone

Flow

doCone

Flow

dodoCone

Flow

doCone

Flow

dodoCone

doFlow

doCone

doFlow

dododoCone

doType

pic

pic

olbs

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

Laboratory 

No.

D100696

D100697

D100698

D-276075

D-276073

D-276026

W-235826

D-276061

D-276060

D-276074

D-284775

D-276063

D-276026

D-276025

D-276036

D-276035

D-276034

D-276024

D-276041

D-276027

D-276042

D-284786

D-276043

D-276029

D-276044

D-276037

D-276030

D-276028

D-276048

D-284782

D-276040

D-276049

D-276031

D-284783

D-276039

D-276032

D-276033

D-276038

D-276047

D-284781

Remar

a

a

a

b

b

b

c

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

k

Major oxides

SiO2

47,

47.

47,

49,

49.

50.

49.

50.

50.

48.

49.

48.

49.

48.

49.

50.

50.

49.

50.

48.

50.

50.

49.

49.

50.

50.

49.

49.

50.

49.

50.

51.

49.

49.

50.

50.

50.

50.

50.

50.

.94

.28

.01

.10

.80

.20

.25

.20

.00

.50

.10

.60

.30

.50

.20

.60

.40

.30

.60

.70

.50

,30

.80

.80

.80

.70

.40

,80

,00

.70

,30

,10

,40

.80

,70

,80

,10

,70

,40

.50

Al

10.

10,

12,

17,

16,

17,

17.

17.

17.

16.

16.

16.

16.

16.

17.

17.

17.

16.

17.

17.

17.

17.

16.

17.

17.

17.

16.

17.

17.

16.

16.

17.

16.

17.

17.

17.

16.

16.

17.

17.

2 °3 Fe2 03

.43

.00

.12

.00

.90

.00

.59

.00

.00

.70

.80

.80

.90

.80

.10

.00

.00

.90

.40

.00

,00

,10

,90

.00

,50

,00

90

,00

.90

,90

,90

,20

.90

,00

,00

,00

,90

,90

,10

10

2

2

2

12

11

12

11

11

11

12

12.

12,

12,

12

11.

11,

11,

12,

10,

12,

11.

11,

11.

11.

11.

11,

12,

12,

10,

11.

11.

11.

12.

11.

11.

11.

11.

11.

11.

11.

.03

.30

.86

.40

.80

.00

.54

.60

.80

.30

.30

.40

.00

.50

.90

.60

.50

.10

.70

.10

.30

.90

.80

.90

.00

.60

.20

.10

.90

.70

.60

.00

.00

.90

.50

.60

.40

,50

,20

.60

FeO

9.54

9.05

9.29

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

MgO

17,

19,

12,

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

3.

3.

4.

4.

3.

4.

3.

4.

4.

4.

3.

3.

4.

4.

3.

4.

3.

3.

4.

4.

3.

3.

3.

3.

3.

3.

.34

.82

.61

.46

.03

.13

.17

.16

.18

.60

.47

.66

.19

.60

.87

.96

.02

.35

.32

.31

,78

.06

.12

.17

.28

.99

.42

,27

.39

.09

.97

.34

.27

.07

.97

.95

,96

,95

,81

,87

CaO

7,

7,

8,

7.

7.

7.

6.

7.

7.

7.

7.

7.

7.

7.

6.

6.

6.

7.

6.

7.

6.

6.

7.

7.

6.

6.

7.

7.

6.

7.

6.

6.

7.

7.

6.

6.

6.

6.

6.

7.

.42

.55

.98

.35

.04

.09

.99

.03

.08

.42

.37

.45

.18

.30

.95

.77

.81

.30

.47

.35

.72

.95

.01

.09

.33

.82

,26

.13

.56

.05

.77

.43

.20

.03

.87

.95

.92

.82

.85

.01

Na2O

1.

1.

2.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

4.

.99

.59

.36

.51

.56

.16

.86

.67

.82

.51

.29

.15

,30

.25

.20

.82

.60

.40

.80

.35

.80

.35

.64

.48

.73

.64

,38

.36

.50

,45

,81

,98

,54

,40

,67

.66

,70

,62

,82

,56

K2 0

0.39

.26

.72

1.76

1.90

1.84

1.86

1.88

1.88

1.70

1.72

1.67

1.77

1.69

1.77

1.93

1.90

1.80

2.08

1.68

2.00

1.88

1.85

1.81

2.04

1.94

1.79

1.82

1.74

1.85

1.92

2.14

1.78

1.88

1.95

1.94

1.96

1.96

2.00

1.94

H2 0

0.58

.51

1.07

.00

.00

.00

nd

.00

.00

.24

.00

.00

.35

.00

1.16

.00

.00

.05

.71

.25

.00

.00

.00

.00

.28

.21

.00

.00

1.24

.58

.00

.10

.04

.05

.00

.00

.04

.00

.02

.00

TiOj

1

1

2

3

2

2,

2,

2.

2,

3,

3.

3.

2.

3.

2.

2.

2.

3.

2.

3.

2.

2.

2.

2.

2.

2.

3.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

.98

.46

.48

.09

.76

.91

.67

.79

.83

.13

.11

.09

.94

.16

.76

.67

.67

.05

.29

.02

.58

.79

.83

.88

.33

.67

.05

.95

.34

.77

.66

.28

.96

.81

.68

.72

.69

.66

.62

.67

P205

0.24

.14

.27

.84

.96

.89

.77

.88

.90

.79

.81

.82

.89

.79

.94

.93

.91

.87

1.26

.90

1.03

.91

.89

.90

1.15

.92

.85

.89

1.28

.89

.92

1.20

.88

.88

.93

.94

.93

.93

1.02

.96

MnO

0.17

.17

.17

.21

.22

.22

.22

.22

.22

.21

.21

.21

.22

.21

.22

.22

.22

.22

.22

.22

.22

.22

.22

.22

.22

.22

.22

.22

.23

.22

.22

.23

.22

.22

.22

.22

.22

.22

.22

.22

C02

0.02

.01

.02

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

Tota

100.

100.

99.

100.

99.

100.

99.

100.

100.

100.

100.

99.

100.

99.

100.

100.

100.

100.

99.

99.

99.

100.

100.

100.

99.

100.

100.

100.

100.

100.

100.

100.

100.

100.

100.

100.

99.

100.

100.

100.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

,

.

.

.

,

,

,

,

,

,
Table 1. Chemical analyses and normative ne, ol, hy, and q in Mauna Kea lavas—Continued.

Sample 

Locality Unit 

No.

GR-40

GR-41

GR-42

GR-43

GR-44

GR-45

GR-46

GS-9

GS-11

GS-15

HP-1

HP-4

HP-5

HP-9

HP-11

HP-13

HP-14

HP-15

HP-17

HP-18

HP-19

HQ-2

HQ-3

HQ-4

HQ-5

HQ-6

HQ-7

HQ-8

HQ-9

HQ-10

HQ-11

HQ-12

HQ-13

HQ-14

HQ-15

HQ-16

HQ-17

HQ-18

HQ-19

HQ-20

HQ-21

HQ-22

HQ-23

HQ-24

HQ-25

HQ-26

HQ-27

HQ-28

HQ-29

HQ-30

HQ-31

HQ-3 2

HQ-33

HQ-34

HQ-35

HQ-3 6

HQ-37

HQ-38

lo

lo

lo

ly

lo

lo

lo

h

h

lo

lo

lo

lo

lo

lo

h

h

lo

lo

h

h

lo

hh

lo

hi

lo

hi

hi

lo

hi

lo

lo

hi

hi

hi

hh

hi

hh

hh

lo

hi

lo

lo

hi

hi

hi

hi

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

Fea- Laborature Type tory 

No.

Flow h/m D-284780

do- h/m D-284779

Cone h/m D-284784

Flow h/m D-278148

Cone h/m D-284778

Flow h/m D-284785

Cone h/m D-284777

Flow bs D-276045

do- bs D-276046

do- h/m D-276050

Cone h/m D-276070

do- h/m D-276068

do- h/m D-276069

Flow h/m D-260896

do- h/m D-260899

do- bs 81-36

do- plbs 81-46

do- h/m 81-32

do- h/m D-260883

do- bs KM-9

do- ppbs 81-19

Cone h/m D-284764

Flow pic H-l

Cone h/m D-276056

Flow bs D-276057

Cone h/m D-276065

do- bs D-284765

Flow plbs D-284774

Cone h/m D-276067

do- bs D-284766

do- h/m D-276066

Flow h/m D-292989

Cone bs D-284773

do- plbs D-284772

Flow bs D-284771

do- olbs D-284770

do- bs D-284767

do- plbs D-284768

do- olbs D-284769

do- h/m D-292990

do- bs D-292944

do- h/m D-292986

do- h/m D-292994

do- bs D-292947

do- bs D-292948

do- bs D-292949

do- plbs D-292943

do- h/m D-292993

do- h/m D-292945

do- h/m D-292946

do- h/m D-292991

do- h/m D-292961

do- h/m D-292957

do- h/m D-292960

do- h/m D-292966

do- h/m D-292958

do- h/m D-292983

do- h/m D-292956

Remar

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

d

d

d

b

d

d

b

d

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

k

Major oxides

Si02

50

50

50

52

50

48

50

46

44

50

50

50

49

49

49

45

45

49

49

47

47

52.

43.

52.

46.

50.

47.

48.

49.

47.

49.

49,

48,

48,

48

48

48

48

48.

50.

47.

50.

52.

47,

47,

47.

47.

51.

50

51.

50

51,

50.

51.

52.

51,

52.

50.

.30

.80

.40

.00

.00

.70

.20

.40

.80

.50

.00

.20

.40

.30

.90

.99

.36

.82

.90

.75

.48

.40

.79

.20

.80

.20

.30

.00

,70

.70

.70

.80

.10

.20

.00

.70

.10

.40

.80

.70

.60

.20

.80

.00

.10

.00

.70

.00

.70

.20

.50

.90

.60

.60

.60

.00

.90

.40

A12 03

16

17

17.

17

16

17

17

14

14

17.

17

17,

17.

16.

17.

13.

14.

16.

16.

13.

14.

17.

9.

17.

14.

17.

14.

14.

17.

14.

17.

17.

13.

14.

13.

13.

14.

13.

13.

17.

14.

17.

17.

14.

14.

14.

14.

17.

16.

17.

17.

17.

17.

17.

17.

17.

17.

17.

.90

.20

.40

.20

.90

.10

.10

.10

.60

.20

.40

.10

.10

,90

.10

.65

.81

.97

.90

.64

.21

.60

.57

.40

.00

.00

.20

.40

,00

.00

10

,20

.90

.40

.90

.30

.00

.30

.50

.30

.10

.10

.30

.10

.20

.50

.30

.40

.90

.20

.10

.30

.00

.20

.60

,10

,30

,20

Fe2 03

11.

11

10

10

11

12

11

14,

13,

11,

11.

11.

11.

12.

12.

14.

14.

11.

12.

14.

14.

10.

13.

10.

15.

11.

14.

13.

11.

14.

11.

11.

15.

13.

14.

13.

14.

13.

13.

11.

14.

11.

9.

14.

14.

14.

14.

11.

10.

10.

11.

10.

11.

10.

9.

11.

9.

11.

.40

.20

.70

.80

.90

.10

.60

.80

.20

.20

.20

.30

.90

.50

.00

.14

.11

.72

.00

.95

,15

.30

,77

,10

,10

40

,60

,70

40

,60

,40

,50

,30

,90

.80

.60

.70

.40

.40

.30

.80

.10

.47

.60

,60

.80

,70

,00

.90

.90

.40

.40

.30

.50

.70

.10

49

,40

FeO

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

MgO

3

3

3,

3

4

4

3,

6.

7,

3,

3,

3,

4.

4.

4.

8.

7.

4.

4.

5.

6.

2.

17.

3.

5.

3.

6.

6.

3.

6.

3.

3.

5.

6.

5.

7.

5.

8,

6,

3.

5.

3.

3.

5.

5.

5.

5.

3.

3.

3,

4.

3,

3.

3.

3.

3.

3.

3.

.96

.88

.56

.61

.21

.03

.82

.21

.90

.56

.39

.96

.05

,51

.09

.32

.45

.04

.18

.31

.42

.97

.84

.00

.75

.83

.19

,67

,84

,25

.78

.86

.48

.25

.81

.29

.64

.05

.97

.62

.65

.59

.11

.85

.81

.99

.85

.47

.55

.50

.01

.33

.87

.67

.04

.72

.05

.92

CaO

6

6

6

6.

6.

7.

6.

10.

12,

6,

6,

6.

7.

7.

7.

10.

10.

6.

6.

10.

10.

6.

9.

6.

10.

6.

11.

11.

6.

11.

6.

6.

10.

11.

10.

11.

10.

11,

11.

6.

10.

6.

5.

10.

10.

11.

11.

6.

6.

6,

6,

6,

6.

6.

5.

6.

6.

7.

.95

.89

.73

.48

.90

.32

.89

.30

.30

.70

.69

.88

.05

,17

.05

.84

.55

.88

.96

.00

.99

.12

.91

.11

.70

.79

.20

.40

,92

,00

,97

.95

.40

.30

.70

.60

.50

.60

.90

.74

.40

.79

.98

.80

.80

.20

.20

.83

.63

.67

.88

.56

.88

.51

.94

.67

.16

.00

Na2 0

4

4

4

4

4

4

4

2

1

4

4

4.

4.

4.

4.

2,

2,

4.

4.

2,

2,

4.

1,

5,

2,

4.

2.

2.

4.

2.

4.

4.

2.

2.

2.

2.

2

2

2

4

3.

4.

5

2.

3.

2

2

4

5

5

4

4

4.

4.

5.

4.

5.

4.

.35

.63

.55

.90

.42

.20

.40

.96

.97

.92

.56

.83

.63

.48

.68

.48

.49

.32

.46

.72

.41

.74

.20

.13

.88

.47

.69

.56

.73

.78

.70

.67

.71

.60

.76

.43

.94

.26

.41

.61

.13

.91

.20

.96

.00

.57

.66

.94

.01

.02

.48

.94

.78

.77

.06

.74

.03

.58

K2 0

1

1

2

2

1

1,

1

2,

1,

1.

1.

1.

1,

1,

1.

2.

2.

1.

1.

1.

1.

2.

1.

2.

2.

1.

1,

2.

2.

2,

1,

2,

1.

2.

2.

2.

2.

1.

.91

.95

.04

.10

.83

.86

.85

.99

.22

.06

.98

.96

.90

.74

.85

.82

.94

.84

.82

.95

.79

.24

.47

.33

.71

.99

.80

.75

,99

.86

.94

.96

.88

.79

.83

.67

.98

.63

.69

.04

.10

.02

.36

.04

.02

.68

.83

.10

.11

.12

.98

.18

.99

.16

.37

.05

.34

.95

H2 0

0.00

.00

.88

.00

.19

.65

.22

.10

1.84

.06

.82

.10

.00

.00

.00

.16

.19

.10

.00

.22

.21

.32

nd

.39

.05

.11

.00

.00

.00

.00

.34

.19

.00

.00

.00

.00

.00

.00

.00

.00

.00

.43

.23

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.02

.00

.14

.00

Ti02

2

2

2

2

2

2

2

4

3

2

2

2

2.

3

2

3.

3

2

2

3

3.

2.

2.

2.

3.

2.

3.

3.

2,

3.

2.

2,

3.

3.

3

3.

3

2

2

2

3.

2.

1

3

3

3.

3

2

2

2

2

2

2

2,

2.

2.

2.

2.

.73

.69

.48

.36

.79

.94

.66

.05

.08

.42

.59

.59

.84

.01

.85

.23

.46

.76

.81

.63

.24

.09

.41

.05

.88

.64

.65

.23

.66

.64

.69

.74

.83

.31

.73

.40

.73

.95

.99

.43

.96

.51

.94

.94

.96

.47

.39

.38

.40

.43

.65

.32

.63

.38

.14

.53

.08

.66

P2 05

0

1

1

1

1.

1.

1.

1,

1,

1

1.

1

1

1.

1

1

1.

1.

.94

.92

.05

.98

.88

.93

.96

.56

.37

.14

.91

.01

.99

.85

.90

.42

.46

.83

.88

.46

.40

.24

.30

.24

.44

.01

.48

.38

.01

.47

.99

.02

.47

.40

.44

.35

.45

.35

.36

.11

.56

.11

.01

.53

.53

.43

.42

.15

.12

.14

.95

.16

.97

.99

.06

.98

.05

.98

MnO

0.22

.22

.21

.23

.22

.22

.22

.20

.18

.22

.22

.22

.21

.22

.22

.20

.18

.22

.22

.20

.20

.23

.19

.23

.20

.21

.20

.19

.21

.20

.21

.21

.21

.19

.20

.18

.20

.18

.19

.21

.20

.22

.21

.19

.19

.20

.20

.21

.22

.23

.22

.23

.22

.21

.22

.22

.22

.22

C02

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

.00

.00

nd

nd

nd

.00

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

Total

99

100

100

100

100,

100

99

100

100,

99

99

100,

100,

100,

100.

100,

100,

99,

100,

99,

100,

100.

99.

100.

100.

99.

101.

101.

99.

101.

99.

100.

101.

101,

101,

101,

101,

101,

101,

100,

101.

99.

99,

101.

101,

100,

101,

100,

99,

100,

100

100

100

99,

99.

100,

99.

100.

.66

.38

.00

.66

.24

.05

.92

.67

.46

.98

.76

.15

.07

.68

.64

.25

.00

.50

.13

.83

.50

.25

.45

.18

.51

.65

.31

.28

.46

.50

.82

.10

.28

.34

.17

.52

.24

.12

.21

.06

.50

.98

.61

.01

.21

.84

.25

.48

.54

.41

.17

.32

.24

.99

.75

.11

.76

.31

0

1

2

2

1

2

2

2

1

2

1

2

1

1
Table L Chemical analyses and normative ne, ol, hy, and q in Mauna Kea lavas—Continued.

Sample 

Locality Unit 

No.

HQ-39

HQ-40

HQ-41

HQ-42

HQ-43

HQ-44

HQ-45

HQ-46

HQ-47

HQ-48

HQ-49

HQ-50

HQ-51

HQ-52

HQ-53

HQ-54

HQ-55

HQ-56

HQ-57

HQ-58

HQ-59

HQ-60

HQ-61

HQ-62

HQ-63

HQ-64

HQ-65

HQ-66

HQ-67

HQ-68

HR-1

HR-2

HR-3

HR-4

HR-5

HR-6

HR-7

HR-8

HR-9

HR-10

HR-11

HR-1 2

HR-13

HR-14

HR-1 5

HR-1 6

HR-17

HR-1 8

HR-1 9

HR-20

HR-21

HR-2 2

HR-23

HR-24

HR-25

HR-2 6

HR-2 7

HR-28

lo

lo

lo

lo

lo

lo

lo

lo

lo

h

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

hi

hh

hh

ly

hh

hi

lo

ly

hi

hi

lo

lo

lo

lo

lo

lo

hi

lo

lo

lo

lo

Feature

dodo -

dododododododoCone

Flow

dododododododododododododododododododoCone

Flow

dodoDike

Cone

Flow

dodododododoCone

Flow

dododo -

dodododododoCone

dodoFlow

Type

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

plbs

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

bs

bs

olbs

h/m

plbs

bs

h/m

h/m

bs

bs

h/m

h/m

h/m

h/m

h/m

h/m

bs

h/m

h/m

h/m

h/m

Laboratory 

No.

D-292959

D-292955

D-292984

D-292967

D-284763

D-292965

D-292964

D-292968

D-292962

D-292992

D-292963

D-292985

D-278155

D-292976

D-292977

D-292979

D-292971

D-292982

D-292978

D-292975

D-292972

D-292973

D-292974

D-292969

D-278154

D-292970

D-292980

D-292981

D-292987

D-292988

D-284758

D-278094

D-276054

D-278093

D-284757

D-284756

D-276051

D-284759

D-284750

D-271469

D-284748

D-284751

D-284752

D-278118

D-284755

D-284753

D-284754

D-278081

D-278082

D-276053

LOF

D-276055

D-284747

D-284749

D-278080

D-276052

D-278119

D-284746

Remar

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

d

b

b

b

b

b

b

b

jj

Major oxides

Si02

51,

50

50.

51,

50,

51.

51.

50.

50.

46.

50.

50.

49.

49.

50.

49.

50.

48.

50.

51.

50.

50.

50.

49.

50.

50.

49.

49.

49.

50.

50.

50.

51.

50.

50.

49.

51.

48.

48.

49.

51.

48.

48.

51.

53.

47.

47.

50.

51.

50.

49.

50.

50.

47.

50.

51.

50.

50.

.60

.90

.80

.00

.70

.30

.50

.10

.80

.00

.70

.20

.80

.80

.20

.70

.30

.80

.10

,30

,60

,50

,10

.40

,30

,10

,90

.80

.60

,50

10

,40

.00

.20

,60

,80

.40

.30

.30

,00

,40

.40

40

.50

.40

,40

.00

.50

,10

,20

,55

,80

.40

,60

.60

.00

.90

.10

A12 03

17

17

17

17

17

17

17

17

17

14

16

17

17

17

16

16

17

17,

16,

17.

17.

16.

16,

17,

17.

17,

17.

16.

17.

17.

17.

17,

17,

16.

17,

17,

17,

14,

12.

12,

17,

14,

14

17,

17,

14

14,

17,

17,

17.

17,

17.

17,

13,

17

17

17,

16.

.40

.20

.20

.10

.20

.40

.30

.40

.10

.80

.80

.20

.00

.00

.90

.80

.10

.20

.80

.10

.20

.90

.60

.00

.00

.00

.00

.90

.10

.00

.00

.10

.40

.90

.20

.10

.30

.00

.90

.90

.20

.50

.40

.10

.20

.40

.00

.10

.20

.50

.10

.30

.00

.70

.20

.30

.10

.90

Fe2 03

10,

11.

11,

10,

11,

10,

10.

11.

11.

14.

10.

11.

11.

11.

11.

11.

11.

11.

11.

10.

11.

11.

11.

11.

11.

11.

11.

11.

11.

11.

11.

11.

10.

11.

11.

11.

10.

13.

13.

13.

11.

13.

13.

10.

10.

14.

15.

11.

10.

11.

11.

11.

11.

15.

10.

10.

11.

11.

.40

.00

.10

.90

.40

.70

.50

.20

.10

.30

.90

.40

,80

.80

.40

.70

.50

.80

.50

,90

.40

.30

,90

,60

.90

.60

,90

,90

,70

30

80

30

,80

,10

,70

.70

,90

,90

,60

10

00

,40

.60

,80

,10

,60

50

,30

80

,00

52

,00

,80

,90

,70

,80

,20

.80

FeO

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

MgO

3.

3,

3,

3,

3,

3,

3,

3.

3.

5.

3.

3.

4.

4.

4.

4.

3.

4.

4.

3.

3.

3.

5.

3.

4.

3.

4.

4.

4.

3.

4.

3.

3.

3.

4.

4.

3.

7.

7.

7.

3.

6.

5.

3.

2.

5.

5.

3.

3.

3.

4.

3.

4.

5.

3.

3.

3.

4.

.50

.87

.62

.55

.59

.30

.41

.73

.69

.88

.68

.55

.06

.33

.10

.49

.96

.07

.63

,55

,88

,72

,20

,94

,18

.99

.22

.22

14

,96

,06

.93

,68

,74

,05

,09

.44

.02

,47

.81

.74

,78

,99

.49

.84

.64

.60

.77

,68

,61

,20

.70

.06

.51

.67

.37

.56

.14

CaO

6

6

6

6

6

6

6

6.

6.

11,

6,

6.

7,

7,

6,

7,

6,

7.

6.

6.

6.

6.

7.

6,

7.

6.

7.

7.

7.

6.

6.

6.

6.

6,

7,

7.

6.

11.

12.

12.

6.

12.

10.

6,

5.

10,

10.

6.

6.

6.

7.

6,

7.

10,

6.

6,

6.

7.

.55

.94

.77

.70

.92

.53

.77

.72

.81

.10

.90

.82

.10

.01

.90

.02

.89

.03

.86

.44

.81

.68

.04

.75

.03

.83

.13

.10

.20

.68

,99

.91

.72

.80

.06

.21

.58

.80

.30

.50

.66

.10

.90

.52

.90

.90

.70

.85

.51

.77

.04

.84

.08

.60

.73

.37

.76

.06

Na2 0

4.82

4.58

4.85

4.97

4.65

4.94

4.72

4.63

4.85

2.48

4.56

4.63

4.67

4.55

4.77

4.50

4.66

4.50

4.72

4.83

4.64

4.68

4.32

4.60

4.65

4.40

4.66

4.60

4.53

4.71

4.60

4.55

4.83

4.55

4.48

4.45

4.99

2.31

2.21

2.27

4.78

2.37

2.63

5.01

4.94

2.59

2.67

4.84

4.87

4.74

5.06

5.01

4.57

2.86

4.86

5.11

4.86

4.61

K2 0

2.

2.

2.

2.

2.

2.

2.

1.

2.

1.

2.

1.

1.

1.

1.

1.

1.

1.

2.

1.

1.

1.

1,

1.

1.

1.

1.

1.

1.

1.

1.

2.

1.

1.

1.

2.

2.

2.

2.

1.

2.

1.

1.

2.

1.

2.

2.

2.

1.

17

02

05

11

06

15

11

96

03

71

92

03

91

82

99

84

94

79

95

11

98

98

82

89

83

94

86

87

88

97

89

95

08

97

95

87

11

68

59

61

04

62

69

13

33

80

69

99

11

95

87

06

87

85

04

13

05

83

H2 0

0.00

.00

.00

.00

.00

.24

.21

.57

.00

.94

.89

.24

.00

.01

.00

.00

.00

.90

.00

.00

.00

.32

.00

.35

.00

.25

.00

.00

.00

.08

.00

.00

.21

.00

.00

.02

.00

.00

.25

.00

.00

.00

.00

.14

.00

.26

.00

.00

.02

.55

nd

.00

.00

.00

.35

.38

.00

.00

Ti02

2.38

2.59

2.49

2.46

2.52

2.27

2.30

2.59

2.52

3.38

2.49

2.52

2.82

2.72

2.57

2.68

2.63

2.78

2.56

2.36

2.61

2.54

2.61

2.67

2.79

2.72

2.84

2.83

2.76

2.64

2.76

2.71

2.53

2.58

2.75

2.84

2.30

2.92

2.89

2.89

2.56

2.80

3.74

2.25

1.99

3.69

3.81

2.61

2.55

2.53

2.84

2.56

2.79

3.77

2.48

2.26

2.45

2.78

P2 05

0.98

.97

1.11

1.11

1.12

1.26

1.13

1.05

1.04

.42

1.03

1.14

.95

.91

1.04

.90

.92

.98

1.02

1.01

.93

.94

.85

.93

.90

.93

.89

.89

.97

.88

.91

.88

1.03

.96

.99

.93

1.15

.36

.34

.32

.89

.34

.34

1.15

1.16

.45

.48

1.07

.93

1.09

.86

1.07

.92

.48

.99

1.16

1.13

.90

MnO

0.21

.22

.22

.22

.22

.22

.22

.22

.22

.19

.22

.22

.21

.22

.22

.22

.22

.22

.22

.22

.22

.22

.22

.21

.22

.22

.22

.22

.21

.22

.23

.21

.22

.22

.22

.22

.22

.19

.19

.18

.21

.18

.18

.22

.24

.20

.21

.22

.21

.23

.20

.22

.22

.21

.21

.22

.22

.22

C02

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

.00

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

Total

100

100

100

100

100

100

100

100

100

100

100

99

100

100

100

99

100

100.

100,

99,

100,

99,

100,

99,

100,

99,

100,

100.

100.

99.

100.

99.

100.

99,

101.

100,

100.

101.

101.

101.

100.

101.

100.

100.

100,

100.

100.

100.

99.

100.

100.

100.

100.

101.

99.

100.

100.

100.

.01

.29

.21

.12

.38

.31

.17

.17

.16

.20

.09

.95

.32

.17

.09

.85

.12

.07

.36

.82

.27

.78

.66

.34

.80

.98

.62

.33

.09

.94

.34

.94

.50

.02

.00

.23

.39

.48

.04

.58

.48

.49

.87

.31

.10

.93

.66

.25

.98

.17

.24

.56

.71

.48

.83

.10

.23

.34
Table L Chemical analyses and normative ne, ol, hy, and q in Mauna Kea lavas—Continued.

Sample 

Locality Unit

No.

HR-29

HR-30

HR-31

HR-32

HR-33

HR-34

HR-35

HR-36

HR-37

HR-38

HR-39

HR-40

HR-41

HR-42

HR-43

HR-44

HR-45

HR-46

HR-47

HR-48

HR-49

HR-50

HR-51

HR-52

HR-53

HR-54

HR-55

HR-56

HR-57

HR-58

HR-59

HR-60

HR-61

HR-62

HR-63

HR-64

HR-65

HR-66

HR-67

HR-68

HR-69

HR-70

HR-71

HR-72

HR-73

HR-74

HR-75

HR-76

HR-77

HR-78

HR-79

HR-80

HR-81

HR-82

HR-83

HR-84

HR-85

HR-86

ly

lo

hi

lo

lo

hi

hi

lo

lo

hi

hi

lo

hi

hh

hh

hh

lo

hh

hh

hi

hi

lo

hh

hi

hh

hh

lo

hi

hh

lo

hh

lo

hh

hh

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

lo

ly

lo

lo

lo

lo

lo

lo

lo

ly

lo

lo

lo

Feature

dododododododoCone

Flow

Dike

doCone

Flow

doCone

Flow

dodo -

doDike

doFlow

dodo -

dodo -

dododododoCone

Flow

dodoCone

Flow

dodododododododoCone

Flow

dodododododoCone

Bomb

Flow

dodoType

h/m

h/m

bs

h/m

h/m

bs

bs

h/m

h/m

bs

bs

h/m

bs

plbs

plbs

ank

h/m

pic

plbs

bs

bs

h/m

bs

bs

bs

bs

h/m

bs

olbs

h/m

plbs

h/m

bs

bs

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

Laboratory

No.

D-284739

D-284745

D-284742

D-278083

D-278117

D-284741

D-284740

D-278144

D-278116

D-278147

D-284731

D-278135

D-278145

D-278146

D-278111

D-292954

D-284743

65-1

D-284737

D-292951

D-292952

D-284762

D-284734

D-284733

D-284735

D-284736

D-278112

D-284738

D-292953

D-284744

D-278113

D-284760

D-278114

D-278115

D-278142

D-278141

D-278110

D-284761

D-278108

D-278143

D-278140

D-278109

D-284732

D-278139

D-278138

D-278107

D-278095

D-278137

D-278098

D-278136

D-278097

D-278096

D-278099

D-278106

D-278105

D-278084

D-278100

D-278085

Remar]£

Major oxides

Si02

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

d

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

52.

50.

47.

51.

50.

47.

48.

50.

49.

48.

47.

51.

48.

48.

47.

47.

50.

46.

48.

47.

49.

51.

47.

47.

48.

48.

49.

48.

48.

51.

46.

49.

47.

50.

50.

49.

48.

50.

48.

49.

50.

48.

50,

51.

50.

49.

50,

50,

50,

51.

49.

51

50

49,

50

49

50

50

.20

.20

.70

.50

.60

90

20

40

60

30

30

40

,70

30

00

60

.60

38

30

30

40

10

80

60

10

00

10

60

60

.00

.30

.90

.70

10

,00

.80

.30

.90

.20

.70

.40

.10

.70

.20

.40

.00

.20

.60

.70

.30

.50

.10

.90

.80

.30

.60

.30

.80

Al

17.

17.

13.

17.

17.

14.

13.

17.

17.

14.

14.

17.

13.

13.

16.

10.

17.

8.

12.

13.

13.

17.

14.

14.

13.

13.

16.

13.

13.

17.

13.

16.

13.

14.

17.

16.

16.

17.

16.

16.

17.

16.

17.

17.

17.

17.

17.

17.

17.

17,

16,

17,

16.

17

17,

16,

17,

17

2 03

20

00

,80

20

10

10

80

00

20

60

00

00

50

90

30

60

20

94

70

10

20

20

80

20

70

50

80

60

10

00

50

90

,70

,00

,00

,80

.80

,10

,80

,80

.00

.80

.20

.00

.20

.00

.00

.00

.00

.10

.90

.30

,90

.10

.00

.90

.10

.20

Fe2 03

10.

11.

15.

10.

11.

15.

15.

11.

11.

13.

15.

11.

15.

14.

11.

13.

11.

13.

13.

16.

15.

11.

13.

13.

15.

14.

12.

15.

12.

10.

14.

11.

13.

13.

11.

11.

12,

11.

12,

11.

11,

12,

11,

10,

11,

12,

11,

11,

11,

10,

11,

10,

11,

11

11

11

11

11

.80

.80

.30

.80

.20

.00

10

40

.10

.80

20

00

.40

.20

40

10

20

.34

20

30

10

10

90

80

50

90

30

50

90

.90

.00

,10

,50

,80

.90

.00

.70

.00

.50

.60

.60

.60

.10

.90

.60

.10

.60

.50

.20

.70

.60

.90

.10

.40

.80

.70

.20

.20

FeO

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

MgO

3.

4.

5,

3.

3.

5.

5.

3.

3.

6.

6.

3.

5.

6.

7.

14.

3.

17.

8.

5.

5.

3.

6.

6.

5.

6.

4.

5.

7 .

3.

9.

3.

7 ,

3,

4.

3.

4,

3,

4,

4,

4.

4

3,

3,

4

4

4

4

3

3

4

3

3

3

4

4

3

3

.36

.11

.53

,38

.85

.46

.65

.93

.79

,03

,00

,36

.17

69

.09

.00

.89

.93

.86

.83

.29

,60

,31

59

,38

.41

.52

.07

.84

.34

.04

.67

.86

.88

.23

.86

.94

.40

.95

.33

.14

.83

.69

.55

.13

.29

.03

.01

.80

.51

.22

.71

.69

.81

.06

.04

.75

.87

CaO

6.

7.

10.

6.

6.

10.

10.

7.

6.

11.

11.

6.

9.

12.

12.

10.

6.

9.

11.

10.

9.

6.

12.

12.

10.

10.

7.

9.

12.

6.

11.

6.

10.

8.

7.

6.

7.

6.

7.

7.

7.

7.

7.

6.

7.

7.

6.

6.

6.

6.

7.

6.

6.

6,

6.

7.

7.

6,

36

07

50

49

98

70

70

02

93

50

00

29

87

00

40

80

94

65

70

30

59

70

20

00

20

90

34

85

00

77

40

44

50

06

20

41

41

66

56

.50

.10

44

,05

,67

,17

,20

.98

.97

.79

,60

.22

.73

.77

.79

.90

.03

.01

.81

Na2 0

4.

4.

2.

5.

4.

2.

2.

4.

4.

2.

2.

5.

3.

2.

2.

1.

4.

1 . 2.

2.

3.

5.

2.

2.

2.

2.

4.

3.

2.

5.

2.

4.

2.

3.

4.

4.

4,

5.

4,

4.

4,

4,

4.

4.

4

4

4.

4,

4,

4

4

4

4,

4

4

4

4

4

.95

,55

.91

.04

.89

.90

93

54

,35

49

59

09

.06

.22

.25

84

.86

.43

.17

71

06

.04

.48

46

.91

.71

47

10

23

,06

,10

.27

.62

.96

.70

.35

.35

.02

.15

.53

.70

.30

.75

.86

.51

.37

.80

.68

.81

.68

.63

.99

.87

.27

.62

.50

.48

.69

K2 0

2.11

1.89

.87

2.16

2.00

.91

.87

1.91

1.95

.61

.53

2.20

1.10

.60

.40

.43

1.97

.35

.57

.87

1.04

2.09

.62

.69

.97

.88

1.75

1.07

.59

2.15

.26

2.01

.74

1.49

1.83

2.15

1.68

2.11

1.63

1.81

1.88

1.70

2.06

2.04

1.91

1.77

1.93

1.94

1.99

2.14

1.84

2.07

2.01

1.93

1.88

1.78

1.94

2.01

H2 0

0.00

.00

.00

.00

.00

.00

.00

.43

.95

.00

.00

.00

.00

.00

.72

.00

.11

.17

.08

.00

.00

.00

.00

.00

.00

.00

.00

.00

.06

.00

1.11

1.79

.19

.00

.00

1.80

.00

.07

.00

.29

.00

.00

.00

.14

.00

1.29

.00

.00

.00

.41

.00

.00

.00

1.90

.00

.06

.51

.00

Ti02 P2 05

2

2,

3

2,

2.

3.

3,

2.

2,

3.

3,

2,

4.

3.

2

2,

2.

1,

2.

4,

4,

2.

2.

3,

3.

3.

3.

4.

2,

2,

3,

2,

3

3

2,

2,

3

2

3

2

2

3

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

.24

.84

.93

.25

.68

.76

.71

.66

.68

.25

.60

.21

.08

.12

.73

.32

.61

.86

.79

.06

.16

.42

.96

.15

,80

.47

.06

.02

.87

.41

.03

.35

.11

.45

.87

.40

.21

.35

.19

.90

.83

.19

.56

.47

.86

.97

.75

.70

.58

.32

.86

.55

.56

.65

.72

.78

.58

.64

1,

1.

1.

1.

1.

1.

1.

1.

1.

1.

1.

1.

1,

1,

1,

1

.08

.89

.49

.19

.02

.49

.47

.96

.02

.40

.43

.34

.54

.36

.31

.26

.00

.23

.33

.42

58

.10

.35

.38

.52

.45

.86

.56

.33

.35

.36

.12

.42

28

.89

.10

.82

.22

.80

.87

.88

.83

.08

.01

.91

.88

.95

.95

.98

.17

.95

.98

.99

.99

.91

.92

.01

.95

MnO

0.23

.22

.21

.23

.22

.21

.21

.22

.22

.19

.21

.23

.21

.19

.16

.18

.22

.18

.18

.22

.21

.22

.19

.19

.21

.20

.21

.21

.18

.22

.19

.21

.19

.22

.21

.21

.21

.23

.20

.21

.21

.21

.22

.22

.21

.22

.22

.22

.22

.22

.21

.21

.21

.22

.22

.22

.22

.22

C02

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

Total

100,

100,

101

100,

100,

101,

101.

100,

99.

101.

100,

100,

101,

101,

100,

101,

100,

100,

100.

101,

101,

100.

101.

101.

101.

101.

100.

101,

100,

100.

101.

99.

100,

100,

100,

99.

100

100,

99,

100,

100

100

100

100

100

101

100

100

100,

100

99

100

100

100

100

99

100

100

.53

.57

.2

.2

.5

.43

.64

.47

.79

.17

.8

.12

.63

.5

.7

.13

.60

.4

.88

.11

.63

.57

.61

.06

.29

.42

.41

,58

.70

.20

.29

.7

.53

.2

.83

.8

.42

.0

.98

.5

.7

.0

.41

.0

.9

.09

.4

.5

.0

.1

.93

.54

.0

.8

.4

.5

.1

.3
Table 1= Chemical analyses and normative ne, ol, hy, and q in Mauna Kea lavas—Continued.

Sample 

Locality Unit 

No.

HR-87

HR-88

HR-89

HR-90

HR-91

HR-92

HR-93

HR-94

HR-95

HR-96

HR-97

HS-1

HS-2

HS-3

HS-4

HS-5

HT-1

HT-2

HU-1

HU-2

HU-3

HU-4

HU-5

HU-6

HU-7

HU-8

10-1

10-2

10-3

10-4

10-5

10-6

10-7

10-8

10-9

10-10

10-11

10-12

10-13

10-14

10-15

10-16

IP-1

IP-2

IP-3

IP-4

IP-5

IP-6

IP-7

IP-8

IP-9

IP-10

IP-11

IP-12

IP-13

IP-14

IP-15

IP-16

iy

lo

lo

lo

iy

lo

lo

lo

lo

lo

iy

lo

lo

lo

lo

iy

lo

h

h

h

h

h

lo

h

h

h

lo

lo

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

lo

h

h

h

h

h

lo

h

h

h

h

h

h

Feature

doCone

Flow

dododo -

dodoCone

doFlow

dodododododododododododoCone

Flow

dodo -

dododododododododododododododododododododododododododododododoType

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

h/m

plbs

bs

bs

plbs

bs

h/m

olbs

ank

bs

h/m

h/m

bs

bs

olbs

bs

plbs

bs

ank

bs

bs

bs

bs

ppbs

bs

plbs

plbs

ppbs

olbs

ben

ppbs

plbs

ppbs

bs

plbs

h/m

olbs

bs

bs

ppbs

bs

ppbs

Laboratory 

No.

D-278101

D-278088

D-278089

D-278102

D-278104

D-278090

D-278091

D-278086

D-278103

D-278087

D-278092

D-277509

D-277508

D-277507

D-277506

D-277505

D-277499

D-277498

D-277500

D-277497

D-277501

D-277493

D-277495

D-277496

D-277491

D-277492

PH-1

D-260903

115-3

115-20

115-4

115-6

D-260901

115-23

115-12

115-14

115-37

D-260902

115-25

115-36

115-35

115-11

D-260897

NO- 9

D-260887

D-260888

73-4

NO- 11

NO- 5

83-17

NO-13

D-260882

D-260889

NO- 14

D-260884

D-260885

71-9

97-2

Remar

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

d

b

d

d

d

d

b

d

d

d

d

b

d

d

d

d

b

d

b

b

d

d

d

d

d

b

b

d

b

b

d

d

'k

Major oxides

Si02 A12 03 Fe2 03

50

51

50

51

49

50

51

50

50

50

51

48

48

48

49

49.

50.

47,

45,

46,

47,

46.

49.

40.

46.

46.

49.

49.

47.

47.

47.

45.

48.

47.

45.

45.

47.

44.

47.

47.

48.

47.

46.

50.

46.

54.

45.

47.

47.

46.

45.

49.

47.

46.

47.

47.

47.

47.

.70 17

.20 17

.80 17

.10 17

.60 17

.40 16

.00 17

.30 16

.60 17

.90 17

.00 17

.60 16

.40 16

.20 16.

.70 17,

.40 16,

.10 17.

.20 13,

.90 14,

.80 13,

.20 14,

.90 14.

.40 17,

.20 13,

.00 10,

.00 13.

.48 16.

,90 17.

,79 14.

.01 13.

,23 12.

.73 14.

.80 14.

,60 14.

,17 10.

.24 14.

.60 13.

.80 14.

.84 13.

.96 14.

.26 14.

.50 15.

.70 13.

,01 14.

.60 14.

.70 17.

,39 14.

.34 15.

,52 13.

,10 14.

.54 14.

,90 17.

30 13.

97 14.

20 14.

30 13.

47 13.

48 14.

.20 11

.10 10

.20 11

.00 10

.10 12

.90 11

.00 11

.90 11

.10 11

.00 11

.10 11

.90 12

.90 12

.90 12

.00 11

.90 12

.10 11

.80 15

.70 14

.60 15

.80 13

.10 14

.10 11

.20 18

.10 12,

.80 15,

.91 11.

.00 12.

,07 14.

.73 13.

.64 12.

,61 15.

.90 13.

,21 13.

,20 12.

,32 16.

.52 14.

.20 17.

.77 14.

.27 12.

.32 12.

.42 13.

.90 15,

.29 13.

.20 14.

.60 9.

.38 13.

.74 13.

.88 13.

,86 15.

.44 13.

.10 12.

60 14.

44 13.

10 14.

20 13.

98 13.

14 12.

.00

.80

.20

.70

.20

.50

.10

.80

.50

.20

.30

.20

.50

.60

.70

.00

.50

.00

.50

.50

.50

.80

.80

.00

.60

.20

.85

.00

.60

.67

.20

.83

.30

.30

.44

.56

.44

.30

.81

.56

.34

.67

.90

.52

.10

.13

.71

.09

.48

.69

.81

.10

,50

.86

.00

.00

.91

.82

FeO

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

MgO

3

3

3

3

4

3

3

4

3.

3,

3,

4,

4,

4,

4.

4,

3,

5,

6.

5,

6.

6.

3.

8.

16.

5.

4.

4.

5.

7.

11.

5.

5.

6.

15.

5.

6.

5.

5.

7.

6.

5.

5.

4.

5.

2.

8.

5.

6.

5.

8.

3.

6.

5.

6.

9.

5.

7.

.71

.50

.83

.31

.36

.99

.73

.00

.80

.78

.90

.44

.56

.80

.02

.29

.71

.62

.39

.69

.57

.61

.95

.19

.10

.08

.17

.26

.17

,26

.23

,05

,81

.05

,06

.09

,31

,16

,57

,20

,80

,25

,60

,26

,72

,25

,04

,63

,91

,15

,16

,99

54

74

14

73

81

46

CaO

6.81

6.49

6.86

6.61

7.24

6.94

6.69

6.90

6.63

6.72

6.80

7.22

7.40

7.51

6.95

7.09

6.59

10.60

10.50

10.30

11.30

11.30

6.90

8.94

10.80

9.26

6.98

7.14

10.24

11.16

11.63

8.28

10.50

11.15

10.98

8.13

10.55

8.29

10.37

11.76

11.81

11.02

10.70

8.78

11.00

4.96

10.93

11.69

11.35

8.31

10.90

6.99

10.80

10.73

10.90

11.80

10.72

11.56

Na2 0

4.64

4.94

4.57

4.89

4.32

4.87

4.85

4.70

4.71

4.87

4.68

4.30

4.28

4.33

4.60

4.62

4.55

2.78

2.54

2.69

2.29

2.26

4.51

3.81

1.67

3.01

4.62

4.74

2.83

2.43

1.68

3.32

2.96

2.51

1.66

3.34

2.48

3.31

2.52

2.13

2.25

2.74

2.83

3.29

2.90

5.73

2.54

2.42

2.57

3.13

2.59

4.68

2.73

2.93

3.00

2.23

2.47

2.23

K2 0

2.03

2.11

1.99

2.17

1.75

1.96

2.03

1.89

1.93

2.02

1.96

1.74

1.70

1.66

1.86

1.82

1.99

.84

.62

.71

.35

.31

1.85

1.28

.47

1.20

1.81

1.82

1.00

.82

.50

1.41

.93

.81

.55

1.43

.89

1.38

.96

.67

.71

.83

.74

1.35

.97

2.60

.85

.72

.82

1.42

.90

1.91

.92

.98

.99

.66

.87

.75

H2 0

0.17

.27

.00

.51

.04

.00

.00

.00

.00

.00

.00

.26

.06

.00

.05

.00

.12

.00

.46

.00

.34

.01

.04

.00

.00

.50

.08

.00

.31

.17

.13

.10

.00

.07

.16

.15

.38

.31

.00

.11

.00

.17

.00

.29

.29

.15

.20

.13

.07

.34

.13

.00

.00

.19

.00

.00

.25

.31

Ti02

2.53

2.42

2.60

2.24

2.91

2.69

2.51

2.68

2.54

2.56

2.61

3.02

3.16

3.25

2.79

2.87

2.59

3.83

3.83

4.12

3.13

3.32

2.78

6.04

2.08

4.85

2.85

2.92

3.54

3.30

2.13

4.57

3.44

3.28

1.91

4.71

3.43

4.93

3.62

2 .77

2.81

3.38

3.96

3.11

3.78

1.60

3.26

2.96

3.32

4.56

3.24

2.79

3.48

3.71

3.75

2.76

3.46

2.98

P2 05

1.01

1.05

.98

1.38

.83

.96

.97

.91

.97

.97

.92

.89

.85

.82

.95

.85

1.03

.49

.35

.44

.34

.34

.96

.80

.26

.65

.78

-84

.49

.42

.27

.75

.47

.42

.27

.74

.44

.74

.47

.32

.35

.40

.41

.75

.52

.98

.42

.36

.40

.75

.42

1.05

.44

.49

.51

.34

.46

.38

MnO

0.22

.23

.22

.22

.21

.22

.22

.22

.23

.22

.22

.22

.21

.21

.22

.22

.23

.20

.19

.20

.19

.20

.22

.20

.17

.20

.21

.22

.20

.18

.16

.22

.18

.19

.18

.23

.20

.23

.20

.18

.17

.19

.21

.21

.18

.23

.19

.17

.19

.22

.19

.21

.19

.19

.18

.17

.19

.18

C02

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

.00

nd

nd

nd

nd

.00

nd

nd

nd

nd

.07

nd

nd

nd

nd

.00

nd

.00

.00

nd

nd

nd

nd

nd

.00

.00

nd

.00

.00

nd

nd

Total

100

100

100

100

100

100

100

100

100

100

100

99.

100,

100,

99,

100,

99,

100.

99,

100,

100,

100,

99.

100,

100.

99.

99.

100.

100.

100.

99.

99.

101.

99.

98.

99.

100.

100.

100.

99.

99.

100.

100.

99.

100.

99.

99.

100.

100.

100.

100.

100.

100.

100.

100.

101.

99.

100.

.0

.1

.2

.1

.5

.4

.1

.3

.0

.2

.4

.7

.0

.2

.8

.0

.5

.3

.9

.0

.0

.1

.5

.6

.2

.7

.7

.8

.2

.1

.8

.8

.2

.5

.5

.9

.2

.7

.1

.9

.8

.5

.9

.8

.2

.9

.9

.2

.5

.5

.3

.7

.5

,2

,7

,1

,5

.2
12 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

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Table 1. Chemical analyses and normative ne, ol, hy, and q in Mauna Kea lavas—Continued.

Sample 

Locality Unit 

No.

IT-4

IT-5

IT-6

IT-7

IT-8

IT-9

JO-1

JO-2

JO-5

JO- 7

JP-1

JP-2

JP-7

JQ-1

JQ-2

JQ-3

JQ-4

JQ-5

JQ-6

JQ-8

JQ-9

JQ-10

JQ-13

JQ-16

JQ-17

JQ-20

JQ-21

JQ-22

JQ-23

JQ-25

JR-1

JR-2

JR-3

JR-4

JR-5

JR-6

JR-7

JR-8

JR-9

JR-10

JR-11

JR-1 2

JR-1 3

JS-1

JS-2

JS-3

JS-4

JS-5

JS-6

JS-7

JS-8

JS-9

JS-10

Ki-1

Ki-2

Ki-3

Ki-4

Ki-5

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

lo

h

lo

h

h

lo

h

h

h

h

h

h

h

h

h

h

h

h

h

lo

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

Feature

dodododododododododododododododododododododododododododododododododododododododododododododododododododododododododoType

olbs

plbs

olbs

bs

olbs

bs

ank

bs

olbs

olbs

olbs

olbs

bs

bs

olbs

olbs

ben

ank

ben

ppbs

bs

ben

ank

olbs

olbs

olbs

bs

olbs

ank

ank

bs

bs

bs

olbs

bs

h/m

bs

bs

bs

bs

olbs

plbs

plbs

bs

bs

bs

plbs

olbs

bs

olbs

bs

ank

olbs

olbs

olbs

pic

pic

pic

Laboratory 

No.

D-271472

D-271476

D-271474

D-271478

D-271475

D-271477

114-9

D-260900

KW-1

D-260744

85-10

D-260187

D-277461

D-260179

D-260178

D-260180

D-260173

D-260181

D-260191

D-260172

D-260171

D-260175

D-260174

D-260192

D-260184

D-260190

D-260182

D-277473

D-277460

D-260183

D-271452

D-271451

D-271454

D-271455

D-271445

D-271446

D-271447

D-271449

D-271448

D-271450

D-271453

D-271456

D-260189

D-271466

D-271457

D-271463

D-271464

D-271465

D-271462

D-271461

D-271459

D-271460

D-271458

Ki-1

Ki-2

Ki-3

Ki-4

Ki-5

Remar

b

b

b

b

b

b

d

b

d

b

d

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

d

d

d

d

d

Major oxides

Si02

47

47

46

47

47

44

47,

48.

47

47

47.

47,

48,

45.

45.

47,

54.

46,

54.

46.

45,

54.

46.

46.

45.

46.

45.

44.

46.

46.

46.

46.

47.

46.

46.

48,

48.

45.

47,

47.

46,

47,

46,

46,

46,

45,

46,

46,

47,

48.

46,

47,

48

45

45,

44,

45

46

.00

.40

.50

.20

.70

.60

.82

.50

.06

.90

.10

.90

.70

.70

.50

.10

.70

.30

.70

.20

.90

.90

.10

.10

.10

.90

.30

.90

.40

.40

.80

.70

.30

.50

.40

.90

.40

.00

.30

.90

.90

.60

.20

.50

.50

.90

.60

.60

.40

.60

.70

.40

.90

.73

.48

.38

.99

.78

Al

12

14

14

14

13

16

12

14

13

14.

10

14

13,

13,

11.

12,

18.

12.

17,

12,

14.

17 .

10,

12.

11.

13.

14.

12.

11.

11.

14.

13.

14,

14,

14.

17.

13.

15.

14.

13,

13,

14.

14,

13,

13,

13,

14,

12

12

13,

13,

10,

13,

13,

12

7,

9,

9,

2 03

.20

.40

.30

.00

.90

.30

.60

.20

.54

.00

.12

.20

.90

.90

.50

.90

.10

.60

.40

.70

.80

.40

.70

.70

.00

.50

.70

.40

.70

,80

.40

.90

.40

.60

.50

.10

.70

.00

.00

.80

.20

.20

.70

.70

.70

.30

.80

.90

.70

.40

.70

.60

.30

.06

.78

.63

.99

.76

Fe2 03

14

14

15

14

12

16

12

13

13

14

12

13

13

14

13

13

8,

13

9

13

14,

9

12

13.

13,

13,

13

13.

13,

12,

14,

15,

13

12

14,

12,

15

16

14,

13

14

14

15

15

15

14

14

14

13

13,

14

12

14

13,

13

13

13

12

.00

.80

.50

.50

.70

.00

.07

.60

.25

.40

.72

.80

.10

.70

.10

.70

.99

.20

.49

.50

.20

.17

.60

.60

.10

.80

.60

.80

.10

.60

.20

.30

.40

.60

.50

.30

.30

.70

.60

.80

.90

.70

.10

.20

.40

.90

.30

.60

.80

.30

.50

.70

.30

.79

.90

.30

.40

.90

FeO

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

MgO

11

6

5

5

8

5

10

6

7

5,

14

6,

6,

7,

13,

9,

2.

11,

2.

10,

6,

2,

15,

9.

14.

7,

6,

11.

12.

13.

6.

5.

6,

8,

6.

4.

4,

4.

5,

6,

7,

6,

5,

5,

5

5,

6,

8,

9

7,

7

14

7,

9,

10

24

17,

16,

.30

.17

.87

.20

.43

.61

.66

.56

.68

.58

.35

.20

.99

.68

.50

.29

.25

.50

.20

.40

.61

.22

.40

.79

.50

.97

.74

.90

.20

,30

.20

.26

.80

.84

.33

.14

.46

.48

.78

.75

.50

.07

.24

.27

.15

.40

.17

.23

.52

.89

.25

.40

.02

.82

.20

.24

.22

.91

CaO

9

10

10

10

12

8

11

11

11

10

10

11

11

10,

10

11

3,

11

4

10

10

4

10

11,

10,

11,

11

10,

11,

11

11,

9,

11

12

11,

7

8

7

10

11

9

10

9,

9

9

9

10,

10

11

11,

9

11

10

10

10

7

9

9

.73

.90

.30

.20

.50

.39

.72

.50

.34

.10

.83

.20

.50

.60

.60

.30

.82

.10

.62

.80

.90

.46

.60

.00

.60

.20

.20

.20

.00

.10

.40

.36

.80

.40

.30

.13

.38

.12

.50

.20

.92

.60

.58

.78

.54

.51

.50

.00

.00

.30

.64

.40

.80

.82

.77

.38

.47

.39

Na2 0

2

2

2

3

2

3

1

2

2

3

1

2

2,

2.

1,

2

5,

2,

5,

2,

2.

5,

1,

2.

1,

2,

2.

1.

1.

1,

2.

3.

2,

2,

2.

4.

3,

3

3.

2,

2

2 ,

2,

3,

3,

3,

2 ,

2

2

2,

3

1

2.

2.

2

1

1,

1,

.37

.63

.59

.16

.24

.05

.71

.56

.46

.13

.63

.56

.33

.19

.76

.24

.25

.02

.42

.20

.36

.60

.74

.26

.72

.59

.27

.68

.93

.93

.73

.26

.49

.01

.49

.24

.25

.22

.19

.71

.98

.93

.59

.26

.15

.08

.70

.94

.66

.37

.53

.74

.50

.23

.42

.08

.40

.25

K2 0

0.62

.67

.73

1.11

.57

1.17

.54

.71

.84

1.13

.57

.70

.64

.50

.55

.56

2.75

.54

2.67

. .73

.56

2.74

.51

.75

.43

.84

.57

.55

.62

.52

.78

1.23

.75

.27

.75

1.80

1.32

1.56

1.03

.83

1.06

.80

.85

1.30

1.34

1.30

.66

1.00

.86

.51

1.22

.43

.61

.64

.64

.08

.21

.39

H2 0

0.01

.00

.64

.00

.00

.20

.23

.00

.09

.00

.07

.00

.05

.86

.00

.00

.96

.00

.34

.60

.99

.00

.10

.26

.73

.09

1.52

1.59

.71

.04

.40

.68

.18

.97

.50

.72

1.03

1.05

.00

.00

.01

.18

.93

.00

.25

.92

.76

.67

.00

.13

.00

.09

.21

nd

nd

nd

nd

nd

Ti02

2.98

3.51

3.74

4.84

2.65

4.22

2.40

3.09

3.12

4.06

2.32

3.17

2.84

3.48

2.54

3.00

1.25

2.58

1.49

2.91

3.44

1.39

2.06

2.99

2.45

3.23

3.42

2.92

2.73

2.26

3.52

4.33

3.41

2.50

3.56

2.94

4.10

5.17

3.88

3.34

3.82

3.75

3.62

4.88

5.00

4.79

3.75

3.54

3.22

3.08

3.83

2.21

3.27

3.09

3.11

1.55

2.17

2.09

PA

0.39

.43

.46

.63

.32

.62

.30

.37

.43

.55

.30

.38

.35

.43

.31

.38

.88

.32

1.06

.37

.43

.98

.25

.39

.29

.42

.41

.34

.33

.26

.44

.65

.43

.28

.42

.97

.67

.85

.54

.42

.55

.52

.52

.71

.75

.73

.34

.52

.44

.34

.64

.26

.39

.36

.35

.16

.21

.21

MnO

0.18

.20

.21

.20

.17

.21

.16

.18

.19

.20

.18

.19

.17

.20

.17

.18

.21

.18

.24

.18

.19

.23

.17

.18

.17

.19

.18

.19

.17

.17

.19

.21

.18

.17

.19

.22

.23

.24

.20

.18

.20

.21

.21

.20

.21

.20

.19

.19

.18

.18

.19

.18

.19

.18

.18

.19

.17

.19

C02

0.00

.00

.00

.00

.00

.00

nd

.00

nd

.00

nd

.00

nd

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

nd

nd

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

nd

nd

nd

nd

nd

Total

100

101

100

101

101

100

100

101

100

101

100,

100

100.

100

99

100

99,

100

99

100,

100.

99

100

100,

100,

100.

99,

100.

100.

100.

101,

100,

101.

101,

100,

100,

100,

100

101,

100.

101

101.

99

100

100

100,

100

101

101,

101,

101

101

101,

99

99

99

100,

99,

.78

.11

.84

.04

.18

.37

.21

.27

.00

.05

.19

.30

.57

.24

.53

.65

.16

.34

.63

.59

.38

.09

.23

.02

.09

.73

.91

.47

.89

.38

.06

.88

.14

.14

.94

.46

.84

.39

.02

.93

.04

.56

.54

.80

.99

.03

.77

.19

.78

.10

.20

.41

.49

.72

.83

.99

.23

.87
Table L Chemical analyses and normative ne, ol, hy, and q in Mauna Kea lavas—Continued.

Sample 

Locality 

No.

Ki-6

Ki-6G

Ki-7

Ki-8

Ki-9

Ki-10

Ki-11

Ki-llG

Ki-101

Ki-lOlG

La-1

La-2

La-3

La-4

La-4G

La- 5

La- 6

La-7

La-7G

La- 8

La-9

La-10

La- 11

La-101

La-102

La-102G

La-103

La-103G

La-104

La-104G

La-105

La-105G

Mu-2

Mu-3

Mu-4

Mu-5

Mu-6

Mu-7

Mu-8

Mu-9

Mu-10

Mu-11

Mu-13

Mu-14

Mu-15

Wa-4

Wa-6

Wa-7

Wa-8

Wa-9

Wa-10

Wa-11

Wa-13

Wa-14

Wa-16

Wa-17

Unit

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

h

hh

hh

hh

hh

hh

hh

hh

hh

hh

hi

hi

Feature

dodododododododododododododododododododododododododododododododododododododododododododododododododododododododoType

olbs

gm

olbs

pic

bs

bs

ank

gm

pic

gm

olbs

bs

bs

ank

gm

ank

pic

bs

gm

olbs

olbs

bs

bs

olbs

olbs

gm

bs

gm

bs

gm

pic

gm

bs

plbs

olbs

olbs

bs

bs

bs

ank

olbs

bs

bs

bs

bs

olbs

bs

olbs

olbs

bs

bs

bs

bs

bs

bs

bs

Laboratory 

No.

Ki-6

D101088

Ki-7

Ki-8

Ki-9

Ki-10

Ki-11

?

13730

D101089

La-1

La-2

La-3

La-4

D101083

La-5

La- 6

La-7

D101087

La- 8

La-9

La- 10

La- 11

14174

13726

D101084

13727

D101085

13728

D101086

K3580

D101082

Mu-2

Mu-3

Mu-4

Mu-5

Mu-6

Mu-7

Mu-8

Mu-9

Mu-10

Mu-11

Mu-13

Mu-14

Mu-15

H-4

H-6

H-7

H-8

H-9

H-10

H-ll

H-13

H-14

H-16

H-17

Remar

d

e

d

d

d

d

d

e

e

e

d

d

d

d

e

d

d

d

e

d

d

d

d

e

e

e

e

e

e

e

e

e

d

d

d

d

d

d

d

d

d

d

d

d

d

d

d

d

d

d

d

d

d

d

d

d

j^

Major oxides

Si02

45

46.

45

46,

47

48,

46,

49,

47,

49.

45.

47,

49.

47,

48,

46.

44.

47.

47.

46.

45.

45.

49.

45.

47.

47.

45.

44.

47.

48.

44.

46.

47.

47.

46,

45,

44,

47

47,

45,

45

46,

47,

46

46.

48,

47

48

48,

48

48

48,

47

47

47.

48

.65

.65

.71

.25

.22

.19

.23

.36

.07

.42

.97

.72

.37

.16

.31

.72

.43

,62

.83

,58

.56

.49

.46

.50

.28

,34

,32

,04

,93

.01

.70

.63

.68

.83

.65

.93

.28

.47

.02

.93

.48

.18

.12

.85

.57

.08

.35

.72

.63

.80

.53

.01

.50

.21

.13

.36

A12 03

13

14

13,

8

13,

14.

7,

14,

9.

12,

13.

14,

13,

10.

14.

10,

10.

13.

13,

13,

12.

13.

13.

13.

13.

14.

14.

14.

14.

14.

8.

12.

14.

14,

13,

14,

15,

14.

12.

9,

11,

14.

14,

15,

14,

11

14,

13,

12

13,

12,

14

14,

13,

14

13,

.10

.23

.41

.78

.57

.14

.61

.88

.73

.64

.82

.60

.24

.32

.16

.66

.47

.34

.99

.20

.97

.03

.43

,56

,98

49

.86

,32

.44

.31

.42

,34

.98

.35

.96

.32

.24

.28

.19

,62

.58

.61

.82

.01

.48

.96

.10

.99

.50

.27

.77

.23

.55

.95

.05

.80

Fe2 03

13,

3

13,

12,

13,

13,

12,

3.

2.

2.

14,

14,

13,

12.

2.

14,

14.

13.

6.

13.

14.

14.

13.

5.

3.

3.

3.

4.

3.

3.

3.

4.

13.

14,

13.

13.

16,

14,

13.

13,

14,

15,

14,

14.

14,

13,

13,

12,

12,

12,

12.

13

13,

15

14,

14,

.89

.15

.93

.71

.76

.24

.31

,25

.52

.89

.00

.20

.20

.89

.25

.40

,34

.56

.02

,80

.00

,00

.58

,22

27

44

,90

.31

,16

.32

,40

,58

.25

.52

.73

.49

.22

.55

.76

.53

.01

.74

.41

.96

.46

.06

.79

.47

.66

.06

.72

.94

.79

.06

.49

.77

FeO

nd

9.27

nd

nd

nd

nd

nd

6.12

9.31

8.64

nd

nd

nd

nd

9.11

nd

nd

nd

6.77

nd

nd

nd

nd

7.85

9.00

9.16

11.25

12.15

10.35

10.55

8.86

7.18

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

MgO

9

6

8,

17

8,

6,

20

7,

18,

9,

8,

6,

6,

14,

7.

12,

15,

7.

6.

8,

9.

9,

6.

9.

8.

6.

4.

5.

5.

5.

22,

9,

6.

5.

8,

7.

5

6,

10,

15

14,

5,

6

6,

6,

9

6,

7,

8

7

7,

5

5

5

5,

4

.14

.50

.68

.89

.60

.38

.13

.66

.68

.13

.49

.62

.61

.20

.21

.57

.90

.77

.31

.55

.66

.64

.05

.88

,07

.57

,96

,05

,79

.29

.03

.99

.82

.93

.05

.93

.76

.28

.76

.93

.28

.15

.03

.25

.74

.98

.15

.07

.31

.90

.96

.66

.91

.64

.83

.80

CaO Na2 0

10

11

11,

10

11,

11,

10

12.

8,

11,

10,

10,

10.

10,

12.

9.

8,

9.

10,

9.

10.

10,

10.

9.

11.

11.

7.

7.

10.

10.

8.

11.

11.

10,

11,

10,

9,

11,

11,

10

9,

8,

10,

10,

11.

11

11,

11,

12

12,

12,

11

11,

10

10,

9.

.84 2,

.91 3.

.08 2.

.29 1.

.23 2.

.25 2.

.66 .

.43 2.

.48 1.

.11 2.

.35 2.

.84 2.

.68 2.

.79 1.

.10 2.

.62 2.

.82 1.

.73 3.

.14 2.

.92 3.

.74 2.

.74 2.

.30 2.

.66 2.

.25 2.

.44 2.

,89 3.

.56 3.

,58 2.

.20 3.

.22 1.

.73 1.

.91 2.

.79 2.

.51 2.

.18 2.

.29 2.

.13 2.

.24 1.

.80 1.

.75 1.

.57 2,

.62 2.

.01 2,

.42 2.

.51 1.

.04 3.

.79 2,

.27 1.

.51 2.

.24 1,

.18 2,

.00 2,

.51 2.

.82 3.

.40 3.

.45

.03

.17

.76

.27

.55

.95

.46

.59

.52

,74

.44

,32

.84

.40

.20

,74

.13

.97

,17

.85

.44

,51

,33

.40

61

.41

.18

89

,07

,17

,84

.14

,52

,04

.80

.84

.36

.39

.26

.71

.90

.66

.61

.18

.75

.14

.18

.82

.00

.98

.21

.56

.55

.21

.35

K2 0

0.70

.79

.66

.12

.17

.70

.23

.62

.32

.30

.55

.19

.54

.45

.62

.71

.32

1.05

1.02

.92

.72

.69

.60

.47

.43

.50

1.65

1.71

.84

.95

.14

.19

.20

.31

.19

.88

.67

.40

.18

.22

.21

1.20

.22

.21

.18

.56

.96

.60

.55

.51

.57

.75

.67

.72

.73

1.07

H2 0

nd

.14

nd

nd

nd

nd

nd

.09

.21

.23

.70

.82

.38

.11

.46

.30

.43

.81

.71

.32

.26

.44

.14

1.81

.70

.58

.75

1.11

.11

.09

.86

1.72

.29

.31

.49

.09

.80

.38

.71

.53

.43

1.56

.85

1.30

.54

.30

.17

.15

.54

.36

.24

.29

.24

.37

nd

nd

Ti02

3.28

3.88

3.41

1.81

2.76

3.03

1.46

2.67

1.90

2.67

3.26

3.17

2.93

2.31

2.92

2.83

2.53

3.17

3.54

3.17

3.20

3.19

3.02

3.20

3.03

3.40

4.79

5.24

3.37

3.65

1.79

2.97

2.62

3.32

3.03

3.28

4.73

3.25

2.74

2.04

2.53

4.83

3.29

3.42

3.32

2.56

3.58

2.81

2.66

2.53

2 .74

3.12

3.31

3.67

3.49

3.76

PA

0.39

.43

.38

.19

.29

.35

.15

.31

.20

.27

.49

.34

.30

.25

.32

.34

.31

.50

.52

.48

.38

.38

.32

.39

.34

.33

.88

.92

.42

.41

.18

.27

.27

.35

.31

.41

.70

.34

.29

.22

.29

.61

.33

.35

.32

.31

.50

.32

.31

.28

.32

.38

.40

.46

.40

.70

MnO

0.18

.18

.19

.16

.19

.18

.16

.14

.18

.17

.20

.19

.17

.18

.17

.20

.19

.19

.18

.19

.19

.19

.19

.18

.18

.18

.22

.23

.20

.20

.18

.16

.19

.19

.17

.17

.20

.19

.19

.19

.18

.21

.19

.20

.20

.18

.19

.19

.18

.17

.19

.19

.19

.21

.20

.21

C02

nd

.00

nd

nd

nd

nd

nd

.01

.01

nd

nd

nd

nd

nd

.01

nd

nd

nd

.01

nd

nd

nd

nd

.01

.00

.01

.01

.01

.01

.01

.04

.00

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

Total

99

100

99,

99

100,

100,

99

100,

100,

99

100,

101,

99,

100,

100.

100,

99,

100.

100,

100,

100,

100,

99.

100.

99.

100.

99.

99,

100,

100.

99,

99,

100.

100.

100.

99.

100,

100,

100,

100

100,

101,

100

101,

100,

100

100,

100,

100,

100,

100,

99,

100,

100

100,

100,

.62

.16

.62

.96

.06

.01

.89

.00

.20

.99

.57

.13

.74

.50

.04

.55

.48

.87

.01

.30

.53

.23

.60

.06

,93

.05

.89

.83

.09

.06

.99

.60

.35

.42

.13

.48

.73

.63

.47

.27

.45

.56

.54

.17

.41

.25

,97

,29

.43

.39

.26

.96

.12

.35

.35

.22
INTRODUCTION 15

156°00' 155°45' 155°30' 155°15' 155°00'

20° 

15'

PACIFIC

20° 

00'

19° 

45'

P.UU HINAI 

("O)

PUU 

ANAHULU

OCEAN

NOHONAO-

:HAE 

(IP)

\KEAMUKU 

(HP)

NAOHUELEELUA 

(GP)

MAKAHALAU 

(IQ)

PUU KOLI 

(GQ)

UMIKOA

MAUNA KEA 

<HR)

KUKAIAU 

(JS)

KEANAKOLU 

(IS)

PUAAKALA 

(HS)

UPPER

PIIHONUA

(GS)

PAPAALQA 

(IT)

30 KILOMETERS

_J

Figure 2. Index map of north half of Island of Hawaii, showing approximate area of Mauna Kea lavas (shading) and locations of U.S. 

Geological Survey IVi quadrangles that cover that area. Also shown are quadrangle-identifier codes (in parentheses), which, in combination with locality numbers, give sample-locality numbers used in tables, figures, and text; see plates 3 and 4 for explanation of samplelocality-numbering system.

break in slope that had previously been maintained at the 

shoreline of the active shield.

A section through the summit and northeast flank of 

Mauna Kea (fig. 3) reveals the shield-stage slope break at a 

depth of approximately 400 m. This submerged slope break 

shows that subsidence continued after the end of shield 

growth and that the gently sloping nearshore bench is essentially a relic of the final surface of the subaerial shield-stage 

lavas. Although there are no subaerial exposures of this 

shield, we approximate its profile by analogy with Mauna 

Loa (fig. IB).

Our view that the gently sloping nearshore bench 

approximately represents the final surface of the subaerial 

tholeiitic shield differs from a recent hypothesis of Moore 

and Clague (1992), who inferred, on the basis of subsidence 

rates estimated from the submergence of dated coral-reef 

deposits, that the voluminous shield-building eruptions of 

Mauna Kea ceased at about 130 ka. By 130 ka, eruptions of 

alkalic and transitional basalt had been occurring for about 

100,000 yr or more (since before eruption of the lava flow

dated at 237±31 ka; see section below entitled "Geochronology"). Subsidence of approximately 400 m in 130,000 yr 

indicates an average subsidence rate of 3 mm/yr. Extrapolated to the period between 130 ka and the end of predominantly tholeiitic-lava production before 237±31 ka, the 3- 

mm/yr subsidence rate implies that an average thickness of 

at least 300 m of alkalic and transitional basalt would have 

had to accumulate above the predominantly tholeiitic shield 

lavas at the present position of the submerged slope break to 

maintain the slope break at sea level until 130 ka. Yet, in 

present seacliff exposures, the lava flow dated at 237±31 ka 

(pi. 4; see fig. 13) occurs only about 100 m below the relict, 

onshore, subaerial surface of the volcano; and lava flows as 

old as 187±40, 149±23, and 153±22 ka (pi. 4; tables 4, 5) 

form parts of the relict subaerial surface of the north and 

northwest flanks. As noted below (see section entitled 

"Hamakua Volcanics"), the lava flows of both the coastal 

sections and the subaerial flanks are predominantly aa 

flows, each representing an individual eruption from a single isolated vent. Large lava shields with extensive flow
16 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

0 30 KILOMETERS 

VERTICAL EXAGGERATION x 5

EXPLANATION

Postshield stage—Consists of: 

Laupahoehoe Volcanics—Hawaiitic lavas and local 

glacial deposits

Hamakua Volcanics—Basalt, predominantly alkalic and 

transitional, and local glacial deposits

Shield stage—Consists of subaerial (S A) and submarine 

(SM) basalt, predominantly tholeiitic

Preshield stage 

Contact

Figure 3. Cross section through northeast flank of Mauna Kea 

(line A—A', fig. \R), illustrating relations between preshield, shield, 

and postshield lavas. Cross section based in part on Moore and 

Fiske (1969, fig. 3). Note downwarping of oceanic crust and lavas 

of Kohala Volcano, preshield stage, and shield stage.

Postshield lava flows and pyroclastic rocks overlie the 

Mauna Kea shield and form the volcano's present subaerial 

surface. Our geologic mapping shows that during the early 

part of this stage only basaltic lavas were erupted (Hamakua 

Volcanics), and during the later part only hawaiitic lavas 

(Laupahoehoe Volcanics). On this basis, we divide the postshield stage of Mauna Kea into two parts: the basaltic and 

hawaiitic substages.

It is instructive to consider the construction of the 

entire volcanic pile in terms of volume versus time (fig. 4). 

Swanson (1972) estimated the average modern magma-supply rate for Kilauea Volcano at approximately 0.1 kmVyr. If 

that rate applied throughout most of the Mauna Kea shield 

stage, a shield as large as that of Mauna Kea could be built 

in 320,000 yr. More likely, however, the rate of 0.1 km3/yr is 

a maximum, appropriate for episodes of sustained eruption, 

and the average long-term magma-supply rate at Kilauea 

ranges from 0.01 to 0.1 kmVyr (Dvorak and Dzurisin, 

1993). Using an intermediate value of approximately 0.05 

kmVyr as our estimate for the average supply rate, we illustrate a 650,000-yr duration for the shield stage in figure 4. 

The relatively small volume of the postshield lavas of 

Mauna Kea, erupted over a period of about 250,000 yr, indicates that postshield magma supply was far less, averaging 

about 0.004 kmVyr.

Decreasing magma supply provides a context for interpreting the magmatic and volcanic evolution of Mauna Kea 

during its shield and postshield stages. The decreasing 

magma supply was accompanied by changing lava composition, from tholeiitic basalt that dominated the shield stage, 

through transitional and alkali basalt that dominated the 

postshield basaltic substage, to hawaiitic lava of the postshield hawaiitic substage. The transition from the shield to 

the postshield stage was also accompanied by a change in 

eruptive style: from fissure eruptions that recurred at the 

summit and along the conspicuous east rift zone, to isolated 

eruptions from numerous individual point-source vents, 

many of which are now marked by cinder cones scattered 

over much of the subaerial part of the volcano.

fields of tube-fed pahoehoe, such as those that comprise 

two-thirds of Kilauea's surface (Holcomb, 1987) and represent the sustained eruptions which are largely responsible 

for maintenance or extension of Kilauea's shoreline, are not 

exposed on Mauna Kea. Therefore, we doubt that the eruptions of alkalic and transitional basalt were able to sustain 

shield growth, as proposed by Moore and Clague (1992), 

and we regard the gently sloping nearshore bench as 

approximately representing the final surface of the predominantly tholeiitic subaerial shield. Because postshield lavas 

are truncated by the coastal seacliffs, the shield-stage lavas 

underlying the nearshore bench evidently are at least partly 

mantled by postshield lava flows.

COMPOSITIONAL DATA SET

This study has generated a new major-oxide data set 

representing 444 analyzed samples (table 1). Samples from 

approximately 85 percent of the individually mapped flows 

have been analyzed; most (354) samples were analyzed for 

major elements by X-ray-fluorescence methods at the U.S. 

Geological Survey's laboratory in Denver, Colo. In addition, samples were analyzed from three gulches along the 

northeast coast (Frey and others, 1991; K.J. Murata, unpub. 

data, 1961-66), from Waikahalulu Gulch on the upper south 

slope, from surface flows on the lower northwest slope 

(Frey and others, 1990), and from shield-stage rocks 

dredged from Hilo Ridge (D.L. Peck, unpub. data, 1965).
INTRODUCTION 17

Preshield stage 

(500 km3)

Shield stage (32,000 km3) Postshield stage

1000 800 600 400 

AGE, IN THOUSANDS OF YEARS

200

Figure 4. Volume versus time for lavas of Mauna Kea, illustrating three stages of growth (modified from Wise, 1982, and Frey 

and others, 1990). Shaded areas are proportional to estimated rock volumes for each stage. Curve shows inferred variation in 

growth rate over time. Growth rate for preshield and shield stages equals magma-supply rate, but because volume of postshield 

stage includes only extruded lava (intruded volume is unaccounted for), growth rate for postshield stage equals lava-supply rate.

MAJOR ROCK CLASSES AND 

PETROGRAPHIC GROUPS

For consistency with usage elsewhere, we generally 

follow the recently accepted International Union of Geodesy and Geophysics' (IUGG) compositional classification 

(Le Bas and others, 1986). The entire data set, on a plot of 

total alkali versus silica contents2 according to the IUGG 

scheme, is shown in figure 5; a clear separation of the 

Hamakua and Laupahoehoe lavas is evident. In this scheme, 

all but four of the Hamakua lavas, including most of the 

evolved basalts, fall within the basalt field. The three 

Hamakua hawaiites are compositionally and petrographically akin to other evolved Hamakua basalts but not to 

Laupahoehoe hawaiites. For simplicity, we refer to the 

Hamakua lavas generally as basalt or designate them by petrographic type, such as plagioclase basalt or ankaramite, on 

the basis of phenocryst type and abundance, as defined in 

table 2. Additional compositionally based basalt groups are 

discussed below in the section entitled "Petrology."

2 Data of table 1 have been adjusted by removal of normative calcite, 

partitioning of Fe to FeO and Fe2O, in the ratio of 88:12, and recalculation 

to 100 percent dry weight for plotting in all diagrams showing major 

oxides or their calculated derivatives.

Early uses of the terms "hawaiite," "mugearite," and 

"benmoreite" largely depended on petrographic determination of the plagioclase composition. Later, Coombs and 

Wilkinson (1969) proposed a set of criteria based on differ40 45 50 55 60 

SiO2 CONTENT, IN WEIGHT PERCENT

65

Figure 5. Na2O+K2O versus SiO2 contents for all analyzed 

Mauna Kea lavas, showing field boundaries of lava types from Le 

Bas and others (1986). Circles, Hamakua Volcanics; dots, Laupahoehoe Volcanics.
18 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM 

Table 2. Petrographic nomenclature for lavas of the Hamakua Volcanics

Rock name Criterion Relative phenocryst abundances

Olivine basalt

Plagioclase basalt

Porphyritic basalt

Basalt

Ankaramite

Picrite

Olivine Olivine > augite or plagioclase 

phenocrysts >5 volume 

percent

Plagioclase Plagioclase > olivine or augite 

phenocrysts >5 volume 

percent

Phenocrysts >5 volume Olivine ~ augite ~ plagioclase 

percent

Phenocrysts <5 volume 

percent

Olivine+augite Olivine ~ augite 

phenocrysts ~25 volume 

percent

Olivine Augite - 0 volume percent 

phenocrysts ~25 volume 

percent

entiation index and the anorthite (an) content of normative 

plagioclase. By these criteria, again a clear separation of the 

Hamakua and Laupahoehoe lavas is evident (fig. 6). However, a significant number of evolved Hamakua lavas fall 

within the hawaiite field, as do nearly all the Laupahoehoe 

lavas. Even though the nomenclature of Coombs and 

Wilkinson was used by West and others (1988) in describing 

Mauna Kea rocks, in this report we use the terminology of 

Le Bas and others (1986) because we expect that it will 

become the more widely used standard. Furthermore, Le 

Bas and others' scheme provides a compositional grouping

80

O

< 40

LU 

DC 

LLJ 

LJ_ 

LJL

Q 20

Trachyte

Benmoreite

Hawaiite Mugearite

70 60 50 40 30 20 

ANORTHITE CONTENT [100an/(an+ab)], IN PERCENT

Figure 6. Differentiation index versus anorthite content in normative plagioclase for all analyzed Mauna Kea lavas, showing 

field boundaries of lava types from Coombs and Wilkinson (1969). 

Circles, Hamakua Volcanics; dots, Laupahoehoe Volcanics.

of basalt versus hawaiite and mugearite that coincides 

nearly perfectly with clear lithologic distinctions which we 

recognize and use in the field. In contrast, we cannot distinguish a Hamakua basalt in Coombs and Wilkinson's scheme 

from a Hamakua hawaiite.

The Laupahoehoe lavas are largely represented in figure 5 by such a tight cluster across the hawaiite-mugearite 

boundary that the distinction seems meaningless for lavas of 

the Laupahoehoe Volcanics. Therefore, we generally refer 

to the lavas represented in that cluster as hawaiitemugearite, to the most evolved lavas as benmoreite, and to 

the entire Laupahoehoe suite as hawaiitic.

STRATIGRAPHIC OVERVIEW

PREVIOUS STRATIGRAPHIC NOMENCLATURE

Surface exposures on Mauna Kea Volcano consist 

largely of lava flows and cinder cones, as well as several 

types of sedimentary deposits. Macdonald (1945, 1949) and 

Stearns and Macdonald (1946) divided the lavas into two 

units, the Laupahoehoe and Hamakua Volcanic Series (fig. 

7), and recognized, but did not map, two sedimentary units, 

fluvial and glacial conglomerates and the Pahala Ash. They 

divided the Hamakua Volcanic Series into a lower member 

(Stearns and Macdonald, 1946, p. 154) composed "very 

largely of olivine basalt with less abundant primitive picritebasalt," and an upper member "largely of olivine basalt" but 

with associated "andesites and picrites of the augite-rich 

type" (ankaramites). The overlying Laupahoehoe Volcanic 

Series was thought to consist of "andesite" and basalt that in 

some localities lay above an erosional unconformity. Where 

an obvious unconformity could not be recognized, relative 

age distinction was based on the thickness of ash or soil
Wentworth and 

Powers (1941)

Stearns(1945)

Stearns and 

Macdonald (1946); 

Macdonald (1947)

Makanaka 

Drift

Waihu Drift

Pohakuloa Drift

Pre-Pohakuloa 

drift

Makanaka 

Drift

Waihu 

Fanglomerate

Volcanic 

explosion 

breccias

Upper member

Lower 

member

Upper 

member

Lower 

member

Porter (1979 a-d)

Waihu Formation

Pohakuloa Formation

Lower member of 

Stearns and Macdonald (1946)

Langenheim and Clague (1987)

Makanaka 

Glacial 

Member

Waihu 

Glacial 

Member

Hopukani 

Volcanic 

Member

Pohakuloa 

Glacial 

Member

Lower member

Figure 7. Correlation diagram comparing stratigraphic terminology for Mauna Kea used by previous workers with that used in this r

unnamed lavas. Dashed line separating Hamakua and Laupahoehoe Series of Stearns and Macdonald (1946) reflects vague distinction betwe
20 GEOLOGY AND PETROLOGY. MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

TIME-STRATIGRAPHIC UNITS

E

0)

M

>»

V)

>»

a

c

0)

a

3

O

Holocene

Series

co 

0)

Pleistocene Ser

Loaloan «

Stage

Kaulan

Stage

Kemolean

Stage

Kuupahaon

Stage

Honaipoean

Stage

Poliahuan 

Stage

Li laean 

Stage

Kilohanan

Stage

preKHohanan

rocks

(undivided)

I4C AND K/Ar 

AGES

44OO ± IIO 

4790 ±70

9O8O ± 2OO

29.7OO ± 5OO 

31,900 ±550 

37,200 ± f400

41,300 ± 8300

69,500 ±.2600 

81,100± 23,600

I7I,900±2800 

174,000 ± 37,400 

I74,400± 26,500

> 94,500 ±6100 

SI 09,80015600 

SII4,IOO±7600 

Sl22,400±7300

278,500 ± 68,500 

382,1 00 ±60,600

ROCK-STRATIGRAPHIC UNITS

Hopukani Formation

lower member of Stearns 

and Macdonald (1946)

Figure 8. Correlation diagram showing time-stratigraphic and rock-stratigraphic units and isotopic ages as reported by Porter (1979a-d) for Mauna Kea. See figure 7 for comparison of Porter's 

stratigraphic units with those used in this report.

mantling a given lava flow. Thus, except that picritic basalts 

were mapped with the Hamakua Volcanic Series, the distinction between the two volcanic series is vague: "Locally, 

the criteria of ash cover and picrite-basalts fail, and the 

assignment of the flow to one series or the other depends 

entirely on the judgment of the field geologist" (Stearns and 

Macdonald, 1946, p. 169). The Laupahoehoe Volcanic 

Series was also divided into two members, an upper member of postglacial (Holocene) age and a lower member of 

Pleistocene age.

Figure 7 shows that several sedimentary units, interbedded with volcanic rocks, were recognized in the summit 

region of Mauna Kea. Porter (1979c) redefined the stratigraphic nomenclature to include these units as formations. 

He renamed the upper member of Stearns and Macdonald's 

(1946) Hamakua Volcanic Series, calling it the Hopukani 

Formation, and assigned its sedimentary interbeds to the 

Pohakuloa Formation, which he determined to represent 

glacial drift. These particular sedimentary deposits were 

first recognized as glacial drift by Wentworth and Powers 

(1941) but were later reinterpreted as explosion breccias by 

Stearns (1945) and included in the upper member of the 

Hamakua Volcanic Series by Stearns and Macdonald

(1946). Porter (1979c) raised the Laupahoehoe Volcanic 

Series to group status, so that it could be divided into a volcanic unit, the Waikahalulu Formation, and two sedimentary 

units of glacial origin, the Waihu and Makanaka Formations. The latter two names had also been introduced by 

Wentworth and Powers (1941), but the Waihu Drift was 

reinterpreted by Stearns (1945) as a fanglomerate.

Porter (1979a-d) described and mapped two separate 

glacial-drift deposits within his Makanaka Formation; thus, 

he indicated that the Mauna Kea sequence recorded four 

glacial episodes. He correlated these sequences with marine 

oxygen-isotope stages 2, 4, 6, and 8 (Porter, 1979d). Porter 

assigned the lavas of Mauna Kea to chronostratigraphic 

stages on the basis of his interpretation of the relations of 

the lavas to the glacial deposits (fig. 8).

CHANGES IN STRATIGRAPHIC DEFINITIONS AND 

NOMENCLATURE

A major result of our mapping of the summit region of 

Mauna Kea is the recognition that basaltic lavas continued 

to be erupted after the Pohakuloa glacial episode and until 

shortly after the Waihu glacial episode. No hawaiitic lavas 

appeared throughout this interval; in fact, no intertonguing
GEOCHRONOLOGY 21

METERS 

4500 -,

4000-

3500-

3000-

2500

Makanaka 

Glacial Member,

Liloe Spring 

Volcanic Member

EXPLANATION

Laupahoehoe Volcanics 

| Glacial deposits

Volcanic rocks 

Hamakua Volcanics

Glacial deposits

Volcanic rocks 

Contact—Dashed where inferred

Makanaka 

Glacial Member

Hopukani Springs 

Waihu Volcanic Member

Glacial

Member

Pohakuloa

Glacial

Member

10 KILOMETERS

I

VERTICAL EXAGGERATION X5

Figure 9. Diagrammatic cross section through summit and upper north and south flanks of Mauna Kea, illustrating spatial relations among stratigraphic units. Cross section runs approximately south to north (left to right). See plate 2 for description of units.

of basalt and hawaiitic lava has been observed anywhere on 

the volcano. In this report, the Hamakua and Laupahoehoe 

Volcanics are redefined to reflect these newly recognized 

compositional distinctions (figs. 7, 9; table 3). We assign all 

of the basaltic lavas to the Hamakua Volcanics and all of the 

hawaiitic lavas to the Laupahoehoe Volcanics. Modifying 

the stratigraphic format of Langenheim and Clague (1987), 

we have identified two new units, the Liloe Spring and 

Hopukani Springs Volcanic Members of the Hamakua Volcanics, to distinguish, respectively, olivine-poor basalts 

above the Pohakuloa Glacial Member from olivine-rich 

basalts below.

Porter's (1979a-d) major focus in his fieldwork was on 

the glacial chronology; in contrast, ours has been on volcanic and magmatic history. Building on Porter's published 

work, we have been able to devote greater attention to the 

lithologic and spatial relations of the volcanic units; therefore, we have significantly revised Porter's stratigraphic 

assignments of the lavas. We believe that field evidence 

does not justify Porter's detailed chronostratigraphic subdivision of the lavas (fig. 8), and so we have not perpetuated 

it. Part of Porter's detailed chronostratigraphic scheme 

hinges on his interpretation of two distinct Makanaka glacial episodes separated by an interglacial interval. Field 

relations (see subsection below entitled "Makanaka Glacial

Member") and new K-Ar ages provide no evidence of a 

major interglacial hiatus, indicating to us only one 

Makanaka glacial episode, which included some retreat and 

readvance of the icecap.

GEOCHRONOLOGY

We report 30 new K-Ar ages (table 4) that significantly 

enlarge the previous data base of K-Ar ages (table 5) and 

provide important new constraints on the Pleistocene geochronology of Mauna Kea. Likewise, six new 14C ages 

(table 6) determined by Meyer Rubin (written commun., 

1987) on charcoal collected from directly beneath lava 

flows appreciably amplify the Holocene geochronology. 

Additional geochronologic evidence derived from the exposure ages determined by Dorn and others (1991) is discussed below in the section entitled "Stratigraphy."

Samples for K-Ar analysis (table 4) were selected on 

the basis of thin-section examination; those selected were 

generally free of alteration products and interstitial glass. In 

some samples, there was minor alteration of olivine to 

iddingsite, but this alteration is thought to be deuteric and, 

because both olivine and iddingsite contain negligible K2O, 

has no effect on the K-Ar age. A few samples contained 

minor (less than 1 volume percent) interstitial glass, but
22 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM 

Table 3. Summary of postshield stratigraphic units of Mauna Kea

Unit Description

Laupahoehoe Hawaiitic lava flows, cinder cones, tephra-fall deposits, and associated glacial deposits. 

Volcanics, Forms much of the subaerial surface of Mauna Kea. Typical exposed thickness: more 

undivided. than 50 m. Type locality: Laupahoehoe Gulch. Reference locality: along road from Hale 

Pohaku to summit of Mauna Kea. Contains the Makanaka Glacial Member. Age: 

younger volcanic rocks member (postglacial), about 13 to 4 ka; older volcanic rocks 

member about 65 to 13 ka.

Makanaka Diamict and gravel. Exposed on upper slopes of volcano. Exposed thickness: 0 to 30-40 

Glacial m. Type locality: Puu Makanaka. Reference localities: in Waikahalulu and Kemole 

Member. Gulches. Age: about 40 to 13 ka, equivalent to late Wisconsin glaciation and marine 

oxygen-isotope stages 2 and 3 (part).

Hamakua Basaltic lava flows and cinder cones and associated glacial deposits. Maximum exposed 

Volcanics, thickness: 170 m. Divided into four formally named members on upper slopes, where 

undivided. glacial deposits are intercalated with the lavas; elsewhere, the formation is undivided. 

Type locality: south wall of Laupahoehoe Gulch and adjacent seacliff. Reference 

localities: Maulua and Kaawalii Gulches and lower northwest flank of Mauna Kea. Base 

not exposed. Age: from about 200-250 ka to 65-70 ka.

Waihu Diamict and gravel. Exposed thickness: generally less than 30 m. Type locality: near 

Glacial Waihu Spring. Reference localities: Waikahalulu and Pohakuloa Gulches. Age: poorly 

Member. constrained by K-Ar dating to between about 150 and 70 ka; exposure age of about 70 to

60 ka (Dorn and others, 1991) suggests approximate equivalence to marine

oxygen-isotope stage 4.

Liloe Basaltic lava flows and cinder cones, composed largely of aphyric to weakly porphyritic 

Spring basalt. Maximum exposed thickness: approximately 50 m. Overlies the Pohakuloa 

Volcanic Glacial Member; underlies and locally overlies the Waihu Glacial Member. Type locality: 

Member. Waikahalulu Gulch. Reference locality: Pohakaloa Gulch, near Liloe Spring. Age: poorly 

constrained, within interval from about 150 to 70-65 ka.

Pohakuloa Diamict and gravel. Exposed in Pohakuloa and Waikahalulu Gulches and in upper part 

Glacial of Wailuku River drainage. Maximum thickness: about 40 m. Type locality: west wall of 

Member. Pohakuloa Gulch. Reference locality: Waikahalulu Gulch. Overlies lavas of the

Hopukani Springs Volcanic Member. Age: equivalent to part of marine oxygen-isotope 

stage 6. Dorn and others (1991) report exposure ages of 156 to 140 ka.

Hopukani Basaltic lava flows and cinder cones, composed largely of porphyritic olivine basalt, 

Springs plagioclase-olivine basalt, and ankaramite. Exposed mainly in gulches on upper slopes 

Volcanic of south side of volcano. Maximum exposed thickness: approximately 30 m. Base not 

Member. exposed. Type locality: Waikahalulu Gulch. Reference locality: Pohakuloa Gulch near 

Hopukani Springs. Age of exposed part: within interval from about 200 to 150 ka.

most were holocrystalline. Samples from flows that contained abundant ultramafic xenoliths, common in some 

hawaiite flows, were avoided.

For each whole-rock K-Ar analysis, a block of rock 

was crushed and sized to 0.5 to 1.0 mm. One aliquant was 

used for Ar analysis, and another was crushed to a fine powder for K2O analysis. Four K2O measurements were done on 

each sample by flame photometry, using the lithium metaborate fusion technique (Ingamells, 1970). Ar analyses were 

done by isotope dilution, using a multiple-collector rare-gas 

mass spectrometer (Dairymple and Lanphere, 1969; Stacey 

and others, 1981).

Because the sampled lava flows are young, radiogenic 

40Ar contents are low, ranging from 0.3 to 10.2 percent, in

most samples less than 6 percent (table 4). Thus, the precisions of the calculated ages, particularly those containing 

less than 3 percent radiogenic 40Ar, are also low. Nevertheless, the K-Ar ages provide reasonable constraints on the 

ages of the mapped units.

Our new K-Ar ages and the analytical data on which 

they are based are listed in table 4. Previously determined 

K-Ar ages (Porter, 1979c; B.D. Turrin, written commun., 

1986) are listed in table 5. Using precise map locations provided by B.D. Turrin and the approximate locations and 

stratigraphic descriptions of Porter, we have fitted these 

samples to our mapped rock units. The entire data set of KAr and 14C ages for the volcanic units is graphically summarized in figure 10; the locations of the dated samples are
GEOCHRONOLOGY 23

Table 4. Analytical data for newly reported whole-rock K-Ar ages on Mauna Kea lavas

[Map localities are listed by plate number and quadrangle identifier; see plates 3 and 4 for locations of samples and explanation of locality-numbering system. 

K2O content is listed as mean and standard deviation of four analyses. Ages calculated using International Union of Geological Sciences constants for 1976 

(Steiger and Jager, 1977): ^B=4.962xl(rl(l/yr, A,E=0.581xl(r 10/yr, and 40K/Ktotapl.l67xlO-4 mol/mol. Error limits are estimates of analytical precision at the 

68-percent-confidence level; mean ages for multiple analyses are weighted by the inverse of the variances, do., ditto]

Field Map Rock type 

sample locality 

No. (pl.f quad)

K20 

(weight pet.)

Argon

Aliquant 

weight "°Arrad <°Arrad 

(g) (ID'13 mol/g) (pet)

Calculated Age

(ka)

Laupahoehoe Volcanics

85G034 

85G038

85G039 

85G044 

85G045

W86G6-29 

W86G6-30

W87H6-310

W87H6-311 

W87H6-312

57-4 

85G040 

85G042 

85G043

T»7O C. T C. O 1 O

W86I6-219 

TATQTUC OQQ

TATQTLJC; OQQ

W87H5-300

W87H5-304

4, IP 

X 3,GR

3,GR 

3,HR 

3,HR

3,GR 

3,GR 

3,HR 

3,HR 

3,HR

3,HQ 

3,HR 

3,HR 

3,HR 

4, IR

4,IR 

3,HR

3,HQ

3,HQ 

3,HQ

Benmoreite

Hawaiite/ 

mugearite. 

do —————

Hr>

<-)/~v

do —————

do —————

Ho -*

do —————

Ho —

Liloe Spring

Basalt 

do —————

do —————

do —————

UQy

do —————

do —————

do —————

do —————

UU

2.579±0.009 

1.812±0.001

1.831±0.049 

1.875±0.011 

1.868±0.005

2.006±0.006 

1.852±0.003 

2.203±0.006 

2.192±0.003 

2. '02710. 007

14.325 

14.853 

15.414 

15.292 

12.581 

15.409 

15.030 

14.997 

10.221 

10.502 

11.586 

10.691 

10.371

2.488 

2.271 

.646 

.274 

1.067 

.845 

.689 

1.918 

1.140 

1.307 

1.678 

3.384 

.968

5.3 

1.7 

.8 

.3 

1.8 

1.8 

2.0 

3.0 

4.6 

2.6 

1.7 

4.4 

2.5

6618

18+10

40+13 

3119

3917

39120 

49121 

53114 

107113 

33112

Volcanic Member of the Hamakua Volcanics

1.057±0.002 

.71110.004 

.951±0.002 

.871±0.004 

.833±0.002

1.131±0.005 

.732±0.009

.89210.000

1.02210.002 

.85210.003

Hopukani Springs Volcanic Member

85G041

85G027

85G036 

85G033 

85G037 

La-7

La-11

P86-2

D Q C. O 7\

P86-21A

3,HR

4, JO

2 4,HP 

2 4,IP 

4,10 

4, IT 

4, IT 

2 4,JP 

2 4,JP 

2 4,JQ

Basalt

Basalt 

do —————

Ho —

do —————

do ————— 

do —————

do ————— 

do —————

0.65710.005

Hamakua Volcanics

1.20010.011

.88510.004 

.880+0.004 

1.45310.005 

1.08110.002 

.59010.003 

.53810.006 

.65410.002 

.58110.004

10.438 

15.995 

14 .544 

15.482 

10.055 

10.109 

10.283 

10.305 

10.815 

11.078 

9.843 

10.843 

10.364

1.981 

1.601 

1.181 

1.252 

2.179 

1.823 

2.359 

1.569 

1.172 

3.206 

1.994 

1.705 

1.395

7.1 

4.3 

1.8 

2.1 

4.5 

4.7 

6.3 

3.0 

1.9 

5.0 

3.7 

1.9 

1.8

130133 

157123 

86122 

100122

167132 

145129 

136+29

218+25

116130 

114+34

of the Hamakua Volcanics

14 .744

(undivided)

16.250 

16.216 

14.377 

17.371 

15.164 

10.299 

10.378 

9.195 

10.340 

10.601

1.447

2.072 

1.017 

1.493 

1.886 

2.151 

3.698 

3.522 

1.982 

2.563 

1.567

1.7

0.8 

.5 

.9 

2.7 

10.2 

5.4 

1.9 

.3 

1.7 

5.1

153138

81 + 36

117150 

149123 

103110 

237131 

4151208 

2561389 

2,72011,360 

187140

1 Sample is from small unmapped lava-flow outcrop.

2 See also plate 1, which shows lava flow from which sample was collected on diagram entitled

"Correlation of Lavas of the Hamakua Volcanics."
24 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Table 5. Other K-Ar ages on Mauna Kea lavas

[Map localities are listed by plate number and quadrangle identifier; see plates 3 and 4 for locations of samples and explanation of locality-numbering system. All samples are from lava flows 

except sample QLA-lOa, which is from a bomb on Puu Waiau. Samples are correlated with 

mapped rock units by using map locations provided by B.D. Turrin (written commun., 1986) and 

approximate locations and stratigraphic descriptions of Porter (1979c). Sources of data: 1, Porter 

(1979c); 2, B.D. Turrin (written commun., 1986)]

Field

sample

No.

Map

locality 

(pi., quad) Source

Age and 

Standard 

Deviation 

Oca)

Laupahoehoe Volcanics

MKL-1

MKL-2

MKL-3

QLA-6d

QLA-lOa

Liloe

QLA-Sc

QLA-4a

QLA-Sc

QLA-7f

QLA-9c,

QLA-15

QLA-17b,

QLA-18

QLA-19

QLA-20

Hopukani

4, HP

4, HP

4, HP

3,HR

3,HR

Spring Volcanic Member of

3,HR

4,IQ

4,IQ

3,HQ

QLA-9d, QLA-9e 3,HR

3,HR

QLA-17C 3,HQ

3,HQ

3,HR

3,HR

Springs Volcanic Member

2

2

2

1

1

24±22

50±14

60±20

41±8

174±37

the Hamakua Volcanics

1

1

1

1

1

1

1

1

1

1

of the Hamakua

70±3

81±24

101±15

174±27

110±6

172±3

114 + 8

95±6

121±4

122±7

Volcanics

QLA-8b 3,HR 279±69

Hamakua Volcanics (undivided)

MKH-4 

QLA-llc

4, 10 

4, JP

2

1

153±22 

382±61

shown on plates 3 and 4. K-Ar ages of several individual 

flows of the Hamakua Volcanics from the northwest flank of 

Mauna Kea are shown on the correlation diagram of plate 1. 

Relative stratigraphic positions are known from field 

relations for many of the samples, especially those from the 

upper flanks of the volcano. This information is useful in 

assessing the errors and reliability of the K-Ar ages. Generally, K-Ar and 14C ages for the Laupahoehoe Volcanics are 

closely grouped between approximately 65 and 4 ka (fig. 

10), a range that is consistently younger than that determined for the underlying Hamakua Volcanics. Only the ages 

for Puu Waiau [our age of 107±13 ka (sample W87H6-311, 

table 4) for the flow from Puu Waiau (flow PW, pi. 2) and an 

age of 174±37 ka (sample QLA-lOa, table 5) reported by 

Porter, 1979c, for a bomb from the Puu Waiau cinder cone] 

overlap the age range of the Hamakua Volcanics, including 

ages determined for flows of the Liloe Spring Volcanic 

Member that are stratigraphically below the Waihu Glacial

Member. These data indicate that the age range of the 

Laupahoehoe Volcanics is approximately 65 to 4 ka and 

possibly as old as 100 ka. However, an exposure age of 

approximately 70 to 60 ka (Dorn and others, 1991) for the 

Waihu Glacial Member, which is older than the lava flow 

from Puu Waiau, supports 65 ka as the approximate older 

limit for the age of the Laupahoehoe Volcanics.

The ages of samples from the Hamakua Volcanics are 

poorer in quality than those from the hawaiitic Laupahoehoe Volcanics because of the substantially lower K2O contents in Hamakua basalts. Stratigraphic control is excellent 

for the Hamakua Volcanics on the upper flanks of Mauna 

Kea because the Pohakuloa and Waihu Glacial Members 

provide excellent mappable stratigraphic markers and the 

sequence is well exposed in continuous canyon-wall sections in Pohakuloa and Waikahalulu Gulches (pi. 2). Our 

ages on samples from the Liloe Spring Volcanic Member 

range from 218 to 86 ka. In spite of apparent internal strati-
STRATIGRAPHY 25

Table 6. Radiocarbon ages on charcoal from beneath Mauna Kea lava flows

[Map localities are listed by plate number and quadrangle identifier; see plates 3 and 4 for locations of samples and explanation of 

locality-numbering system. Age of sample 15292 from Porter (1971) and of sample W5541 from Rubin and others (1987); age of 

AA6795 determined by accelerator mass spectrometry at the University of Arizona (Meyer Rubin, written commun., 1991); all other 

ages from Meyer Rubin (written commun., 1987). Do., ditto]

Laboratory Map 

No. locality

{pi ., quad)

Collector 14 C Age 

(yrs BP)

Description

15292

W5825

W5776

W5779

W5823

AA6795

W5773

W5541 

W5821

X 3,GR S.C. Porter———4,4001110

4,IR M.A. Kuntz ———— 4, 4101150

3,GR E.W. Wolfe————4, 5101150

3.GR do——————————4,550±150

4.HS W.S. Wise—————4, 8501150

4,IS P.M. Vitousek--5,085±97

3,GR E.W. Wolfe————5,3201150

3,GR J.P. Lockwood—5,6301200

4,IR M.A. Kuntz———7,1001150

Flow from Puu Kole (south flank)

Flow from Puu Lehu.

Flow from Puu Kole (south flank)

Do. 

Flow from Puu Kanakaleonui.

Do.

Flow originating 1 km 

southeast of Hale Pohaku.

Flow from Kalaieha.

Flow from Puu Kole (north flank)

1 Location not shown on plate 3; Porter (1971) describes location as "2195 m in gully 

1.8 km northeast of Puu Loaloa on north side of Keanakolu Road."

graphic inconsistency (fig. 11), none of these ages differs 

significantly at the 95-percent-confidence level except for 

sample W87H5-298, which has an apparent age of 218±25 

ka. Our remaining ages are consistent with an age of from 

about 150 to 100 ka for the Liloe Spring Volcanic Member, 

and one age of 70±3 ka (Porter, 1979c; sample QLA-3c, 

table 5) suggests that the Liloe Spring Volcanic Member 

could be as young as 70 ka. An exposure age of approximately 70 to 60 ka, determined by Dorn and others (1991) 

for the Waihu Glacial Member of the Hamakua Volcanics, 

supports an age of 70 ka or slightly younger for the upper 

part of the Liloe Spring Volcanic Member, because the 

youngest lava flows of the Liloe Spring Volcanic Member 

overlie the Waihu Glacial Member.

We dated only one sample from the Hopukani Springs 

Volcanic Member. It has an apparent age of 153±38 ka, 

which does not differ at the 95-percent-confidence level 

from Porter's (1979c) previously reported age of 279±69 ka 

(table 5). Considered together with the range in ages for the 

Liloe Spring Volcanic Member, these results suggest that 

the age of the upper part of the Hopukani Springs Volcanic 

Member is approximately 200 to 150 ka.

Ages of samples of the Hamakua Volcanics from the 

lower flanks of Mauna Kea are generally consistent with 

those of samples from the upper flanks. Three samples (La11, P86-2, P86-2A) are of such poor quality and have such 

large error limits that they provide no useful age information and so are omitted in figure 10. The remaining ages,

which range from 237±31 to 81±36 ka, suggest that the 

shield-building stage of Mauna Kea, lavas of which are not 

exposed on the subaerial part of the volcano, ended before 

about 250-200 ka.

STRATIGRAPHY

HAMAKUA VOLCANICS

GENERAL STATEMENT

The Hamakua Volcanic Series was named for exposures of basalt in the seacliffs and gulches along the 

Hamakua coast from Hilo to Honokaa (Macdonald, 1945; 

Stearns and Macdonald, 1946). The type section is along the 

old coastal highway south of Laupahoehoe Gulch. The road 

has been abandoned since 1953 and now is so completely 

overgrown that the original section is no longer accessible 

(see Stearns and Macdonald, 1946, p. 195, pi. 46B, for a 

view and detailed description of this section).

As noted above in the subsection entitled "Previous 

Stratigraphic Nomenclature," Stearns and Macdonald's definition of the Hamakua Volcanic Series is vague; the 

Hamakua contains both basalt and "andesite." Our mapping 

shows that all of the hawaiitic lavas of Mauna Kea overlie 

all of the basaltic lavas and that there is no interlayering of 

these two compositional types. Accordingly, we here redefine the Hamakua Volcanics to include all the exposed
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STAGE POSTSHIELD KEA MAUNA 

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STRATIGRAPHY 27

Porter (1979c)

Field sample No. (ka) Age

QLA-3C 70±3\

QLA-15 17213 —

QLA-19 121+4— 

QLA-71 174127-^

QLA-18 9516 '/

QLA-17b, 17c 114±8X

QLA-9C, 9d, 9e 11016\

QLA-20 122+7^

QLA-8b 279169^

Unit

"\^^ ^^~--^~^ ^^^. *~^\~~~~~^~~~^

/ Waihu 

<^ Glacial

/ Member JT^' '"^

/ Liloe

Spring ._

Volcanic Member ._

^^

\^\. .^^^

Pohakuloa

Glacial

Member

Hopukani .^

Springs

Volcanic

Member

This report

(ka) Age Field sample No.

^--- 1 30+33 57-4

^-136129 W87H6-288

167+32 W86I6-218

^-145+29 W86I6-219 

\218±25 W87H5-298

"^157123 85G040 

—— 100+22 85G043

^86122 85G042

^114+34 W87H5-304

^116130 W87H5-300

^153138 85G041

Figure 11. Summary of K-Ar ages for lavas of the Liloe Spring and Hopukani Springs 

Volcanic Members of the Hamakua Volcanics, showing relative stratigraphic positions of 

samples with respect to the Waihu and Pohakuloa Glacial Members of the Hamakua Volcanics. At left, ages from Porter (1979c) (see table 5); at right, newly reported ages (see 

table 4). Ages for samples QLA-4a and QLA-5c (table 5) are omitted because stratigraphic relation of these samples to the Waihu Glacial Member is unknown. See plate 2 

for description of units.

basaltic flows and pyroclastic deposits of Mauna Kea Volcano, as well as the sedimentary units interlayered with 

them. Generally, the formation is exposed in two major 

areas of the volcano: (1) on the lower slopes, a belt around 

the volcano that is largely between sea level and about 

1,000-m elevation but extends locally to higher elevations; 

and (2) the upper slopes, extensive but discontinuous exposures within kipukas above approximately 2,000-m elevation (fig. 12).

No consistent criteria exist for stratigraphic subdivision of the Hamakua lavas exposed on the lower slopes of 

the volcano. However, the glacial interbeds allow the upperflank exposures to be subdivided into four formally named 

members, two volcanic and two glacial (fig. 7; table 3). 

Therefore, we describe first the undivided Hamakua Volcanics of the lower flanks and then the members of the upper 

flanks.

HAMAKUA VOLCANICS (UNDIVIDED)

DEFINITION AND OCCURRENCE

On the lower slopes of Mauna Kea, the Hamakua Volcanics consists of all the basaltic flows, cinder cones, and 

minor pyroclastic deposits that lie stratigraphically below 

the Laupahoehoe Volcanics. Typical sequences are well 

exposed in the seacliffs and gulches along the Hamakua 

Coast between Hilo and Honokaa, and surfaces of individual flows are best exposed on the north and northwest flanks 

of the volcano between Honokaa and Kawaihae.

The type section of Stearns and Macdonald (1946) in 

the walls of Laupahoehoe Gulch is appropriate for the undivided Hamakua Volcanics of the lower flanks. It is supplemented by additional measured reference sections in 

Laupahoehoe Gulch and in nearby Kaawalii and Maulua 

Gulches (figs. 12, 13). Because these gulches are distant
155°45' 155°30' 155°15'

EXPLANATION

Laupahoehoe Volcanics 

Lava flows and cinder 

cones, undivided

PACIFIC OCEAN

Hamakua Volcanics

Undivided part

Lava flow

Cinder cone

Upper slope

Lava flow

Cinder cone

Laupahoehoe 

Gulch

PACIFIC 

OCEAN:

South-flank kipukas

Figure 12. Geologic map of Mauna Kea, showing generalized distribution of the Hamakua Volcanics. Internal contacts distinguish individual lava flows and cinder 

cones. Queries mark limits of mapping at edge of dense rain forest. The Hamakua Volcanics on upper slopes consists of the Liloe Spring and Hopukani Springs Volcanic Members and the Waihu and Pohakuloa Glacial Members (see pi. 2 for distribution of

all mappable outcrops on Mauna Kea of these four members). Local porphyritic basalt flows above 2,000-m (6,560 ft) elevation on upper part of north flank are assigned to the undivided Hamakua Volcanics because their stratigraphic relation to the Pohakuloa Glacial Member is unknown. Geology simplified from plates I and 2 and Wolfe and Morris (1996).
STRATIGRAPHY 29

Kaawalii 

Gulch

Laupahoehoe Gulch 

(Northwest) (Southeast)

Maulua 

Gulch

METERS

60-

50-

40-

30-

20-

10-

SEA

LEVEL"

-2.5km 1 km 6 km

- La-5

La-104

Ki-4

VH- La-101 

- La-105

Conglomerate

Basalt

Tholeiite

EXPLANATION 

Olivine basalt 

Plagioclase basalt 

Ankaramite

Picrite 

High-Ti basalt

Figure 13. Stratigraphic sections of the Hamakua Volcanics 

exposed in Kaawalii, Laupahoehoe, and Maulua Gulches, showing Stratigraphic positions of sampled units. Sections from 

Kaawalii, Maulua, and northwestern part of Laupahoehoe 

Gulches from Frey and others (1991); section from southeastern 

part of Laupahoehoe Gulch from Stearns and Macdonald (1946). 

Type of outcrop is shown in parentheses to left of column; gap in 

column indicates break in outcrop exposure. Dashed line, correlated lava flows; short horizontal line to right of southeast Laupahoehoe Gulch column, position of boundary between Stearns and 

Macdonald's (1946) upper (U) and lower (L) members of the 

Hamakua Volcanic Series. Horizontal axis not to scale; approximate distance between gulches shown for reference. See plate 4 

for locations of traverses associated with sample-locality numbers. Chemical analyses are listed in table 1; see table 2 for 

description of basalt types.

from the Hamakua vents, as well as from the east rift zone 

of the volcano, the measured sections represent typical 

lower-flank lava-flow sequences. The maximum exposed 

thickness of the Hamakua Volcanics on the entire volcano is 

170 m, in the Maulua Gulch section.

Many individual flows and their cinder cones are 

exposed on the north and northwest slopes of Mauna Kea 

(fig. 12). These cones, which are 10 to 30 km from the 

present summit, represent vents that were not covered by 

later Hamakua and Laupahoehoe flows. Exposures on the
30 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

lower northwest flank constitute a reference locality for 

these flows and cinder cones (pi. 1). K-Ar analyses indicate 

that these northwest-flank flows are generally younger than 

200 ka; thus, they postdate the flows exposed deepest in the 

gulch sections along the Hamakua Coast.

PREVIOUS WORK

Stearns and Macdonald (1946) and Macdonald (1949) 

recognized petrologic differences between the stratigraphically lowest basalts exposed along the Hamakua Coast and 

those higher in the sequence. On this basis, they separated 

the Hamakua Volcanic Series into two members: a lower 

member containing abundant olivine basalt and some 

picrite, and an upper member containing abundant olivine 

basalt and some hawaiite ("andesite") and ankaramite 

("picrite-basalts of the augite-rich type"). In a few gulches, 

red soil zones between certain lava flows were mapped as 

the boundary between these members (see Macdonald, 

1949, pi. 12). During recent sampling and description of 

sections in the major gulches of the Hamakua Coast (Frey 

and others, 1991) and in our geologic mapping, the distribution of rock types was verified (fig. 13), but it proved 

impossible to map a consistent boundary.

Porter (1979c) retained the lower member of Stearns 

and Macdonald (1946) and assigned lavas of the upper 

member, on the lower flanks of the volcano, to his Hopukani Formation.

GEOLOGIC OBSERVATIONS

The Hamakua basalts vary widely in lithology, primarily because of variations in abundance and size of phenocrysts—olivine, augite, and plagioclase. These phenocrysts 

range most commonly from 1 to 4 mm in diameter but in 

rare flows may reach 2 cm. The most common abundances 

are less than 10 volume percent; in only a few flows does 

phenocryst content exceed 30 volume percent. Completely 

aphyric basalts are few. Although local variations in the 

phenocryst assemblage occur in some lavas, generally each 

flow and its vent deposits have a persistent phenocryst 

assemblage, which, in most flows, differs recognizably 

from that of its neighbors. These differences provide the primary basis for recognizing and mapping individual flows.

In the seacliff and roadcut exposures on the Hamakua 

Coast, individual flows range in thickness from 0.3 to 20 m. 

Most flows appear to have a wide lateral extent, at least 

across the width of any exposure. Judging from the lateral 

extent of flows mantling the surface immediately above 

these cliffs, most flows are from 0.5 to 2.5 km wide. 

Although Laupahoehoe and Kaawalii Gulches are only 2.4 

km apart, no single flow can be correlated between the sections measured in these two gulches (fig. 13).

Most of the lavas exposed in the coastal sections are 

dense, thick (more than 3 m) aa flows with rubble at the tops 

and bases. Several thick (max 20 m) accumulations of olivine basalt pahoehoe are composed of individual flows less 

than 1 m thick. The lavas on the northwest flank also are 

predominantly aa flows with rare pahoehoe sequences. The 

basaltic lavas flowing off the northwest flank of the volcano 

spread out, building a gently sloping saddle and turning seaward as they approached the flank of Kohala Volcano. Some 

of these flows were more than 20 km long and averaged 2 

km in width; one late olivine basalt pahoehoe flow spread 

out over an area of 20 km2 south of Waimea (flow 33, pi. 1).

Cinder cones formed at all the Hamakua vents exposed 

on the lower slope. Most are single, crescentic cones in 

which part of the wall was rafted away as lava welled out of 

the conduit. A few vents are represented by cone complexes; for example, Puu Pa, near Waimea (pi. 1), was built 

by a sequence of eruptions from the same conduit system. 

Because most of the cones are older than 100 ka, their 

shapes have been degraded by erosion and mass wasting. 

These remnants range in width from 120 to 925 m and in 

height from 25 to 140 m.

Exposed Hamakua cinder cones are mainly concentrated on the north and northwest slopes (fig. 12). A few 

additional cinder cones, which overlie the landward extension of the shield-stage Hilo Ridge rift zone (fig. 1), are 

exposed on the lower east flank north of Hilo. The distribution of cinder cones is partly due to burial by later Laupahoehoe lavas and, probably, by Mauna Loa lavas, in the 

saddle between Mauna Kea and Mauna Loa. However, 

much of the Laupahoehoe Volcanics on the lower flanks is 

only a single flow thick, insufficient for burial of many 

Hamakua cones. Therefore, Hamakua flows of the northeast 

slope were derived from vents high on the volcano, whereas 

those of the lower northwest slope largely were locally 

derived.

Mildly porphyritic lava types are distributed throughout the gulch sections and over all the slopes. The strongly 

porphyritic lava types, however, are restricted in occurrence. As Stearns and Macdonald (1946) noted, picrites and 

olivine-rich basalts generally are restricted to the lowest 

exposures along the Hamakua Coast. No picrites are 

exposed in surface flows anywhere on the lower slopes. 

Conversely, ankaramite, plagioclase-rich basalt, and flows 

of highly evolved basalt are exposed only in the upper parts 

of coastal exposures and form surface flows on all the 

flanks of the volcano.

AGE

New K-Ar ages on samples of Hamakua basalt flows 

from the lower flanks of Mauna Kea range from 237+31 ka 

to 81+36 ka (tables 4, 5). An age of 382+61 ka (sample 

QLA-llc, table 5) previously reported by Porter (1979c) is
STRATIGRAPHY 31

Pl^w^:

Figure 14. Members of the Hamakua Volcanics exposed in 

west wall of Waikahalulu Gulch. Contacts dashed where approximately located. Hawaiian Volcano Observatory photograph 

88.3.10EW135A#20.

stratigraphically inconsistent; field relations (pi. I) show 

that the sample is from a flow stratigraphically above the 

one with an age of 81±36 ka.

HOPUKANI SPRINGS VOLCANIC MEMBER

DEFINITION AND OCCURRENCE

The herein-named Hopukani Springs Volcanic Member consists of basalt flows and rare cinder-cone deposits 

that lie stratigraphically below the Pohakuloa Glacial Member. We assign lavas to the Hopukani Springs Volcanic 

Member only on the upper flanks of Mauna Kea, where the 

Pohakuloa Glacial Member is present and serves as a stratigraphic marker. The unit is extended locally beyond the outcrop of the Pohakuloa Glacial Member by lithologic 

correlation. Elsewhere on the volcano, well beyond the limit 

of the Pohakuloa Glacial Member, similar basalt is assigned 

to the undivided Hamakua Volcanics (fig. 7).

Hopukani Springs lavas are the oldest exposed rocks 

on the upper flanks of Mauna Kea. Exposures occur in and 

near Pohakuloa and Waikahalulu Gulches on the south flank 

and Waipahoehoe Gulch on the upper east flank of the volcano (pi. 2). Their maximum exposed thickness in these 

gulches is about 30 m.

Owing to their good exposure and relative ease of 

access, we designate the outcrops along Waikahalulu Gulch, 

between approximately 2,775-m (9,100 ft) and 3,095-m 

(10,160 ft) elevation, as the type section of the Hopukani 

Springs Volcanic Member (fig. 14). The unit is named for 

exposures in Pohakuloa Gulch, near the Hopukani Springs, 

which are just west of Pohakuloa Gulch, at 3,175-m (10,420 

ft) elevation.

PREVIOUS WORK

Stearns and Macdonald (1946) and Macdonald (1949) 

mapped the south-flank exposures of the Hopukani Springs 

Volcanic Member as part of the upper member of their 

Hamakua Volcanic Series. Their upper member included 

basalts of the lower flanks of Mauna Kea except for those in 

a narrow band of outcrops near sea level on the northeast 

flank.

Porter (1979a-c) applied the name "Hopukani Formation" to most of the lavas that Stearns and Macdonald 

(1946) had referred to the upper member of their Hamakua 

Volcanic Series. Porter's Hopukani Formation included 

lavas exposed below the Pohakuloa Glacial Member in 

Pohakuloa and Waikahalulu Gulches and excluded lavas 

above the Pohakuloa Member. Our usage of the name 

"Hopukani Springs Volcanic Member" applies, on the upper 

flanks, to the same lavas as does Porter's usage of the name 

"Hopukani Formation" but differs in excluding basalts of 

the lower flanks.

GEOLOGIC OBSERVATIONS

Hopukani Springs basalt is predominantly porphyritic, 

vesicular pahoehoe and, locally, aa, in which phenocrysts of 

olivine, plagioclase, and clinopyroxene compose about 10 

to 20 volume percent of the rock. Olivine phenocrysts are 

normally conspicuous, and where plagioclase phenocrysts 

are abundant, the laths commonly radiate from cumulophyric plagioclase-clinopyroxene-olivine clots, giving an 

appearance on the outcrop of plagioclase rosettes. Weakly 

porphyritic basalt, aphyric basalt, and picrite are subordinate rock types.

Vent deposits are represented by two eroded cinder 

cones along Waipahoehoe Gulch and by a third cone (not 

mapped) exposed in the steep west wall of Waikahalulu 

Gulch, where it is overlain by diamict of the Pohakuloa Glacial Member (fig. 15). The bulk of exposed Hopukani 

Springs flows must have been erupted from vents that are
32 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Figure 15. West wall of Waikahalulu Gulch, showing members 

of the Hamakua Volcanics—basalt cinder cone of the Hopukani 

Springs Volcanic Member, overlain by approximately 40 m of 

diamict and gravel of the Pohakuloa Glacial Member, in turn overlain by flows of the Liloe Spring Volcanic Member. Contacts 

dashed where approximately located. Hawaiian Volcano Observatory photograph 88.2.23EW135A#16.

now buried by younger volcanic and glacial deposits high 

on the upper slopes or summit of Mauna Kea.

AGE

The K-Ar age of a lava flow sampled 26 m below the 

top of the Hopukani Springs Volcanic Member in Waikahalulu Gulch is 153±38 ka (table 4). An additional sample collected from the Hopukani Springs Volcanic Member 

immediately below the Pohakuloa Glacial Member in Waikahalulu Gulch gave a K-Ar age of 279±69 ka (table 5; 

Porter, 1979c), comparable to our age at the 95-percentconfidence level. These results, along with the range in 

K-Ar ages for the overlying Liloe Spring Volcanic Member 

(fig. 11), suggest that the age of the upper part of the

Hopukani Springs Volcanic Member is approximately 150 

to 200 ka.

POHAKULOA GLACIAL MEMBER

DEFINITION AND OCCURRENCE

The Pohakuloa Glacial Member consists of till 

between the underlying Hopukani Springs and the overlying 

Liloe Spring Volcanic Members. The Pohakuloa Glacial 

Member is exposed on the south and upper east flanks of 

Mauna Kea. Exposures on the south flank occur only in the 

most deeply incised sections of Pohakuloa and Waikahalulu 

Gulches and in a small gulch 400 m southeast of Pohakuloa 

Gulch (pi. 2; figs. 14, 15). On the upper east flank, the unit 

is exposed in the headwaters of the Wailuku River and in a 

kipuka along Waipahoehoe Gulch. There, the Liloe Spring 

Volcanic Member is absent, and the Pohakuloa Glacial 

Member is directly overlain by flows of the Laupahoehoe 

Volcanics. The type section was defined by Porter (1979c) 

as an exposure deep in Pohakuloa Gulch at approximately 

2,935-m (9,630 ft) elevation.

PREVIOUS WORK

Wentworth and Powers (1941) described three glacial 

drifts of pre-Makanaka age on the south flank of Mauna 

Kea. They named them, in ascending order, "pre-Pohakuloa 

drift," the "Pohakuloa Drift," and the "Waihu Drift." They 

assigned the deep canyon-wall exposures of Pohakuloa 

Gulch and of the neighboring small gulch to their prePohakuloa drift. The drift outcrops between Pohakuloa and 

Waikahalulu Gulches, here all considered parts of the Waihu 

Glacial Member, were divided into two units, the Pohakuloa 

Drift and the Waihu Drift, and the deep canyon-wall exposure in Waikahalulu Gulch was assigned to their Pohakuloa 

Drift.

Stearns (1945) greatly clarified the map distribution of 

Waihu and pre-Waihu sedimentary units, assigning the 

Pohakuloa Drift (of Wentworth and Powers, 1941) on the 

slopes between Pohakuloa and Waikahalulu Gulches to the 

Waihu. Stearns, however, challenged the interpretation of 

Wentworth and Powers that the pre-Makanaka sedimentary 

units are glacial-drift deposits and referred the pre-Pohakuloa drift of Pohakuloa Gulch and the Pohakuloa Drift of 

Waikahalulu Gulch to a unit of "explosion deposits."

Porter (1979c) assigned the deep canyon-wall outcrops 

of gravel and diamict in Pohakuloa and Waikahalulu 

Gulches to his Pohakuloa Formation and designated an 

exposure in Pohakuloa Gulch as the type section. Thus, the 

present type section of the Pohakuloa Glacial Member is an 

outcrop that Wentworth and Powers (1941) had assigned 

to their pre-Pohakuloa drift. Applying the terminology of 

Langenheim and Clague (1987), we assign these same out-
STRATIGRAPHY 33

crops in Pohakuloa and Waikahalulu Gulches to the 

Pohakuloa Glacial Member.

GEOLOGIC OBSERVATIONS

The Pohakuloa Glacial Member is exposed in discontinuous outcrops along 1.5 km of Pohakuloa Gulch between 

approximately 2,740- -and 3,170-m (9,000 and 10,400 ft) 

elevation. It forms a continuous exposure, nearly 800 m 

long, in the west wall of Waikahalulu Gulch (talus buries 

the unit in the east wall), between approximately 2,800- and 

3,110-m (9,200 and 10,200 ft) elevation. The Pohakuloa 

Glacial Member is essentially concordant with lava flows in 

the underlying and overlying volcanic members, and all the 

layers dip approximately parallel to the mountain flank, 

which slopes about 15°-25°. In the excellent Waikahalulu 

Gulch exposure, the unit gradually thickens southward from 

approximately 12 m near the north (uphill) end of the exposure to nearly 40 m before abruptly wedging out, thinning to 

the south, so that overlying Liloe Spring flows descend 

steeply to rest directly on underlying Hopukani Springs 

flows (fig. 9).

In the south-flank exposures, the Pohakuloa Glacial 

Member consists of matrix-supported diamict (till), with 

some interlayered gravel that is distinctly bedded and 

sorted. The unit is light gray except where oxidized red by 

the overlying basalt flows. In the diamict, subangular to 

subrounded cobbles and boulders, as large as about 1 m in 

diameter, occur in a moderately indurated, massive, 

unsorted, silty to pebbly matrix. The boulders are of vesicular porphyritic basalt lithologically identical to flows of the 

underlying Hopukani Springs Volcanic Member. The gravel 

facies is particularly well developed near the south end of 

the Waikahalulu Gulch exposure (fig. 16), where it consists 

of framework-supported, bedded gravel containing pebbles, 

cobbles, and boulders lithologically similar to those of the 

interlayered diamict. Steep dips and coarse fabric suggest 

that these particular beds were formed by energetic runoff 

over the downhill face of the Pohakuloa deposit. Porter 

(1979c) identified these diamict and gravel facies, which he 

examined and described in detail and interpreted, respectively, as glacial till and outwash.

Exposures on the upper east flank of the volcano display about 10 m of bouldery till and minor bedded sandy 

gravel overlying porphyritic basalt of the Hopukani Springs 

Volcanic Member. The till consists of subangular to subrounded cobbles and boulders of basalt in a massive, 

unsorted, moderately indurated, light- to medium-gray 

matrix. The boulders include porphyritic basalt similar to 

exposed underlying Hopukani Springs flows, as well as an 

unusual basalt containing abundant, coarse-grained plagioclase phenocrysts, as large as 1 cm across. Near its upper 

contact, the unit has been oxidized red by the overlying lava 

flows. Where the surface of the drift deposit is exposed in a

Figure 16. Beds of diamict and gravel of the Pohakuloa Glacial 

Member of the Hamakua Volcanics exposed in west wall of Waikahalulu Gulch (see fig. 15 for location). Gravel beds dip 30°-35° 

SW., slightly more steeply than overlying flows of the Liloe 

Spring Volcanic Member of the Hamakua Volcanics (upper left 

corner). Pole is 1.5 m long. Hawaiian Volcano Observatory photograph 88.2.23EW135A#18.

kipuka just southwest of Waipahoehoe Gulch—the only surface exposure of the Pohakuloa Glacial Member—the boulders are weathered dark brown. The Liloe Spring Volcanic 

Member is absent in these upper-east-flank exposures, and 

the drift is directly overlain by the Laupahoehoe Volcanics. 

Porter (1979a) included the underlying basalts in his Laupahoehoe Group and mapped this drift as his Waihu Formation. We assign this drift to the Pohakuloa Glacial Member 

because its porphyritic-basalt clasts indicate that the source 

rocks included only lavas of the Hopukani Springs Volcanic 

Member.

To assess the origin of the Pohakuloa sedimentary 

deposits, which was controversial because of the conflicting 

glacial-drift (Wentworth and Powers, 1941) and explosionbreccia (Stearns, 1945) hypotheses, Porter (1979c) exhaustively studied the outcrops, analyzed their size distribution 

and fabric, and compared the results with similar studies of 

historical and prehistoric explosion breccias in unspecified 

outcrops at Kilauea Volcano. Porter found a striking dissimilarity between the Pohakuloa sedimentary deposits and the 

Kilauea explosion breccias. However, he demonstrated a 

strong similarity between the Pohakuloa deposits and the 

younger Waihu and Makanaka deposits, which, as discussed 

below, are definitely glacial-drift deposits. Thus, Porter 

showed that the Pohakuloa is a glacial-drift deposit. His evidence included the following: (1) Though rare, polished and 

striated fragments are present; (2) though difficult to find
34 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

because of limited exposure, grooves and striations occur on 

abraded or polished underlying bedrock surfaces; (3) the 

Pohakuloa deposit is similar in thickness to the Waihu and 

Makanaka deposits and has similar gravel and diamict 

facies; (4) size and fabric analyses show a similar size distribution and poor sorting of the matrices of the Pohakuloa, 

Waihu, and Makanaka diamicts, a similar degree of rounding of the clasts (predominantly subrounded to subangular), 

and development of a strong unidirectional clast fabric in 

diamicts of each of the three deposits.

By analogy with the younger, well-exposed Makanaka 

Glacial Member, the Pohakuloa till and associated gravel 

exposed in south-flank gulches represent terminal- or lateral-moraine deposits that formed an annulus surrounding 

the glacially eroded summit of the volcano. Thus, uphill 

from these morainal deposits, in exposures along the upper 

parts of Pohakuloa and Waikahalulu Gulches, Pohakuloa 

glacial deposits are absent, and basalt of the Liloe Spring 

Volcanic Member rests directly on that of the Hopukani 

Springs Volcanic Member (fig. 9).

AGE

The age of the Pohakuloa Glacial Member is bracketed 

by basalt of the underlying Hopukani Springs Volcanic 

Member, with a K-Ar age of approximately 150 to 200 ka, 

and the overlying Liloe Spring Volcanic Member, which 

includes flows with an age within the range 100-150 ka, 

and possibly younger (fig. 11). Dorn and others (1991) 

reported exposure ages of 140 to 156 ka based on varnish 

cation ratios from weathered boulder surfaces in the Waipahoehoe Gulch exposure. Thus, the age of the Pohakuloa 

Glacial Member corresponds approximately to some part of 

marine oxygen-isotope stage 6 (fig. 10).

LILOE SPRING VOLCANIC MEMBER

DEFINITION AND OCCURRENCE

The herein-named Liloe Spring Volcanic Member of 

the Hamakua Volcanics consists of the basaltic lava flows 

and vent deposits that lie between the underlying Pohakuloa 

Glacial Member and the overlying hawaiitic rocks and sedimentary deposits of the Laupahoehoe Volcanics. Till and 

gravel of the Waihu Glacial Member form a lens enclosed, 

at least in part, by the Liloe Spring Volcanic Member. 

Although Porter (1979a, c) assigned these rocks to his 

Laupahoehoe Group, we assign them to the Hamakua Volcanics because, like all the other Hamakua lavas, they are 

basalts.

Lavas of the Liloe Spring Volcanic Member are 

exposed in kipukas surrounded by flows of the Laupahoehoe Volcanics on the south, northwest, and north flanks of 

Mauna Kea. The most extensive exposures, covering an

area of more than 20 km2 , are on the south flank (pi. 2). 

There basaltic lavas of the Liloe Spring Volcanic Member 

are exposed from the mountain base, in the saddle between 

Mauna Kea and Mauna Loa at approximately 1,930-m 

(6,320 ft) elevation, to within about 300 m of the summit, in 

the upper reaches of Pohakuloa Gulch at approximately 

3,900-m (12,790 ft) elevation. An additional nearly 10 km2 

of exposure is on the upper north and northwest flanks (fig. 

12). Deep, steep-walled Waikahalulu and Pohakuloa 

Gulches on the south flank provide excellent exposures of 

the Liloe Spring Volcanic Member and of its relations to 

underlying and overlying stratigraphic units.

The type section of the Liloe Spring Volcanic Member 

is in a near-vertical exposure in the west wall of Waikahalulu Gulch, at approximately 3,100-m (10,170 ft) elevation 

(fig. 17). A supplementary section, exposing part of the 

Waihu Glacial Member and, overlying the Waihu, the 

uppermost part of the Liloe Spring Volcanic Member (fig. 

18), is in the west wall of Waikahalulu Gulch, approximately 800 m farther upstream, at 3,270-m (10,720 ft) 

elevation. The name is derived from Liloe Spring, about 

0.5 km west of Pohakuloa Gulch, at 2,720-m (8,921 ft) 

elevation.

PREVIOUS WORK

Stearns and Macdonald (1946) mapped the pre-Waihu 

lavas, including lavas of the Liloe Spring Volcanic Member, 

as part of their Hamakua Volcanic Series in and near the 

upper parts of Waikahalulu and Pohakuloa Gulches. They 

showed much of the Liloe Spring outcrop area of the southflank kipukas—including outcrops of the Waihu Glacial 

Member and all the slopes below—as alluvium and talus of 

Quaternary age. Macdonald's (1949) more generalized map, 

however, includes most of these kipukas in the Hamakua 

Volcanic Series. Stearns and Macdonald also included exposures of Liloe Spring basalt in the upper parts of the north 

and northwest flanks (pi. 2; fig. 12) in their Laupahoehoe 

Volcanic Series.

Porter (1979c) defined his Laupahoehoe Group to 

include all strata younger than the Pohakuloa glacial deposits. Accordingly, he (1979a) assigned most of the basaltic 

lavas exposed in south-flank kipukas to his Waikahalulu 

Formation, the volcanic facies of his Laupahoehoe Group. 

He also included most Liloe Spring basalt exposed in the 

upper parts of the north and northwest flanks of Mauna Kea 

in his Waikahalulu Formation.

Porter (1979c) designated exposures, which include 

Liloe Spring lavas, along Pohakuloa and Waikahalulu 

Gulches as reference sections for his Waikahalulu Formation and Laupahoehoe Group. In addition, he designated 

exposures of the stratigraphic interval between the Pohakuloa and Waihu glacial deposits in Pohakuloa Gulch as the 

type section for his Liloean Stage, the oldest age division
oto 

>T3

Figure 17. Type section of the Liloe Spring Volcanic Member of the 

Hamakua Volcanics in west wall of Waikahalulu Gulch at approximately 3,100-m (10,170 ft) elevation. Contacts dashed where approximately located, 

queried where uncertain. Cinder-cone deposits, formed during an early Liloe 

Spring eruption, overlie the Pohakuloa Glacial Member of the Hamakua Volcanics. Light-colored lenses on north (right) flank of cinder cone consist of 

palagonitized hyaloclastite, Cone is overlapped and buried by sequence of aa 

flows exposed in walls of gulch. Three dikes, one of which is discernible in

photograph, intrude sequence, Surface outcrop of dike, along with its enveloping scoria, forms small knob on canyon rim (top center). Lower extent of dike is queried because it is not evident through rubble on outcrop surface. Terminal 

moraine of the Waihu Glacial Member of the Hamakua Volcanics, which overlies the Liloe Spring Volcanic Member in this area, forms low ridge on skyline (upper left and center), Hawaiian Volcano Observatory photographs 

88.2.24EW135B#20, 88.2.24EW135B#22, and 88.2.24EW135B#23.
36 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Figure 18. Supplementary type section of the Liloe Spring Volcanic Member of the Hamakua Volcanics in west wall of Waikahalulu Gulch at 3,270-m (10,720 ft) elevation. Contacts dashed 

where approximately located, dotted where concealed by slumped 

block, queried where not discernible through rubble on outcrop 

surface. The Hamakua Volcanics is represented by till of its Waihu 

Glacial Member and a single overlying basalt flow of the Liloe 

Spring Volcanic Member. Poorly consolidated slope deposits, 

which overlie Liloe Spring basalt flow, are both overlain by

and intercalated with a hawaiitic flow of the Laupahoehoe Volcanics. Slope deposits include bedded ashy fluvial deposits (f) that 

contain pebbles and pebble layers, air-fall lapilli (af), and a_shy 

eolian deposits (e) that envelop colluvial boulders derived 

from nearby Laupahoehoe flow. Weakly consolidated, bouldery 

till of the Makanaka Glacial Member of the Laupahoehoe Volcanics caps sequence. Hawaiian Volcano Observatory photograph 

88.3.9EW135A#13.

within his Laupahoehoe Group (fig. 8), named for nearby 

Liloe Spring. As mapped, Porter's (1979a) Liloean Stage 

includes some basaltic lavas that we assign to our Liloe 

Spring Volcanic Member, among which is the basalt 

sequence of our type section along Waikahalulu Gulch. 

Thus, our Liloe Spring Volcanic Member corresponds in 

part to the lavas of Porter's Liloean Stage. However, significant errors in stratigraphic interpretation are reflected in 

Porter's mapping. He mapped extensive outcrops of our 

Liloe Spring basalt as Laupahoehoe lava of his Poliahuan 

and Hanaipoean Stages, both of which he interpreted as 

younger than his Liloean Stage. Furthermore, Porter's 

Liloean-, Poliahuan-, and Hanaipoean-Stage rocks all 

include hawaiitic cinder cones and flows of our Laupahoehoe Volcanics, as well as basaltic lavas of our Hamakua Volcanics. As noted above, our mapping shows that the

hawaiitic lavas (our Laupahoehoe Volcanics) are distinct 

from and younger than the basaltic lavas (our Hamakua Volcanics). We observed no interlayering of basaltic and hawaiitic lavas.

GEOLOGIC OBSERVATIONS 

LITHOLOGY

Most basalt of the Liloe Spring Volcanic Member is 

aphyric to weakly porphyritic. Plagioclase is the dominant 

phenocryst phase; its abundance normally ranges as high as 

about 2 volume percent, and it occurs as randomly oriented, 

subequant crystals, 1 to 2 mm in diameter. Scattered, small 

(generally less than 2 mm diam) olivine and clinopyroxene 

phenocrysts are common; together, olivine and clinopyrox-
STRATIGRAPHY 37

ene phenocrysts generally compose less than 1 volume percent of the rock. Scattered, small (generally less than 2 cm 

diam) gabbroic xenoliths occur locally.

A few flows and related vent deposits are slightly more 

porphyritic. In these rocks, plagioclase phenocrysts compose as much as about 5 volume percent, and olivine phenocrysts as much as about 2 volume percent. Because of 

their more porphyritic texture, these lavas are easily distinguished from the more common, less porphyritic Liloe 

Spring basalts and so are here mapped separately (pi. 2).

The relative paucity of phenocrysts and predominance 

of plagioclase among the phenocryst phases distinguishes 

Liloe Spring basalt from stratigraphically lower Hopukani 

Springs basalt. Almost all the Hopukani Springs lavas are 

much more porphyritic and, in particular, much richer in olivine phenocrysts. Except in a few aphyric or more porphyritic lavas, the scattered, small, randomly oriented, 

subequant plagioclase phenocrysts are a hallmark of the 

Liloe Spring Volcanic Member. Along with scattered olivine 

phenocrysts, they distinguish Liloe Spring lavas from stratigraphically higher Laupahoehoe lavas, which are aphyric 

or, if plagioclase phyric, contain thin, tabular plagioclase 

phenocrysts in a well-developed preferred orientation.

The groundmass of Liloe Spring basalt is normally 

dense, fine grained, and dark gray. In contrast, Laupahoehoe 

flows normally have lighter gray groundmasses that commonly are conspicuously plagioclase rich and trachytic.

LAVA-FLOW CHARACTERISTICS

The Liloe Spring Volcanic Member consists predominantly of aa flows stacked one above another in alternating 

layers of dense, massive basalt and breccia (figs. 14, 15, 

17); thin-layered pahoehoe is rare but occurs locally. 

Exposed sequences of these flows give the impression that 

the member consists of many thin flows that are commonly 

from about 0.5 to 2 m thick. Gully-wall exposures of the 

Liloe Spring Volcanic Member differ in their thin layering 

from most gully-wall exposures of thick, massive hawaiitic 

flows of the overlying Laupahoehoe Volcanics. The flow 

layering dips downslope approximately parallel to the surface of the volcano, commonly 15°-25°. Pyroclastic deposits or other sedimentary materials are rare between flows 

except near the top of the Liloe Spring Volcanic Member, 

where diamict or gravel of the Waihu Glacial Member and 

lenses of hyaloclastite tuff are present. The maximum 

exposed thickness of the Liloe Spring Volcanic Member is 

about 50 m.

Although some thin flow layers may represent individual eruptions, at least some of the layering is caused by 

alternation of scoriaceous basalt breccia (aa) and dense, 

massive basalt within a single flow (for example, the Liloe 

Spring flow shown in fig. 18) or within a group of related 

flows generated in a single prolonged eruption. A good

example of such a group is exposed in the west wall of 

Pohakuloa Gulch, at about 2,680-m (8,800 ft) elevation. 

There, a thick sequence of thin aa flows, represented by 

alternating massive and brecciated layers, extends downslope from a cinder cone. The cinder cone and the lava 

layers are all composed of the same distinctive plagioclasephyric basalt and are products of the same eruption. Downslope from the cone, thin-layered, plagioclase-phyric basalt 

composes the entire canyon-wall sequence, which is as 

much as about 30 m thick.

The Liloe Spring Volcanic Member on the northwest 

slope is only one to three flows thick. Along Kemole Gulch, 

one weakly porphyritic basalt flow overlies strongly porphyritic basalt (unmapped, resembling basalt of the Hopukani Springs Volcanic Member) and underlies two 

Laupahoehoe hawaiite-mugearite flows. About 2 km northeast of Kemole Gulch, thin Liloe Spring flows surround 

kipukas of more porphyritic Hamakua basalt; one of these 

kipukas includes a Hamakua cinder cone that was partly 

buried by a Liloe Spring basalt flow. Along Hanaipoe 

Gulch, several Liloe Spring flows, totaling about 25 m in 

thickness, are exposed above Hamakua basalt flows.

Broad flow-surface outcrops of Liloe Spring basalt 

have commonly been eroded, either by ice or running water, 

and so little original aa fabric remains; such surfaces, as 

seen in aerial photographs, are relatively smooth.

HYALOCLASTITE TUFF

The best exposures of hyaloclastite tuff are high on the 

walls of Waikahalulu Gulch. Although most tuff lenses are 

separated from the overlying Waihu Glacial Member by a 

basalt flow, locally Waihu sedimentary deposits rest directly 

on hyaloclastite. The tuff lenses are 0 to 2 m thick and consist of yellowish- to reddish-orange, palagonitic lapilli. In 

some outcrops, these lapilli are accompanied by scattered, 

coarser grained, darker scoria fragments. The lapilli are 

highly vesicular, with thin vesicle walls, so that hand-lens 

examination reveals a delicate honeycomb or foamlike texture. Thin sections show that the lapilli consist of yellowishorange isotropic glass; their yellowish-orange color presumably reflects palagonitization of normally light-brown basalt 

glass.

Additional hyaloclastite lenses are associated with 

Liloe Spring lava in exposures near Keanakakoi, in rare 

exposures along Pohakuloa Gulch, and on the north flank of 

a small cinder cone exposed at the base of the Liloe Spring 

Volcanic Member in Waikahalulu Gulch (fig. 17). Proximity 

of much of the palagonitic hyaloclastite tuff to deposits of 

Waihu drift, as well as to flows with ice-contact fabric 

(described below), suggests that the tuff records interaction 

between lava and meltwater which resulted in quenching 

and fragmentation of the lava and subsequent hydration of 

the glass.
38 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

ICE-CONTACT FABRIC

Fabrics suggestive of rapid quenching at the time of 

eruption of the Liloe Spring lavas are pervasive in the broad 

outcrop areas immediately south and east of Puu Kookoolau 

and in the upper reaches of the Pohakuloa Gulch drainage 

west and southwest of Puu Waiau. Similar fabrics are also 

found in the top two flows on the west rim of Waikahalulu 

Gulch in the locality illustrated in figure 17 and, across the 

gulch on the east wall, on the uppermost Liloe Spring flow, 

which rests on thin, unmapped Waihu till. The dominant 

feature of this fabric is mosaic jointing, a network of fractures bounding polygonal fragments and blocks with flat to 

gently curved faces that intersect in sharp, straight boundaries. Mosaic-jointed lava commonly is very fine grained or 

glassy. Oxidized, brecciated spiracles extend upward in 

places into these flows, bounding more massive, mosaicjointed zones with curving, glassy, orange to reddish-brown, 

palagonitic margins reminiscent of pillow structure. Scattered cavelike voids, from tens of centimeters to several 

meters across, also are common in these flows, particularly 

at the flow bases. Porter (1979a, c, 1987) ascribed the development of such features to emplacement of flows in contact 

with glacial ice; we agree with his interpretation. In addition, well-developed subhorizontal sheeting occurs locally 

in association with these ice-contact fabrics in Liloe Spring 

basalt flows. The ice-contact fabric was handsomely illustrated for a Laupahoehoe flow near the summit of Mauna 

Kea by Porter (1987, figs. 21.11,21.12).

VENTS

Four cinder and spatter cones are exposed in the southflank kipukas (pi. 2), all in the lower part of the south flank, 

below 3,000-m (9,840 ft) elevation. One of these cones is 

beautifully exposed in cross section in the west wall of 

Pohakuloa Gulch, at approximately 2,700-m (8,860 ft) elevation. As noted above, another cone, which is unmapped, 

is exposed within the basal part of the Liloe Spring Volcanic 

Member in the Waikahalulu Gulch exposure (fig. 17). Three 

additional cones are exposed on the upper northwest flank 

(fig- 12).

Prominent, south-facing, sharp-crested scarps of dense, 

dark-gray basalt and red agglutinated scoria, along with 

minor yellowish-orange hyaloclastite tuff, project westward 

and northeastward from beneath Puu Kookoolau (fig. 19), 

which is a hawaiitic Laupahoehoe cinder cone. Dense basalt 

of these scarps was extensively quarried by prehistoric 

Hawaiians for adzheads; thus, the northeast scarp has the 

geographic designation "Keanakakoi" (adz-making cave). 

Cruikshank (1986) provided an informative discussion of 

prehistoric human activity in this area.

Ice-contact fabric is well developed in the scarps, as 

well as in the flows that extend southward from them. Porter

(1979a, c, 1987) also recognized the ice-contact fabric of 

these scarps and interpreted them as the terminus of a subglacial flow from Puu Waiau. However, the flow from Puu 

Waiau (flow PW, pi. 2) is a Laupahoehoe hawaiite, lithologically and compositionally distinct from the basalt that composes the scarps. The flow from Puu Waiau overlies basalt 

of the scarps and locally terminates immediately uphill from 

the scarps (pi. 2), a relation suggesting that the scarp crests 

were actually ridge crests against which the flow from Puu 

Waiau ponded. The occurrence of agglutinated scoria and 

the linearity of the scarp crests suggest that these crests 

mark the trace of a fissure-vent system which supplied some 

of the Liloe Spring basalt flows to the south. The ice-contact 

fabric and occurrence of hyaloclastite tuff imply that the fissure ridge formed in a subglacial setting, and the stratigraphy indicates that this eruption occurred during the Waihu 

glacial episode. Later, Makanaka ice vigorously eroded both 

the scarps and the superjacent flow from Puu Waiau.

Three topographic prominences in the upper part of 

Pohakuloa Gulch contain deposits of cinders or agglutinated 

scoria, as well as mosaic-jointed and strongly sheeted 

basalt. The assemblage of fabrics resembles that of the 

Keanakakoi scarp, and we interpret them as indicative of 

additional vents (pi. 2) formed beneath Waihu ice. Like the 

Keanakakoi scarp, they underwent significant later erosion 

during the Makanaka glacial episode.

DIKES

Dikes of aphyric or weakly porphyritic basalt, interpreted as local feeders for Liloe Spring lavas, are exposed at 

several localities along Pohakuloa and Waikahalulu Gulches 

(pi. 2). Most of these dikes range in thickness from about 

0.3 to 2 m and are generally similar in texture to the dense, 

massive parts of the flows; they probably chilled fairly rapidly against the shallow country rocks.

An unusually wide (8 m) dike occurs in Pohakuloa 

Gulch at approximately 3,750-m (12,300 ft) elevation. It 

apparently crystallized more slowly than most. Except for 

10-cm-wide, fine-grained, chilled margins, the dike consists 

of megascopically crystalline, aphyric, diktytaxitic basalt. 

Vesicles are confined to a 20-cm-wide zone just inside the 

chilled margin and to scattered, vertical vesicle pipes, about 

10 cm in diameter; otherwise, the dike is massive.

One dike, exposed where Waikahalulu Gulch transects 

segments of the Keanakakoi scarp (pi. 2), is compositionally and mineralogically zoned. Porphyritic basalt at the 

center, containing plagioclase and olivine phenocrysts, 

grades to aphyric basalt at the margins. The dike, about 30 

cm wide, cuts scoria and hyaloclastite tuff at the base of a 

Liloe Spring basalt flow. At this same locality, the Liloe 

Spring Volcanic Member overlies porphyritic pahoehoe 

flows of the Hopukani Springs Volcanic Member. Although 

this dike is somewhat off the trend of the nearby Keanaka-
STRATIGRAPHY 39

Puu Poliahu

Figure 19. South-summit region of Mauna Kea. Prominent 

scarps (arrows, center), which consist of basalt of the Liloe Spring 

Volcanic Member of the Hamakua Volcanics, are interpreted as 

remnants of possible subglacial fissure ridge. Scarps extend westward (to left) and northeastward (to right) from beneath Puu Kookoolau, cinder cone of older volcanic rocks member of the Laupahoehoe Volcanics. Note pit crater (pc) in front of Puu Kookoolau. 

Field relations among cones and flows in foreground determine 

probable stratigraphic sequence of flows of younger volcanic rocks 

member of the Laupahoehoe Volcanics (see subsection of text 

entitled "Younger Volcanic Rocks Member"; see pi. 2). Sharprimmed cinder cone that has large bowl-shaped crater (bottom center) is Puu Keonehehee, cinder cone of younger volcanic rocks 

member of the Laupahoehoe Volcanics. Ledges inside north crater 

wall are outcrops of broad, dark lava flow A exposed uphill from 

Puu Keonehehee. Low knob filling crater bottom is hawaiitic lava 

extruded after explosive enlargement of crater. Flow A and cones 

A (source of flow A), D, and E are mapped as older volcanic rocks 

member of the Laupahoehoe Volcanics; flow B and cones 

B (source of flow B) and C are mapped as younger volcanic rocks 

member of the Laupahoehoe Volcanics (see pi. 2). View 

northwestward; Hawaiian Volcano Observatory photograph 

88.7.11EW135A#21.

koi scarp segments, its proximity to the scarps supports our 

interpretation that the scarp crests record the trace of a Liloe 

Spring vent.

Three closely spaced dikes cut the Liloe Spring 

sequence exposed in the deeply incised part of Waikahalulu 

Gulch (because of limited space, only two dikes are shown 

on pi. 2). One of these dikes penetrates the capping flow of 

the canyon-wall sequence and forms a low knob on the west 

canyon rim (fig. 17). An envelope of red agglutinated scoria

between the uppermost part of this dike and the enclosing 

flows that it intruded records vesiculation and fragmentation as the dike neared the ground surface. Even though this 

dike apparently reached the ground surface, we recognize 

no associated lava flow that it fed.

The positions and strikes of five mapped dikes and the 

segments of the inferred fissure ridge (pi. 2) define a narrow, 3-km-long arc between 3,730- and 3,790-m (12,240 

and 12,440 ft) elevation. The angular width of this arc is
40 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

about 120°; its radius is about 1.5 to 2 km, and its center of 

curvature is approximately 1 to 1.5 km southwest of the 

summit of Mauna Kea in the vicinity of Puu Waiau. 

Exposed tops of these dikes are now at a level that was no 

more than a few meters below the mountain surface when 

the dikes were emplaced; we presume that they were feeders for some Liloe Spring flows. These dikes and the fissure 

ridge were apparently emplaced along a set of circumferential fractures—possibly related to buried, preexisting 

caldera-bounding faults or to a shallow, contemporaneous 

magma reservoir that fed ring dikes.

INFERRED NEAR-SUMMIT VENTS

Liloe Spring basalt flows are exposed uphill from the 

topographically highest vents and dikes in the Pohakuloa 

Gulch drainage, and no exposed vents are related to the 

topographically highest Liloe Spring flows on the north 

flank of Mauna Kea. Therefore, we infer that near-summit 

vents, now buried by the overlying Laupahoehoe Volcanics, 

supplied a significant volume of the Liloe Spring flows.

AGE

The age of the Liloe Spring Volcanic Member is not 

well determined by K-Ar dating (fig. 11); 10 new K-Ar ages 

range from about 85 to 218 ka. All but the oldest determination, which is stratigraphically inconsistent, suggest an age 

of approximately 100 to 150 ka, and a K-Ar age (sample 

QLA-3c, table 5) previously reported by Porter (1979c) 

indicates that the upper part may be as young as 70 ka. Dorn 

and others (1991) reported an exposure age of approximately 60 to 70 ka for the Waihu Glacial Member, which is 

overlain by the youngest lava flows of the Liloe Spring Volcanic Member.

WAIHU GLACIAL MEMBER

DEFINITION AND OCCURRENCE

The Waihu Glacial Member is a lens of till and gravel 

enclosed, at least in part, by the upper part of the Liloe 

Spring Volcanic Member (fig. 9). Because overlying flows 

of the Liloe Spring Volcanic Member are discontinuous, 

most Waihu outcrops occur as kipukas (pi. 2; fig. 20) surrounded by either Liloe Spring basalt or the still-younger 

Laupahoehoe Volcanics. Wentworth and Powers (1941) designated as the type locality conspicuous outcrops of the 

Waihu Glacial Member west of Pohakuloa Gulch near 

Waihu Spring, at about 2,960-m (9,700 ft) elevation.

Discontinuous outcrops of Waihu drift form an arcuate 

pattern across the upper south flank of the volcano (pi. 2; 

fig. 20). This arc is approximately concentric to the summit 

of Mauna Kea; its lower topographic limit is at about 2,740-

m (9,000 ft) elevation. The exposure is limited eastward and 

westward by large flows of the Laupahoehoe Volcanics. 

Additional, thin (0-3 m thick), discontinuous, unmapped 

exposures of the Waihu Glacial Member occur locally 

between lava flows of the upper part of the Liloe Spring 

Volcanic Member in the steep canyon walls of Waikahalulu 

Gulch and along Hanaipoe Gulch, on the north flank of 

Mauna Kea. In addition, outwash deposits are locally 

exposed in a small gulch west of Pohakuloa Gulch.

PREVIOUS WORK

Wentworth and Powers (1941) interpreted the belt of 

south-flank outcrops as representing two separate glacialdrift deposits: the Pohakuloa Drift, which they considered to 

be older, and the Waihu Drift, which they considered to be 

younger. They showed the distribution of these units in a 

schematic map that is difficult to relate precisely to the geology as now mapped.

Stearns (1945) recognized that the Pohakuloa and 

Waihu Drifts of Wentworth and Powers (1941), where 

exposed on the interfluves and in the shallow drainages 

between Pohakuloa and Waikahalulu Gulches, belong to a 

single unit. He clarified their map distribution and assigned 

all of these outcrops to the Waihu. However, he disputed the 

interpretation of Wentworth and Powers that these sedimentary rocks were deposited as glacial drift. Instead, he interpreted the Waihu as fanglomerate that could have been 

deposited by floods resulting from eruptions which melted 

an icecap during early Wisconsin time.

Porter (1979c), in his thorough study of Mauna Kea 

glacial deposits, conclusively showed that this south-flank 

belt of Waihu sedimentary rocks represents a lobate end 

moraine, modified by erosion and partly buried by younger 

lava. He assigned the end-moraine deposits, as well as sedimentary deposits farther downhill that he interpreted as outwash, to his Waihu Formation.

GEOLOGIC OBSERVATIONS

Numerous gulch-wall exposures show that the Waihu 

Glacial Member consists predominantly of massive to 

crudely layered till (fig. 21) in which subangular to subrounded cobbles and boulders of Liloe Spring basalt are 

enclosed in a moderately indurated, gray through yellowishbrown to reddish-brown, unsorted matrix. Locally, on the 

west rim of Waikahalulu Gulch, this matrix contains abundant hyaloclastite fragments, which impart a yellow color to 

the lower part of the deposit. The boulders range in size to 

as large as about 2 m across. The maximum thickness of the 

unit is about 30 m.

More distinctly sorted and layered gravel occurs 

locally, particularly near the downslope end of the southflank outcrop belt. One especially conspicuous exposure of
STRATIGRAPHY 41

Figure 20. Part of south flank of Mauna Kea, showing approximate extent of end moraine of the Makanaka Glacial Member (m) of the 

Laupahoehoe Volcanics and conspicuous exposures of end moraine of the Waihu Glacial Member (w) of the Hamakua Volcanics. Contacts 

dashed where approximately located. Aqueduct gulch is an informally named feature. Hawaiian Volcano Observatory photograph 

88.7.11EW120A#4.

the gravel facies is on the west rim of Pohakuloa Gulch, at 

approximately 2,740- to 2,800-m (9,000 to 9,200 ft) elevation. There, the gravel, which is not mapped separately from 

the till, buries a cinder cone of the Liloe Spring Volcanic 

Member exposed in the west wall of the gulch (pi. 2). 

Coarse, bedded, indurated gravel interpreted as Waihu outwash is also exposed in a small gulch about 0.7 km northwest of Pohakuloa Gulch (see fig. 33).

Boulders and cobbles are concentrated as a lag deposit 

in surface exposures, where they form a rough pavement. 

The boulder surfaces are dark gray to brown or, locally, reddish brown. Spalled boulders are common. The dark, spalled boulder surfaces contrast markedly with the fresher, 

light-gray to yellowish-brown boulder surfaces on 

Makanaka glacial deposits.

In surface exposures, Waihu moraine segments form 

low, smooth, gently convex hills—like the bowls of inverted 

spoons—that are elongate downslope (fig. 20). They are 

easily recognized on aerial photographs because of their 

gentle convexity and smoothness and because they are virtually devoid of the scrub trees that grow on parts of the 

nearby lava flows and slope deposits. Porter (1979c) concluded that these segments represent lateral moraines

formed at the margins of small ice lobes and that younger 

lava flows commonly had buried the terminal loops.

Our map pattern (pi. 2) for Waihu morainal deposits is 

generally similar to that shown by Porter (1979a) but differs 

greatly in detail. In particular, he showed a significant part 

of each of the spoonlike morainal hills as composed of outwash. Except for local gravel, such as that described above 

on the west rim on Pohakuloa Gulch, we find that the hills 

composed of Waihu drift are monotonously uniform, and 

we are unable to identify and map Porter's separate till and 

outwash facies on these surfaces. Furthermore, the long 

streams of Waihu outwash that Porter showed extending 

far downslope include various younger air-fall and sedimentary slope deposits (see subsection below entitled 

"Slope Deposits").

The map pattern also differs because Porter (1979a) 

purposely mapped only the morainal deposits that he interpreted as end moraines. However, we have included areas of 

more or less continuous ground moraine, such as the elongate outcrop of Waihu drift just west of Waikahalulu Gulch, 

above 3,140-m (10,300 ft) elevation (pi. 2; fig. 20). A postWaihu flow of Liloe Spring basalt apparently buried this 

ground moraine near Waikahalulu Gulch. Thin (1-3 m
42 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Figure 21. Consolidated diamict (till) of the Waihu Glacial 

Member of the Hamakua Volcanics exposed in northwest wall of 

unnamed gulch about 3.3 km northwest of Pohakuloa Gulch, at 

about 3,020-m (9,900 ft) elevation. Diamict fabric, largely 

expressed by orientation of long axes of boulders, dips downslope 

(to left), parallel to volcano surface and to contact between the 

Waihu Glacial Member and overlying flows (outside of photograph) of the Liloe Spring Volcanic Member of the Hamakua Volcanics. Pole is 1.5 m long and approximately vertical. Hawaiian 

Volcano Observatory photograph 88.3.2EW135A#29.

thick) unmapped diamict occurs below the uppermost Liloe 

Spring basalt flow in the west wall of Waikahalulu Gulch 

(fig. 18), just east of the mapped ground moraine. Locally, 

the underlying basalt surface is abraded and striated. Similar 

thin diamict, overlain and baked by the uppermost Liloe 

Spring flow, is exposed farther downstream in the east wall, 

where the gulch is deeply incised.

Like Makanaka drift, which is younger, Waihu drift 

formed an annulus surrounding glacially eroded rocks 

nearer the volcano summit. Thus, uphill from the mapped 

Waihu drift deposits, between them and the Makanaka 

moraine, we have mapped kipukas of glacially eroded Liloe

Spring basalt that was scoured by the Waihu icecap. Downslope from the outcrops of Waihu drift, we are unable to distinguish post-Waihu Liloe Spring basalt from older Liloe 

Spring flows. The virtual absence in Waihu drift of boulders 

derived from the distinctive porphyritic basalt of the Hopukani Springs Volcanic Member indicates that the summit of 

Mauna Kea was extensively capped by Liloe Spring basalt 

at the time of the Waihu glacial episode.

AGE

The age of the Waihu Glacial Member is not well constrained by K-Ar dating, but it must be in the range 100-150 

ka, possibly as young as 70 ka (fig. 11). This age corresponds to some part of marine oxygen-isotope stages 4 

through 6 (fig. 10). Dorn and others (1991) report varnish 

cation-ratio exposure ages of approximately 65 ka for striated Liloe Spring basalt eroded by Waihu ice and for a 

basalt boulder in Waihu drift. This boulder also gave a 36C1 

exposure age of approximately 68 ka. Both the boulder and 

the striated lava-flow surface are from exposures 200 to 300 

m west of Waikahalulu Gulch. These results suggest that the 

Waihu glacial episode corresponds approximately to marine 

oxygen-isotope stage 4.

LAUPAHOEHOE VOLCANICS

GENERAL STATEMENT

The Laupahoehoe Volcanics form the magmatically 

evolved cap of Mauna Kea Volcano; the lavas consist exclusively of hawaiite, mugearite, and benmoreite that overlie 

the basaltic Hamakua Volcanics. We estimate the volume of 

Laupahoehoe flows and pyroclastic deposits at approximately 25 km3 . About 90 percent of the lavas is hawaiite 

and mugearite, and 10 percent is benmoreite. As noted 

above in the subsection entitled "Major Rock Classes and 

Petrographic Groups," we refer to the range of Laupahoehoe compositions collectively as hawaiitic. Furthermore, we 

refer to the hawaiite and mugearite lavas collectively as 

hawaiite-mugearite. We divide the unit into three members: 

older volcanic rocks (lavas and pyroclastic deposits of late 

Pleistocene age), younger volcanic rocks (postglacial lavas 

and pyroclastic deposits of latest Pleistocene? and Holocene 

age), and the Makanaka Glacial Member (till and outwash 

of late Pleistocene age). In addition, we have also mapped 

(pi. 2) air-fall deposits (ash and lapilli of late Pleistocene 

and Holocene age) within the Laupahoehoe Volcanics.

Macdonald (1945) and Stearns and Macdonald (1946) 

applied the term "Laupahoehoe Volcanic Series" to the 

younger volcanic rocks of Mauna Kea. They designated 

Laupahoehoe Point as the type locality. There, a hawaiitemugearite flow, occupying a canyon eroded in basaltic
STRATIGRAPHY 43

rocks of the Hamakua Volcanics, had built a lava delta at the 

coast.

As reviewed above in the subsection entitled "Stratigraphic Overview," definition of the Laupahoehoe Volcanic 

Series was vague. Stearns and Macdonald (1946) believed 

that there was a gradation between the predominantly basaltic lavas of the Hamakua Volcanic Series and the predominantly andesitic (hawaiitic in our terminology) lavas of the 

Laupahoehoe Volcanic Series. Thus, they indicated that 

each series contained both basaltic and andesitic rocks.

In their mapping, Stearns and Macdonald (1946: see 

Macdonald, 1949) included most south-flank exposures of 

our Liloe Spring Volcanic Member in their Hamakua Volcanic Series. In remapping this area, Porter (1979a) included 

the basalts of our Liloe Spring Volcanic Member and the 

intercalated tongue of Waihu drift in his Laupahoehoe 

Group.

Our mapping shows that hawaiitic flows and pyroclastic deposits overlie basaltic lavas of the Hamakua Volcanics. 

No interleaving or gradation occurs between the older 

basaltic lavas and the younger hawaiitic lavas. Therefore, 

we redefine the Laupahoehoe Volcanics to correspond to the 

cap of hawaiitic lavas, including the intercalated Makanaka 

Glacial Member; all the underlying basaltic lavas, as well as 

the Waihu Glacial Member, are excluded (figs. 5, 7; table 3). 

Exposures along the road from Humuula Saddle to the summit of Mauna Kea constitute a useful and readily accessible 

reference locality for the Laupahoehoe Volcanics.

Laupahoehoe volcanism continued throughout the 

period of growth and disappearance of the Makanaka icecap 

and into Holocene time. The presence of Makanaka glacial 

deposits and the glacially and periglacially enhanced erosion and weathering of the volcano surface during latest 

Pleistocene time provide a means for us to distinguish the 

postglacial Laupahoehoe lavas. Because the style of volcanism, as well as the composition and lithology of Laupahoehoe lavas, was constant from Pleistocene to Holocene time, 

we describe the general characteristics of the older and 

younger volcanic rocks members together and, thereafter, 

discuss the characteristics and relations that pertain to each 

member individually.

gray and commonly displays a megascopic trachytic texture, as well as platy jointing. Euhedral, reddish-brown 

biotite crystals are common on vug walls. Two of the flows 

contain scattered to common gabbroic and ultramafic xenoliths. Because none of these characteristics is sufficient to 

distinguish the benmoreite from flows of hawaiitemugearite, we base the distinction on chemical analyses.

The benmoreite flows are mostly extensive. The flow 

from Kaluamakani is 20 km long, and that from Puu Pueo 

extended 20 km to the present coastline. The flows are of 

aa, with remnants of branching and rejoining channels preserved on their surfaces. These channels are bounded by 

prominent levees, spaced 400 to 500 m apart, and contain 

conspicuous transverse pressure ridges. The ridges have a 

local relief of 5 to 10 m and commonly are bowed, ogivelike, so as to be convex downslope as seen in plan view. 

Average flow thicknesses range from about 20 to 25 m. 

Each of the two larger flows has a volume of about 0.8 km3 .

HAWAIITE-MUGEARITE 

LITHOLOGY

Hawaiite-mugearite is dark gray to light gray and most 

commonly aphyric. In hand specimen, the trachytic texture 

of the groundmass gives the rock a sheen that is not seen in 

the basalts. Some flows (possibly 20 percent) contain plagioclase microphenocrysts (less than 1 mm diam), and a 

very few flows contain plagioclase phenocrysts (1-3 mm 

diam). The microphenocrysts and phenocrysts normally 

have the same crystallographic orientation as plagioclase of 

the trachytic groundmass, and so they participate in the trachytic sheen. These phenocrysts and microphenocrysts form 

conspicuous reflecting plates in the plane of trachytic layering, but because the plates are thin, these crystals are indistinct in hand-specimen surfaces oblique to the trachytic 

layering. In contrast, the subequant plagioclase phenocrysts 

common in basalt of the Liloe Spring Volcanic Member are 

randomly oriented and equally conspicuous on all fresh 

rock surfaces. Gabbroic and ultramafic xenoliths and xenocrysts are common in about 20 to 30 percent of the flows 

and cinder cones.

BENMOREITE FLOWS AND CINDER CONES

All the benmoreite occurs in the northwest sector of 

the volcano (fig. 22). The vent cinder cones (Kaluamakani 

and Puu Pueo) for two of the flows are exposed, but the 

vents and proximal ends of the other flows have been buried 

by younger hawaiite-mugearite flows. Interestingly, the 

benmoreite flows are among the oldest of the Laupahoehoe 

lavas; however, the flows from Kaluamakani and Puu Pueo 

overlie earlier hawaiite-mugearite flows.

Except for one flow containing abundant plagioclase 

microphenocrysts, the benmoreite is aphyric. It is all light

LAVA FLOWS

Exposed surfaces of the hawaiite-mugearite flows consist mostly of clinkery to blocky aa. These flows are commonly about 5 to 10 m thick; aa as thick as 25 m or more 

occurs locally. Pahoehoe occurs locally, particularly in the 

proximal areas of some flows, where branching pahoehoe 

lava-tube structures are evident. Such pahoehoe is thick and 

relatively massive and dense, unlike the thinner layered, 

vesicular, basaltic pahoehoe of the Hamakua Volcanics or of 

the active tholeiitic shield volcanoes, Mauna Loa and
155°45' 155°30' 155°15'

EXPLANATION

v-.'.-.'i.vj Ash dunes and alluvial deposits 

Laupahoehoe Volcanics

Younger volcanic rocks member 

Hawaiite-mugearite How 

Cinder cone

Makanaka Glacial Member 

Older volcanic rocks member 

Hawaiite-mugearite flow Benmoreite flow 

Cinder cone _ 

Hamakua Volcanincs

PACIFIC OCEAN

Laupahoehoe 

Point PACIFIC 

OCEAN

Lava flows and cinder cones 

undivided

Figure 22. Geologic map of Mauna Kea, showing generalized distribution of flows, cinder cones, and glacial deposits of the Laupahoehoe Volcanics. Queries mark limits of 

mapping at edge of dense rain forest. Internal contacts distinguish individual lava flows and cinder cones. Contour showing 4,000-m (13,120 ft) elevation is omitted for simplicity. 

Geology simplified from plate 2 and Wolfe and Morris (1996).

mDR

n
STRATIGRAPHY 45

Figure 23. Cinder cones and lava flows of older volcanic rocks 

member of the Laupahoehoe Volcanics on upper west flank of 

Mauna Kea. Flows that display conspicuous ridge-and-trough fabric emanate from lower flanks or bases of cones; some flows 

breached their source cones. Seven small, aligned cones (arrows) 

of cinder or spatter that vented lithologically similar lavas probably formed during one fissure eruption. Short-dashed line, inferred

trace of fissure; long-dashed line, crest of prominent ridge formed 

by several larger, similarly aligned cones. Lava from these larger 

cones flowed both northwestward and southwestward, down 

flanks of ridge. Late-stage explosive activity deposited excavated 

basalt blocks on rim of large breached cone at upper left. View 

southeastward; Hawaiian Volcano Observatory photograph 

88.7.11EW135A#5.

Kilauea. Broad, subhorizontal pahoehoe surfaces, interspersed with aa, occur in the Pohakuloa Training Area on 

the gently sloping Laupahoehoe flow (flow PTA, pi. 2) that 

extends northwestward parallel to the sharp base of Mauna 

Kea's south flank.

Gully walls commonly expose thick, dense, massive 

flow interiors overlying and capped by aa rubble. In some 

outcrops, the massive facies and the aa breccia facies are 

complexly interlayered within single flows. Locally, flows 

rest on deposits of air-fall lapilli.

The longest flows extend 15 to 25 km from their 

sources, but their thicknesses increase only moderately from 

their proximal to their distal ends; the flow from Puu Hinai, 

for example, is approximately 7 m thick near its source and 

12 m thick at its terminus. Flow widths range from about 

0.5 to 7 km, but elongate lobes as narrow as 50 m extend 

hundreds of meters down steep slopes from some flows. 

Volumes of individual flows range from very small (much

less than 1 million m3) to very large; for example, the volume of the flow from Puu Keekee is approximately 0.4 km3 .

The surfaces of flows that descended slopes steeper 

than about 5° are typically marked by networks of subparallel, discontinuous, linear to gently curving, locally anastomosing, longitudinal ridges. In aerial photographs (figs. 23, 

24), these flow surfaces appear corrugated to braided. The 

ridges and the intervening troughs are generally hundreds of 

meters to several kilometers long, with a crossflow spacing 

of about 30 to 200 m. The ridges are as much as about 15m 

high, although most are appreciably lower. Troughs on the 

older flows are partly filled by air-fall and eolian deposits 

and, particularly on the upper slopes, by colluvium.

Some of the ridges branch; some truncate earlierformed neighbors. The trends of the ridge segments parallel 

the flow directions, and, at some flow boundaries, the ridgeand-trough networks display crosscutting contacts from 

which interflow age relations can be interpreted (fig. 24).
46 GEOLOGY AND PETROLOGY, MA UNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Figure 24. Puu Lehu (Holocene), showing nearby lava flows and 

cinder cones of the Laupahoehoe Volcanics on upper northeast 

flank of Mauna Kea. North is to right; illumination is from eastsoutheast. Cones and craters of Puu Lehu (pic) are aligned northeastward; asterisks mark secondary vents on flow-field surface 

north and northeast of Puu Lehu. Edge of dark, fresh flow from 

Puu Lehu (plf), which is virtually devoid of ash or colluvium, 

crosscuts partly debris-filled ridge-and-trough fabrics of older

flows to south and west. Dark annulus adjacent to south and west 

flanks of Puu Lehu is deposit of air-fall cinders and bombs. 

Sharply defined, prominent ridges that bound narrow channel 

northwest of Kaula Gulch represent coherent cores of aa flow 

levees that have been stripped of loose rubble by torrential meltwater. Part of U.S. Department of Agriculture, Agricultural Stabilization and Conservation Service aerial photograph EKL-14CC-126, 

taken March 7, 1965.

Some of the ridges are levees that bounded lava-channel segments; others are narrow, steep-sided flow lobes, 

some of which have narrow channels along their axes. 

Foshag and Gonzalez R. (1956) observed the development 

of similar channel-and-levee morphology on parts of the 

complex flow field that was emplaced during the first 2Vi 

years of the Paricutin eruption. They described (p. 467) a 

narrow (6 m wide) lava stream approximately paralleled by 

"irregular low ridges of clinkers, apparently old levees 

formed on preceding days when the lava had flowed by a 

somewhat different course." They also illustrated (Foshag 

and Gonzalez R., 1956, pi. 50) narrow, steep-sided, elongate 

flow lobes composed of aa levees bounding a central channel and a complex network of such flow lobes, with conspicuous channel-and-levee segments, that developed over a 

period of several months.

By analogy with the Paricutin eruption, we suppose 

that typical Laupahoehoe flows were emplaced during eruptions that lasted for months or years. The corrugated or 

braided Laupahoehoe flow surfaces are largely composites 

of narrow, elongate, steep-sided flow lobes, most of which 

were created by relatively short-lived lava channels encased 

in their own levees. The discontinuity of channel segments 

suggests that the surface channels originated not only at the 

eruptive vent but also on the flow-field surface, as channeled lava broke through the confining levee walls or as 

lava from the molten flow interior (represented by the dense 

outcrops seen in stream exposures) leaked through the capping aa rubble.

On lower slopes, particularly in the terminal parts of 

flows, Laupahoehoe aa tended to advance more nearly as 

broad sheets, as in the zone of dispersed flow recognized by
STRATIGRAPHY 47

Lipman and Banks (1987) near the toes of Mauna Loa aa 

lobes. In these areas, channels tend to be broader, with 

levees less well defined than on the steeper slopes or even 

absent; and hummocks and ogivelike transverse pressure 

ridges abound. These features record buckling of the lavaflow carapace in response to compressive forces from the 

downslope movement of the more fluid flow interior.

VENT DEPOSITS

Most of the hawaiite-mugearite flows were erupted 

from single, point-source vents. In most places, pyroclastic 

deposits accumulating at such a vent built a large cinder 

cone. Wentworth (1938) included all of these cinder cones 

in the "central cone phase" of his Waiau Formation. Flows 

commonly issued from the bases or lower flanks of the 

associated cinder cones (fig. 23) or from tube-fed vents that 

built small shields or small, steep lava domes in the proximal part of the flow field (fig. 24). Some flows carried away 

part of the cone, leaving a crescentic remnant. Observations 

at Paricutin (Foshag and Gonzalez R., 1956), where the 

main cone closely resembles many Laupahoehoe cones, 

show that continued pyroclastic activity may repeatedly 

"heal" the flanks of a cone that has failed or been breached 

by a lava flow. Local shifts of the vent during the course of 

some Mauna Kea eruptions built overlapping cones and 

complex flow fields (fig. 24). Porter (1972b) fully described 

the morphology and size frequency of the cinder cones. His 

observations are summarized as follows. The cones consist 

of ejecta of strombolian-type eruptions, cinders 1 to 10 cm 

in diameter, and ubiquitous spindle bombs that mostly are as 

much as about 0.5 m long but may be as much as 3 m long. 

Cone diameters range from less than 100 m at the base to as 

much as 1,250 m. Their maximum height is about 200 m. 

Most cones, however, are 200 to 600 m in basal diameter 

and 30 to 100 m high, with a nearly constant height/width 

ratio of 0.18. Many cones have craters; the ratio of craterrim diameter to basal cone diameter is generally about 0.4. 

Craters are commonly from a third to a half filled by colluvium and air-fall tephra. Maximum slopes on most cones 

are 25°-27°. Steep slopes occur where cones are capped by 

consolidated spatter or where the flanks have been steepened by eroding glacial ice. Most cones are asymmetric, 

probably because of accumulation of ejecta during persistent winds.

Paricutin Volcano provides a useful modern example 

of the growth of a cinder cone similar to those of the Laupahoehoe Volcanics. The main cone at Paricutin grew quickly 

from a rapid accumulation of bombs, ash, and lapilli ejected 

by closely spaced explosions that generated a varying, pyroclast-laden eruption column which was sometimes as much 

as 5 or 6 km high (Foshag and Gonzalez, R., 1956).

Some Laupahoehoe vents produced little or no pyroclastic ejecta; eruption at such a vent produced a flow with a

low lava dome at its source. One good example is the flow 

of the younger volcanic rocks member that issued approximately 1 km southeast of Hale Pohaku (pi. 2).

A few fissure vents with low spatter ramparts, as much 

as about 10 m high, have been found. In addition, local 

occurrences of aligned cones of cinders or spatter (figs. 23, 

24) at the sources of lithologically similar flows may record 

fissure eruptions.

Late, explosive eruptive activity at several Laupahoehoe cinder cones excavated blocks of older, subsurface lava 

flows, depositing the blocks on the crater rims, cone flanks, 

and beyond. These explosive eruptions also deposited local 

blankets of air-fall tephra and probably enlarged the cindercone craters. Good examples are Puu Kookoolau, Puu 

Keonehehee, Puu Kanakaleonui, and a broad unnamed cinder cone that crests at 3,900-m (12,800 ft) elevation, 3.4 km 

northwest of the summit of Mauna Kea (pi. 2; fig. 23).

Glacial erratics, as well as ejecta blocks, occur on both 

Puu Kookoolau and the unnamed cinder cone mentioned 

above. In both places, however, the ejecta includes porphyritic basalt that is absent in the nearby glacial deposits and 

can have originated only from eruptive excavation of the 

substrate. The rim and flanks of Puu Keonehehee are littered by light-gray ejecta blocks of hawaiite-mugearite; a 

quarried hawaiite-mugearite flow is exposed in steep outcrops in the lower part of the crater wall (fig. 19).

The most extraordinary example of quarrying by 

explosive eruption and the most extensive ejecta blanket 

clearly related to such an explosive eruption are at Puu 

Kanakaleonui (fig. 25). Black air-fall tephra mantles part of 

the cinder cone and extends as a thick, continuous blanket 

for approximately 0.5 to 1 km beyond the buried base of the 

cone (pi. 2). Only part of the flow that exited through the 

breached crater rim is mantled, an observation suggesting 

that the explosive phase of the eruption occurred after part 

of this flow had been extruded. The air-fall-tephra blanket is 

littered by basalt blocks that are mostly 10 to 50 cm in 

diameter but that may be as much as 3 m long. The eruption 

quarried a large variety of porphyritic basalt types from 

flows of the Hamakua Volcanics; some of these rock types 

are unknown in surface exposures anywhere else on the volcano. The nearest outcrops of Hamakua basalt are 9 km 

away, downslope to the northeast.

Distribution of Cinder Cones

Laupahoehoe cinder cones are scattered over the upper 

flanks of Mauna Kea and in the western part of Humuula 

Saddle (fig. 22). All but four cones, low on the west flank, 

are above 1,400-m (4,920 ft) elevation and within 20 km of 

the summit. Thus, the upper flanks of the volcano are peppered with Laupahoehoe cones, whereas the lower flanks 

are essentially devoid of them.

A weak preferred concentration of Laupahoehoe cinder 

cones in sectors west, northeast, and south to southeast of
48 GEOLOGY AND PETROLOGY, MA UNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Figure 25. Blanket of dark air-fall tephra partly surrounding and mantling Puu Kanakaleonui (foreground). Maximum width of crater is 

approximately 700 m, and air-fall blanket is about 3.5 km wide. Bright surface in lower part of photograph is unmantled lava flow from 

Puu Kanakaleonui. View southwestward, toward summit of Mauna Kea (top center); Hawaiian Volcano Observatory photograph 

88.7.11EW120B#10.

the volcano summit is shown in figure 22. Macdonald 

(1945) and Porter (1972b) previously pointed out these 

zones of more closely spaced cinder cones and referred 

to them as having erupted along rift zones radial to the 

summit.

The best defined of the three areas of more closely 

spaced vents is the western cluster, which extends about 11 

km westward of the summit and has a maximum width, 

north-south, of 2.5 km. Eruptions in this zone built a prominent west-trending ridge; Laupahoehoe flows extend northwestward and southwestward down its flanks from the vents 

on the ridge crest (pi. 2). Some cone alignments along the 

ridge crest (fig. 23) may reflect fissure eruptions and 

strongly enhance the sense of linearity and east-west elongation of the cone cluster. Furthermore, a topographic bulge 

in this sector of the volcano extends westward of the Laupahoehoe lavas that cap and flank this western ridge. Cinder 

cones and lava flows of Hamakua basalt form this more 

westerly bulge, a relation suggesting that this sector of the 

volcano was a preferred locus of Hamakua as well as 

Laupahoehoe eruptions.

The northeastern cluster extends about 9 to 12 km from 

the summit, depending on which cones are selected for 

inclusion in it. Its width, from Puu Lehu to Puu Kanakaleonui, is about 5 km; thus, the zone is not strikingly elongate. 

However, a concentration of about a dozen cinder cones in a 

6-km-long by 1-km-wide zone extending northeastward 

through Puu Makanaka and Red Hill (pi. 2) gives a sense of 

elongation and alignment radial to the summit. Predominance of the same alignment through the overlapping cinder 

cones of Puu Lehu (fig. 24) suggests that the Puu Lehu 

eruption occurred along a short radial fissure.
STRATIGRAPHY 49

The cluster of more closely spaced cinder cones south 

to southeast of the summit is broad, and its boundaries are 

indistinct, with no suggestion of radial elongation. Local 

alignments of cinder cones radial to the summit of the volcano summit are identifiable within this cluster, but they are 

insufficient to indicate the existence of a convincing preferred radial fabric. Furthermore, several Holocene cinder 

cones in this sector of the volcano, from Kalaieha through 

Puu Kole, are aligned north-northeast, oblique to any radial 

structure. The lava flows related to these aligned cones are 

all chemically identical.

The distribution of Laupahoehoe cinder cones scarcely 

resembles the well-defined vent alignments of other Hawaiian volcanoes, such as Kilauea, with active rift zones. Furthermore, no preferred concentration or alignment of 

Laupahoehoe cinder cones is evident on the east flank, 

where we would most expect it, coincident with the landward extension of Hilo Ridge (fig. 1). Thus, we conclude 

that Laupahoehoe cinder-cone distribution is not significantly controlled by preexisting rift-zone structure but 

records only varying radial-stress anisotropies, possibly 

related to gravitationally induced deformation of the 

volcano.

Macdonald (1945) and Porter (1972b) recognized arcuate alignments of Mauna Kea cinder cones concentric to the 

summit of the volcano. Both workers suggested that these 

alignments might reflect the presence of arcuate, concentric 

fissures along which magma had intruded. We doubt the 

reality of significant concentric cone alignments and suggest that the arcuate patterns discerned among the cones 

by previous workers are unlikely to have any structural 

significance.

Scattered Laupahoehoe cinder cones occur between 

approximately 1,600- and 2,000-m (5,250 and 6,560 ft) elevation, in the western part of the broad saddle (Humuula 

Saddle) between Mauna Loa and Mauna Kea. This part of 

the saddle apparently formed where relatively fluid lava 

flows of Mauna Loa Volcano ponded and were diverted 

westward by the steep opposing front of Mauna Kea Volcano. Laupahoehoe cinder cones of the saddle, which are 

found as far as 8 km southwest of the steep Mauna Kea 

mountain front, must have erupted through the gently sloping north flank of Mauna Loa; many of these cones and 

their related flows were subsequently surrounded, and some 

evidently completely buried, by younger Mauna Loa lavas. 

Thus, the Laupahoehoe cinder cones exposed in the saddle 

record intertonguing between the lavas of Mauna Loa and 

Mauna Kea.

Several Laupahoehoe flows in the saddle extend northnorthwestward, parallel to the steep mountain front of 

Mauna Kea. The terminus of the flow from Puu Keekee 

underlies a cinder cone (Puu Iwaiwa) and flow compositionally related to Hualalai Volcano. Thus, the far-western 

part of the saddle is a zone of interlayering of lavas from all 

three volcanoes, Mauna Kea, Mauna Loa, and Hualalai.

PIT CRATERS

Two small, shallow pit craters occur on the upper south 

flank of Mauna Kea. They most probably formed during 

eruptive activity at the nearest Laupahoehoe vent and record 

collapse of the roof above a shallow part of the local magmatic plumbing system then active. The first pit crater, an 

oval about 150 by 250 m across at the rim and 15 to 25 m 

deep, cuts Liloe Spring basalt adjacent to the southeast base 

of Puu Kookoolau (fig. 19). A few glacial erratics occur 

within this crater, and loose scoria from Puu Kookoolau 

spills into its northwest end; it is unclear from field evidence whether Puu Kookoolau predates or postdates the pit 

crater. However, the crater formed before or during the 

Makanaka glacial episode and is most likely related in origin to the Puu Kookoolau eruption.

The second pit crater, 1.5 km north of Hale Pohaku at 

about 3,300-m (10,840 ft) elevation, is nearly circular, about 

150 m in diameter, and 15 to 20 m deep. Its east rim cuts the 

edge of a flow of the younger volcanic rocks member of the 

Laupahoehoe Volcanics. This crater apparently records collapse related to the eruption of the young Laupahoehoe vent 

centered about 300 m to the north-northeast.

OLDER VOLCANIC ROCKS MEMBER

DEFINITION AND OCCURRENCE

We map the hawaiitic lava flows and vent deposits that 

are older than or coeval with the Makanaka Glacial Member 

as the older volcanic rocks member of the Laupahoehoe 

Volcanics. They overlie basaltic rocks of the Hamakua Volcanics. The older volcanic rocks member covers the summit 

and most of the upper flanks of Mauna Kea. Individual 

flows extend locally onto the lower flanks (fig. 22), and several flows reach the present coastline.

PREVIOUS WORK

Stearns and Macdonald (1946) included many of the 

same flows arid cinder cones in the lower member of their 

Laupahoehoe Volcanic Series that we include in our older 

volcanic rocks member. Their map differs in detail, however, because they included some basaltic cones and flows 

of our Hamakua Volcanics in their Laupahoehoe Volcanic 

Series and some hawaiitic cones and flows of our Laupahoehoe Volcanics in their Hamakua Volcanic Series. 

Furthermore, Stearns and Macdonald (1946) recognized 

fewer Holocene cones and flows, and so their lower member includes several cones and flows that we map with 

the younger volcanic rocks member of the Laupahoehoe 

Volcanics.

Porter (1979a) reassigned some of the basaltic cones 

and flows of the Laupahoehoe Volcanic Series of Stearns 

and Macdonald (1946) to his Hamakua Group and reas-
50 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

signed some of the hawaiitic cones and flows from the 

Hamakua Volcanic Series of Stearns and Macdonald (1946) 

to his Laupahoehoe Group. Furthermore, Porter recognized 

some additional Holocene cinder cones and lava flows, 

which he mapped accordingly. Thus, Porter's (1979a) map 

agrees better in some respects with ours than does that of 

Stearns and Macdonald. However, Porter included rocks of 

our Liloe Spring Volcanic Member and the intercalated lens 

of our Waihu Glacial Member (Porter's Waihu Formation) 

in his Laupahoehoe Group.

Detailed chronostratigraphy was a major emphasis of 

Porter's (1979a) study. On the basis of his interpretations of 

the relations between groups of lava flows and the intercalated glacial deposits, he recognized seven chronostratigraphic stages represented among the lavas of his 

Laupahoehoe Group. Porter's (1979a) stratigraphic scheme 

and the K-Ar and 14C ages that were then available are summarized in figure 8.

GEOLOGIC OBSERVATIONS 

MODIFICATION OF FLOW AND CINDER-CONE SURFACES

Within the annular Makanaka morainal belt (pi. 2), the 

surfaces of flows of the older volcanic rocks member, 

whether preglacial or synglacial, were extensively modified 

by glacial erosion that generally stripped away the aa breccia and rubble, exposing the massive, dense flow interiors. 

On parts of some lava flows, however, such as the flows 

from Puu Wekiu, Puu Mahoe, and Puu Pohaku (flow PPH), 

that are in the "lee" of their source cinder cones, erosion 

was minimal or absent. As pointed out by Porter (1979c), 

many of the Laupahoehoe cinder cones within the 

Makanaka glacial limit also were glacially eroded. Some of 

these cones have oversteepened slopes, and many have glacial erratics on their flanks or summits. However, some of 

the oversteepening, as well as some occurrences of erratics, 

has probably been obscured by more recent mass wasting of 

unconsolidated cinders on the flanks of the cones.

Surfaces of lava flows of the older volcanic rocks 

member beyond the Makanaka glacial limit have been modified by weathering and erosion that reflect periglacial conditions, as well as the greater age of these flows than of 

flows of the younger volcanic rocks member. Particularly, 

on the steeper flanks of the volcano, colluvium fills longitudinal troughs on the flow surfaces (fig. 26). This colluvium 

consists primarily of aa fragments and ash but locally 

includes glacial erratics as well.

Locally, within a few kilometers of the glacial boundary, some flow surfaces were eroded by glacial meltwater. 

In the most extreme cases, meltwater torrents stripped all 

unconsolidated aa rubble from the flow surface, exposing 

the underlying welded aa breccia as delicate ridges and 

spines (fig. 26) and leaving rounded erratic boulders 

wedged into the stripped flow surface. The welded cores of

aa flow levees have been etched into sharp relief by such 

meltwater erosion on some flow surfaces; an excellent 

example is just northwest of Kaula Gulch (fig. 24).

With decreasing elevation on the volcano, erosion of 

the flow surfaces, as well as transport and deposition of colluvium, diminished, but flows of the older volcanic rocks 

member are extensively mantled by air-fall and reworked 

deposits of ash and lapilli derived from the eruption columns that built the numerous Laupahoehoe cinder cones. 

Commonly, this mantle fills only depressions on the flow 

surfaces, but, locally, extensive areas of flow surface are 

completely buried by ash and lapilli (see subsection below 

entitled "Laupahoehoe Air-Fall Deposits").

On the east flank of the volcano, below approximately 

1,950-m (6,400 ft) elevation, relatively thick, deeply weathered ash deposits form a nearly continuous mantle on some 

flows and cinder cones; these deposits now consist largely 

of yellow to orange-brown clay. Such a deposit, estimated at 

about 3 to 10 m thick, mantles a flow(s) immediately south 

of the Puu Oo Ranch, as well as the cinder cones 0.5 km 

southwest and 1.2 km southeast of the ranch (pi. 2). The 

thickness and intense weathering of this ash deposit imply 

that these thickly mantled Laupahoehoe cones and flows are 

older than their thinly and discontinuously mantled neighbors. Wentworth (1938) included this thick, weathered ash 

deposit in the "yellow tuff phase" of his Waiau Formation.

PUU WAIAU, PUU POLIAHU, AND RELATED FLOWS

Because glacial erosion and periglacial processes 

affected both pre- and syn-Makanaka flows, the distinction 

between pre- and syn-Makanaka flows and cinder cones is 

generally difficult, if not impossible, on the basis of field 

evidence. The best pre-Makanaka candidates in the summit 

region are Puu Waiau and Puu Poliahu and their related 

flows. The flows from these two cones (PW and PPL flows, 

respectively, pi. 2), both of hawaiite-mugearite typical of 

the Laupahoehoe Volcanics, extend southward and westward over Liloe Spring basalt of the south-flank kipukas. 

Both flows disappear beneath Makanaka morainal deposits 

and reappear to the south and southwest beyond the 

Makanaka glacial limit (pi. 2); locally, they rest directly on 

Waihu drift. We interpret the thin, unmapped diamict or 

gravel between the flow from Puu Waiau (PW flow, pi. 2) 

and underlying Liloe Spring basalt at and below approximately 3,500-m (11,000 ft) elevation in Pohakuloa Gulch as 

Waihu drift. Otherwise, we found no sedimentary deposits 

beneath these two Laupahoehoe flows within the Makanaka 

glacial limit. No ice-contact features are evident on these 

flows. Upslope from the Makanaka moraine, the two flows 

have been deeply eroded; they are unusual in that local erosional outliers have been isolated by Makanaka glacial erosion (pi. 2).

The vent cinder cones for these flows, Puu Waiau and 

Puu Poliahu (fig. 19), are the most conspicuously gullied
STRATIGRAPHY 51

Figure 26. Eroded surface of lava flow (flow A, pi. 2; see fig. 

19) of older volcanic rocks member of the Laupahoehoe Volcanics, 200 m east of Waikahalulu Gulch at 3,100-m (10,200 ft) 

elevation. Torrential meltwater runoff stripped away loose aa carapace, exposing delicate ridges and spines of welded aa and depositing large rounded hawaiite-mugearite boulders directly on eroded 

flow surface (center, near pole). Flow surface, which extends

beyond skyline at center and left, is partly mantled by ash (lower 

right); colluvium forms surficial deposit in foreground and in 

trough between lava spines (at pole) and more distant low ridge. 

Part of Mauna Loa's slope is visible at upper right. Pole is 1.5 m 

long. View east-southeastward; Hawaiian Volcano Observatory 

photograph 88.3.10EW135A#36.

and otherwise-eroded cones of the Laupahoehoe Volcanics. 

Their flanks appear to have retreated back from the proximal parts of their flows, particularly along the southeast and 

south flanks of Puu Waiau, where the uphill edge of the 

flow parallels the base of the cone but is locally separated 

from the cone by an alluvium-filled moat. Furthermore, a 

medial moraine composed of cinders extends nearly 1 km 

southward from the present base of Puu Waiau. This 

moraine apparently was formed fiom cinders eroded from 

Puu Waiau by tongues of Makanaka ice that split around the 

cinder cone and rejoined at its south base.

The relatively intense gullying of Puu Waiau and Puu 

Poliahu is at least partly related to their mineralogy. The 

materials of these cones are ash, lapilli, and bombs. The ash 

and lapilli were once glassy and commonly are highly 

vesicular; some fragments are palagonitic. The internal 

structure of the cones, as expressed by layering and the distribution of bombs, resembles that of other cinder cones.

Unaltered deposits of red or black cinders are exposed in 

each cone, but parts of the cones have been pervasively 

altered. Glass and phenocrysts in a sample from Puu Poliahu are nearly completely altered to the sulfate mineral 

alunite, which presumably formed as hot, sulfur-bearing 

magmatic gas percolated upward through the cone. The 

glassy components of a sample from Puu Waiau are largely 

altered to smectite, and voids are encrusted with the zeolites 

phillipsite and gismondine(?). These minerals record percolation of warm water or steam through the cone during or 

soon after its eruption. In both cones, the alteration products 

weakly cemented the pyroclasts and reduced the permeability of the deposits. Because of reduced permeability, such 

cones are more susceptible to gullying; water runs off 

instead of percolating downward. The reduced permeability 

also apparently accounts for retention of water to form 

a small permanent lake (Lake Waiau) within the crater of 

Puu Waiau.
52 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Similarly altered deposits occur locally in a few other 

Laupahoehoe cones, for example, on the north flank of Puu 

Hauoki and near the summit of Puu Wekiu. Such alteration, 

however, is unknown in most Laupahoehoe cones, including those that have been deeply quarried for cinders. One 

significant exception is a large Laupahoehoe cone incised 

by Waikahalulu Gulch west of Puu Haiwahine. There, 

stream erosion has exposed altered cinders much like those 

of Puu Waiau or Puu Poliahu, suggesting that such alteration has no necessary connection to the presence of glacial 

ice. Indeed, similarly altered cones occur in the San Francisco volcanic field of northern Arizona (Wolfe and others, 

1987a, b), where they are far removed from glacial effects. 

In those cones, hydrothermally altered sectors are profoundly gullied; unaltered sectors are undissected and 

resemble typical, relatively smooth-surfaced Laupahoehoe 

cinder cones.

Puu Waiau and Puu Poliahu and their flows are pivotal 

to a major difference in mapping and stratigraphic interpretation between our work and the earlier work of Porter 

(1979a, c, 1987), who concluded that these two cones are 

the oldest within the Makanaka glacial limit. He interpreted 

the altered pyroclastic deposits as hyaloclastite tuff formed 

in standing water as these cones grew beneath the Waihu 

icecap. He assigned the cones and their flows, as he mapped 

them, to his Poliahuan Stage, equivalent in age to the Waihu 

glacial deposits and overlain to the south by lavas of his 

Hanaipoean Stage. His subglacial interpretation derived 

additional support because he mapped the scarp east and 

west of Puu Kookoolau as the terminus of the flow from 

Puu Waiau. As described above in the subsection entitled 

"Liloe Spring Volcanic Member," ice-contact features 

abound in that scarp.

The critical relations that underlie our revised interpretation are as follows: (1) The scarp exposures consist of 

basalt (Liloe Spring Volcanic Member of the Hamakua Volcanics); (2) the flows from Puu Waiau and Puu Poliahu consist of hawaiite-mugearite (older volcanic rocks member of 

the Laupahoehoe Volcanics) overlying basalt (Liloe Spring 

Volcanic Member) with a pervasive ice-contact fabric 

related to the Waihu icecap; (3) and no ice-contact fabrics 

are exposed in the hawaiite-mugearite flows from Puu 

Waiau and Puu Poliahu.

A subaerial origin for these two cones seems more 

probable than a subglacial one. Previously described stratigraphic relations indicate that the Puu Waiau and Puu Poliahu eruptions occurred not during a glacial episode but 

between the Waihu and Makanaka glacial episodes. The 

structure of the cones, the presence of normal red or black 

cinder deposits in parts of them, and the occurrence of typical blocks and spindle-shaped bombs suggests that normal, 

subaerial, Strombolian eruptive processes formed the cones. 

Beds containing some delicately vesicular, palagonitic fragments may record short-lived phreatomagmatic events during the eruptive activity.

ICE-CONTACT FEATURES

Some, at least, of the other cones and flows of the older 

volcanic rocks member of the Laupahoehoe Volcanics 

exposed within the Makanaka glacial limit erupted while 

the Makanaka icecap was present. Four flows, from vents at 

or near the summit, have distinct ice-contact margins (pi. 2); 

and a fifth, erupted from the south flank of Puu Wekiu, has 

local mosaic-jointed zones on its surface. (For a discussion 

of ice-contact fabrics, see the subsection above entitled 

"Liloe Spring Volcanic Member"; for illustrations of Laupahoehoe ice-contact fabrics, see Porter, 1987, figs. 21.11, 

21.12.) The surfaces of all five of these flows were eroded 

by Makanaka ice that reformed over them, and all but one 

flow are partly buried by Makanaka till. Porter (1979a, c, 

1987) recognized the same ice-contact features and assigned 

these flows to his Kuupahaan Stage (fig. 8), equivalent in 

age to his older Makanaka drift.

The ice-contact flow that originates at the base of Puu 

Hau Kea buried the north rim of Puu Waiau. A small lobe of 

this flow extended into the crater, where an isolated remnant 

now occurs, along with Makanaka drift, on the south side of 

Lake Waiau. The relative freshness of the flow surface 

between Puu Waiau and Puu Hau Kea suggests that thick, 

strongly eroding ice did not reform in the lee of Puu Hau 

Kea. Thus, the small, intracrater flow remnant probably was 

not isolated by deep glacial erosion. The flow may have 

extended into the crater on a bridge of glacial ice or through 

a narrow channel in the ice; as the ice melted, the missing 

flow connection collapsed into the crater, where it was buried by talus and other crater-filling sedimentary deposits.

Most of the vent deposits for these ice-contact flows 

are cinder cones that resemble the numerous Laupahoehoe 

cones which formed beyond the Makanaka glacial limit. 

These ice-contact cones (for example, Puu Hau Kea, fig. 19) 

display no special features indicative of subglacial eruption. 

One distinctive vent deposit, adjacent to the northeast flank 

of Puu Poliahu, consists of a low mound of spatter and 

bombs, rather than the normal steep-sided cinder cone; this 

vent deposit, too, shows no features that we recognize as 

indicative of subglacial eruption. Steep slopes may have 

facilitated drainage instead of ponding of meltwater around 

subglacial vents on Mauna Kea, or insufficient ice thickness 

may have prevented formation of deep englacial ponds. 

Thus, conditions suitable for subaqueous eruption and production of hyaloclastite cones probably were not sustained. 

An alternative suggestion by Porter (1987) is that some of 

these cones may have hidden cores of hyaloclastite which 

was buried by subaerially erupted pyroclasts as the cones 

grew.

FLOW FROM PUU POEPOE

A short flow that extends 1 km eastward from the base 

of Puu Poepoe apparently was erupted as the Makanaka ice
STRATIGRAPHY 53

was retreating. Gregory and Wentworth (1937) and Stearns 

and Macdonald (1946) mapped this flow as postglacial, and 

Porter (1979a) interpreted it as older than his "Younger 

Makanaka drift." Puu Poepoe and the flow that issued from 

its northeast flank have been glacially eroded and are overlain by till. A later eruption constructed a small satellitic 

cone low on the southeast flank of Puu Poepoe and 

emplaced the aforementioned small flow to the east. That 

flow overlies Makanaka drift and has not been glacially 

eroded. However, the presence of a few erratic boulders 

resting on the flow near its edges suggests that the flow was 

erupted against stagnant ice as the Makanaka glacial episode was waning.

AGE

Most K-Ar ages for lava flows of the older volcanic 

rocks member of the Laupahoehoe Volcanics range from 

approximately 18 to 66 ka (fig. 10). Two K-Ar ages are 

older, both related to Puu Waiau. Porter (1979c) reported an 

age of 174±37 ka (sample QLA-lOa, table 5) on a bomb 

collected from the rim of Puu Waiau. Our new K-Ar age for 

the lava flow from Puu Waiau (PW flow, pi. 2) is 107±13 ka 

(sample W87H6-311, table 4), which does not differ significantly from Porter's at the 95-percent-confidence level. 

Although these ages for Puu Waiau and its lava flow overlap 

many of those for basalts of the Liloe Spring Volcanic 

Member of the Hamakua Volcanics that are stratigraphically 

beneath the Waihu Glacial Member of the Hamakua Volcanics (fig. 10), the flow from Puu Waiau is stratigraphically above the Waihu Glacial Member (pi. 2). On the basis 

of physiographic similarity, we would expect Puu Waiau 

and its flow to be comparable in age to Puu Poliahu and its 

lava flow (PPL flow, pi. 2), which has a K-Ar age of 53±14 

ka (sample W87H6-310, table 4). Furthermore, Dorn and 

others (1991) reported an exposure age of approximately 60 

to 70 ka for the Waihu Glacial Member of the Hamakua Volcanics, which predates the lava flow from Puu Waiau.

Considered alone, the K-Ar data suggest an older age 

limit for the Laupahoehoe Volcanics of at least 65 ka, possibly as much as 100 ka. However, the exposure-age results 

indicate that 65 ka is a more likely older limit. As noted 

below in the subsection entitled "Makanaka Glacial Member," the Makanaka glacial episode apparently ended about 

13 ka. Thus, the probable age of the older volcanic rocks 

member of the Laupahoehoe Volcanics is approximately 13 

to 65 ka.

MAKANAKA GLACIAL MEMBER

DEFINITION AND OCCURRENCE

The Makanaka Glacial Member consists primarily of 

till that forms ground- and end-moraine deposits encircling

the summit of Mauna Kea. Local gravel deposits interpreted 

as glacial outwash extend beyond the morainal limits. The 

Makanaka Glacial Member postdates the oldest flows of the 

older volcanic rocks member, is coeval with much of the 

older volcanic rocks member, and predates the younger volcanic rocks member of the Laupahoehoe Volcanics. Most of 

the Makanaka Glacial Member overlies flows and cones of 

the older volcanic rocks member. Locally, adjacent to or 

within south-flank kipukas, it rests on basalt of the Liloe 

Spring Volcanic Member or on the Waihu Glacial Member 

of the Hamakua Volcanics (pi. 2).

Wentworth and Powers (1941) named the Makanaka 

Drift for Puu Makanaka, against which is banked conspicuous blocky till. Porter (1979c) designated Puu Makanaka as 

the type locality. He identified additional reference localities along Kemole Gulch between 3,350- and 3,600-m 

(11,000 and 11,800 ft) elevation, along Waikahalulu Gulch 

at about 3,260-m (11,700 ft) elevation, on the west rim of 

Pohakuloa Gulch between 2,865- and 3,500-m (9,400 and 

11,500 ft) elevation, and near the head of Hanaipoe Gulch.

PREVIOUS WORK

The glacial features of Mauna Kea have long attracted 

geologic interest. Early observations that the upper slopes of 

Mauna Kea had been glaciated were based on brief visits to 

the area. R.A. Daly was the first geologist to publish a 

report (Daly, 1910) that the uppermost slopes of Mauna Kea 

had been glaciated. W.A. Bryan of the College of Hawaii 

visited the summit briefly in 1916. Apparently unaware of 

Daly's observation, he recognized and examined the glacial 

features. His "discovery" was described in a Honolulu 

newspaper, the Pacific Commercial Advertiser (Bryan, 

1916), and he later published a scientific notice (Bryan, 

1918). T.A. Jaggar visited the upper slopes, amplified the 

descriptive record (Jaggar, 1925), and recognized the presence of postglacial as well as preglacial lavas. He also 

described the extensive alluvial deposits in the western part 

of Humuula Saddle and interpreted them as glacial outwash.

Gregory and Wentworth (1937) published the first 

comprehensive study of glacial effects on Mauna Kea, 

focusing on the latest (Makanaka) glacial episode. They 

mapped the reconstructed distribution and thickness of the 

ice and described many important geologic features and 

relations.

Wentworth and Powers (1941) documented the record 

of repeated, episodic glaciation of Mauna Kea. They formalized the glacial stratigraphy, applying the name 

"Makanaka" to the latest glacial episode and its products. 

They correlated the Makanaka glacial episode with the Wisconsin glaciation of North America.

Porter (1979a, c) mapped and described the Makanaka 

deposits in detail. He investigated the stratigraphic relations 

between the lavas of his Laupahoehoe Group and the glacial
54 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Figure 27. Detail of poorly consolidated till in lateral moraine 

of the Makanaka Glacial Member of the Laupahoehoe Volcanics in west wall of Waikahalulu Gulch, at 3,270-m (10,720 ft) 

elevation (same locality as in fig. 18). More friable eolian 

slope deposits underlie till at base of pole. Larger divisions on 

pole are 10 cm wide. Hawaiian Volcano Observatory photograph 

88.3.9EW135A#19.

deposits and recognized specific lava flows that had been 

extruded within the Makanaka icecap. Porter identified and 

mapped separate older and younger drift units within his 

Makanaka Formation; he interpreted these units as representing two distinct glacial episodes, which he correlated 

(Porter, 1979d) with marine oxygen-isotope stages 2 and 4.

GEOLOGIC OBSERVATIONS

The Makanaka morainal deposits are primarily massive, poorly consolidated till (figs. 18, 27) composed of 

angular to subrounded cobbles and boulders, as much as 2 

m or more in diameter, in an unsorted, finer grained, gray to 

light-yellowish-brown matrix. The cobbles and boulders are 

mostly dense, light- to medium-gray hawaiitic rock, 

although admixed basalt occurs locally. Boulders are concentrated as a lag over much the surface of the deposit; 

matrix exposures are rare. The surface boulders are much 

less weathered than those on Waihu drift. The surfaces of 

Makanaka boulders are mostly light gray to tan or yellowish 

brown and highly reflective. As seen from a distance, these 

boulders give the surface of Makanaka till a distinctly 

bright, light-gray, or pale-tan hue. Porter (1979c) reported 

many additional details, including the results of fabric and 

size analyses.

As mapped in this report (pi. 2), Makanaka till forms a 

thin ground moraine and, near the downslope limit of the 

deposit, thicker end moraines. Lateral moraines occur where

ice lobes extended downslope between cinder cones or 

along preexisting topographic lows. The thickness of the till 

ranges from 0 to 30-40 m; maximum thicknesses occur in 

prominent lateral moraines near Pohakuloa and Hanaipoe 

Gulches.

The downslope map boundary of Makanaka till is distinct and agrees well with the outer boundary of Makanaka 

drift as mapped by Porter (1979a). The position of our inner 

boundary is somewhat arbitrary because of a gradation 

downslope from well-exposed, deeply eroded, glacially striated lava flows, through lava flows with discontinuous till, 

to more or less continuous till. Our inner boundary differs 

from that shown by Porter (1979a) because he chose to portray only the till that forms end moraines; his map shows 

many additional details of end-moraine crests.

Thin deposits of subrounded to rounded bouldery 

gravel extend locally downslope from the lower limit of the 

Makanaka moraine. The more extensive and continuous of 

these deposits are mapped as Makanaka outwash deposits. 

The boulders are similar in composition, degree of weathering, and color to those of the till.

A topographically distinct morainal front, within 

Makanaka till north of the summit, extends 3 km northeastward from Kemole Gulch (pi. 2). Two Laupahoehoe lava 

flows extend from beneath this inner morainal front and 

overlie the till downslope from it (fig. 28); thus, these flows 

separate older and younger tills. In addition, a prominent 

pair of parallel lateral moraines occurs about 0.5 km east of 

Hanaipoe Gulch; the inner moraine of the pair overlaps the 

outer one, extending farther downslope.

Porter (1979c) concluded that these two till units represented separate glacial episodes, which he referred to as the 

older and younger drifts of his Makanaka Formation. Distinguishing the two tills on the basis of subtle weathering 

and morphologic characteristics, he identified and mapped 

discontinuous outcrops of the older (outer) till in many 

localities at the perimeter of the younger till. The differences between the two Makanaka till units, however, are so 

subtle that we could not distinguish them except on the 

north flank, where they have distinct morphologic expressions and the intervening intercalation of the two lava flows 

is unmistakable. Therefore, we have mapped a single unit of 

Makanaka till everywhere except on the north flank (pi. 2).

The similarities in degree of weathering and general 

surface characteristics between the older and younger 

Makanaka tills suggest that their age difference is slight. 

Evidently, the Makanaka glacial episode was complex, with 

alternating advance and retreat of the glacier front. We cannot determine whether the Makanaka icecap actually disappeared and reformed. Evidence from the two intertill lava 

flows (fig. 28) neither supports nor refutes Porter's (1979c) 

hypothesis of an ice-free interval within the Makanaka glacial episode.

The more northwesterly intertill lava flow (flow 2, fig. 

28) displays no ice-contact fabric, nor is its exposed surface
STRATIGRAPHY 55

155°30'

•'•'•''• '\* • ° a -°- ' ° '

'.•V:-;•• :•:_•':[flow "| ]!x^.'*°' °--°: °'. °

EXPLANATION

Younger till 

Older till

Intertill lava flow—Showing flow surface eroded by 

Makanaka icecap (stipple pattern)

Cinder cone—Source of intertill lava flow

Older lava flows and cinder cones, undivided—Overlying 

surficial deposits omitted for simplicity

Figure 28. Geologic map of part of upper north flank of Mauna 

Kea, showing relations among intertill lava flows and older and 

younger tills of the Laupahoehoe Volcanics. Geology from plate 

2; alluvial and colluvial deposits are omitted for simplicity. 

Bracketed numbers denote intertill lava flows discussed in text;

- Contact—Dashed where inferred or approximately located; 

dotted where concealed

-• — -—-— Contact between older and younger end moraines

-•——•— Ice-contact flow margin—Dashed where approximately 

located; dotted where interpreted to be buried by till. 

Teeth identify zones of ice-contact fabric on margin of 

flow erupted onto or within Makanaka icecap

Location of Hanaipoe Gulch

parenthetic numbers denote intertill lava flows where buried by 

younger till. Units of the Laupahoehoe Volcanics: Imt, till of the 

Makanaka Glacial Member; loc, cinder cones of older volcanic 

rocks member; lof, lava flows of the older volcanic rocks member. See plate 2 for description of units.

glacially eroded. It locally buried the older till, which is 

exposed in small kipukas within the flow, and subsequently 

was partly buried by the younger till. Field evidence indicates only that after deposition of the older till, the ice 

retreated sufficiently for the lava flow to be emplaced 

beyond the ice front; thereafter, the ice readvanced to 

deposit the younger till.

The more southerly intertill lava flow (flow 1, fig. 28) 

has an ice-contact margin. Its surface has been glacially 

eroded except for the northern part of its more easterly lobe, 

including the small lava-flow tip exposed between outcrops 

of the older and younger tills. That flow tip is within a deep 

reentrant in the outer margin of the younger till. Apparently, 

the lava flow was erupted within glacial ice. The ice front
56 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

had retreated from the limit represented by the outer margin 

of the older till and, when flow 1 was erupted, was no 

higher than approximately 3,730-m (12,240 ft) elevation, 

which is the lowest elevation at which we recognize icecontact fabric in flow 1 (see pi. 2). After the eruption of 

flow 1, glacier movement was reestablished over much of 

the surface of the new lava flow. However, the flowing ice 

split around the prominent eastern lobe of the lava flow, 

forming a reentrant in the younger moraine front.

An additional lava flow, from an unnamed cinder cone 

(cone A, pi. 2; see fig. 19) on the upper south flank of the 

volcano, is known to separate Makanaka glacial deposits. 

This flow (flow A, pi. 2; see fig. 19), which forms the east 

rim of Waikahalulu Gulch, overlies an unmapped gravel 

deposit that contains large hawaiite-mugearite boulders and 

probably represents Makanaka outwash. The flow is, in 

turn, locally overlain by Makanaka till and outwash (pi. 2; 

fig. 26). Like flow 2 on the north flank of Mauna Kea, flow 

A displays no ice-contact fabric, a feature suggesting that 

the ice front was upslope from the vent when the lava flow 

was emplaced.

AGE

Field relations suggest that Puu Poliahu and its lava 

flow (flow PPL, pi. 2), dated at 53±14 ka, predate the 

Makanaka Glacial Member. K-Ar ages on two different icecontact lava flows (fig. 10) suggest that the Makanaka glacial episode was underway by about 40 ka. K-Ar ages for 

two lava flows, flow 1 (fig. 28) and flow A (pi. 2; see fig. 

19), that are bracketed by deposits of the Makanaka Glacial 

Member are 33±12 and 31 ±9 ka, respectively.

Dorn and others (1991) reported exposure ages, based 

on varnish radiocarbon dating and 36C1 dating, of approximately 16 to 21 ka for the younger till on the north flank of 

Mauna Kea and for glacially eroded lava near the summit. 

Varnish radiocarbon ages for the older till range from about 

20 ka to greater than 37 ka.

Study of cores of the sediment that accumulated 

beneath the floor of Lake Waiau, in Puu Waiau, indicate that 

lakebeds began accumulating in the crater between 14 and 

13 ka (J.W. King, oral commun., 1990); the Makanaka glacial episode must have terminated at about that time.

The Makanaka glacial episode apparently began during 

marine oxygen-isotope stage 3 and continued into stage 2. It 

coincided, at least in part, with the late Wisconsin glaciation 

of North America.

YOUNGER VOLCANIC ROCKS MEMBER

DEFINITION AND OCCURRENCE

The younger volcanic rocks member of the Laupahoehoe Volcanics consists of hawaiitic cinder cones and lava

flows of post-Makanaka age. Interpretation of its stratigraphic position is based on various criteria, including 

demonstrable superposition, relative freshness of lava-flow 

surfaces, paucity of mantling ash or colluvium, and 14C 

ages. The unit is exposed on the upper north and northeast 

flanks and on the southeast flank of Mauna Kea (fig. 22).

PREVIOUS WORK

Jaggar (1925) alluded to volcanic rocks that partly 

bury glacial deposits, and Gregory and Wentworth (1937) 

described and mapped flows east of Puu Poepoe and along 

Waikahalulu Gulch that they interpreted as postglacial. 

Wentworth and Powers (1941) also recognized these flows 

as post-Makanaka. Stearns and Macdonald (1946) identified 

several additional postglacial flows: from Puu Lehu, from 

Puu Kole (south flank), and from 1 km southeast of Hale 

Pohaku. They mapped the group of post-Makanaka flows 

and their vent deposits as the upper member of their Laupahoehoe Volcanic Series.

Porter (1973) recognized an additional group of postMakanaka cones, flows, and air-fall deposits northeast of 

Humuula Sheep Station on the south flank of Mauna Kea. 

He indicated that these units overlie his Humuula soil, having buried it about 4.5 ka. Subsequently, Porter (1979a, c) 

assigned the post-Makanaka lavas to his Loaloan stage, 

named for Loaloa, a large cinder cone in the group of cones 

northeast of Humuula Sheep Station.

GEOLOGIC OBSERVATIONS

Lava flows of the younger volcanic rocks member are 

mostly rubbly to blocky aa; pahoehoe occurs locally, for 

example, in the proximal part of the flow from Puu Kole 

(south flank). The flow surfaces generally appear distinctly 

fresher than those of nearby flows of the older volcanic 

rocks member. The more distinct freshness reflects not only 

less weathering and erosion of surface detail but also, in 

most places, the absence or near-absence of mantling eolian 

or air-fall deposits.

Cinder cones of the younger volcanic rocks member 

have been less modified by erosion and mass wasting than 

those of the older volcanic rocks member. Although the 

visual differences are subtle, a morphometric reconnaissance by J.C. Dohrenwend (written commun., 1986) shows 

that cones of the younger volcanic rocks member have 

greater mean maximum slope angles (31°-34°; average of 

steepest 50 percent of each of four to six representative 

slope profiles of the unbreached periphery of the cone) than 

nearly all cones of the older volcanic rocks member. With 

rare exceptions, cones of the older volcanic rocks member 

with comparably steep flanks are glacially eroded cones 

within the Makanaka glacial limit. Furthermore, Dohrenwend found that cones of the younger volcanic rocks mem-
STRATIGRAPHY 57

her have sharply defined crests and essentially unmodified 

craters. In comparison, cones of the older volcanic rocks 

member show rounding of their crests, lower crater-wall 

slope angles, and crater infilling by colluvial, air-fall, or 

eolian deposits.

A probable stratigraphic sequence of flows of the 

younger volcanic rocks member on the south flank can be 

determined from field relations (pi. 2). The northwesternmost flow (flow B, pi. 2; see fig. 19) is tentatively considered the oldest in the sequence. This flow issued as two 

lobes from a small cinder cone and an adjacent mound of 

spatter (cones B and C, respectively, pi. 2; see fig. 19) near 

the east rim of Waikahalulu Gulch, at about 3,540-m 

(11,600 ft) elevation. Colluvium buries the proximal end of 

the eastern lobe, and so it cannot be traced to its source. 

Lava of the two lobes flowed over a thin Makanaka moraine 

and then spilled over the east rim of Waikahalulu Gulch. 

The two lobes merged within the gulch and flowed approximately 2 km along the gulch floor, which had already been 

incised to its present level by runoff from the melting 

Makanaka icecap. The occurrence on the eastern lobe of 

rare hawaiitic blocks that resemble those ejected from Puu 

Keonehehee suggests that this Waikahalulu Gulch flow predates Puu Keonehehee.

We consider Puu Keonehehee (fig. 19) to be postglacial because both the cone and its crater have been virtually 

unmodified by mass wasting and because the short lava 

flow from its west flank overlies a small, isolated outcrop of 

Makanaka drift. Late, explosive eruptive activity exposed 

the underlying lava in the crater wall; subsequently, a small 

hawaiitic flow filled the crater floor. These features are not 

mantled by younger deposits.

Stearns and Macdonald (1946) and Porter (1979a) 

mapped Puu Keonehehee as Pleistocene in age and a small 

red cinder cone (cone D, pi. 2; see fig. 19) adjacent to its 

northwest flank as postglacial. However, we map them in 

reverse sequence because Puu Keonehehee ejecta overlaps 

the small red cinder cone. The stratigraphic relation is 

ambiguous, however, between the small red cinder cone and 

a small black cone (cone E, pi. 2; see fig. 19) immediately to 

the southwest that is partly overlain by Makanaka drift. 

Nevertheless, we interpret the small red cone as Pleistocene 

because several 1-m-diameter glacial boulders rest against 

the northeast flank of the cone. In the present postglacial 

setting, no mechanism for the transport of these boulders 

onto the cone is apparent, although they may have been 

transported by colluvial processes from the nearby 

Makanaka glacial front across snow and ice that formerly 

buried the surface upslope from the cone. We note that the 

ice was thick enough less than 1 km upslope from cone D to 

deposit till on the crest of cone A (fig. 19).

The Puu Keonehehee eruption produced black air-fall 

tephra deposits that partly mantle the flow from Puu Keonehehee. Similar tephra is overlain by an aa flow that originated from a vent less than 1 km southeast of Puu

Keonehehee, at approximately 3,400-m (11,150 ft) elevation. The relation between the younger flow and the underlying ash is well exposed in a roadcut in a switchback at 

approximately 2,900-m (9,500 ft) elevation. There, the hot 

lava flow oxidized the weathered upper surface of the 

underlying ash deposit. No ash overlies the aa flow surface 

in this area, and, in comparison with nearby flows of the 

older volcanic rocks member, the surface has been very little modified by erosion or mass wasting. These relations 

indicate that the aa flow is postglacial and younger than Puu 

Keonehehee.

Approximately 1 km east of Hale Pohaku, the abovementioned aa flow is overlain by two small cinder cones; 1 

km southeast of Hale Pohaku, it is overlain by a thick, 

blocky flow of the younger volcanic rocks member that 

built a low lava dome at the vent but no cinder cone. This 

blocky flow, which originated southeast of Hale Pohaku, 

extended downslope at least as far as the line of cones and 

flows of the younger volcanic rocks member northeast of 

Humuula Sheep Station.

The west edge of the lava flow from Puu Kole (south 

flank) truncates flow structure of the flow that originated 

southeast of Hale Pohaku; thus, the flow from Puu Kole is 

younger. Distinct superposition relations indicate a decrease 

in the age of the flows and related cinder cones from Puu 

Kole through Loaloa. Except for the flow from Huikau, 

which differs only because its surface is mantled by scoria 

and bombs, the flows of the younger volcanic rocks member, from the flow from Loaloa (flow L, pi. 2) southwestward through the flow from Kalaieha, are lithologically and 

chemically indistinguishable. The contacts separating these 

flows (pi. 2) are largely based on photointerpretation of 

morphology, much of which is subtle; thus, significant parts 

of these contacts are conjectural. The distal part of the flow 

from Loaloa is marked by rugged relief, expressed as steepsided knobs and longitudinal ridges. Such positive features 

form Puu Kahiliku and numerous other exposures of the 

flow from Loaloa within kipukas to the south and southeast 

that are surrounded by lava from Mauna Loa (pi. 2).

Flows from the Puu Kole-Kalaieha cone alignment are 

not only lithologically similar but also virtually identical in 

composition. In combination with the general alignment of 

the cinder cones, this similarity suggests that this group of 

cones and flows represents a magma batch delivered to the 

surface along a single intruding dike.

Relatively fresh, youthful-appearing flows issued from 

vents on the north and northeast flanks of Mauna Kea at Puu 

Kole (north flank), Puu Lehu, and Puu Kanakaleonui. 14C 

data indicate middle Holocene ages for all three of these 

flows (see next subsection).

Puu Lehu overlies a lava flow with its source at a low 

lava dome northeast of Puu Hoaka. This flow, in turn, overlies a still-older flow that originates at Puu Hoaka. North of 

Kaula Gulch, the flow from Puu Hoaka has been strikingly 

eroded by glacial meltwater and has erratic boulders scat-
58 GEOLOGY AND PETROLOGY, MA UNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

tered on its surface. Flow levees etched into sharp relief by 

meltwater stripping of the flow from Puu Hoaka are shown 

in figure 24. The flow from the low lava dome northeast of 

Puu Hoaka is much fresher; its surface shows no sign of glacial-meltwater scouring, and no erratics rest on it. Because 

it was not scoured by meltwater, we tentatively interpret it 

as postglacial.

AGE

Porter (1971) reported six I4C ages of approximately 

4,400 to 4,800 yr B.P on charcoal collected from his 

Humuula soil. One age (4,400±110 yr B.P., table 6) was 

determined on charcoal from beneath the flow from Puu 

Kole (south flank); the other ages were determined on charcoal from beneath tephra layers interpreted as derived from 

the eruptions of Puu Kole (south flank) and Loaloa. Porter 

(1973) concluded that the Humuula soil was buried and 

wood fragments within the soil carbonized at about 4,500 yr 

B.P, during the eruptions that formed the line of cinder 

cones northeast of Humuula Sheep Station.

New 14C ages (table 6) confirm Porter's (1973) estimate of a middle Holocene age for the Puu Kole (south 

flank)-Kalaieha group of vents and flows and extend the 

chronology to the northeast and north flanks of Mauna Kea. 

These data suggest a striking concentration of eruptive 

activity from about 5.6 to 4.4 ka: Lava was vented southeast 

of Hale Pohaku, along the group of cinder cones of the 

younger volcanic rocks member northeast of Humuula 

Sheep Station, and at Puu Kanakaloenui and Puu Lehu during that brief period. The only other dated lava flow of the 

younger volcanic rocks member is the flow from Puu Kole 

(north flank), which has a 14C age of approximately 7.1 ka.

Evidence from the sediment that accumulated in Lake 

Waiau indicate that the Makanaka glacial episode was over 

by about 13 ka (see subsection above entitled "Makanaka 

Glacial Member"). Thus, the potential age range for the 

younger volcanic rocks member of the Laupahoehoe Volcanics is approximately 4 to 13 ka.

LAUPAHOEHOE AIR-FALL DEPOSITS

DEFINITION AND OCCURRENCE

Deposits of bedded, black air-fall lapilli and ash are 

mapped (pi. 2) where they are thick enough to form a 

locally continuous blanket on the underlying lava flows and 

cinder cones. Local sheets and dunes of reworked black ash 

occur within and near some of these deposits; conspicuous 

deposits of such reworked ash occur north and northeast of 

Puu Kanakaleonui and on the steep south-facing slopes 

northwest of Puu Haiwahine and east of Waikahalulu Gulch. 

The air-fall deposits are scattered over the upper flanks of 

the volcano. Deeply weathered ash, now represented by 3 to

10 m of clay mantling apparently older lava flows and cinder cones south and east of the Puu Oo Ranch (see subsection above entitled "Older Volcanic Rocks Member"), is not 

mapped with these relatively fresh deposits of ash and 

lapilli.

PREVIOUS WORK

Wentworth (1938) assigned all the pyroclastic deposits 

on Mauna Kea Volcano to his Waiau Formation. These airfall deposits, though not specifically addressed by Wentworth, would have been included within the "central cone 

phase" of his Waiau Formation.

Porter (1973) interpreted the tephra stratigraphy and 

the sequence of eruptions that it represents on the lower 

south flank of Mauna Kea in an area approximately 

bounded by Puu Haiwahine, Puu Kole, and Humuula Sheep 

Station. He identified the late Pleistocene and Holocene 

Humuula soil, which he used as a marker in distinguishing 

between Pleistocene and Holocene tephra deposits.

GEOLOGIC OBSERVATIONS

Continuous deposits of air-fall tephra occur only close 

to the source vents. Many of the mapped deposits are adjacent to single, isolated cinder cones that mark individual 

source vents. In some places—for example, at Puu Lehu, 

Puu Kanakaleonui, and Puu Keonehehee—the air-fall 

tephra deposit forms a collar partly surrounding its related 

cinder cone (pi. 2; figs. 24, 25). At Puu Kanakaleonui, the 

dark-gray air-fall tephra is also distinguished and mapped 

where it overlies the redder scoria of the cinder cone. As at 

Puu Kanakaleonui, some of these tephra deposits were 

vented by late-stage explosive activity that enlarged the cinder-cone crater and excavated blocks from underlying, older 

lava flows (see subsection above entitled "Vent Deposits").

An extensive blanket of air-fall tephra, as much as 15 

m thick, extends about 3 km westward and southward of 

Hale Pohaku (pi. 2). Locally, this deposit is intricately gullied. It is situated among a cluster of cinder cones of the 

older volcanic rocks member of the Laupahoehoe Volcanics. 

Several individual late Pleistocene eruptions probably contributed to the deposit; Porter (1973) identified the Puu Haiwahine eruption as a major source. This tephra deposit is 

continuous with air-fall tephra surrounding Puu Keonehehee, a cinder cone of the younger volcanic rocks member, 

and overlying the lava flow from Puu Keonehehee. Thus, 

the Holocene Puu Keonehehee eruption also contributed to 

the deposit.

A black air-fall tephra deposit mantles the northwest 

slopes of Puu Makanaka and Red Hill. Its position suggests 

that it may represent a late eruptive episode at Puu 

Makanaka. The black tephra deposit locally overlies 

Makanaka till and buries the upper reaches of Makanaka
STRATIGRAPHY 59

outwash deposited along Kaula Gulch. Therefore, the tephra 

is apparently postglacial. A Makanaka moraine, however, is 

banked against Puu Makanaka, and the lava flow from Puu 

Makanaka is overlain locally by Makanaka till and outwash. 

Thus, the tephra deposit may reflect renewed eruption during latest Pleistocene or Holocene time from a late Pleistocene vent.

Renewed pyroclastic activity at Puu Makanaka may 

have been related to eruption of the lava flow of the younger 

volcanic rocks member 2 km north of Puu Makanaka (pi. 2). 

A low lava dome but no cinder cone was built at the vent for 

that flow. The nearly universal occurrence of prominent cinder cones at the vents for Laupahoehoe lava flows indicates 

that large volumes of exsolved gas and vesiculating magma 

normally escaped through the eruptive vent, forming a 

tephra-laden eruption column. Where no cinder cone 

formed, the exsolved gas must have found a vent separate 

from the one that supplied the lava flow. Thus, exsolved gas 

and tephra may have been erupted at Puu Makanaka while 

degassed lava issued quietly 2 km to the north.

Similarly, the flow of the younger volcanic rocks member that was erupted southeast of Hale Pohaku has no cinder 

cone at its vent. One or more cinder cones of the younger 

volcanic rocks member uphill (to the north) from the source 

of that flow may mark the vent through which magma supplying that flow degassed.

Modern analogs of lava emission from one vent with 

simultaneous degassing through another are found in the 

recent eruptive activity of Mauna Loa and Kilauea. During 

the 1984 Mauna Loa eruption, magmatic fume continued to 

be emitted profusely throughout the 3-week-long eruption 

from vents at 3,400-m (11,150 ft) elevation, even though 

after the first day all the lava was emitted from vents 

approximately 7 km to the northeast at 2,800-m (9,190 ft) 

elevation. Greenland (1987) concluded that the gases emitted at the noneruptive 3,400-m (11,150 ft)-elevation vents 

originated from magma in transit through the conduit system to the active vents at 2,800-m (9,190 ft) elevation. From 

July 1986 to February 1992, relatively degassed lava issued 

nearly continuously from a new lava shield, Kupaianaha, in 

the middle east rift zone of Kilauea (Clague and Heliker, 

1992). During this period, copious magmatic gas issued 

through the orifice of Puu Oo3 , a spatter cone built 3 km 

uprift at the previously active vent for the same Kilauea 

eruption, which began in 1983. Although these examples 

differ from the Puu Makanaka occurrence on Mauna Kea in 

their absence of significant tephra ejection, they effectively 

document degassing of magma at one vent and extrusion of 

lava partly depleted in gas at a topographically lower vent.

1 Two cones on the Island of Hawaii are named Puu Oo: One is on the 

southeast flank of Mauna Kea, about 13 km from the summit (pl.2); the 

other, to which we here are referring, is on the east flank of Kilauea, about 

20 km from the summit caldera.

AGE

To avoid unnecessary proliferation of map units on 

plate 2, we have assigned all of the Laupahoehoe air-fall 

deposits to a single unit of Pleistocene and Holocene age. 

However, a mapped air-fall tephra deposit is coeval with its 

source vent(s). Thus, air-fall deposits specifically associated 

with cinder cones of the younger volcanic rocks member 

(for example, Puu Kanakaleonui) are of Holocene age, and 

those specifically associated with cinder cones of the older 

volcanic rocks member (for example, Puu Kookoolau) are 

of late Pleistocene age. As noted above, an apparent exception to this age equivalence occurs at Puu Makanaka, where 

the air-fall deposit postdates till that is banked against the 

cinder cone. Air-fall tephra near Hale Pohaku issued from 

vents of both late Pleistocene and Holocene age. Because 

we are unable to differentiate and map separately the late 

Pleistocene and Holocene components, we interpret this 

tephra deposit as Pleistocene and Holocene in age.

ALLUVIAL, COLLUVIAL, AND EOLIAN DEPOSITS

SLOPE DEPOSITS

DEFINITION AND OCCURRENCE

The slope deposits are a complexly interlayered assemblage of ash-rich sedimentary materials that include air-fall 

lapilli and ash, eolian sand, fluvial sand and sandy gravel, 

colluvial gravel, and diamict deposited as debris flows. All 

are weakly consolidated or unconsolidated except for the 

diamicts, which are locally moderately to well consolidated 

and form ledges. The slope deposits are distributed across 

much of the surface of the south-flank kipukas below 

approximately 3,050-m (10,000 ft) elevation. Much of the 

unit occurs on brushy slopes. Its mapped boundaries are 

largely approximate; further field work would probably 

reveal additional scattered outcrops.

Instructive exposures occur in a small steep gully 

about 0.7 km northwest of Pohakuloa Gulch. Because this 

gully is near the aqueduct from Hopukani Springs, we refer 

to it as the aqueduct gulch (see fig. 20). A useful reference 

section for the slope deposits is in the west wall of the aqueduct gulch, at 2,720-m (8,920 ft) elevation (see subsection 

below entitled "Geologic Observations").

PREVIOUS WORK

Wentworth and Powers (1941) reported indurated 

deposits that they referred to as till at several localities on 

the lower slopes of the south-flank kipukas. One particular 

deposit, which they described and sketched as being as low 

as at 2,100-m (6,900 ft) elevation, is probably an indurated 

diamict exposed near Puu Koohi.

Stearns (1945) referred to deposits of the Waihu Fanglomerate as low as at 2,100-m (6,900 ft) elevation; pre-
60 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

sumably, these deposits were the same outcrops described 

by Wentworth and Powers (1941) as till. Stearns (1945) also 

reported "ashy hillwash deposits" characterized by "thin 

bedding, abundant vitric ash commonly containing cinders, 

poor sorting, weak consolidation, and boulders that show 

little diversity in rock types." Although he indicated that 

these deposits occur as "lenses exposed between lavas of all 

ages in the southwestern slope of the mountain," his 

description seems to apply to our slope deposits. With a few 

exceptions, we have not found such deposits exposed in vertical section between lavas.

Stearns and Macdonald (1946) mapped most of the 

surface of the south-flank kipukas as unconsolidated and 

consolidated alluvium and talus. This unit includes (1) their 

Waihu Fanglomerate, which incorporated the Waihu 

moraines and included indurated sedimentary deposits on 

the lower slopes; and (2) younger gravels, formed in part by 

reworking of the older deposits. The younger gravels were 

deposited before the present major canyons were incised 

and, Stearns and Macdonald (1946) believed, were largely 

deposited by glacial meltwater.

Porter (1979a) mapped elongate trains of Waihu outwash extending downslope from the Waihu moraines. He 

showed additional outcrops of Waihu outwash on the gently 

sloping alluviated surface from Puu Koohi to the mouth of 

Waikahalulu Gulch. Porter's Waihu outwash coincides in 

part with our slope deposits.

GEOLOGIC OBSERVATIONS

The slope deposits are well exposed across the southflank kipukas from Waikahalulu Gulch westward to the long 

narrow lobe of the flow from Puu Poliahu that extends 

downslope to 2,680-m (8,800 ft) elevation, 0.7 to 0.8 km 

northwest of Pohakuloa Gulch. The following detailed 

observations are on these exposures.

All facies of the slope deposits are exposed along the 

aqueduct gulch between approximately 2,560- and 2,740-m 

(8,400 and 9,000 ft) elevation. Most of these facies are well 

exposed in a reference section (fig. 29; table 7) in the west 

wall of the gulch at 2,740-m (8,920 ft) elevation. There, the 

slope deposits consist of approximately 9 m of bedded, pebbly fluvial sand (fig. 30) and sandy gravel, plane-laminated 

and crosslaminated, well-sorted eolian sand (fig. 31), and 

sandy diamict (fig. 31). An additional facies, black air-fall 

lapilli and ash, occurs within the sequence elsewhere along 

the aqueduct gulch.

Except for the air-fall deposits, in which lapilli dominate, the matrices of all of these sedimentary facies consist 

chiefly of very fine to fine volcanic sand; silt- and clay-size 

fragments are virtually absent. Winnowed volcanic ash was 

apparently the major source of sediment. Pebbles and cobbles within the fluvial units and those locally incorporated 

into the basal parts of diamicts are fragments of aa rubble

from the surfaces of nearby lava flows; these fragments represent colluvial materials reworked into the ashy fluvial 

deposits or thin sheets of colluvium formed between other 

depositional events.

The diamicts in the reference section are less than 1 m 

thick; however, throughout the slope deposits, they are as 

much as about 2 m thick. Like unit 4 in the reference section, all are massive, yellowish brown to brown, and well 

enough indurated to form resistant ledges; they contain subangular to rounded cobbles and boulders enclosed in a pebbly-sand matrix. Thin sections show that the matrix consists 

predominantly of highly angular, very fine to fine sand, with 

a continuum of grain sizes through granules to pebbles. The 

fragments are yellowish orange to black, glassy, and vesicular; like the hawaiitic lavas of the Laupahoehoe Volcanics, 

many of these fragments contain abundant plagioclase microlites. Some grain boundaries of sand-size fragments are 

vesicle-wall segments, a feature that, in addition to the 

angularity of these fragments, suggests that they originated 

as pyroclasts.

Boulders in the diamicts of the slope deposits are as 

large as about 1 m in diameter. Lithologically, they are similar to either lava flows or boulders in glacial drift exposed 

upslope. Thus, the diamicts exposed along the aqueduct 

gulch include abundant boulders of Liloe Spring basalt 

derived either from Liloe Spring basalt flows or from boulders of the Waihu Glacial Member. The diamict exposed 

along the lower reaches of Waikahalulu Gulch contains both 

basaltic and hawaiitic boulders, including boulders of the 

distinctive xenolith-rich flow of Puu Haiwahine (older volcanic rocks member of the Laupahoehoe Volcanics), on 

which the Waikahalulu Gulch diamict rests.

The larger boulders in the slope-deposit diamicts are 

fairly well rounded and smooth. Although spalled fragments 

are absent, the fresh surfaces seem to have been exposed by 

exfoliation, apparently before the boulders were incorporated into the diamict. Thus, because of their size, shape, 

and apparent exfoliation, the boulders on the surfaces of the 

diamicts resemble the spalled boulders on the surface of 

Waihu drift. Evidently, the appearance of these boulders, 

occurring within an indurated, massive diamict largely 

exposed at elevations lower than that of the Waihu moraine, 

was responsible for the previous reports of till, Waihu fanglomerate, or Waihu outwash on the lower slopes of the 

south-flank kipukas. However, as discussed below, the slope 

deposits, including the diamicts, are stratigraphically above 

the Waihu Glacial Member and in many places clearly postdate some flows of the older volcanic rocks member of the 

Laupahoehoe Volcanics.

The slope deposits of the reference section in the 

aqueduct gulch overlie a Liloe Spring basalt flow, which, in 

turn, overlies Waihu drift (pi. 2). Thus, these particular 

slope deposits postdate the Waihu and cannot be Waihu outwash. The reference section occurs within a 100-m-wide 

band of slope deposits that filled a topographic trough
STRATIGRAPHY 61

Figure 29. Reference section of slope deposits exposed in west wall of the aqueduct gulch 0.7 km northwest of Pohakuloa Gulch, at 2,720-m (8,920 ft) elevation (see figs. 1C and 20 for location). Numbers 1 through 9 denote units listed in 

table 7. Contacts dashed where approximately located, queried where not discernible through debris on outcrop surface. 

Pole is 1.5 m long. Hawaiian Volcano Observatory photograph 88.2.17EW135A#20.
62 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Table 7. Reference section of slope deposits

[Section located in aqueduct gulch at 2,720-m (8,920 ft) elevation (see fig. 29)]

Unit Description Thickness (m)

Weathered bouldery rubble

Diamict, indurated, yellowish-brown to brown, massive, 

consisting of unsorted, very fine sand to granules; 

basal part incorporates a layer of angular pebbles and 

cobbles derived from aa.

Poorly exposed, brown pebbly sand, 0.5m thick, overlying 

a covered interval, 0.9m thick.

Diamict, thin, resistant ledge similar to unit 8; basal 

part incorporates angular pebbles and cobbles derived 

from aa (see fig. 30).

Sand, dark-brown to brownish-gray, weakly consolidated, 

sorted, with scattered pebbles and layers of pebbles, 

bedded (see fig. 30) .

Diamict, yellowish-brown to dark-yellowish-brown,

moderately indurated, massive, containing subangular to 

subrounded cobbles and boulders, as large as 0.5 m in 

diameter, in a matrix of unsorted, very fine sand to 

pebbles, as large as 1 cm; boulders are concentrated in 

upper part of unit (see fig. 31).

Sand, eolian, dark-gray, laminated, partly crossbedded, 

fine-grained, well-sorted, unconsolidated to weakly 

consolidated.

Pebbly sand and sandy gravel, brown, weakly consolidated; 

angular pebbles and cobbles derived from aa rubble occur 

as layers and lenses, as much as 0.6 m thick; fragments 

are matrix supported, angular, 1 to 25 cm in diameter, 

mostly 2 to 5 cm in diameter.

2.0

.4

1.4

.1

2.1

.7

Basalt, aa, plagioclase-phyric

1.5

1.2

aligned downslope between a lobe to the west of the flow 

from Puu Poliahu (older volcanic rocks member of the 

Laupahoehoe Volcanics; flow PPL, pi. 2) and a low ridge to 

the east composed of Waihu drift and an overlying flow of 

Liloe Spring basalt.

The west edge of the aqueduct gulch group of slope 

deposits is exposed in a small gulch eroded along the east 

edge of the narrow lobe of the flow from Puu Poliahu, at 

2,700-m (8,800 ft) elevation. Two sedimentary units in the 

west wall of this gulch separate Liloe Spring basalt from the 

overlying flow from Puu Poliahu (fig. 32). The sedimentary 

units are a lower yellowish-gray deposit, 20-50 cm thick, of 

angular boulders of Liloe Spring basalt in a silty to sandy 

matrix and an upper discontinuous deposit, as much as 40 

cm thick, of crudely layered, pebbly sand and laminated, 

black eolian sand. The yellowish-gray rubble is a preLaupahoehoe colluvial deposit, possibly derived from 

Waihu till that was exposed upslope; the overlying sandy 

deposits resemble the fluvial pebbly sands and well-sorted 

eolian sands seen elsewhere in the slope deposits.

A few meters to the east, in the east wall of this small 

gulch, the Laupahoehoe flow is missing. In its place, eolian 

sand, fluvial pebbly sand, and diamict of the slope deposits 

overlie the yellowish-gray rubble and the Liloe Spring 

basalt flow on which the rubble rests. Boulders in diamict 

exposed in the east gully wall include hawaiite-mugearite 

derived from one or more Laupahoehoe lava flows. Because 

the flow from Puu Poliahu is the oldest known Laupahoehoe flow in this sector of the volcano, we infer that most of 

the slope-deposit sequence in the east gully wall was deposited after the Puu Poliahu lobe was in place.

At approximately 2,560-m (8,400 ft) elevation along 

the aqueduct gulch, slope deposits consisting of bedded and 

crossbedded sand and pebbly sand and a 1-m-thick diamict 

(fig. 33) overlie indurated gravel containing basalt boulders 

with light-gray surfaces. We believe that this small outcrop 

of indurated gravel represents Waihu outwash overlain by 

the slope deposits. Upgulch, at about 2,650-m (8,700 ft) elevation, approximately 10 m of slope deposits overlies similar coarse, indurated gravel capped by yellowish- to light-
STRATIGRAPHY 63

••'•^i?*^xJ^^:.*'"*:"'"s* -«,/-'**•*». ^jilHL.*^1 --'•!^i ~ v'ii4

!-* i^fc,

Figure 30. Bedded, dark pebbly sand in unit 5 in slope deposits 

and 10-cm-thick diamict of unit 6, which incorporates angular 

fragments derived from aa rubble, exposed in west wall of the 

aqueduct gulch (see fig. 29; table 7). Unit 6 is overlain by covered 

part of unit 7. Larger divisions of pole are 10 cm wide. Hawaiian 

Volcano Observatory photograph 88.2.17EW135A#24.

gray bouldery rubble (fig. 34). At the upstream end of this 

outcrop, a lens of Liloe Spring basalt separates the lower 

coarse gravel and the light-gray rubble from the overlying 

slope deposits. We interpret the coarse gravel and the lightgray bouldery rubble as Waihu outwash and colluvium 

locally separated by a Liloe Spring basalt flow from the 

overlying sand and diamict of the slope deposits.

Clear stratigraphic relations are exposed farther east. 

Near Waikahalulu Gulch, the slope deposits consist of scattered outcrops of a single diamict that formed a thin sheet 

extending downhill from about 2,440-m (8,000 ft) elevation 

onto the gentle slope below the mouth of Waikahalulu 

Gulch at about 2,070-m (6,800 ft) elevation (pi. 2). This 

diamict was lobate; it widened downslope to about 1 km. 

The diamict overlies the lava flow from Puu Haiwahine 

(older volcanic rocks member of the Laupahoehoe Volcanics; flow PH, pi. 2). Much of this diamict caps the rims of 

Waikahalulu Gulch; apparently, its deposition preceded 

incision of the gulch.

Another diamict, which impinged against the northeast 

flank of Puu Koohi (older volcanic rocks member of the 

Laupahoehoe Volcanics), overlies a small lava flow from 

Puu Koohi (pi. 2). This flow from Puu Koohi overlies a 

deposit of air-fall ash and lapilli east of Puu Koohi that was 

most likely derived from the Puu Koohi vent. The air-fall 

deposit, in turn, overlies the flow from Puu Haiwahine. The 

Puu Koohi diamict emerges downslope from a thick deposit

Figure 31. Diamict of unit 4 in slope deposits (see fig. 29; table 

7), showing boulders in upper part of layer. Diamict overlies laminated and crosslaminated eolian sand of unit 3. Pole is 1.5 m long. 

Hawaiian Volcano Observatory photograph 88.2.17EW135A#22.

of reworked lapilli and ash and scattered large lava boulders 

that forms the slope-deposit outcrop northeast of Puu 

Koohi, above 2,130-m (7,000 ft) elevation. This sedimentary deposit, apparently derived in part from the nearby 

Laupahoehoe air-fall deposit, extends up the steep south 

flank of Mauna Kea to about 2,350-m (7,700 ft) elevation 

and locally overlies a lobe of the lava flow from Puu Waiau 

(older volcanic rocks member of the Laupahoehoe Volcanics; flow PW, pi. 2). Subsequent canyon cutting has incised 

the deposit.

Farther west, slope deposits overlap the cinder cone (of 

the older volcanic rocks member of the Laupahoehoe Volcanics) immediately east of the mouth of Pohakuloa Gulch. 

At this locality, the slope deposits consist of a sequence of 

two diamicts interlayered with air-fall lapilli and ash. Like 

their counterparts to the east, these deposits postdate part of 

the older volcanic rocks member and predate the erosional 

event that incised Pohakuloa Gulch.

Additional ashy slope deposits occur upslope along the 

east rim of Pohakuloa Gulch, as high as at approximately
64 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Figure 32. West wall of small gulch about 0.7 km northwest of 

Pohakuloa Gulch at 2,700-m (8,800 ft) elevation. Yellowish-gray 

rubble (at top of pole) consists of angular boulders of Liloe Spring 

basalt; rubble overlies plagioclase-phyric basalt flow of the Liloe 

Spring Volcanic Member of the Hamakua Volcanics. Discontinuous sand and pebbly-sand deposits, which resemble ashy sand beds 

exposed elsewhere in slope deposits, are present between rubble 

and overlying aphyric lava flow (PPL, pi. 2) of older volcanic 

rocks member of the Laupahoehoe Volcanics. Contacts dashed 

where approximate. Pole is 1.5 m long. Hawaiian Volcano Observatory photograph 88.2.17EW135A#3.

2,800-m (9,200 ft) elevation. At their upper limit, these 

slope deposits contact the bouldery Waihu Glacial Member. 

This contact is indistinct; apparently, colluvium from the 

Waihu Glacial Member supplied this part of the slope 

deposits. The effect, right at the contact, is that the slope 

deposits appear to be a downslope facies of the Waihu Glacial Member. Within a short distance downslope, however, 

their less consolidated, ash-rich characteristics become 

apparent; unlike broad, undissected surfaces of Waihu 

morainal deposits, broad outcrops of these slope deposits 

are cut by closely spaced gullies. As previously noted, 

stratigraphic relations downslope indicate that the slope 

deposits are much younger than the Waihu Glacial Member. 

The westernmost slope deposits, west of the aqueduct 

gulch, have the same, apparently gradational relation to the 

Waihu outcrops immediately upslope, and the mapped contacts (pi. 2) are approximate. Broad surfaces of these westernmost slope deposits are gullied like those of their 

counterparts east of Pohakuloa Gulch, and these exposures 

indicate that the unit consists of similar, essentially unconsolidated, ash-rich sand and gravel. We have not seen a 

definitive stratigraphic relation between these westernmost 

slope deposits and lobes of the Laupahoehoe lava flow from 

Puu Poliahu (flow PPL, pi. 2). We surmise that, like their 

counterparts farther east, which flanked preexisting topographic ridges, the westernmost slope deposits may also 

have flanked a preexisting topographic ridge capped by the 

lava flow from Puu Poliahu.

The slope deposits described thus far are local surficial 

units that are mostly, if not entirely, stratigraphically equivalent to some part of the older volcanic rocks member of the 

Laupahoehoe Volcanics. Unmapped slope deposits interlayered with lava flows of the older volcanic rocks member are 

exposed along Waikahalulu Gulch. In a steep, gully-wall 

outcrop (fig. 18) at 3,270-m (10,720 ft) elevation, air-fall 

tephra and bedded pebbly sand overlie a post-Waihu basalt 

flow of the Liloe Spring Volcanic Member and are overlain 

by a hawaiitic lava flow of the older volcanic rocks member. 

Eolian sand postdates this Laupahoehoe flow, and all the 

rocks are overlain by Makanaka drift.

Outcrops farther downstream, below approximately 

3,100-m (10,200 ft) elevation, show that an identical, most 

likely the same, lava flow of the older volcanic rocks member is the second flow below the east rim of Waikahalulu 

Gulch. Bedded ashy, pebbly sand occurs beneath this second flow, and ashy gravel containing large hawaiitic boulders separates this flow from the top flow (flow A, pi. 2). 

Map relations still farther downstream show that flow A 

predates Puu Haiwahine, which, in turn, predates the Waikahalulu Gulch and Puu Koohi diamicts. We conclude that the 

slope deposits accumulated over an extended time period 

during which recurring eruptions formed numerous flows 

and cinder cones of the older volcanic rocks member of the 

Laupahoehoe Volcanics.

AGE AND ORIGIN

We interpret the slope deposits exposed in the aqueduct 

gulch as younger than the Laupahoehoe lava flow from Puu 

Poliahu (flow PPL, pi. 2). The K-Ar age of that flow is 

53±14 ka. Slope deposits occur beneath lava flows of the 

older volcanic rocks member of the Laupahoehoe Volcanics 

along Waikahalulu Gulch upslope from Puu Haiwahine; the 

K-Ar age of the youngest of these lava flows, flow A, which 

caps the east rim above Puu Haiwahine, is 31 ±9 ka. In addition, slope deposits overlie two additional flows, from Puu 

Haiwahine and Puu Koohi, that we know are younger than 

flow A. Thus, the slope deposits near the lower part of 

Waikahalulu Gulch and near Puu Koohi are younger than 

31±9ka.

Apparently, the south-flank gulches were deeply 

incised after at least some of the slope deposits were
STRATIGRAPHY 65

-. ^---t^xY^Jtt 

r.|^^^.^A>^

IJ&&V -', -\» \-

,0fdpiic1 tof 

deposits .

Figure 33. Slope deposits overlying indurated coarse gravel and sandy gravel, which are interpreted as outwash of the Waihu Glacial 

Member of the Hamakua Volcanics, in west wall of aqueduct gulch at approximately 2,560-m (8,400 ft) elevation (see figs. 1C and 20 for 

location). Slope deposits consist of about 1 m (near pole) of bedded and crossbedded sand and pebbly sand, and an overlying 1-m-thick 

diamict. Contacts dashed where approximate. Pole is 1.5 m long. Hawaiian Volcano Observatory photograph 88.2.18EW135A#7.

emplaced. In Waikahalulu Gulch, the occurrence as remnants on the canyon rims of slope deposits representing a 

single debris flow indicates that canyon cutting occurred 

after the approximately 31,000-yr-old lava flow A, the Puu 

Haiwahine lava flow (flow PH, pi. 2), and the slope deposits 

were in place. Along Pohakuloa Gulch, the slope deposits 

also form remnants capping the canyon rims. The stratigraphic evidence, therefore, is that the slope deposits are of 

late Pleistocene age and accumulated mostly, if not entirely, 

during the Makanaka glacial episode.

The occurrence of air-fall tephra interstratified with 

other facies of the slope deposits and the abundance of 

reworked ash throughout the slope deposits imply that airfall tephra was the ultimate source of the bulk of the slope 

deposits. Although we have mapped a few Liloe Spring cinder cones within the south-flank kipukas (pi. 2), we found

virtually no air-fall deposits in the canyon-wall exposures of 

Liloe Spring basalt flows. However, we know that abundant 

tephra was erupted during formation of the many large 

Laupahoehoe cinder cones. Furthermore, superposition relations show that at least some of the slope deposits formed 

during an interval of Laupahoehoe volcanism. On the basis 

of these observations, we believe that the slope deposits are 

equivalent in age to the older volcanic rocks member of the 

Laupahoehoe Volcanics. The ash that dominates these 

deposits was reworked from air-fall tephra derived from 

eruptions that formed the numerous nearby cinder cones of 

the older volcanic rocks member.

Thick deposits of tephra reworked by wind have accumulated locally on and beyond the air-fall lapilli and ash 

sheets. Such ash deposits fill gullies and bury much of the 

lava-flow surface on the steep slope east of Waikahalulu
Figure 34. Outwash of the Waihu Glacial Member of the Hamakua Volcanics, overlain, in turn, by bouldery rubble and overlying slope deposits, exposed in west wall of 

aqueduct gulch at approximately 2,650-m (8,700 ft) elevation (see figs. 1C and 20 for 

location). Slope deposits are approximately 10m thick and consist of fluvial pebbly sand, laminated eolian sand, and diamict. Waihu outwash consists of coarse, indurated basaltic gravel that is capped by conspicuous light-gray layer of bouldery rubble. At far right,

basalt flow of the Liloe Spring Member of the Hamakua Volcanics separates slope deposits from Waihu outwash and light-gray rubble. Slope deposits dip southwest (to left), downhill and away from gulch. Thick air-fall deposits occur within these slope deposits 

just downstream (to left) from this exposure. Contacts dashed where approximately 

located. Pole (circled) is 1.5 m long. Hawaiian Volcano Observatory photographs 

88.2.18EW135A3 through 88.2.18EW135A5.

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D 

O3on

5

<O

R

> 

Z 

&S
STRATIGRAPHY 67

Gulch and northwest of Puu Haiwahine. They are obvious 

analogs of the eolian facies of the slope deposits, as well as 

of the source of the ashy sand that dominates all facies of 

the slope deposits.

The pebbly sands record reworking of the windblown 

ash and of pebbles and cobbles from the rubbly surfaces of 

nearby aa flows. These sands are apparently products of fluvial processes on broad slope surfaces. We are unaware of 

significant redistribution of ash by such fluvial processes at 

present on the slopes of Mauna Kea. Thus, the fluvial slope 

deposits may have accumulated during periods of heavier 

rainfall or vigorous snowmelt—probably under periglacial 

conditions in either case.

The massiveness and widely varying grain size of the 

diamicts (very fine sand to boulders) indicate that they were 

deposited by debris flows. The debris flows were sufficiently competent to entrain the abundant large boulders 

that are enclosed in the sandy matrices of the diamicts. The 

map pattern of the Waikahalulu Gulch diamict suggests that 

it was emplaced as a broad, but thin, sandy slurry that 

spread downslope and laterally, seeking topographic lows in 

the surface of the lava flow from Puu Haiwahine (flow PH, 

pl. 2).

Because of the evidence that eruptions occurred within 

the Makanaka icecap, we were intrigued by the possibility 

that these debris flows were generated by eruptions within 

the ice. However, the abundance of ash, the scarcity of siltand clay-size components, and our inability to trace any 

debris-flow deposit upslope to a source lava flow or even to 

the Makanaka moraine all militate against an origin by 

eruption within the icecap. More likely, thick, rapidly 

formed, wind-winnowed ash deposits blocked drainageways at times. Saturation of such an ash accumulation by 

heavy rainfall, by water from snowmelt, or by meltwater 

discharged from the icecap would have led to gravitational 

instability, which was relieved by failure of the saturated 

ash and generation of a debris flow. Because the debris 

flows formed only during late Pleistocene time, they were 

probably a consequence of periglacial climate, in combination with voluminous Laupahoehoe ash production.

EOLIAN DEPOSITS

Sand-dune deposits blanket part of the lower west 

flank of Mauna Kea. They overlie lavas of both the 

Hamakua and Laupahoehoe Volcanics and are locally overlain by Laupahoehoe lavas. Local outcrops near the east 

limit of these dunes are shown near the west boundary of 

plate 2. Porter (1975) noted that the dune crests strike eastwest and the beds dip north or northwest. He concluded that 

these dunes, as well as loess deposits mantling the lower 

northwest flank, originated from deflation during Pleistocene time of alluvial deposits, now buried by younger lava 

flows, along the southwest base of Mauna Kea. Charcoal

from beneath cinder layers interleaved with the dune sand 

gives I4C ages ranging from approximately 30 to 37 ka (Porter, 1975, 1979c).

The dunes are formed of unconsolidated, bedded, very 

fine to fine, angular to subangular sand. The grains are of 

black to yellowish-orange, glassy, vesicular ash. Because 

black grains dominate, overall the sand is dark gray. The 

yellowish-orange grains, however, which commonly are 

extremely vesicular, give the deposit a salt-and-pepper 

aspect at hand-specimen scale. North-dipping foreset beds 

of these sand-dune deposits are well exposed in a roadcut 

approximately 3 km south of Waikii.

The major body of dune-sand deposits is bounded on 

the south by the Laupahoehoe lava flow of Puu Keekee (fig. 

22). K-Ar ages on that flow are 50±14 and 60±20 ka. Thus, 

there is no alluvial source immediately south of the dune 

sands, nor has there been one for at least the past 50,000 yr. 

An alternative to Porter's (1975) suggested origin for these 

sands—deflation of alluvial deposits—seems more plausible: The dune sands are deposits of reworked ash derived 

from tephra related to Laupahoehoe eruptions along the 

lower southwest flank of Mauna Kea. Such cinder cones as 

Ahumoa or Puu Keekee are possible sources. The delicate 

glassy fragments are pyroclasts, unlike the diverse lithic and 

mineral fragments that compose the very fine to fine sand 

component of alluvium from Pohakuloa Gulch. The angularity and delicacy of the sand-dune pyroclasts imply that 

they have undergone only minimal transport since their initial deposition from an eruption-related ash cloud. Good 

analogs for these western dune deposits are the ash dunes 

near the north edge of the Puu Kanakaleonui tephra blanket 

or near the west edge of the complex tephra deposit between 

Hale Pohaku and Waikahalulu Gulch.

LOESS

Loess, consisting of soft, yellowish-orange, massive, 

flourlike silt, mantles much of the lower southwest, west, 

and northwest flanks of Mauna Kea. Although the deposit is 

widespread and as much as about 2 m thick, we have not 

mapped it separately on plates 1 and 2. A good exposure 

occurs in a roadcut approximately 3 km south of Waikii. 

There, 0.5 to 2 m of loess overlies the ash-dune deposits 

described above. The loess in this outcrop contains thin 

interbeds of ashy eolian sand and air-fall lapilli and ash. 

This loess is composed of yellowish-brown particles that 

are isotropic to slightly birefringent and, as shown by X-ray 

diffraction, amorphous. There is no X-ray evidence of the 

presence of clay minerals. We interpret this material to be 

largely hydrated volcanic glass, probably derived from 

hawaiitic ash.

The occurrence of loess mantling cinder cones and 

flows of the older volcanic rocks member of the Laupahoehoe Volcanics, as well as ash dunes apparently derived from
68 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

tephra of the older volcanic rocks member, implies that at 

least some of the loess could be as young as latest Pleistocene or Holocene. It could have been winnowed directly 

from ash-rich eruptive columns during Laupahoehoe eruptions or stripped by wind from the surfaces of Laupahoehoe 

air-fall deposits. Transport by wind is easy for us to imagine; we have witnessed dense clouds of yellowish-orange 

silt transported many kilometers by wind blowing across the 

western part of Humuula Saddle, where human activities 

have disturbed the vegetation and the ground surface.

ALLUVIUM AND COLLUVIUM

Unconsolidated alluvium and colluvium are mapped 

on plates 1 and 2 only where the deposits are areally extensive or where they conceal map units or contact relations 

that we would otherwise map. In other words, we have 

ignored small outcrops of alluvium or colluvium wherever 

possible.

Jaggar (1925) recognized that the broad alluvial deposits at the south base of Mauna Kea were largely deposited 

by glacial meltwater. Porter (1979a) mapped the alluvial-fan 

surfaces near the mouths of Waikahalulu and Pohakuloa 

Gulches and near the gulch mouth 0.7 km northwest of Puu 

Pohakuloa as coalesced deposits of Makanaka outwash.

We agree that the bouldery sand and gravel of these fan 

deposits were largely deposited as meltwater from the 

Makanaka icecap incised the deep gulches. An exposure age 

of 12 to 13 ka (Dorn and others, 1991) for boulders on the 

alluvial-fan surface just below the mouth of Pohakuloa 

Gulch (approx 1 km northeast of Mauna Kea State Park) 

supports this view. However, we cannot confidently distinguish the margins of the youngest fan and channel deposits, 

which are graded to the floors of the deep gulches and have 

been recently active. The topographically recognizable fan 

deposits grade westward into a nearly flat alluvial plain. The 

alluvial-fan deposits, as well as the deposits of this flat alluvial plain, overlap the relatively young flow PTA (older volcanic rocks member of the Laupahoehoe Volcanics, pi. 2). 

Thus, the surfaces of these alluvial deposits are of latest 

Pleistocene or Holocene age.

Kemole Gulch is the only one of the several gulches 

that fed meltwater off the north side of Mauna Kea to contain extensive alluvial deposits (pi. 1). This alluvium, 

formed during late Pleistocene time, has since been incised 

down to the preexisting bedrock surface. Meltwater draining down Hanaipoe Gulch apparently emptied directly into 

the ocean, leaving only minor deposits along its streamcourse.

Less extensive deposits of alluvium or colluvium have 

been mapped at numerous localities (pi. 2), mostly on the 

upper slopes. In particular, trains of scoria fragments burying adjacent flow surfaces extend downslope from some 

cinder cones. Stone stripes and solifluction lobes abound on

the upper slopes, attesting to the vigor of frost-related processes in redistributing the surface debris.

PETROLOGY

INTRODUCTION

CHARACTERISTICS OF POSTSHIELD LAVAS

Even though the first petrologists to visit Mauna Kea 

(Daly, 1911; Washington, 1923) recognized that the capping 

lavas are distinctly "andesitic," not until most of the Hawaiian Islands had been mapped at least on a broad scale was it 

realized that each volcano has evolved through approximately the same stages (Stearns, 1946). From many new 

analyses of lavas from the major volcanoes, Macdonald and 

Katsura (1962, 1964) were able to recognize two different 

types of Hawaiian volcanoes on the basis of the characteristics of the postshield stage: the Haleakala and Kohala types. 

Wright and Clague (1989), with further study, increased the 

number of types to four:

(1) Haleakala type—characterized by a thick, transitional zone of interbedded tholeiitic basalt, transitional basalt, and ankaramite. These are 

overlain by hawaiite and mugearite. Most analyzed "alkalic basalt" in 

this type is close to saturation and may be either slightly hyperstheneor slightly nepheline-normative. Other volcanoes of this type are 

Mauna Kea (Macdonald and Katsura, 1964) and East Molokai (Beeson, 1976).

(2) Kohala type—mafic alkalic rocks are subordinate. The dominant rock 

types are hawaiite and mugearite, which form a thin cap of lava that 

was erupted from vents scattered on the tholeiitic shield. Trachyte may 

be present, although in Kohala itself, the most differentiated rocks are 

benmoreite. As in the first type, "alkalic basalt" in these alkalic series 

is close to saturation. Other examples, are Waianae and West Maui 

(Macdonald and Katsura, 1964).

(3) Hualalai type—characterized by a bimodal suite of alkalic basalt and 

trachyte (Macdonald, 1968; Clague and others, 1980). There are no 

other representatives this type.

(4) Koolau type—alkalic postshield series is either absent or occurs only 

as a few flows at the top of the tholeiitic sequence. Other examples are 

Lanai (Bonhommet and others, 1977), Niihau, Kahoolawe, Kauai 

(Macdonald and others, 1983), and West Molokai (D.A. Clague, 

unpub. data).

In our investigation of the geology and petrology of 

Mauna Kea, we have defined the transitional zone of basaltic lavas of Wright and Clague (1989) as the basaltic substage and have found that these lavas consist of rare 

tholeiite, abundant transitional basalt, and some alkali 

basalt. These rocks include many lavas that have evolved 

from the latter two types either by crystal accumulation or 

by crystal removal. Overlying these basalts are hawaiite, 

mugearite, and benmoreite lavas of the Laupahoehoe Volcanics, which we refer to the hawaiitic substage.

DEVELOPMENT OF PETROGENETIC CONCEPTS

The recognition that the Hawaiian volcanoes were 

built largely from primary tholeiitic magma and capped
PETROLOGY 69

with alkalic basalt (Tilley, 1950; Powers, 1955) was a major 

turning point in basalt petrology. Previously, tholeiites were 

thought to have originated from alkalic basalts through 

crustal contamination (Kennedy, 1933). This reversal drew 

much attention to the origin of the alkalic basalts, and early 

attempts to relate the two types through crystal fractionation 

were unsuccessful.

Because each of. the Hawaiian volcanoes evolved 

through the same sequence of basalt types, petrologists 

sought a parent common to both series. For example, Macdonald (1968) found olivine-control lines for each series 

converging with high MgO contents, and he hypothesized 

that such picrites might be the common parent.

Recent geochemical studies of the tholeiitic and alkalic 

lavas of Kohala (Feigenson and others, 1983; Lanphere and 

Frey, 1987; Hofmann and others, 1987), Kauai (Feigenson, 

1984), and Haleakala (Chen and Frey, 1985) have resulted 

in the consideration of partial-melting models. Isotopic 

compositions, trace- and major-element data, and inversion 

techniques relate the magma type to the degree of partial 

melting in the mantle source (Frey and others, 1991). Wise 

(1982) suggested that the shield-building stage, with its high 

rate of magma production, resulted from high degrees of 

partial melting. As the production rate diminished by an 

order of magnitude, the degree of partial melting also 

decreased, and the magma type changed toward alkalic 

compositions of the postshield stage.

ISOTOPIC COMPOSITIONS

Frey and others (1990) analyzed a range of basalts and 

hawaiites for Nd-, Sr-, and Pb-isotopic compositions; their 

results are summarized in figure 35. These plots show that 

in terms of 143Nd/144Nd versus 87Sr/86Sr ratios (fig. 35A), 

there is no isotopic distinction among Hamakua lavas or 

between Hamakua and Laupahoehoe lavas. However, 

Laupahoehoe lavas and several Hamakua lavas have 

slightly lower 206pb/204pb ratios (fig 35fi) than Hamakua

basalts generally (Frey and others, 1990). These isotopic 

compositions are similar to those of the postshield Kula Volcanic Series of Stearns and Macdonald (1942) of Haleakala 

(fig. 35A; Chen and Frey, 1985). Variations in Sr- and Ndisotopic ratios from the shield stage through the postshield 

and rejuvenated stages of Haleakala are evidence for differing amounts of at least two source components in each stage 

(Chen and Frey, 1985). Within any single stage, however, 

the spread of isotopic ratios is almost within experimental 

error and is similar to the field of points for the Mauna Kea 

postshield stage.

Frey and others (1990) interpreted the isotopic ratios in 

Mauna Kea lavas as indicating that the source region was 

largely homogeneous with respect to Sr, Nd, and Pb. Possible contamination of some magmas with other source mate0.5132

0.5131

0.5130

0.5129

18.45

18.40

18.35

18.30

g° o o

B

0.7030 0.7032 0.7034 0.7036

87 Sr/ 86 Sr

0.7038 0.7040

Figure 35. Isotopic compositions of Mauna Kea postshield lavas 

(Frey and others, 1990). A, 143Nd/144Nd versus 87Sr/86Sr ratios in 

Mauna Kea lavas in comparison with Haleakala lavas (Chen and 

Frey, 1985). B, 206Pb/204Pb versus 87Sr/86Sr ratios in Mauna Kea 

lavas. Circles, Hamakua Volcanics; dots, Laupahoehoe Volcanics; 

triangles, Haleakala shield stage; squares, Haleakala postshield 

stage; stars, Haleakala rejuvenated stage. Horizontal and vertical 

bars, 2a error limits.

rial may account for the slight differences in Pb-isotopic 

compositions.

SCOPE OF THIS PETROLOGIC STUDY

The following sections contain descriptions of critical 

petrographic features and the chemical compositions of 

groups of Hamakua and Laupahoehoe lavas. Our goal is to 

assess the evolution of postshield magmas. We describe and 

interpret the wide compositional variation within the basaltic lavas and the origin of and compositional variation 

within the hawaiitic lavas. Because the geochemistry, 

including trace-element and isotopic compositions, was 

fully discussed by Frey and others (1990, 1991), we do not 

attempt here to repeat that approach to the study of Mauna
70 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Kea lavas. Our investigation is based on extensive field 

observations and a large data set of major-element chemical 

analyses of samples from mapped lava flows and measured 

stratigraphic sections (table 1).

HAMAKUA VOLCANICS

COMPOSITIONAL GROUPS

Hamakua lavas consist almost entirely of alkali basalt 

(ne normative) and transitional basalt (ol and hy normative) 

that occupies the compositional space between tholeiitic 

and alkali basalt in a plot of alkalis versus SiO2 contents 

(fig. 36A). Figure 36 also shows evolved alkali and transitional basalt (containing less than 7.2 weight percent MgO), 

as well as ankaramite and picrite, which we identify on 

lithologic grounds (table 2).

The Hamakua sample suite includes two samples (La3, La-11, table 1) of tholeiitic basalt from Laupahoehoe 

Gulch (fig. 13) that represent the only two tholeiitic basalt 

flows known from the subaerial part of Mauna Kea. Except 

for an unusual plagioclase basalt (sample IP-2, table 1) and 

one basalt (sample Wa-11, table 1) from the Hopukani 

Springs Volcanic Member that contains a trace of normative 

quartz, the two Laupahoehoe Gulch tholeiites are the only 

q-normative basalts in the sample set.

The distinction between olivine-rich tholeiites, which 

have low SiO2 contents, and alkali-poor Hamakua basalts is 

unclear in the plot of alkalis versus SiO2 contents (fig. 36A). 

The problem is easily resolved, however, in a plot of CaO 

versus SiO2 contents (fig. 365), where olivine-rich tholeiites 

define a field, with less CaO at any SiO2 content, that 

excludes most transitional or alkali basalts. The few evolved 

Hamakua basalts that plot within this field have high 

Na2O+K2O contents that clearly distinguish them from 

tholeiitic basalts in the plot of alkalis versus SiO2 contents.

ALTERATION OF BASALTS

Feigenson and others (1983), Chen and Frey (1985), 

and Frey and others (1990) noted that samples of some of 

the lavas of Haleakala, Kohala, and Mauna Kea have lost K 

and Rb, probably through reaction of ground water with the 

glassy parts of the rocks. The apparent depletion of K is evident when K2O content is compared with P2O5 content. 

Both K and P exhibit incompatible behavior over the full 

range of basaltic compositions and so might be expected to 

occur in an approximately constant ratio. The K2O/P2O5 

ratio for most samples of Hamakua flows from the north 

and northwest slopes (the dry side), where rainfall is about 

10 percent of that on the windward slopes, ranges from 1.75 

to 2.25 (fig. 37A). For all of the remaining Hamakua samples, collected over an area receiving a widely varying rainfall, the K2O/P2O5 ratio ranges from 0.5 to 2.2. For many of

these samples, this ratio is appreciably less than the minimum for the dry-side samples, suggesting that many 

Hamakua basalts have lost part of their original K2O 

through posteruptive leaching (Frey and others, 1990).

Although preferential leaching of K2O is evidently 

reflected in the wide variation in K2O/P2O5 ratios, weathering is apparently not the sole cause of this variation; thus, 

the assumption of a limited initial K2O/P2O5 ratio of about 2 

may be an oversimplification. Comparison of figures 36A 

and 31B shows that low (less than 1.75) K2O/P2O5 ratios 

occur among Hamakua flows only in transitional and 

evolved transitional basalts, ankaramites, and picrites; alkali 

basalts and evolved alkali basalts are unaffected, an unlikely 

consequence of weathering alone. Furthermore, K2O/P2O5 

ratios for the three samples dredged from Hilo Ridge, which 

have been uniformly exposed to seawater but never exposed 

to subaerial weathering, range from 1.63 (sample Er-20) to 

2.70 (sample Er-22). Because no basalt exposed on the dry 

side has a low K2O/P2O5 ratio, we conclude that K2O has 

probably been leached in areas of high rainfall, although we 

have no certain means for distinguishing between K2O 

leaching and initially low K2O/P2O5 ratios.

MINERAL COMPOSITIONS

Most Mauna Kea lavas contain only three crystalline 

silicate phases—olivine, augite, and plagioclase—in association with magnetite and, less commonly, ilmenite. Mineral 

compositions were determined by electron-microprobe 

analysis, using the ARL-EMX microanalyzer at the University of California, Santa Barbara. This microprobe is 

equipped with both wavelength- and energy-dispersive 

detectors; the beam is typically 15 kV, with a sample current 

of 10 nA, and the spot size is 5 to 10 |um. Reference materials are analyzed silicates, such as albite, anorthite, microcline, augite, hypersthene, olivine, and rhodonite, and the 

oxides hematite, rutile, spinel, and chromite. Output from 

the two detector systems is combined and corrected for 

interelement effects.

Typical analyses of phenocryst and groundmass crystals from various rock types are listed in table 8. Although 

limited variation in mineral compositions occurs between 

rock types, several generalities are worth noting. The maximum Fo content of olivine is near 87 percent, and this value 

occurs in phenocryst cores of several different basalt types. 

All clinopyroxenes are augitic, with high Ca contents and 

low Ti, Al, and Na contents. As is typical of Hawaiian clinopyroxenes, these augites contain iron in both oxidation 

states (avg Fe2O3/FeO ratio, 0.12; Basaltic Volcanism Study 

Project, 1981, p. 345). The compositional variation of augites through even the most evolved basalts is slight.

Compositions of plagioclase phenocryst cores generally vary only slightly throughout a thin section. However, 

compositions in some basalts range from An75 to An85 , 

suggesting two periods of crystallization or mixing of
PETROLOGY 71

4 UJ

UJ

12

UJ 

O

01 11

LU ' '

Q.

ICD

LU

Hawaiite

Tephrite

or 

basanite

Picrobasalt

O

O

Basalt

+ +

+

+

O

O * 

O +

o

o

o

o

44 45 46 47 48 49

SiO2 CONTENT, IN WEIGHT PERCENT

50 51 52

Figure 36. SiO2-variation diagrams for lavas of the Hamakua 

Volcanics and Hilo Ridge in comparison with Kilauea lavas. A, 

Na2O+K2O versus SiO2 contents, showing compositional fields 

of Le Bas and others (1986). B, CaO versus SiO2 contents, 

showing approximate boundary between fields of tholeiitic 

basalt and transitional and alkali basalt. Lavas of the Hamakua 

Volcanics: large stars, alkali basalt; small stars, evolved alkali

basalt; large crosses, transitional basalt; small crosses, evolved 

transitional basalt; triangles, tholeiitic basalt; diamonds, ankaramite and picrite. Other lavas: large dots, picrite and basalt 

dredged from Hilo Ridge (samples Er-20, Er-21, Er-22, table 

1); small dots, basalt from Kilauea (from Wolfe and Morris, 

1996).
72 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

2.4

2.0

1.6

1.2

0.8

0.4

OCM

Q_

b

+ •

—— —— —— ——K2O/P2O5 = 1.75—— ——

10 13 16 

MgO CONTENT, IN WEIGHT PERCENT

19 22 25

LLJ 

O 

DC 

LU

a. iCD 

111

0

+.

0

0

0

0

0

0 0 0

B 0

0

©

44 45 46 47 48 49

SiO2 CONTENT, IN WEIGHT PERCENT

50 51 52

Figure 37. Variation diagrams for lavas of the Hamakua Volcanics and Hilo Ridge. A, K2O/P2O5 ratio versus 

MgO contents. B, Na2O+K2O versus SiO2 contents. Plotted lava compositions: crosses, samples of the Hamakua Volcanics from dry (west) side of Mauna Kea (Kamuela, Kawaihae, Keamuku, Nohonaohae, and Puu Hinai 

quadrangles; see fig. 2); dots, samples of the Hamakua Volcanics from elsewhere on Mauna Kea and samples 

from Hilo Ridge; circles, samples for which K2O/P2O5 ratio is <1.75.
Table 8. Representative electron-microprobe analyses of minerals in basalts of the Hamakua Volcanics

[All values in weight percent, ctl, crystal; grd, groundmass; mph, microphenocryst; phn, phenocryst. Fe2O3/FeO ratio calculated by charge balance in formula unit]

Plagioclase:

Host- — -Olivine 

basalt

Occur- phn 

rence .

SiO2 - —— 48.21 

A12 03 —— 32.97 

CaO ——— 16.47 

Na2 O —— - 2.33

K2 0 ———— .12

Total-100.10 

An ———— 79.1

Or ——— - .7

Clinopyroxene :

Host Olivine 

basalt

Occur- phn 

rence.

SiO2 —— - 52.57 

TiO2 ——— .67 

A12 O3 —— 2.35 

Cr2 O3 —— .20 

Fe2 03 —— 1.11 

FeO ——— 4.68

MnO —— - .02 

MgO ——— 17.04 

CaO ——— 21.18 

Na2 O —— - .27

Total-100.09

Wo ———— 41.8 

En ———— 50.8

High-Ti 

basalt

grd

52.90 

29.55 

11.67 

5.01 

.48

99.61

54.7 

42.6 

2.7

High-Ti 

basalt

grd

46.03 

4.02 

4.46 

.10 

4.08 

7.19 

.15 

11.72 

21.50 

.62

99.87

44.2 

39.1 

16.6

Ankara- Olivine 

mite basalt

phn mph

47.82 49.01 

33.03 32.40 

16.41 15.31 

2.35 3.04 

.07 .12

99.68 99.88

79.0 72.9 

20.5 26.3 

.5 .8

Ankaramite

phn1 mph

50.24 50.36 

1.61 0.91 

3.62 3.94 

.10 .26 

2.33 3.16 

6.10 3.56 

.06 .18 

15.20 16.27 

20.09 20.96 

.56 .31

99.91 99.91

40.2 41.0 

48.4 52.1 

11.5 6.9

grd

50.96 

31.49 

13.82 

3.57 

.20

100.04

67.3 

31.5 

1.2

Olivine 

basalt

mph

45.91 

2.91 

6.44 

.22 

4.49 

'4.43 

.13 

13.34 

21.43 

.37

99.67

42.1 

47.6 

10.3

Olivine Picrite Xenobasalt lith

phn mph ctl

47.61 50.61 52.77 

33.80 31.26 29.81 

17.07 15.12 12.74 

2.01 3.30 4.25 

.09 .15 .28

100.58 100.44 99.85

81.9 71.0 61.5 

17.5 28.1 37.0 

.6 .9 1.5

Olivine Xenobasalt lith

phn ctl2

48.48 50.66 

1.85 1.25 

4.78 3.00 

.19 .13 

3.57 .13 

5.28 7.88 

.16 .03 

14.59 16.52 

20.48 20.01 

.37 .39

99.75 99.30

40.2 40.8 

48.5 45.1 

11.3 14.1

Compositions used in mass-balance calculations: Clinopyroxene, tables 10, 

13, 17, and 22; magnetite and ilmenite, tables 10, 13, 15, and 17. 

2 Augite composition used in mass-balance calculations (see table 15).

Olivine:

Host- — -Olivine 

basalt

occurrence

Si02 ——— 

FeO ——— 

MnO ——— 

NiO —— - 

MgO ----

Total- -

Fo - ——

phn

40.52 

11.64 

.15 

.27 

46.12 

.34

99.04 

87.6

Magnetite :

Host Olivine 

basalt

Occurrence.

TiO2 —— - 

A12 03 —— 

Fe2 03 —— 

FeO ——— 

MnO ——— 

MgO ———

Total- -

grd1

19.06 

1.47 

31.27 

45.71 

.43 

1.81

99.75

Ilmenite:

Host Olivine 

basalt

Occurrence .

A12 U3

Fe2 03 —— 

FeO - —— 

MnO - —— 

MgO ———

grd

48.69 

.36 

9.84 

37.09 

.56 

3.43

High-Ti Ankarabasalt mite

grd

38.11 

24.65 

.25 

.10 

36.12 

.40

99.63 

72.3

High-Ti 

basalt

grd

24.58 

2.10 

20.03 

50.14 

.73 

2.14

99.73

High-Ti 

basalt

grd

49.47 

.17 

7.61 

39.63 

.62 

2.37

Oliv

basa

phn mph 

40.59 40, 

13.60 13. 

.16 

.22 

44.88 44, 

.32

99.77 99. 

85.5 85

Ankaramite

grd

19.42 

1.59 

30.11 

46.95 

.56 

1.17

99.80

Ankaramite

grd1

49.24 

.09 

9.09 

38.67 

.56 

2.83

.05 

.73 

.40 

.22 

.87 

.28

.55 

.3 

Ol

ba

gr

23.

0.

23.

48.

.

2.

99.

Ol

ba

gr

48.

.

9.

38.

.

2.

Total-- 99.97 99.87 100.48 99.
74 GEOLOGY AND PETROLOGY. MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

magmas. The most sodic plagioclases, groundmass crystals 

in the most evolved basalts, are approximately An55 in 

composition.

PRIMARY MAGMAS AND PICRITES

Considerable progress has been made in the understanding of basalt magma genesis during the past few 

decades. Particularly important is the composition of the 

primary magma generated in the mantle under each volcano. Several lines of reasoning suggest that such melts are 

MgO rich (15-18 weight percent), which, if crystallized, 

would be olivine rich, like picrites. There has been some 

disagreement, however, over the interpretation of picrites as 

primary basaltic magmas. Field observations by early 

petrologists, such as Macdonald (1949) and Powers (1955), 

suggested that picrites are olivine accumulations in basaltic 

magma. However, when high-pressure-melting studies of 

peridotite and eclogite (for example, Green and Ringwood, 

1967; O'Hara and Yoder, 1967) showed that primary melts 

forming in the mantle must contain 16 to 18 weight percent 

MgO, Hawaiian picrites were reexamined.

Two other lines of evidence support the early conclusions of Macdonald (1949) and Power (1955) that picrites 

are not primary magmas. First, in a recent study of picrites 

from Kilauea and Mauna Loa, Wilkinson and Hensel (1988) 

showed that the olivine phenocrysts are not in equilibrium 

with their host magma. The Mg-Fe olivine phenocryst-"liquid" partition coefficient KD [=(FeO/MgO)olivinex(MgO/ 

FeO)iiquid] between olivine and whole rock is greater than 

0.30 (Roeder and Emslie, 1970), implying that the olivine 

crystals are too iron rich to be in equilibrium with a magma 

of the whole-rock composition and thus would not have 

crystallized from such a magma. Second, the compositions 

of suites of closely associated olivine-rich rocks from 

Kilauea and Mauna Loa define linear trends (olivine-control 

lines) on MgO diagrams (Wright, 1973; Maaloe and others, 

1988). These trends are consistent with the addition or subtraction of olivine of nearly constant composition from a 

basaltic magma, indicating that these phenocrysts generally 

are not in equilibrium with the "bulk rock.

If picrites are not primary magmas, do these picritic 

rocks or any other basalt retain enough of the characteristics 

of the original melt to allow us to infer the composition of 

the primary magma? If olivine and minor chrome-rich 

spinel inclusions are the only phases removed during the 

ascent of basaltic magma, these phases can be added in sufficient quantities to return the "liquid" to equilibrium with 

an assumed crystal composition (Wright, 1984).

The most magnesian olivine in any Mauna Kea lava, 

whether a basalt or picrite, is Fo87 (table 8). None of these 

phenocrysts appear to be in equilibrium with their host magmas. The KD values for Hamakua picrites and this olivine 

range from 0.50 to 0.60, indicating that the olivine is too

iron rich. The Fo85 olivine phenocrysts in olivine-bearing 

basalts, for which the KD values range from 0.21 to 0.24, are 

too magnesian. The MgO content of the magma that crystallized these Fo85 olivine phenocrysts can be approximated by 

adding (or subtracting, in the case of picrites) this olivine to 

the basalt until A^O.30. For example, sample IP-20 is an 

olivine-bearing basalt containing about 8.0 weight percent 

MgO. For magma with the composition of sample IP-20 to 

be in equilibrium with its Fo85 3 olivine phenocrysts, olivine 

must be added sufficiently to increase the MgO content to 

10.7 weight percent (table 9). For the magma to be in equilibrium with mantle olivine (Fo91 ) (Kuno, 1969), assuming 

0.33 as an average KD value between the mantle and surface 

(Takahashi and Kushiro, 1983), sufficient olivine must be 

added to increase the MgO content to 18.3 weight percent 

(table 9).

These relations between olivine phenocryst and basalt 

whole-rock compositions suggest that each primary 

Hamakua magma had an MgO content near 18 weight percent. As these magmas ascended from the mantle, high-Mg 

olivine crystallized and was removed. By the time the 

magma reached a level of neutral buoyancy somewhere 

within the volcano, its MgO content was between 10 and 12 

weight percent, and the crystallizing olivine had a composition of about Fo85 (fig. 38). Further olivine fractionation 

changed the magma composition only along the olivinecontrol line until the MgO content reached about 7 weight 

percent. Lavas erupted from shallow magma chambers at 

this stage of fractionation contain varying amounts of olivine, all of about Fo86 composition. Many magmas resided 

in such chambers sufficiently long to begin fractionation of 

olivine+augite or olivine+augite+plagioclase, causing compositions to depart markedly from olivine control. As long 

as a magma remains olivine controlled, its composition is a 

function only of original melt composition and the proportion of olivine fractionated.

ALKALI, TRANSITIONAL, AND THOLEIITIC BASALTS

We refer olivine-controlled lavas of the Hamakua Volcanics to the alkali (ne normative) and transitional (ol plus 

hy normative) basalt groups. Their compositions differ from 

primary compositions only by the addition or removal of 

olivine. These basalts have undergone neither extensive 

low-pressure fractionation nor extreme accumulation of 

crystals. Thus, they provide the closest representatives of 

possible parental magmas for the varieties of accumulative 

basalts, such as the ankaramites and picrites, or for the 

evolved basalts, which differentiated beyond olivine control 

in shallow reservoirs. We use 7.2 weight percent MgO as a 

convenient boundary between these olivine-controlled 

basalts and the less magnesian, evolved basalts, which 

record fractionation of other silicate crystalline phases in 

addition to olivine. Although the two Hamakua tholeiites
PETROLOGY 75

Table 9. Chemical compositions of basaltic magma, adjusted by addition of olivine to be in equilibrium with 

olivine phenocrysts (Fo85 3 ; see table 8) and mantle olivine (Fo91 ; Kuno, 1969)

[All values in weight percent. Analysis of sample IP-20 recalculated from data of table 1 to 100 percent dry weight after 

partitioning of Fe to FeO and Fe2O3 in the ratio 88:12.]

IP-20 IP-20, in equilibrium IP-20, in equilibrium 

with Fo85 3 phenocrysts with Fo91 mantle olivine

SiO2 ——— -

A12 03 —— -

Fe2 03 — —

FeO- —— --

MgO- —— --

CaO ——— --

Na2 O -----

K2O —— ---

TiO2 -----

P2 05 — ——

MnO —— — -

———— 47,

———— 13,

——— - 1,

———— 10,

——— - 7,

—— -- 11,

———— 2,

———— 3,

.60

.90

.61

.66

.87

.03

.56

.84

.30

.44

.18

47.

12.

1.

10.

10.

10.

2,

3,

.05

.84

.63

.79

.68

.23

.37

.78

.05

.41

.20

45

10

1

10

18

8

1

2

.76

.42

.56

.30

.25

.28

.92

.63

.47

.33

.18

12

11

10

Beginning of (clinopyroxene) and 

plagioclase crystallization

—— Actual erupted-lava

composition (sample IP-20)

-Hypothetical parental-magma 

composition (in equilibrium 

with Fo85 3 olivine)

Hypothetical primitive-melt

composition (in equilibrium

with Fo91 olivine)

10 15 

MgO CONTENT, IN WEIGHT PERCENT

20

Figure 38. CaO versus MgO contents for sample IP-20 (table 9), 

with olivine contents adjusted to illustrate relations among erupted 

basalt composition, parental-magma composition, and primary 

composition. Olivine-controlled fractionation paths: dashed line, 

as magma ascends to shallow magma chamber; solid line, while 

magma is contained in shallow magma chamber.

(samples La-3, La-11) are evolved, as indicated by an MgO 

content less than 7.2 weight percent, we include them in this 

discussion, which deals largely with the genesis of parental 

magmas.

The petrographic features of the alkali, transitional, 

and tholeiitic basalts are similar. Each type has varying 

amounts (0-10 volume percent) of olivine, augite, and plagioclase phenocrysts (see table 8 for mineral compositions).

The groundmass of most samples is nearly completely crystalline and is composed predominantly of brown augite and 

plagioclase, with lesser amounts of olivine, magnetite, and 

ilmenite.

The olivine-controlled basalts form broad bands on 

MgO-variation diagrams (fig. 39). The breadth of these 

bands suggests that they represent a whole family of olivine-control lines, one for each different composition of 

basalt.

To compare this suite of lavas without the effect of 

variations in olivine content, their compositions are 

projected in figure 40 onto the CS-MS-A plane of the 

C-M-S-A tetrahedron of O'Hara (1968). To have the plotted points represent magmas close to melt compositions, 

samples from lavas containing few phenocrysts, or containing only olivine phenocrysts, and having MgO contents 

greater than 7.2 weight percent were used. Tholeiite sample 

La-3, containing 6.6 weight percent MgO, is the single 

exception to these requirements. All of the points form an 

array near the 30-kbar liquidus phase boundaries of O'Hara 

(1968). This univariant boundary representing liquids 

in equilibrium with olivine+garnet+clinopyroxene was 

extended, using data on alkaline compositions determined 

by Takahashi and Kushiro (1983); it almost exactly bisects 

the array of Hamakua basalt compositions. Furthermore, the 

points are essentially sequenced with respect to the degree 

of silica saturation, that is, normative ne decreasing or hy 

increasing from left to right. Before interpreting this array 

as representing a series of melts controlled by univariant 

mantle phase equilibria, we first discuss this sequence with 

respect to the low-pressure cotectic.

A peculiarity of the olivine projection in the 

C-M-S-A tetrahedron is the near-coincidence of the position of the 30-kbar univariant curve representing liquids in 

equilibrium with clinopyroxene, garnet, and olivine with the 

1-bar curve representing liquids in equilibrium with plagioclase, clinopyroxene, and olivine (fig. 41). Because most of
76 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

52

50

48

46

44

17.00

15.75

14.50

LU 

O

£ 13.25

a. i55

LU 12.00

Z 16.0

Z 14.5

O

O

LU

§ 13'°

11.5

10.0

13.0

11.5

10.0

8.5

7.0

SiO

A A

0 H*

AI2O3

FeO+ 

0.9 FeO

CaO

+ *

6789 

MgO CONTENT, IN WEIGHT PERCENT

10 12

Figure 39. MgO-variation diagrams for basaltic rocks of the Hamakua Volcanics, exclusive of picrites and ankaramites. 

Large stars, alkali basalt; small stars, evolved alkali basalt; large crosses, transitional basalt; small crosses, evolved transitional basalt; triangles, tholeiitic basalt.
PETROLOGY 77

4.2

3.2

2.2

1.2 

1.8

1.2

LJJ 

£0.6

LJJ 

Q_

II

O

LJJ

§ 0.0

- 5.4

O 

O

Q LJJ 4 4-

X

O

3.2

Na?O

+

+ +

K0

+ .-

*«?;

TiO,

*^r * + ++

* +> +>+

2.1 

1.5

1.0

0.5

0.0

P.Oc

789 

MgO CONTENT, IN WEIGHT PERCENT

10 11 12

Figure 39. Continued.
78 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

30 

<§>

20

10

gar(+oliv+L)

JS-8(ne 3.6)

HP-13(ne 0.1)

JQ-16(hy1.6) 

IP-20(hy4.65)

JQ-2(hy 4.4) 

IP-21 (hy 7.8) 

HQ-16(hy11.7)

La-8(ne 2.3)

, La-10(ne 0.8) 

j-5(ne 0.9)

i-JS-7(hy14.3)

La-3(q1.7)

opx(+oliv+L)

Wa-8(hy19.0)

\

cpx(+oliv+L)

V \

30

<? 

20 

^

10
PETROLOGY 79

Figure 40. Selected compositions of basalt of the Hamakua 

Volcanics projected from olivine onto CS-MS-A plane of CM-S-A tetrahedron of O'Hara (1968). Components of tetrahedron (see O'Hara, 1968, for full discussion of projection): A, 

(molecular proportion Al2O3+Cr2O3+Fe2O3+Na2O+K2O+ 

TiO2 )xl01.96; C, (molecular proportion, CaO -3 '/3P2O5+ 

2Na2O+2K2O)x 56.08; M, (molecular proportion, FeO+MnO+ 

NiO+MgO-TiO2)x40.31; S, (molecular proportion, SiO2- 

2Na2O-K2O)x60.09. Plotted lava compositions, showing sample numbers and normative-mineral-component contents (in 

weight percent; see table 1): circles, nepheline (ne) normative; 

dots, hypersthene (hy) normative; plus, quartz (q) normative. 

Light lines, 30-kbar phase boundaries of O'Hara (1968); heavy 

line, phase boundary (cpx, clinopyroxene; gar, garnet) as indicated by liquid compositions (x's) determined by Takahashi 

and Kushiro (1983); dotted lines, boundaries between fields of 

alkali basalt (ne normative), transitional basalt (hy normative), 

and tholeiitic basalt (q normative). opx(+oliv+L) [orthopyroxene(+olivine+liquid)], cpx(+oliv+L), and gar(+oliv+L) fields 

are separated by experimentally determined phase boundaries, 

which represent liquid compositions from partially melted 

mantle peridotite.

the plotted Hamakua basalt compositions lie very near the 

1-bar cotectic, we consider that the plotted compositions 

may either be related by low-pressure fractionation processes or have at least been modified by low-pressure crystal removal.

Several lines of evidence support the conclusion that 

low-pressure fractionation has not affected the magma compositions plotted in figure 41. (1) All of the compositions 

could be derived from a single parent, because the points 

plot on both sides of a thermal divide, near sample HP-13 if 

based on normative minerals or near sample IP-21 if based 

on the dry-melting experiments of O'Hara and Yoder 

(1967). (2) A test of crystal fractionation may be made by 

using mass-balance calculations with the crystal compositions of phenocryst or microphenocryst phases in the tested 

daughter rock (table 10). Such an attempt, using samples 

IP-21 and HP-13, gives a fairly close fit for the derivation 

of the daughter product. However, a subtle, but important, 

mismatch for SiO2 and alkalis indicates that the chosen 

parental magma is somewhat more alkaline than the daughter, and so the two magmas cannot be related by crystal fractionation. Other pairs of basalts along the sequence in figure 

41 give similar results.

The array of points in figure 40 from samples JS-8 to 

HQ-16 can be interpreted as a succession of melts formed 

along a univariant curve controlled by garnet+clinopyroxene+olivine. Progression along this univariant curve from 

the most alkaline composition toward higher degrees of silica saturation represents melting with increasing temperature and, therefore, with increasing degrees of partial 

melting in the peridotite assemblage (fig. 42). Sample Wa-8 

represents magma from a part of the source region in which

garnet was depleted before clinopyroxene, whereas sample 

JS-7 represents magma generated by melting in which the 

clinopyroxene was depleted slightly before garnet. The 

tholeiitic sample, La-3, followed a path similar to that of 

sample JS-7, but much more orthopyroxene was melted.

We note that the above model assumes that the mantle 

source is a garnet peridotite, and the curves of figure 42 are 

for dry melting. The melting in this model in the range 

between transitional and tholeiitic compositions is not controlled by univariant mantle phase equilibria; olivine and 

orthopyroxene are the only remaining liquidus phases 

within this interval. This polyvariant melting agrees somewhat with the melting model of Wright (1984); however, the 

model of Hofmann and others (1984), which is based on 

trace-element abundances, requires that both garnet and clinopyroxene remain in the source.

PICRITES AND ANKARAMITES

On Mauna Kea, picrite flows are generally exposed 

only in the deeper part of the Hamakua Volcanics along the 

Hamakua Coast (fig. 13), whereas ankaramite flows are 

near the tops of gulch sections and locally form the present 

ground surface (figs. 13, 43). However, picrite is included in 

the uppermost part of the exposure of the Hopukani Springs 

Volcanic Member in Waikahalulu Gulch, at 3,785-m 

(12,420 ft) elevation, and forms an additional extensive 

exposure of the Hopukani Springs Volcanic Member above 

Mauna Kea State Park (see pi. 2). Ankaramite flows, though 

sparse, are evenly distributed on the surface of the lower 

flanks of the volcano (fig. 43); an additional small exposure, 

not individually mapped, occurs in the uppermost part of 

Pohakuloa Gulch, at 3,735-m (12,260 ft) elevation (pi. 2).

Picrites and ankaramites are visually striking both in 

outcrop and in thin section (figs. 44A, 44B) because of their 

abundant large crystals. The petrographic features of Mauna 

Kea picrites are similar to those of picrites from other 

Hawaiian volcanoes (Wilkinson and Hensel, 1988) in that 

the size distribution of olivine is bimodal or trimodal. The 

largest crystals are blocky, 4 to 5 mm across, and range in 

composition from Fo84 to Fo86 . Microphenocrysts 0.5 to 1 

mm across have compositions near Fo82 , and groundmass 

olivine ranges in composition from Fo75 to Fo80 . The 

groundmass of the picrites typically consists of small grains 

of olivine, augite, plagioclase, titanomagnetite, and ilmenite 

with a pilotaxitic to intergranular texture.

Ankaramites, like the picrites, also exhibit several 

sizes of phenocrysts. Olivine is similar in size and composition to that in the picrites described above, and clinopyroxene phenocrysts are diopsidic augites, 5 to 10 mm long, 

whereas microphenocrysts are slightly more iron rich and 

1 to 2 mm long (fig. 445; see table 8 for representative 

crystal compositions). Some ankaramites contain as much 

as 8 volume percent plagioclase phenocrysts (An80). For 

example, Puu Pa (fig. 43) was the source for at least two
80 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

30 30

20

10

TV

opx(+oliv+L)

cpx(+oliv+L)

V V V

20

10

Figure 41. Selected compositions of basalt of the Hamakua Volcanics, projected from olivine onto CS-MS-A plane 

of C-M-S-A tetrahedron of O'Hara (1968). See figure 40 for algorithm used to derive components of tetrahedron. 

Heavy lines, 1-bar phase boundaries (cpx, clinopyroxene; plag, plagioclase; opx, orthopyroxene) of O'Hara (1968), 

showing thermal divide (dotted line) and arrows that indicate direction of liquid path with falling temperature; light 

lines, 30-kbar phase boundaries of O'Hara (1968), adjusted for consistency with data of Takahashi and Kushiro (1983) 

(see fig. 40). Plotted lava compositions: circles, nepheline normative; dots, hypersthene normative; plus, quartz normative. Sample HP-13 is modeled as parental magma of sample IP-21 (see table 10 for mass-balance calculations); oliv, 

olivine; L, liquid.
PETROLOGY 81

Table 10. Mass-balance calculations testing the relation by 

crystal fractionation among the basalts plotted in figure 40

[All values in weight percent, calculated to 100 percent dry weight; modeled composition (b) determined using the matrix-inversion method of 

Bryan and others (1969)]

Parental 

magma 

(sample HP-13)

Daughter 

(sample IP-21)

observed 

(a)

SiO2 --

A1 2U3

Fe (as

MgO ——

Na2O --

2U5

MnO ——

—————— 46.

—————— 13.

FeO) --12.

————— 10.

————— 3.

.01 

,83 

,90 

.43 

.99 

.51 

.83 

.27 

.43 

.20

47, 

13, 

12, 

7 

11 

2

3

.68 

.92 

.14 

.88 

.05 

.56 

.84 

.31 

.44 

.18

modeled 

(b)

47 

13 

12 

7, 

11, 

2

3

.60 

.88 

.09 

.86 

.04 

.68 

.92 

.26 

.47 

.20

residual 

(a-b)

1 0.08 

.05 

.04 

.02 

.01 

:-.12 

l-.08 

.05 

-.03 

-.02

m.A

Phases removed from parental magma 

in calculating modeled composition:

Olivine-------Fo74

Plagioclase---An79 

C1inopyroxene2 

Magnetite2 - — - 

Ilmenite2 -----

-2.80

-4.07

-2.22

-1.86 

.21

l ln general, a sum of the squares of residuals less 

than 0.10"is a close match. In this case, the mismatch 

in these oxides shows that the hypothetical daughter 

has too much SiO2 and insufficient alkalis to be 

derived by crystal fractionation from this parent.

2 See table 8 for compositions of these phases; 

clinopyroxene is ankaramite phenocryst of table 8.

ankaramite flows, the second of which contains about 3 volume percent plagioclase phenocrysts. The groundmass in 

ankaramites is pilotaxitic and consists of the same five minerals as in the picrites.

Analyses of several typical Mauna Kea picrites and 

ankaramites are listed in table 11, and the compositions of 

all the samples of these rocks in our data set are plotted in 

figures 45 and 46. A few picritic samples, such as HR-46, 

contain moderate amounts of augite and thus have compositions between those of picrite and ankaramite.

One of the most notable features of Mauna Kea picrites 

and olivine basalts is the absence of a single olivine-control 

line on a plot of CaO versus MgO contents (fig. 45). For a 

given MgO content—for example, 18 weight percent—the 

CaO content varies by 3 weight percent. This variation is 

related to the type of parental magma, which is better illustrated in a CS-MS-A projection (fig. 46), where the spread 

of points ranges from tholeiite nearly to alkalic basalt.

One demonstration that picrites with varying CaO contents are crystal cumulates in basaltic magma is provided by

the analyses obtained by KJ. Murata (see table 1). Murata 

collected picrite samples from two gulch sections on the 

Hamakua Coast (fig. 13) and analyzed the whole rock and 

groundmass (by mechanical removal of the phenocryst 

phases). Two pairs of these analyses are indicated in figure 

45, in which the connecting lines are approximately Fo86 

olivine-control lines.

Similarly, Murata analyzed the whole rock and groundmass for two ankaramite flows from the gulch sections on 

the Hamakua Coast. The line connecting the compositions 

of one pair, shown in figure 45, has a slope equivalent to a 

control line of Fo86 olivine and clinopyroxene in approximately a 1:1 ratio, whereas the line connecting the other pair 

has a slope indicative of a 3:2 ratio. The addition of clinopyroxene to basaltic magma displaces points toward the 

ankaramitic augite composition in a CS-MS-A projection 

(fig. 46).

These results show that the picritic lavas have developed through the accumulation of olivine, in magmas of not 

only tholeiitic composition but also varying transitionalbasalt compositions (fig. 46). Any of these picrites could 

have formed by emplacement of a basaltic magma in the 

superstructure of the volcano, where only the crystallization 

of olivine takes place before eruption. Basaltic lava, somewhat depleted in olivine, and picrite could be erupted from 

such a magma chamber.

Ankaramitic lavas, cumulates of both olivine and clinopyroxene, develop primarily in magmas of transitionalbasalt composition (fig. 46) and require somewhat-different 

crystallization conditions. Their parental magmas are 

emplaced at levels deeper in the volcano than those developing picrites. These parental magmas crystallize much 

smaller amounts of olivine before augite begins to form, 

because pressure tends to enlarge the clinopyroxene field at 

the expense of olivine (Mahood and Baker, 1987). This 

observation suggests that with approximately the same 

degree of cooling, a moderately deeply emplaced basaltic 

magma can crystallize and accumulate both olivine and 

augite, whereas a shallow magma can crystallize and accumulate only olivine.

EVOLVED ALKALI AND TRANSITIONAL BASALTS

INTRODUCTION

Evolved basalts, which we define as those containing 

less than 7.2 weight percent MgO, occur in the upper parts 

of the gulch sections on the Hamakua Coast (fig. 13) and are 

widely distributed over the flanks of Mauna Kea. On MgOvariation diagrams (fig. 39), the broad bands of points representing MgO contents greater than approximately 7.2 

weight percent reflect the variety of parental magmas. The 

sharp inflection in trends on a plot of CaO versus MgO contents at approximately 7.2 weight percent MgO indicates the 

end of olivine control and the beginning of clinopyroxene
82 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

and (or) plagioclase crystallization. However, the exact 

MgO content at the inflection point depends on the CaO 

content of the parental magma. Distinct compositional similarities, stratigraphically and spatially related occurrences, 

and distinct petrographic similarities serve in varying combination to suggest significant grouping among the evolved 

basalts. Therefore, we describe and discuss the origins of 

four major groups of evolved basalts: (1) high-Ti basalts, (2)

basalts of the Liloe Spring Volcanic Member, (3) plagioclase-rich basalts, and (4) basalts of the Hopukani Springs 

Volcanic Member.

HIGH-Ti BASALTS

High-Ti basalts are defined on the basis of their distinctly large TiO2 contents (greater than 4.5 weight percent);
PETROLOGY 83

<- Figure 42. Selected compositions of basalt of the Hamakua 

Volcanics, projected from olivine onto CS-MS-A plane of CM-S-A tetrahedron of O'Hara (1968). See figure 40 for algorithm used to derive components of tetrahedron. Plotted lava 

compositions: circles, nepheline normative; dots, hypersthene 

normative; plus, quartz normative; x's, average compositions 

of tholeiites from Kilauea (K) and Mauna Loa (ML) (Macdonald and Katsura, 1964, table 9); squares, coexisting mineral 

compositions of three mantle silicate phases (cpx, clinopyroxene; opx, orthopyroxene; gar, garnet) as determined from 

Hawaiian olivine eclogite xenolith (Kuno, 1969). Shaded areas, 

solid-solution range of phases (boundary dashed where extrapolated); heavy black lines, 30-kbar phase boundaries of O'Hara 

(1968), adjusted for consistency with data of Takahashi and 

Kushiro (1983) (see fig. 40); dotted lines, boundaries between 

fields of alkali basalt (nepheline normative), transitional basalt 

(hypersthene normative), and tholeiitic basalt (quartz normative). Thick gray lines show inferred melting paths of garnet 

peridotite, based largely on dry-melting experiments of O'Hara 

(1968); arrows indicate direction of increasing degree of partial 

melting. Path from point A to point E is controlled by assemblage garnet+clinopyroxene(+olivine, oliv). If clinopyroxene is 

depleted before garnet (for example, sample JS-7), liquid (L) 

trends toward point C; from point E to point C, controlling 

assemblage is garnet-t-orthopyroxene(-t-olivine). After all garnet 

is melted, liquid trends toward orthopyroxene apex (from point 

C to point D). If garnet is depleted before clinopyroxene (for 

example, sample Wa-8), liquid trends toward point F; path 

from point E to point F is controlled by clinopyroxene+orthopyroxene(-t-olivine). After all clinopyroxene is melted, liquid 

again moves toward orthopyroxene apex (from point F to point 

G). With increasing degree of melting of orthopyroxene (for 

example, sample La-3), liquid approaches compositions seen 

in tholeiites of Kilauea and Mauna Loa.

all of these basalts have evolved to MgO contents of less 

than 6.0 weight percent. These lavas are aphyric to very 

weakly porphyritic and contain microphenocrysts of plagioclase, augite, and olivine. Where these microphenocrysts 

occur, they are typically skeletal, less than 0.5 mm long, and 

make up about 10 volume percent of the rock. In samples 

from well-crystallized flow interiors, the groundmass minerals, olivine, augite, plagioclase, titanomagnetite, and 

ilmenite (see table 8), form intergranular to diktytaxitic textures (fig. 44F). Biotite is a rare but persistent constituent of 

well-crystallized high-Ti basalts.

The distribution of high-Ti basalts on the surface of 

Mauna Kea is shown in figure 47 (see also, pi. 1). These 

basalts are among the latest Hamakua lavas. In gulch sections (fig. 13), they occur either at the top or within a flow 

or two of the top. High-Ti basalts show no obvious preferential association with any other particular basalt type.

Chemical analyses and normative compositions of several representative high-Ti basalts are listed in table 12. On 

the basis of Al2O3/CaO ratios, these basalts can be divided 

into two groups, those with a ratio above 1.6 and those with 

a ratio below 1.6. These groups occupy mutually exclusive

fields on such plots as CaO versus MgO contents and A12O3 

versus SiO2 contents (fig. 48), as well as in the CS-MS-A 

plane of the C-M-S-A tetrahedron (fig. 49).

The positions of points representing the high (greater 

than 1.6)- and low (less than 1.6)-Al2O3/CaO-ratio groups 

of high-Ti basalts in figure 48A, at the ends of parallel liquid-descent lines, suggests that these two compositional 

types reflect fractionation of olivine, augite, and plagioclase 

in approximately the same proportions. Such an interpretation, however, is not supported by the scatter representing 

the same compositions in figure 48fi. Because the two 

groups project into different fields on the CS-MS-A plane 

(fig. 49) and on the DI-OL-NEPH plane of Sack and others 

(1987) (fig. 50), fractionation probably occurred under different pressures. To evaluate this interpretation, the proportions of fractionating phases were determined through 

mass-balance calculations, assuming that all the high-Ti 

basalts came from the same general parental magma.

The results of mass-balance calculations, using a 

weakly alkaline basalt (sample HP-13) as parental magma 

to derive a representative high-Ti basalt (samples La-103, 

JS-2) from each group, are listed in table 13. The same mineral compositions were used for each daughter magma, and 

the resulting proportions reveal two important differences. 

Even though sample La-103 is richer in MgO than sample 

JS-2, derivation of its composition requires less olivine 

removal, compensated by greater augite removal. The different ratios of olivine to augite and of augite to plagioclase 

can be explained by enlargement of the clinopyroxene field, 

as illustrated in the system diopside-anorthite-forsterite 

(Presnall and others, 1978), as pressure increases (fig. 51).

The different ratios of olivine to augite and of augite to 

plagioclase in the fractionating assemblages are caused by a 

reversal of the appearance of augite and plagioclase on the 

liquidus. This reversal can be illustrated by comparing the 

liquid-descent lines on variation diagrams (LP, HP, fig. 48). 

The two paths coincide as long as only olivine is being 

removed. With the onset of augite crystallization on the 

higher-pressure trend and of plagioclase on the lower-pressure trend, the paths diverge, as is especially evident on a 

plot of A12O3 versus SiO2 contents (fig. 48B).

Although we cannot calibrate the separation of the two 

groups of high-Ti basalts in figures 49 and 50 in terms of 

pressure, the group with higher A12O3 and lower CaO contents probably fractionated in magma chambers much 

deeper within the volcanic system than did those with 

higher CaO contents.

The arbitrary selection of 4.5 weight percent TiO2 as 

the lower limit for high-Ti basalts eliminates several intermediate compositions. Four such compositions are plotted 

in figure 48. Mass-balance calculations demonstrate that 

these compositions require removal of crystals amounting 

to 25 to 40 weight percent of the parental magma.

In summary, this group of basalts with the characteristic compositional signature of high TiO2 content represents
155°45' 155°30' 155°15'

EXPLANATION

Laupahoehoe Volcanics

Lava flows and cinder 

cones, undivided

PACIFIC OCEAN

Hamakua Volcanics

Ankaramite lava

Lava flowCinder cone

Picrite lava

PACIFIC 

OCEAN:

Other lava flows and 

cinder cones, 

undivided

Lava ofvMauna/Loa

Figure 43. Geologic map of Mauna Kea, showing generalized distribution of all extensively exposed ankaramite and picrite lava flows of the Hamakua Volcanics. Internal contacts distinguish individual lava flows and cinder cones. Queries mark limits of mapping at edge of dense rain forest. Geology simplified from plates 1 and 2 and Wolfe and Morris 

(1996).
PETROLOGY 85

Table 11. Major-oxide and normative-mineral compositions of typical ankaramites and picrites of the 

Hamakua Volcanics and Hilo Ridge

[Major-oxide compositions and Cross, Iddings, Pirsson, and Washington (CIPW) norms in weight percent; major oxides 

adjusted to 100 percent dry weight after partitioning of Fe to FeO and Fe2O3 in the ratio 88: 12. See table 1 for original analyses and analysts]

Picrites

Sample

Si02 --

A_L 2 U3

Fe2 03 - 

FeO — -

MgO — -

Na2O -- 

Kf\

2U5

MnO — -

Q

ab —— -

di —— -

Vr>r ny 

ol —— -

mt —— -

,' T

ap —— -

——— Er-20

- ——— 48.

- ——— 10.

- ——— 1.

1 n

- ——— 17.

i

- ——— 1.

- ——— 0.

- ——— 16.

1 Q

- ——— 13.

.23 

.49 

.52 

.06 

.45 

.44 

.00 

.39 

.99 

.24 

.17

.00 

.30 

.92 

.49 

.00 

.50 

.20 

.02

.20 

.78 

.57

La- 6

45. 

10. 

1. 

11. 

16. 

9.

1.i

2.

0. 

1. 

15. 

20.

18. 

7. 

29.

2.

4.

,44 

,71 

,76 

,60 

,26 

,02 

,78 

.33 

.59 

.32 

.19

,00 

,95 

.06 

.26 

.00 

.02 

.43 

.07

,55 

,92 

.76

La-105

Major

45 

8 

1 

10 

22 

8

1

i

1

CIPW

0

9

17

17 

10 

37

2 

3

oxides

.22 

.52 

.61 

.61 

.29 

.26 

.18 

.14 

.81 

.18 

.18

norms

.00 

.83 

.98 

.54 

.00 

.77 

.20 

.50

.33 

.44 

.43

IO-9

46. 

10. 

1. 

10. 

15. 

11, 

1,

1,

0, 

3. 

14. 

19.

0. 

28.

28.

2, 

3,

.42 

.48 

.53 

.11 

.48 

.28 

.71 

.57 

.96 

.28 

.19

.00 

.37 

.17 

.24 

.16 

.04 

.00 

.44

.22 

.72 

.66

Ankarami tes

JQ-13

46. 

10. 

1. 

10. 

15. 

10. 

1.

2.

0. 

3. 

14. 

20.

25. 

2. 

27,

2, 

3.

.56 

.81 

.52 

.07 

.55 

.71 

.76 

.52 

.08 

.25 

.17

.00 

.07 

.89 

.06 

.00 

.25 

.43 

.57

.20 

.95 

.59

La-5

47.21 

10.77 

1.74 

11.51 

12.70 

9.72 

2.22 

.72 

2.86 

.34 

.20

0.00 

4.25 

18.79 

17.30 

.00 

23.22 

6.57 

21.12

2.52 

5.43 

.81

1Low K2O/P2O5 suggests that posteruptive depletion of K2O may have occurred

Samples:

Er-20. Tholeiitic picrite dredged from Hilo Ridge.

IO-9. Ankaramite flow from Puu Pa (see fig. 43).

JQ-13. Ankaramite flow from Puu lo (see fig. 43).

La-5. Ankaramite in Laupahoehoe Gulch (see fig. 13).

La-6. High-Ca picrite in Laupahoehoe Gulch (see fig. 13).

La-105. High-Ca picrite in basal part of measured section at

Laupahoehoe Gulch (see fig. 13).

a type of late-stage process in Hamakua magmatic activity. 

Slightly alkalic parental magma emplaced at moderate to 

deep levels within the volcano had sufficiently long periods 

of time to crystallize as much as about 50 percent of the 

starting volume before the remaining magma was erupted. 

We note that the erupted lavas carry very few, if any, fractionated phenocrysts and no xenoliths. Furthermore, no 

preferential spatial relations are evident between these lavas 

and those with accumulated phenocryst phases, such as 

ankaramite, that might be expected to be complementary 

accumulative products.

BASALTS OF THE LILOE SPRING VOLCANIC MEMBER

A distinctive group of nearly aphyric basalts constitutes the Liloe Spring Volcanic Member of the Hamakua 

Volcanics. As previously described, these basalts crop out in 

kipukas on the upper flanks of the volcano (pi. 2; fig. 12). 

These lavas represent the latest Hamakua magmatic activity

in the summit region. The analyses listed in table 14 span 

the compositional range of basalts of the Liloe Spring Volcanic Member. Some flows (for example, sample IO-13, 

table 14) on the lower slopes of Mauna Kea are similar in 

composition and petrography to those of the upper flanks. 

Mapped exposures of Liloe Spring basalt, as well as of 

those lower-flank flows that are petrographically and chemically similar, are shown in figure 52. Because these lowerflank flows may represent voluminous eruptions from the 

same summit vents as the Liloe Spring flows, they are 

included in the following descriptions and interpretations.

The more mafic basalts of the Liloe Springs Volcanic 

Member (for example, sample HR-8, table 14) are moderately porphyritic, containing 1- to 2-mm-diameter phenocrysts of olivine, plagioclase, and augite in approximately 

equal proportions and totaling 5 to 6 volume percent in 

abundance. The groundmass consists of rare olivine and 

abundant plagioclase, augite, magnetite, and ilmenite in a 

pilotaxitic texture. Basalts with more evolved compositions 

contain few phenocrysts; they have similar groundmass
86 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM
PETROLOGY 87

<— Figure 44. Photomicrographs of Mauna Kea lavas and xenoliths. Plane-polarized light. A, Picrite (sample Ki-5), containing abundant olivine phenocrysts, as much as 3 mm long. 

B, Ankaramite (sample JQ-13), containing augite (cpx) and 

olivine (ol) phenocrysts, as much as 1 mm or more in diameter. 

Groundmass texture is intergranular. C, Tholeiitic basalt (sample La-3), containing intergranular groundmass of augite, plagioclase, rare olivine, ilmenite, and magnetite. D, Transitional 

olivine-bearing basalt (sample HP-13), containing olivine phenocryst embedded in fine-grained, intergranular groundmass. 

E, Plagioclase basalt (sample IP-6), containing plagioclase 

phenocrysts, as much as 2 mm long. Intergranular groundmass contains plagioclase, augite, rare olivine, and magnetite. 

F, High-Ti basalt (sample IO-6), containing groundmass of 

plagioclase, augite, olivine, ilmenite, and magnetite. Texture is

intergranular to diktytaxitic. G, Hawaiite (sample IO-2), containing coarse-grained groundmass of plagioclase, olivine (ol), 

augite, magnetite, and ilmenite. Texture is trachytic. 

H, Benmoreite (sample JQ-6), containing trachytic to intergranular groundmass that includes larger crystals of apatite 

(ap), biotite (bio), and olivine (ol). /, Gabbroic xenolith in 

evolved basalt exposed near sample locality HR—41 (pi. 3). 

Augite and plagioclase exhibit equilibrium crystal boundaries 

with host basalt. J, Gabbroic xenolith in hawaiite-mugearite 

(sample HQ-61). Olivine crystal (ol) projects into host rock, 

unlike augite (cpx), which is preferentially embayed, indicating 

that part of augite dissolved into hawaiitic magma. This relation represents best petrographic evidence that augite is not in 

equilibrium with hawaiitic magma at lower pressures.

Figure 44. Continued.
GEOLOGY AND PETROLOGY, MA UN A KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

13

12

111 

O 

DC 

HI 

CL

C5 

HI

10

8 9 

OCO

O

KJ-11G

La-1050

Ki-11

3/2

La-105

KD

A

A

n

ML

10 13 16

MgO CONTENT, IN WEIGHT PERCENT

19 22 25

Figure 45. CaO versus MgO contents in ankaramite and 

picrite (see table 1) of the Hamakua Volcanics, in comparison with phenocryst-poor basalt (bs, table 1) of the Hamakua 

Volcanics and picrites from Hilo Ridge, Kilauea, and Mauna 

Loa. Solid lines (dashed where projected) are mineral or 

mineral-assemblage control lines (cpx, clinopyroxene; oliv, 

olivine) that connect related whole-rock and groundmass 

"compositions (circled symbols indicate groundmass-separate 

samples; numbers refer to samples listed in table 1). Olivine 

compositions and olivine/clinopyroxene ratios represented

mineralogy and texture but lack ilmenite. A few basalts of 

the Liloe Spring Volcanic Member (for example, sample 

HQ-14, table 14) are distinctly more plagioclase phyric, 

containing 2- to 3-mm-diameter plagioclase phenocrysts in 

abundances as high as 3 to 5 volume percent, accompanied 

by less abundant olivine and augite.

The phenocrysts in most basalts of the Liloe Spring 

Volcanic Member exhibit reverse zoning on rounded cores, 

and, in a few samples, strings of glass inclusions decorate 

the core-rim boundary. These features show that earlyformed phenocryst phases later became unstable, either by 

decompression of the magma or by the introduction of new 

magma into the chamber. Several basalts contain glomeroporphyritic clots of olivine, plagioclase, and augite, but 

discrete gabbroic xenoliths were found in only one of the 

most evolved basalts (sample HR-^1, table 14). Edges of 

the xenolith crystals in contact with the host basalt are sharp

by control lines were calculated from compositional differences between related whole-rock and groundmass-separate 

samples. Plotted whole-rock compositions: x's, ankaramite 

of the Hamakua Volcanics; pluses, high-Ca picrite of the 

Hamakua Volcanics; dots, phenocryst-poor basalt of the 

Hamakua Volcanics; triangles, tholeiitic picrite from Hilo 

Ridge; squares, average compositions of picrites from 

Kilauea (K) and Mauna Loa (ML) (Wilkinson and Hensel, 

1988).

and euhedral (fig. 447), showing that the xenolith phases 

(table 8) are in equilibrium with their host basalt. Even 

though many phenocrysts show evidence of disequilibrium, 

possibly from magma mixing, these phases were fractionated from the magma to produce the evolved basalts.

The compositions of basalts of the Liloe Springs Volcanic Member are plotted in figure 53, which shows a distribution somewhat similar to those of the high-Ti basalts. The 

apparent trend of points on a plot of CaO versus MgO contents suggests a consistent removal of olivine, augite, and 

plagioclase. However, the scatter in terms of A12O3 and SiO2 

contents shows that the fractionation sequence is substantially more complex. Projected onto the CS-MS--A plane 

(fig. 54), these compositions form a cluster above the 30- 

kbar phase boundary. The spread of points extends from 

slightly alkaline compositions to compositions more silica 

saturated than those of the high-Ti basalts. The lower-flank
PETROLOGY

30

20

10

V

30

20

10

Figure 46. Selected compositions 

of picrite and ankaramite, projected 

from olivine onto CS-MS-A plane 

of the C-M-S-A tetrahedron of 

O'Hara (1968). See figure 40 for algorithm used to derive components 

of tetrahedron. Solid lines, 30-kbar 

phase boundaries of O'Hara (1968); 

dotted lines, boundaries between 

fields of alkali basalt, transitional 

basalt, and tholeiitic basalt. Plotted 

lava compositions: squares, ankaramite from Mauna Kea; pluses, 

high-Ca picrite from Mauna Kea; 

triangles, tholeiitic picrite from Hilo 

Ridge; circles, average compositions 

of picrites from Kilauea (K) and 

Mauna Loa (ML) (Wilkinson and 

Hensel, 1988); large dot, composition of clinopyroxene phenocryst in 

ankaramite of the Hamakua Volcanics (table 8).

<§><£>
155°45' 155°30' 155°15'

PACIFIC OCEAN

PACIFIC 

OCEAN:

La

Y/

Figure 47. Geologic map of Mauna Kea, showing generalized distribution of two types of high-Ti basalt lava flows of the Hamakua Volc

vidual lava flows and cinder cones. Queries mark limits of mapping at edge of dense rain forest. Geology simplified from plates 1 and 2 an
PETROLOGY 91

Table 12. Major-oxide and normative-mineral compositions of high-Ti basalts of the Hamakua Volcanics

[Major-oxide compositions and Cross, Iddings, Pirsson, and Washington (CIPW) norms in weight percent; major oxides 

adjusted to 100 percent dry weight after partitioning of Fe to FeO and Fe2O3 in the ratio 88:12. See table 1 for original analyses and analysts]

Al 2O3 /CaO>l.

SiO2 -- ---

AJ AI o - -2U3

Fe2 03 - —— 

FeO —— ——

MgO ————— 

p-,n

Na2O - ——— 

KPI

T-i Pi _

^2U5

MnO —— ---

•---IO

—— 46

—— 14

—— 1

-L £t

— - 5

—— 3

—— 1

—— 4

-6

.49 

.85 

.93 

.73 

.13 

.42 

.38 

.43 

.65 

.76 

.22

La-103

45 

15 

1 

13 

5, 

7, 

3, 

1, 

4,

.82 

.02 

.99 

.13 

.01 

.96 

.45 

.67 

.84 

.89 

.22

.60 Al 2O3 /CaO<1.60

Mu-11

Major

46 

14 

1 

12 

5 

8 

2 

1 

4

oxides

.84 

.82 

.91 

.63 

.22 

.69 

.94 

.22 

.90 

.62 

.21

IT-7

47 

14 

1 

11 

5, 

10, 

3, 

1, 

4,

.32 

.04 

.74 

.50 

.21 

.23 

.17 

.11 

.85 

.63 

.20

JS-1

46 

13 

1 

12 

5 

9. 

3, 

1, 

4,

.76 

.78 

.83 

.09 

.30 

.83 

.28 

.31 

.91 

.71 

.20

TO O

46.80 

13.79 

1.86 

12.26 

5.18 

9.60 

3.17 

1.35 

5.03 

.75 

.21

CIPW norms

q ——— —

or -----

ab ————

an - - - - -

ne - - - - -

di ————

hy ————

ol ————

mt ————

il

ap ————

———— 0.

———— 8.

———— 28.

———— 21.

———— 13.

———— 15.

———— 2.

———— 1.

.00

.45

.60

.12

.00

.03

.09

.30

.80

.83

.80

0.

9.

27.

20.

1.

10.

16.

2.

9.

2.

.00

.87

.25

.57

.05

.91

.00

.22

.89

.19

.11

0,

7.

24,

23,

12.

10.

7.

2.

9.

1.

.00

.21

.88

.64

.00

.79

.70

.28

.77

.31

.47

0

6

26

20

21,

2

8,

2,

9,

1,

.00

.56

.82

.80

.00

.32

.47

.83

.52

.21

.49

0

7

26

19

20

11,

2,

9,

1,

.00

.74

.49

.01

.68

.77

.00

.68

.65

.33

.68

0.

7.

26.

19.

19.

1.

10.

2.

9.

1.

.00

.98

.82

.41

.00

.30

.61

.90

.70

.55

.78

Samples:

IO-6. Flow exposed in Kamakoa Gulch (see pis. 1, 4).

IT-7. Flow forming northwest rim of Maulua Gulch (see pi. 4 for 

location).

JS-1. Top flow of Kaawalii Gulch section (see fig. 13).

JS-2. Flow along southeast side of Kukaiau Gulch, Hamakua coast (see pi. 

4 for location).

La-103. Flow near top of southeastern Laupahoehoe Gulch section (see 

fig. 13).

Mu-11. Flow near top of Maulua Gulch section (see fig. 13).

basalts with compositions similar to basalts of the Liloe 

Spring volcanic member would plot within this same cluster. All sampled basalts of the Liloe Spring Volcanic Member have compositions that have been affected by 

plagioclase and (or) augite fractionation (fig. 53).

The basalts of the Liloe Spring Volcanic Member must 

have evolved within a magma chamber sufficiently shallow 

in the volcano to feed vents at or near the summit during the 

later part of the basaltic substage. Because this magma system persisted over a period of several tens of thousands of 

years, it is important to determine the composition of the 

parental magma and the fractionation process. Because all

the basalts of the Liloe Spring Volcanic Member contain 

less than 7.0 weight percent MgO, none was erupted without some fractionation. Therefore, we have no direct evidence of the parental-magma composition. Transitional 

basalt (sample IP-21) has a composition similar in degree 

of silica saturation to much of the Liloe Spring cluster. 

Mass-balance calculations, using this transitional basalt as a 

parental magma and various Liloe Spring basalts as daughter magmas, give moderately good fits (see table 15; liquiddescent line, fig. 53). Because results with these parents and 

various possible Liloe Spring daughters show fits that are 

better for some pairs than for others, there is probably not a
92 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

13

12

LU

8 11 

LU

UJ

10

D

O

O

789 

MgO CONTENT, IN WEIGHT PERCENT

10 11 12

UJ 

O DC 

UJ 0_

LUIz

O

O

17

16

15

14

13

12

11

O

B

44 45 46 47 48 

)2 CONTENT, IN WEIGHT PERCENT

49 50 51
PETROLOGY 93

Figure 48. Variation diagrams comparing high-Ti basalts 

(containing more than 4.5 weight percent TiO2) with other 

basalts of the Hamakua Volcanics, showing hypothetical paths 

of magma evolution. A, CaO versus MgO contents. B, A12O3 

versus SiO2 contents. Diamonds, high-Ti basalts with A12O3/ 

CaO ratios of >1.6; squares, high-Ti basalts with Al2O3/CaO 

ratios of <1.6; x's, basalts containing 4.0 to 4.5 weight percent 

TiO2 ; circle, sample HP-13 (basalt of the Hamakua Volcanics), 

which is modeled as parental magma of high-Ti basalts (see 

table 13); dots, other basalts of the Hamakua Volcanics. On 

each diagram, two liquid-descent lines are shown; both start 

from point P, composition of hypothetical parental magma, but 

diverge at point A. Along lower-pressure path (LP), from point 

P to point D, only olivine is removed from magma; from point 

D to point E, olivine+plagioclase is removed; and from point E 

to point F, olivine+plagioclase+augite is removed. Along 

higher-pressure path (HP), from point P to point A, only olivine 

is removed; from point A to point B, olivine+augite is 

removed; and from point B to point C, olivine+augite+plagioclase is removed.

parental magma common to all basalts of the Liloe Spring 

Volcanic Member. Furthermore, several flows within the 

Liloe Spring Volcanic Member are alkaline in composition 

(fig. 54; for example, samples HQ-24, Wa-16, table 1) and 

evolved from parental magmas similar in composition to 

sample HP-13 (fig. 49).

Inconsistent results of calculations to test crystal fractionation between various pairs of basalts of the Liloe 

Spring Volcanic Member (for example, samples HR-8, 

HQ-14, table 15) show that few of these lavas are truly 

comagmatic. In contrast, samples of lavas shown to be from 

the same vent but with different lithologies and compositions (for example, samples HQ-13, HQ-14) do give the 

expected low residuals (see table 15; liquid-descent line, 

fig. 53.)

Our interpretation of the field and petrographic observations and the results of mass-balance calculations is that 

the basalts of the Liloe Spring Volcanic Member were 

erupted from a long-lived (approx 104-105 yr), relatively 

shallow magma chamber beneath the summit of the volcano. Magma batches of differing composition periodically 

fed this chamber and, after remixing of the new and residual 

magmas, cooled sufficiently to allow the separation of 5 to 

20 percent of crystals before the next eruption. Some eruptions may have produced voluminous flows, which traveled 

as far as the lower flanks.

PLAGIOCLASE-RICH BASALTS

Basalts unusually rich in plagioclase phenocrysts 

(more than 8-10 volume percent) were erupted late in the 

basaltic substage (see pi. 1). The vents for these flows are 

concentrated on the west flank of the volcano, although several flows are on the surface of the northeast flank (fig. 55).

Nearly 75 percent of the exposed vents on the west flank 

erupted plagioclase-rich basalts.

All of these plagioclase-rich basalts contain plagioclase phenocrysts (An77-An82) that are blocky, 3 to 4 mm 

across, and complexly twinned. Accompanying the plagioclase in subordinate amounts are olivine and augite phenocrysts, set in a pilotaxitic groundmass of plagioclase, augite, 

and magnetite (fig. 44E). Chemical compositions of these 

basalts generally show somewhat higher A12O3 contents 

than in most other Hamakua basalts (see fig. 56; table 16), 

suggesting either the removal of clinopyroxene, as in the 

high-Ti basalts, or the addition of plagioclase.

Mass-balance calculations, using sample IP-20 (table 

17) as a likely parental magma, suggest that plagioclase 

addition is important in at least some of the basalts (for 

example, samples IP-6, IQ-16). The plagioclase-rich 

basalts contain more phenocrysts of plagioclase relative to 

phenocrysts of olivine and augite than do other Hamakua 

basalts. Genesis of the plagioclase-rich basalts must have 

involved the emplacement of basaltic magma at a level 

within the volcano superstructure where slow crystallization 

of the three silicate phases proceeded. Some olivine and 

augite were removed from the magma, but plagioclase crystals, kept in suspension, were concentrated before eruption. 

It is tempting to speculate that all of the west-slope vents 

(fig. 55) represent eruptions from the same fractionating 

magma chamber under that part of the volcano during late 

Hamakua time.

A few lavas in this system were fractionated almost to 

the limit of the basalt field. Sample IP-2 (fig. 56; table 16) 

is a plagioclase-bearing basalt that is not as porphyritic as 

those described above; mass-balance calculations (table 17) 

suggest the removal of much more augite and plagioclase.

The plagioclase-rich basalts were erupted from numerous vents on the west flank of Mauna Kea, as well as at scattered localities elsewhere on the volcano (fig. 55). This 

basalt type, which appeared late in the basaltic substage, 

could have been erupted contemporaneously with the activity that produced the basalts of the Liloe Spring Volcanic 

Member. The plagioclase-rich basalts originated by crystal 

fractionation of a subalkaline parental magma slightly less 

silica saturated than basalts of the Liloe Spring Volcanic 

Member.

BASALTS OF THE HOPUKANI SPRINGS VOLCANIC MEMBER

The basalts of the Hopukani Springs Volcanic Member, 

which crop out on the upper south and east flanks of the volcano (pi. 2), represent eruptions from the summit region. 

The exposed lavas do not represent as long a timespan as 

those in the coastal gulches.

The Hopukani Springs lavas include picrite, 

ankaramite, olivine basalt, plagioclase basalt, and various 

weakly porphyritic, evolved basalts. The porphyritic basalts
94 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

30 30

20

10

TV

V V

20

10

Figure 49. Selected compositions of high-Ti basalt of the Hamakua Volcanics, projected from olivine onto CSMS-A plane of C-M-S-A tetrahedron of O'Hara (1968). See figure 40 for algorithm used to derive components of 

tetrahedron. Heavy lines, 1-bar phase boundaries of O'Hara (1968); light lines, 30-kbar phase boundaries of O'Hara 

(1968). Dashed lines delineate two groups of high-Ti basalt samples that are distinguished on the basis of Al2O3/CaO 

ratios (see table 12 for compositions of representative samples): dots, samples with ratios of <1.6 that are inferred to 

have fractionated at relatively low pressure; circles, samples with ratios of >1.6 that are inferred to have fractionated 

at relatively high pressure. Plots of two groups are displaced toward successively higher-pressure cotectic positions 

(cotectic lines not shown) of O'Hara (1968). Square, composition of sample HP-13 (basalt of the Hamakua Volcanics), which is modeled as parental magma of high-Ti basalts. See table 13 for mass-balance calculations.
PETROLOGY 95

Diopside

OL NEPH

Figure 50. Selected compositions of high-Ti basalt of the 

Hamakua Volcanics, projected from plagioclase onto DI-OLNEPH plane of Sack and others (1987). Components of triangular projection (see Sack and others, 1987, for full 

discussion of projection): DI, (CaO+TiO2+Na2O+K2O)-(Al2O3+ 

Fe2O3); NEPH, 1A( 11 Na2O+l 1 K2O+3CaO+Al2O3+Fe2O3+FeO+ 

MnO+MgO)-1/2(SiO2+2TiO2); OL, 1/2(FeO+MnO+MgO+Al2O3+ 

Fe2O3-CaO-Na2O-K2O). Curves show cotectic lines at different 

pressures. Two groups of high-Ti basalts are distinguished on the 

basis of Al2O3/CaO ratios (see table 12): squares, samples with 

ratios of <1.6, which cluster near 1-bar cotectic line; diamonds, 

samples with ratios of >1.6, which plot closer to 8- to 30-kbar 

cotectic line, suggesting that they represent liquids derived at 

higher pressures.

contain plagioclase, olivine, and augite phenocrysts, 2 to 4 

mm across. In some flows, these minerals also occur in clots 

that appear to be accumulations of fractionated phases. 

Where the groundmass for all of these basalts is nearly 

holocrystalline, it is pilotaxitic and consists of minor 

olivine, abundant plagioclase and augite, and scattered 

titanomagnetite and ilmenite.

The compositions of representative Hopukani Springs 

lavas are listed in table 18. Data for these and another 15 

samples are projected onto the CS-MS-A plane in figure 

57, where most data points are included within one of four 

groups (A-D) within which the lavas are related by composition and proximity. Each group was derived from a unique 

parental magma, and its members are probably related by 

crystal fractionation.

The samples in group A are unique among the 

Hamakua Volcanics because of their high CaO content 

(more than 12 weight percent) and SiO2 content. All of 

these samples come from a section of olivine-bearing lavas 

exposed in Waikahalulu Gulch at 2,925-m (9,600 ft) elevation. A parental magma for group A is similar to sample 

Wa-8 (table 18).

Anorthite Forsterite

Figure 51. Liquidus boundaries in diopside-anorthite-forsterite 

system (from Presnall and others, 1978), showing different crystallization paths at different pressures. Solid lines, 1-bar phase 

boundaries; dashed lines, 3-kbar phase boundaries. Clinopyroxene 

field is larger at 3 kbars than at 1 bar; therefore, more clinopyroxene crystallizes before composition of liquid reaches boundary 

with plagioclase, causing higher augite/plagioclase ratios in fractionating crystals. See table 13 for mass-balance calculations.

The samples in group B were collected in both 

Pohakuloa and Waikahalulu Gulches. Several of these lavas 

contain more than 7 weight percent MgO (for example, 

sample HQ-16, table 18), but they are so phenocryst rich 

that their compositions may reflect accumulation of crystals 

and clots of crystals.

The three samples in group C are from exposures on 

the east side of the volcano near Waipahoehoe Gulch (pi. 2; 

for example, sample HR-59, table 18). Finally, the three 

samples in group D are from a sequence of flows in the 

uppermost part of Pohakuloa Gulch, at 3,700-m (12,400 ft) 

elevation (for example, sample HR-51, table 18).

Mass-balance calculations show that each of these 

groups is compositionally distinct. The compositions of the 

samples within each group are sufficiently similar to indicate that the lavas could be comagmatic. Comparison of the 

spread of points in figure 57 with those for the Hamakua 

Volcanics in general (fig. 40) shows some overlap, but the 

compositions of the samples in group A are unique. The 

parental magmas for all analyzed Hopukani Springs lavas 

were less alkaline than many of the Hamakua lavas, suggesting that the melts feeding vents near the summit 

resulted from higher degrees of partial melting than for 

many of the lavas erupted on the lower flanks.

Comparison of figures 54 and 57 shows that the samples in group B are similar in degree of silica saturation to 

many Liloe Spring lavas. However, we were unable to find 

a parental-magma composition from group B that yielded
96 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Table 13. Mass-balance calculations testing the derivation of high-Ti basalts 

[All values in weight percent, calculated to 100 percent dry weight]

Parental 

magma Daughter 

(sample HP-13) (sample La-103)

Si02 ———— -

AJ-2^3

Fe (as FeO)

MgO ————— -

PaO — ___—_.

Na2 0 ————— -

P2 O U5 ——__——-—

MnO —————— -

Sum r\f t-ho

- —— 46.61 

- —— 13.83

—— 12.89 

• —— 8.43

.— — — in Q Q

2

C "1

Q "3

3

9 Q

- —— .42

Observed 

(a)

45.93 

15.05 

14.93 

5.02 

7.98 

3.46 

1.67 

4.85 

.89 

.22

Modeled 

(b)

45.97 

15.06 

14.96 

5.02 

7.97 

3.40 

1.64 

4.86 

.89 

.25

Residual 

(a-b)

-0.04 

-.01 

-.03 

.0 

.01 

.06 

.03

-.01 

.0 

-.03

nnft

Daughter 

(sample JS-2)

Observed 

(a)

46.88 

13.81 

13.97 

5.19 

9.62 

3.18 

1.35 

5.04 

.75 

.21

Modeled 

(b)

46.88 

13.80 

13.99 

5.16 

9.61 

3.15 

1.44 

4.92 

.80 

.25

Residual 

(a-b)

0.0 

.01 

-.02 

.03 

.01 

.03

-.09 

.12 

-.05

-.04

r>9d

Phases removed from parental magma 

in calculating modeled composition:

Olivine-------

Clinopyroxene1 - 

Plagioclase—— 

Magnetite1 ———•

(Fo74 ) 

(An60 )

Total-

-6.12

-24.13

-19.23

-2.87

-52.35

-8.15

-18.28

-21.36

-3.20

-50.99

: Augite composition: Wo40 En48 Fs 12 , with 1.61 weight percent Ti02 and 3.62 weight 

percent A12 03 (see table 8); magnetite composition: see table 8.

low residuals in mass-balance calculations to derive any 

Liloe Spring lava. An important feature of Hamakua lavas 

erupted from the summit region, in both the Hopukani 

Springs and Liloe Spring Volcanic Members, is the predominantly high degree of silica saturation. These lavas, erupted 

from the summit of the volcano above the inferred, earlier 

shield-stage summit reservoir (see subsection below entitled 

"Shield Stage"), appear to represent magmas that were generated with the highest degrees of melting of all those 

erupted during the postshield stage.

BASALT FROM KANOA

Basalt containing about 3 volume percent of small (1 

mm diam) olivine phenocrysts was erupted northwest of 

Hilo from Kanoa and a nearby cone (fig. 12). These flows 

are older than the ankaramite flow from Kauku that wraps 

around the two cones. The composition of this basalt, which 

is unique on Mauna Kea, is listed in table 19; it shows some 

of the features of evolved Hamakua rocks and some of 

strongly alkaline basalts. The high TiO2, total Fe, and alkali 

contents are similar to those of the high-Ti basalts, but the 

low SiO2 and high MgO contents are similar to those of 

nephelinitic lavas of the Honolulu Volcanics (Macdonald,

1968), which have much lower Fe and TiO2 contents. The 

high MgO content suggests that this composition mest 

likely represents a magma that has not evolved owing to 

crystal fractionation. However, the high Fe, TiO2, and alkali 

contents suggest a primitive melt with a very low degree of 

partial melting.

LAUPAHOEHOE VOLCANICS

INTRODUCTION

A major result of our mapping of the entire surface of 

Mauna Kea is recognition that the boundary between the 

Hamakua and Laupahoehoe Volcanics is petrologic as well 

as stratigraphic. As shown in figures 5 and 6, the lavas of 

these two formations are compositionally distinct. Wherever hawaiitic lavas are found in contact with basalt, the 

basalt is invariably older. Therefore, a striking conclusion is 

that hawaiitic lavas were erupted only after basalt production ceased at or earlier than approximately 70 ka.

A distinct compositional gap separates the Laupahoehoe and Hamakua Volcanics (figs. 5, 6). Although early 

interpretations of the hawaiitic lavas as "andesitic" differentiates (Daly, 1911; Washington, 1923) appears intuitively 

correct, the connection is far from straightforward. West
PETROLOGY 97

Table 14. Major-oxide and normative-mineral compositions of representative lavas of the 

Liloe Spring Volcanic Member and of a similar flow from the northwest flank of Mauna Kea

[Major-oxide compositions and Cross, Iddings, Pirsson, and Washington (CIPW) norms in weight percent; major oxides adjusted to 100 percent dry weight after partitioning of Fe to FeO and Fe2O3 in the 

ratio 88:12. See table 1 for original analyses and analysts]

.

| n

FeO ------

MgO ------ 

CaO ------

Na2 O ———— 

K/-^i

MnO —— - —

q — -— — -

ab — — ——

di — — ——

hy — — ——

mt -------

il

ap —————

Uf~\

—— 14

—— 1

—— 5

—— 10

3

—— 0

—— 4

—— 24

23

—— 3

10

—— 7

—— 1

-5

.22 

.13 

.82 

.05 

.80 

.80 

.91 

.72 

.91 

.44 

.20

.00 

.25 

.62 

.37 

.00

.62 

.63 

.42

.64 

.43 

.04

Liloe Spring

HQ-13 I

48. 

13. 

1. 

12. 

5. 

10. 

2.

3.

0. 

5. 

22. 

23.

21. 

12. 

3.

2. 

7. 

1.

Major

14 

91 

83 

11 

48 

41 

71 

88 

83 

47 

21

CIPW

00 

20 

93 

19 

00

06 

66 

93

65 

27 

11

Volcanic

iQ 14

oxides

48.15 

14.39 

1.66 

10.99 

6.24 

11.29 

2.60 

.79 

3.31 

.40 

.19

norms

0.00 

4.67 

22.00 

25.26 

.00

23.18 

8.31 

6.97

2.41 

6.29 

.95

Member

HR-8

48 

13 

1 

10 

7 

11 

2

2

0 

4 

19 

25

24 

10 

6

2 

5

.18 

.97 

.66 

.97 

.00 

.77 

.30 

.68 

.91 

.36 

.19

.00 

.02 

.46 

.79 

.00

.87 

.42 

.67

.41 

.53 

.85

HR-41

48 

13 

1 

12 

5 

9 

3 

1 

4

0 

6 

25

19

21 

10 

4

2 

7 

1

.57 

.47 

.84 

.15 

.16 

.84 

.05 

.10 

.07 

.54 

.21

.00 

.50 

.81 

.81 

.00

.16 

.22 

.85

.67 

.73 

.28

Northwest 

Flank

10-13

48 

13, 

1, 

11, 

5, 

10, 

2,

3,

0, 

5, 

21 

23

20, 

14, 

2,

2, 

6,

1

.42 

.94 

.79 

.86 

.64 

.49 

.55 

.97 

.66 

.48 

.20

.00 

.73 

.58 

.73 

.00

.86 

.98 

.47

.60 

.95 

.14

Samples:

HQ-5. Nearly aphyric basalt from surface flow on slope above 

Pohakuloa Training Area (see pis. 2, 3).

HQ-13. Nearly aphyric basalt from cinder cone exposed in 

west wall of Pohakuloa Gulch (same cone as for sample HQ14; 'see pis. 2, 3) .

HQ-14. Plagioclase-phyric basalt from cinder cone exposed in 

west wall of Pohakuloa Gulch (same cone as for sample HQ-13; 

(see pis. 2, 3).

HR-8. Moderately porphyritic basalt from small gulch west of 

Waikahalulu Gulch (see pis. 2, 3).

HR-41. Aphyric basalt from fissure ridge west of Keanakakoi 

(adz quarry) (see pis. 2, 3).

IO-13. Weakly porphyritic basalt flow north of Kamakoa Gulch 

(see pis. 1, 4).

and others (1988) pointed out that fractionation trends in 

the two series are offset, suggesting that derivation of 

hawaiite from basalt is not likely to be a matter of lowpressure differentiation.

In this section, we review the petrologic features of 

Laupahoehoe lavas and discuss the origin of the group as a 

whole in the context of the development of the postshield 

stage of the volcano.

PREVIOUS INVESTIGATIONS

Several recent petrologic and geochemical studies have 

focused primarily on the origin of the Laupahoehoe Volcanics. Jackson and others (1982) and Fodor and Vandermeyden (1988) studied the mafic and ultramafic xenoliths that 

occur in 20 to 30 percent of the cinder cones and lava flows. 

Because these xenoliths are common in the hawaiitic lavas
155°45' 155°30' 155°15' vo oo

EXPLANATION

Laupahoehoe Volcanics 

H Lava flows and cinder cones, 

undivided PACIFIC OCEAN

Hamakua Volcanics

Liloe Spring Volcanic Member 

Lava flow Cinder cone

Lava flow similar to that of the 

Liloe Spring Volcanic 

Member

[' [ Lava flow 

^^^1 Cinder cone

PACIFIC 

OCEAN:

Other lava flows and cinder 

cones, undivided

Figure 52. Geologic map of Mauna Kea, showing generalized distributions of basalts of the Liloe Spring Volcanic Member of the Hamakua Volcanics on upper flanks and of 

lavas of similar age and composition on lower flanks. Internal contacts distinguish individual lava flows and cinder cones. Queries mark limits of mapping at edge of dense rain 

forest. Geology simplified from plates 1 and 2 and Wolfe and Morris (1996).

COD 

O
PETROLOGY 99

13

12

UJ 

O

0_ICD 

UJ

10

UJ

I »

O

O 

eo O

HQ-13 HQ-14

789 

MgO CONTENT, IN WEIGHT PERCENT

10 11 12

17

16

LU 

O

w 15 Q_

Io

UJ

? 14

UJ

O 13 

O

12

11

Area of figure 53C

' D

B

45 46 47 48 49

SiO2 CONTENT, IN WEIGHT PERCENT

50 51

Figure 53. Variation diagrams comparing basalts of the 

Liloe Spring Volcanic Member of the Hamakua Volcanics 

(squares) with all other basalts of the Hamakua Volcanics 

(dots), showing hypothetical paths of magma evolution. A, 

CaO versus MgO contents. B, C, A12O3 versus SiO2 contents. Sample IP-21 (circle) is a hypothetical parental

magma (see table 15), and liquid-descent lines (dashed 

where uncontrolled by compositions of specific samples) 

are shown for parent-daughter pairs listed in table 15. Scatter of data points in figure 535 reflects a range of parentalmagma compositions, possibly a result of mixing in an open 

magma chamber.
100 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

o

14.50

14.25

14.00

13.75

13.50

-B-r

HQ-14

IP-21

47.50 47.75 48.00 48.25

SiO2 CONTENT, IN WEIGHT PERCENT

Figure 53. Continued.

48.50

leagues noted that incompatible trace elements, such as P or 

Ce, are twice as abundant in the hawaiitic lavas as in the 

basaltic lavas, showing that hawaiitic magma represents 

residual liquid after crystallization of approximately half of 

a reasonable basaltic parental magma. However, Sr content 

also increases between the two series, exhibiting incompatible behavior. Because Sr is fractionated into plagioclase, 

Frey and others (1990) interpreted these observations to 

indicate that fractionation could not involve much, if any, 

plagioclase and thus would have to take place at a pressure 

sufficiently high to suppress plagioclase crystallization. The 

fractionation was modeled by Frey and others (1990) and 

Fodor and Vandermeyden (1988) with this high-pressure 

constraint.

West and others (1988) studied the compositional variation within a group of Laupahoehoe samples from the summit and south flank of Mauna Kea; they found neither 

temporal nor spatial control of the composition. Major- and 

trace-element variations were shown to result from crystal 

fractionation, which was interpreted as a likely result of 

crystal growth along conduit or magma-chamber surfaces 

over a range of pressures.

but not in the underlying basalts, the gabbros were used by 

Fodor and Vandermeyden to model crystal fractionation 

from basalt to hawaiite.

Trace-element analysis of Hamakua basalts and Laupahoehoe hawaiites by Frey and others (1990) provides the 

basic model for the fractionation process. Frey and his colPETROGRAPHY

Laupahoehoe lavas, whether hawaiite, mugearite, or 

benmoreite, are typically aphyric. In hand specimen, they 

are dense, medium to dark gray, and contain very few discernible crystals. A few flows are weakly porphyritic,

Table 15. Mass-balance calculations illustrating the origin of some basalts of the Liloe Spring Volcanic Member 

[All values in weight percent, calculated to 100 percent dry weight]

Parental magma 

(sample IP-21)

Daughter (sample HR-8), 

using sample IP-21 as parent

Observed 

(a)

Si02 ———— -

A12 03 ———— - 

Fe (as FeO)

MgO —————— -

CaO ————— -

Na2O ———— -

J. _LV_/2

2U5

MnO —————— -

—— 48

—— 14

— 11

—— 12

—— 2

.14 

.06 

.47 

.07 

.04 

.26 

.58 

.87 

.34 

.17

48 

13 

12 

7 

11 

2

2

.26 

.99 

.50 

.01 

.79 

.31 

.68 

.92 

.36 

.19

Modeled Residual 

(b) (a-b)

48.25 

13.98 

12.49 

7.01 

11.79 

2.39 

.66 

2.90 

.39 

.18

0.01 

.01 

.01 

.0 

.0 

-.08 

.02 

.02 

-.03 

.01

m n

Daughter (sample HQ-14), 

using sample HR-8 as parent

Observed 

(a)

48 

14 

12 

6 

11 

2

3

.22

.41 

.52 

.25

.31 

.60 

.79 

.31 

.40 

.19

Modeled Residual 

(b) (a-b)

48.28 

14.45 

12.56 

6.27 

11.31 

2.46 

.74 

3.35 

.39 

.20

-0.06 

-.04 

-.04

-.02 

.0

.14 

.05

-.04 

.01 

-.01.

n'so

Daughter (sample HQ-13), 

using sample HQ-14 as parent

Observed 

(a)

48. 

13. 

13. 

5. 

10. 

2.

3]

23

94 

80 

49 

43 

72 

88 

84 

47 

21

Modeled Residual 

(b) (a-b)

48.20 

13.92 

13.78 

5.48 

10.43 

2.75 

.93 

3.82 

.49 

.21

0.03 

.02 

.02 

.01 

.0 

-.03

-.05 

.02 

-.02 

.0

nnc

Phases removed from or added to parental magma in calculating modeled compositon:

——————— (An 76 ) -6.03

H . DO

- —————— +.95 3

UO78 J -l.Ub

(An 76 ) -1.78

-5.48

+ .75

iro78 j -1.03

(An70 ) -8.92

-.45

-.03

gabbro xenolith; see table 8 for composition.

2 See table 8 for composition.

'Addition of magnetite is an unreasonable crystal—fractionation process; none of the parental magmas of the Hamakua 

Volcanics had Fe contents sufficiently high to derive the composition of sample HR-8 without requiring the addition of 

iron as magnetite.
PETROLOGY 101

"o 

30 30

20

10

7\

V V

20

10

<§><

Figure 54. Selected compositions of basalt of the Liloe Spring Volcanic Member of the Hamakua Volcanics (circles), projected from olivine onto CS-MS-A plane of C-M-S-A tetrahedron of O'Hara (1968). See figure 40 for 

algorithm used to derive components of tetrahedron. Heavy lines, 1-bar phase boundaries of O'Hara (1968); light 

lines, 30-kbar phase boundaries of O'Hara (1968); dotted line, boundary between fields of alkali basalt and transitional basalt; dashed lines, boundaries of plots of two groups of high-Ti basalts from figure 49. Compositions of 

basalts of the Liloe Spring Volcanic Member are offset from those of high-Ti basalts toward greater silica saturation 

and plot closer to lower-pressure (1 bar) phase boundary.
o to

155°45' 155°30' 155*15'

Laupahoehoe Volcanics 

Lava flows and cinder 

cones, undivided

Hamakua Volcanics 

Plagioclase-rich basalt 

Lava flow Cinder cone

Figure 55. Geologic map of Mauna Kea, showing generalized distribution ot plagioclase-rich (plagioclase phenocrysts >8 volume percent) basalt of the Hamakua Volcanics. Internal contacts distinguish individual lava flows and cinder cones. Queries mark limits of mapping at edge of dense rain forest. Geology simplified from plates 1 and 2 and Wolfe and Morris (1996).
PETROLOGY 103

17

16

14

LU

LU

o o

om13

12

11

D

IP-6

D

IO-16

D

IQ-16

D

D D 

D

" . . • D

D

IO-7

n

IP-2.

:• IP-20 0

45 46 47 48 49 50 51

SiO2 CONTENT, IN WEIGHT PERCENT

Figure 56. A12O3 versus SiO2 contents of plagioclase-rich basalts (squares) in comparison with other basalts of the Hamakua Volcanics (dots). Sample IP-20 (circle), hypothetical parental magma (see table 17); chemical analyses and normative-mineral compositions of other numbered samples are listed in table 16.

containing plagioclase phenocrysts and olivine microphenocrysts. Thin-section examination reveals a little more variation in texture and mineralogy. Several flows are characterized by plagioclase phenocrysts, thin (max 2-3 mm in 

longest dimension) plates, as high as 10 volume percent in 

abundance. Olivine and magnetite microphenocrysts, 0.2 to 

0.5 mm long, are present in nearly every specimen. The 

groundmass of all specimens is plagioclase rich, with tiny 

augite grains filling interstices. Olivine and magnetite are 

scattered throughout; ilmenite and apatite occur in rare glass 

pools (fig. 44G). The texture of holocrystalline rocks from 

flow interiors is trachytic, tending toward pilotaxitic, 

whereas specimens collected near the surface of a flow are 

glassier and have hyalopilitic groundmass textures.

Benmoreite flows contain, besides the above-mentioned minerals, microphenocrysts of biotite (max 0.25 mm 

diam) and brown apatite (fig. 44H). The appearance of the

apatite is similar to that in the benmoreites of Mount Etna 

described by Klerkx (1966), who noted that the dark color 

and pseudopleochroism is a result of minute inclusions of 

titanomagnetite or hematite.

Many Laupahoehoe lavas carried mafic and ultramafic 

xenoliths to the surface during eruption. A few of these 

flows contain abundant xenocrystic olivine, recognized by 

irregular shapes and, in a few examples, kink bands. Xenocrysts of plagioclase are much less common. Clinopyroxene 

is unstable in hawaiitic magma, as evidenced by extensive 

solution of xenolithic augite in contact with hawaiitic host 

(fig. 44J). Augite never occurs as phenocrysts and only 

rarely as xenocrysts.

Microprobe analyses of minerals from hawaiitic lavas 

were reported by West and others (1988). Phenocrysts and 

microphenocrysts of plagioclase range in composition from 

An57 to An60, and olivine microphenocrysts are typically
104 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Table 16. Major-oxide and normative-mineral compositions and phenocryst modes of 

representative plagioclase-rich basalts and porphyritic basalt

[Major-oxide compositions and Cross, Iddings, Pirsson, and Washington (CIPW) norms in weight percent; major 

oxides adjusted to 100 percent dry weight after partitioning of Fe to FeO and Fe2O3 in the ratio 88:12; phenocryst 

modes in volume percent. See table 1 for original analyses and analysts]

Plagioclase-rich basalts

Sample -10-16 IQ-16 10-7 IP-6

Major oxides

CIPW norms

Phenocryst modes

Porphyritic 

basalt

IP-2

SiO2 ———— -

A12O3 - —— -

Fe2 03 ——— -

FeO-- ——— - MgO — ——— -

CaO ———— --

Na2 O —— ---

K2O - —— ---

TiO2 —— — -

P2 05 ———— - MnO —— —— -

- ———— 47

- ———— 15

- ———— 1

- ———— 10

- ———— 5

- ———— 11

- ———— 2

- ———— 3

.89

.55

.65

.90

.29

.11

.76

.84

.41

.40

.19

47,

15,

1,

10,

6

11

2,

3,

.97

.32

.59

.52

.14

.39

.59

.80

.10

.40

.18

48

14

1

10

5

10

2

3

.75

.88

.59

.51

.80

.49

.96

.93

.44

.47

.18

47

15

1

10

5

11

2,

2

.84

.91

.58

.47

.69

.81

.45

.73

.99

.36

.17

50,

14,

1,

10

4

8

3,

1,

3,

.84

.53

.65

.87

.33

.93

.34

.37

.16

.76

.21

q ——— ___.

or -------

ab ———— -

an -------

ne -------

di

hy ———— -

ol ——— ---

mt -------

il ———— .

ap--- —— -

- ———— 0.

- ———— - 4.

- ————— 23,

- ————— 27,

- ————— 20.

--- ——— 7,

- ————— 2,

- ————— 6,

.00

.96

.35

.56

.00

.65

.16

.41

.39

.48

.95

0.

4.

21,

27,

21.

6.

8.

2,

5,

.00

.73

.92

.81

.00

.47

.75

.21

.31

.89

.95

0,

5,

25,

24,

20,

8,

6,

2

6

1,

.00

.50

.05

.57

.00

.10

.48

.38

.31

.53

.11

0

4

20

30

21

7

6

2

5

.00

.31

.73

.26

.00

.45

.71

.73

.29

.68

.85

0

8

28

20

15

16

2

6

1

.50

.10

.26

.61

.00

.62

.75

.00

.39

.00

.80

plagioclase1 --- !3.4 

.3

.1

13.0

5.4

14.1 

4.7

7.5

21.0 

3.9

3.6

4.0 

.0

4.0

1 Includes microphenocrysts. 

Samples:

IO-7. Plagioclase-rich basalt flow in Kamakoa Gulch (see pis. 

1,4) .

IO-16. Plagioclase-rich basalt flow (see pis. 1,4).

IP-2. Porphyritic basalt flow north of Auwaiakeakua Gulch (see 

pis. 1,4) .

IP-6. Plagioclase-rich basalt flow from Puu Papapa (see pis. 

1,4) .

IQ-16. Plagioclase-rich basalt of Puu o Kale (see pi. 4).

Fo75 . Typical groundmass-mineral compositions are listed in 

table 20. The compositions of coexisting magnetite and 

ilmenite from one hawaiite flow suggest that these minerals 

crystallized at temperatures near 1,060°C and an oxygen 

fugacity of lO' 10- 1 bar.

COMPOSITION

Individual flows have been mapped in most of the area 

covered by Laupahoehoe lavas. Samples collected from 

each of these flows have been analyzed for major elements
PETROLOGY 105

Table 17. Mass-balance calculations to derive the compositions of plagioclase-rich basalts and porphyritic basalt 

[All values in weight percent, calculated to 100 percent dry weight]

Parental magma 

(sample IP-20)

Daughter 

(sample IQ-16)

Observed 

(a)

Si02 —— —— ——

A12 03 —————— 

Fe (as FeO) —

MgO ———————— 

r* -i c\

Na20 ———————

P2 05 —— — — —

MnO — — —— ——

47 

13 

12 

7 

11 

2

3

.68 

.92 

.14 

.88 

.05 

.56 

.84 

.31 

.44 

.18

48 

15 

11 

6 

11 

2

3

.04 

.34 

.98 

.15 

.41 

.59 

.80 

.11 

.40 

.18

Modeled Residual 

(b) (a-b)

47 

15 

11 

6 

11 

2

3

.97 

.30 

.93 

.13 

.40 

.70 

.87 

.06 

.47 

.18

0.07 

.04 

.05 

.02 

.01

-.11

-.07 

.05 

-.07 

.0

niA

Daughter 

(sample IP-6)

Observed 

(a)

47 

15 

11 

5 

11 

2

2

.75 

.95 

.89 

.68 

.88 

.57 

.76 

.98 

.36 

.17

Modeled Residual 

(b) (a-b)

47.70 

15.92 

11.86 

5.66 

11.88 

2.64 

.81 

2.95 

.42 

.17

0.05 

.03 

.03 

.02 

.03 

-.07 

-.05 

.03 

-.06 

.0

ni T

Daughter 

(sample IP-2)

Observed 

(a)

50.78 

14.51 

12.35 

4.33 

8.92 

3.62 

1.37 

3.16 

.76 

.21

Modeled Residual 

(b) (a-b)

50.75 

14.50 

12.33 

4.32 

8.92 

3.65 

1.41 

3.14 

.77 

.21

0.02 

.01 

.02 

.01 

.0 

-.03 

-.04 

.02 

-.01 

.0

nn/i

Phases removed from or added to parental magma in calculating modeled compositon:

l£"es' o.ou

——————— (An79 ) +2.98 

o o c

- ———— +.75

—————— -.97

\rU85 J 1.11

(An79 ) +8.16 

+ .25 

+2.10 

-1.46

(An79 ) -14.97 

-17.03 

-1.46 

-1.77

1 From ankaramite phenocryst; see table 8 for composition. 

2 See table 8 for composition.

(table 1); this set of 215 analyses is the basis for much of the 

following descriptions and discussion. A selection of analyses spanning the full compositional range is listed in table 

21. MgO-variation diagrams of the full data set (fig. 58) 

show that Laupahoehoe lavas range in composition from 

hawaiite containing as much as 5.0 weight percent MgO to 

benmoreite containing about 2.2 weight percent MgO; however, most samples fall within a much narrower range 

between 3.5 and 4.5 weight percent MgO.

The compositional trends (fig. 58) clearly suggest crystal fractionation; their curvature reflects changes in the 

compositions of the fractionating phases, particularly plagioclase. The sharp inflection at approximately 3.0 weight 

percent P2O5 indicates that apatite fractionation occurred in 

the most evolved magmas.

The fractionation trend represented by the samples 

listed in table 21 also involves a steady increase in the 

degree of silica saturation. The most mafic hawaiites contain about 2 weight percent normative nepheline, whereas 

the benmoreites contain normative hypersthene.

The compositions of Laupahoehoe lavas have been 

plotted on the DI-OL-NEPH diagram of Sack and others 

(1987) and projected onto the CS-MS-A plane of O'Hara 

(1968) (figs. 59 and 60, respectively). Laupahoehoe lavas 

plot on the diagram of Sack and others between the trends 

of liquids on the olivine+orthopyroxene+clinopyroxene 

cotectic at 8 to 30 kbars and at 1 bar, suggesting that the 

magmas may represent liquids from a plagioclase+augite+olivine cotectic at elevated pressure. The displacement 

of points on O'Hara's projection from the low-pressure 

cotectic (fig. 60) also suggests fractionation at pressures 

higher than in shallow magma reservoirs.

ORIGIN OF THE MOST MAFIC HAWAIITE

Frey and others (1990) used trace-element abundances 

to argue that the most mafic hawaiites must be derived from 

basaltic magma by fractionation of a clinopyroxene-dominated assemblage. A plot of Sr versus P2O5 contents (fig. 

61) shows the strong contrast between the Sr contents of 

Hamakua and Laupahoehoe lavas and the diverse trends. 

The positive slope of the Hamakua trend results from both 

olivine control and variation in the degree of silica saturation of the parental magmas; the most alkaline lavas have 

the highest Sr and P2O5 contents. The few Hamakua samples with higher P2O5 contents, offset from the main trend, 

reflect extensive fractionation, as in the formation of the 

high-Ti basalts. The negative slope of the Laupahoehoe 

trend reflects the predominance of plagioclase fractionation 

in the evolution of the hawaiitic magmas.

For a Hamakua basaltic magma to be parental to the 

most mafic hawaiite requires fractionation that would allow 

a twofold increase in Sr content. Comparison of the A12O3/ 

CaO ratios and Sc contents of basalts with those of the more 

mafic hawaiites suggests that clinopyroxene must dominate 

this fractionation (Frey and others, 1990). Furthermore,
106 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Table 18. Major-oxide and normative-mineral compositions of representative basalts of the 

Hopukani Springs Volcanic Member

[Major-oxide compositions and Cross, Iddings, Pirsson, and Washington (CIPW) norms in weight percent; major 

oxides adjusted to 100 percent dry weight after partitioning of Fe to FeO and Fe2O3 in the ratio 88:12. See plate 

3 for locations and table 1 for original analyses and analysts]

Sample HQ-16 HR-44 HR-51

Major oxides

HR-59

SiO2 -- —— -

A12 03 ——— -

Fe2 03 ——— -

FeO - — - — -

MgO —— ----

CaO —— —— -

Na2 O —— — -

K2 O ——— — -

TiO2 ——— --

P2 05 ———— -

MnO ————— -

or --------

ab ————— -

an --------

ne --------

di ————— -

hy ————— -

ol ————— -

mt —— ——— -

il ————— -

ap ——— —— -

- ———— 48.

- ———— 13.

- ———— 1.

- ———— 10.

--- —— 7.

- ———— 11.

- ——— - 2.

- ———— 3.

--- —— 0.

--- —— 3.

- ———— 20.

- —— --23.

- ———— 25.

- ———— 11.

- ———— 4.

- ———— 2.

- ———— 6.

.55

.26

.62

.73

.27

.56

.42

.67

.39

.35

.18

.00

.96

.48

.34

.00

.97

.70

.96

.35

.44

.83

47

10

1

10

14

10

1

2

(

0

2

15

19

26

9

19

2

4

.62

.60

.57

.37

.01

.80

.84

.43

.32

.26

.18

:IPW

.00

.54

.57

.39

.00

.16

.64

.41

.28

.41

.62

47.

14.

1.

10.

6,

12,

2,

2.

norms

0.

3,

20,

27,

25.

4.

9.

2.

5.

.62

.75

.66

.96

.29

.15

.47

.62

.95

.35

.19

.00

.66

.90

.33

.00

.29

.58

.43

.41

.60

.83

46

13

1

11

9

11

2

3

0

1

17

26

22

9

11

2

5

.80

.65

.69

.20

.14

.52

.12

.26

.06

.36

.19

.00

.54

.94

.96

.00

.70

.96

.80

.45

.81

.85

49

12

1

10

8

12

1

2

0

3

15

24

28

18

2

5

.24

.66

.54

.14

.41

.42

.84

.56

.69

.31

.18

.00

.31

.57

.63

.00

.50

.96

.97

.23

.11

.73

Samples:

HQ-16. Olivine basalt in Pohakuloa Gulch.

HR-44. Ankaramite in upper part of Pohakuloa Gulch.

HR-51. Weakly porphyritic basalt in upper part of Pohakuloa 

Gulch.

HR-59. Plagioclase basalt in Waipahoehoe Gulch. 

Wa-8. Olivine basalt in Waikahalulu Gulch.

to avoid depleting Sr, plagioclase fractionation must be 

minimal.

Frey and others (1990) used mass-balance calculations 

to model the derivation of a high-MgO hawaiite by removal 

of olivine and augite from several different Hamakua magmas. In making these calculations, they used a clinopyroxene containing 8.6 weight percent A12O3 , on the basis of the 

compositions experimentally determined by Mahood and 

Baker (1987) for basalt-to-hawaiite fractionation at 8 kbars. 

None of the clinopyroxenes from xenoliths on Hawaiian 

volcanoes (Kuno, 1969; Fodor and Vandermeyden, 1988) 

contains more than about 5 weight percent A12O3 . The derivation of our most MgO rich hawaiite from a slightly alkaline basalt (sample Mu-5), using three different clinopyroxenes, is illustrated in table 22. Clearly, the higher the

A12O3 content of the pyroxene, the less plagioclase is 

involved in the fractionation.

Fractionation dominated by aluminous clinopyroxene 

is a reasonable hypothesis for pressures higher than 5 to 7 

kbars, which greatly expands the clinopyroxene field 

(Mahood and Baker, 1987). This effect is illustrated by the 

liquidus-phase relations in the system diopside-forsteriteanorthite (Presnall and others, 1978), which are summarized 

in figure 62. Elevated pressure enhances clinopyroxene 

crystallization, and the basaltic parental magma crystallizes 

olivine and augite before the melt composition reaches the 

three-phase cotectic with plagioclase. The composition of 

the liquid on this cotectic at 5 to 7 kbars is well within the 

low-pressure plagioclase field, and decreasing pressure during magma ascent shifts the three-phase cotectic from E to
PETROLOGY 107

Figure 57. Selected compositions 

of basalt of the Hopukani Springs 

Volcanic Member of the Hamakua 

Volcanics (dots), projected from olivine onto CS-MS-A plane of C-MS-A tetrahedron of O'Hara (1968). 

See figure 40 for algorithm used to 

derive components of tetrahedron. 

Solid lines, 30-kbar phase boundaries of O'Hara (1968); dashed 

lines, field boundaries for groups of 

compositionally distinct lavas (AD) discussed in text.

30

20

10

V

30

20

10
108 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Table 19. Major-oxide and normative-mineral compositions of 

basalt from Kanoa and nepheline basanite of the Honolulu 

Volcanics, Oahu

[Major-oxide compositions and Cross, Iddings, Pirsson, and Washington 

(CIPW) norms in weight percent. Values for sample HU-6 adjusted to 100 

percent dry weight after partitioning of Fe to FeO and Fe2O3 in the ratio 

88:12. See table 1 for original analysis and analysts of sample HU-6]

Basalt from Kanoa Nepheline basanite

(sample HU-6) (Macdonald and Katsura, 

_______________1964, table 10, no. 2)

Major oxides

SiO2 ——— --

A12 03 ——— -

Fe2 03 ——— -

FeO ———— --

MgO ——— ---

CaO ———— --

Na2O ——— --

K2O ———— --

TiO2 —— ---

P2 o5 ——— -

MnO ——— ---

q —————— ~-

or --------

ab ————— -

an --------

ne --------

di ————— -

hy ————— -

ol ————— -

mt - —— ----

il ————— -

ap --- —— --

- ———— 40.

- ———— 13.

--- —— 2.

- ———— 14.

- ———— 8.

- ———— 9.

- ———— 3.

--- —— 1.

- ———— 6.

- ———— 0,

--- —— 7.

- ———— 9,

- ———— 15.

--- —— 12.

------ 19.

- ———— 18,

--- —— 11.

- ———— 1.

,58

,33

,18

,38

,27

,03

,85

,29

,10

,81

.20

CIPW norms

,00

.62

,11

.28

.71

.83

.00

.84

.16

.59

.92

44.

12.

3.

9.

11.

10.

3.

2.

0.

6.

11,

15.

10.

27.

17,

4,

5.

1,

,33

,80

,38

,14

,05

,52

,60

,99

,65

,43

.15

,00

.12

,53

.57

.22

.18

.00

.60

.87

.02

.01

E' (fig. 62). Thus, plagioclase phenocrysts form in the 

ascending magmas, and clinopyroxene phenocrysts or 

xenocrysts dissolve in these magmas (see fig. 447).

As recognized by Frey and others (1990), a serious difficulty remains with this model: It does not permit a sufficient increase in Sr content to match the Sr contents of 

hawaiitic lavas (West and others, 1988). Using Sr partition 

coefficients of 0.001 for olivine, 0.07 for clinopyroxene, 

and 1.7 for plagioclase, the bulk D value for the fractionation listed in table 22 is 0.342, which allows Sr content to 

increase from about 600 ppm in a parental magma to only 

995 ppm in a derived mafic hawaiite. Other trace elements, 

such as Rb and Ba, also are insufficiently abundant in 

potential parental magmas (for example, sample Mu-5, 

table 22) to yield the abundances found in hawaiites.

We conclude from these arguments that although the 

hawaiitic magmas probably did fractionate from basaltic 

magma at a level below the base of the crust, the parental 

magma has not been erupted onto the surface of Mauna 

Kea. This parental magma must have an Sr content greater 

than that in any of the known basalts, at least 800 ppm, and

other incompatible trace elements must also be about 20 

percent more concentrated than in known basalts. Although 

increases in these trace-element abundances might occur 

through the incorporation of liquids derived from small 

degrees of partial melting of the lithosphere (Chen and Frey, 

1985), no corresponding change is evident in the Sr-isotopic 

composition of Mauna Kea lavas (fig. 35).

FRACTIONATION WITHIN THE HAWAIITIC SUITE

The trends of major-oxide variation with respect to 

MgO (fig. 58) suggest that the compositional variation 

within the Laupahoehoe lavas is related to crystal fractionation of such phases as clinopyroxene and plagioclase (West 

and others, 1988). To assess the fractionation process and to 

understand the spread of points and changes in trend slopes, 

we used mass-balance calculations to model the evolution 

of magma compositions. Compositions of the minerals that 

are used in these calculations are based on electron-microprobe analyses of microphenocryst or groundmass-mineral 

phases (olivine, magnetite, ilmenite, apatite, biotite; see 

table 20) and on hypothetical compositions (plagioclase, clinopyroxene) that allow the best fits.

Selected analyses from across the compositional range 

were used to model a stepwise fractionation process from 

the most mafic hawaiite to benmoreite; the results are plotted in figure 63 and listed in table 23. Important features of 

this fractionation process are as follows. (1) Plagioclase, clinopyroxene, olivine, and magnetite are the most important 

phases, composing about 90 percent of the fractionating 

assemblage at each step. (2) The ratios among these four 

minerals are approximately constant across the full range of 

fractionation. (3) Biotite removal is necessary to accurately 

model the K2O distribution, and biotite fractionation must 

occur across the full compositional range, even though 

biotite is observed only in the benmoreites. (4) Simple fractionation cannot account for the scatter of compositions 

along the trends shown for oxides in figure 58. For example, 

the high P2O5 contents of samples containing from 3.3 to 3.5 

weight percent MgO cannot be derived by fractionation 

from the most mafic hawaiite; either apatite must have been 

added, or, more likely, the parental magma was slightly 

more enriched in P2O5 .

Biotite fractionation accounts for some of the puzzling 

trace-element behavior observed by West and others (1988), 

mainly the limited enrichments of K, Rb, and Ba. The small 

(5-10 percent) decoupling of trace- and major-element 

abundances (West and others, 1988) could be a result of 

variation in parental magmas.

West and others (1988) suggested that the aphyric texture of the Laupahoehoe lavas might reflect crystallization 

on magma-chamber or conduit walls. Furthermore, they 

concluded that polybaric crystallization, which we assume 

would have been controlled by decreasing pressure during 

magma ascent, might account for the compositional varia-
PETROLOGY 109

Table 20. Electron-microprobe analyses of representative minerals in hawaiitic lavas of the Laupahoehoe Volcanics, and compositions of 

minerals used in mass-balance calculations

[All values in weight percent, grd, groundmass; mph, microphenocryst; phn, phenocryst; xen, xenocryst]

Plagioclase:

Occurrence.

Ai2u3 —————— 

Fe (as FeO)-

Vf — f\

An ————————

Clinopyroxana

Occurrence.

Si02 ——————

A12U3 ————————

* G2U3 —————————

MgO ———————

Na2 0 ——————

Total —————

En ————————

IT a ______«___

Magnatita :

Occurrence.

Al2Uj —————————

Fe20, ——————

MgO ——————— 

Ti02 —————— 

MnO ———————

Total ————

phn1

53.66 

29.26

.59 

11.40 

4.44 

.29

99.64

57.6 

40.6 

1.8

grd2

47.89 

4.07 

3.21 

7.26 

11.96 

21.67 

.72 

3.05 

.32

100.15

44.2 

39.6 

16.2

grd

1.05 

23.66 

48.90 

1.93 

23.38 

1.08

100.00

mph2

53.70 

29.07 

' .47 

11.33 

4.98 

.32

grd grd

53.64 54.25 

29.86 28.90

11.46 10.62 

4.99 5.40 

.31 .47

99.87 100.26 99.64

55.2 55.0 50.7 

43.9 43.3 46.7 

1.9 1.7 2.6

grd2

46.68 

4.40 

3.97 

7.43 

11.53 

21.39 

.73 

3.67 

.34

100.14

43.4 

39.0 

17.6

grd3

0.93 

23.40 

49.38 

1.28 

22.98 

.84

98.81

cpxl 3 ' 4

48.36 

8.56 

.00 

6.80 

13.31 

20.00 

.73 

2.24 

.10

100.10

38.1 

47.0 

14.9

grd

56.07 

27.67

9.93

6.16 

.45

100.28

45.9 

51.6 

2.5

cpx23 ' 5

50.3 

4.1 

2.63 

3.13 

15.7 

22.0 

.38 

1.1 

.07

99.41

43.4 

50.6 

6.0

Olivina:

Occurrence .

MnO ———————

MgO ———————

Total —————

Fo ————————

Biotita:

Occurrence.

A12U3 ———— ———

Fe (as FeO) -

MgO ———————

Na20 ———————

MnO ———————

mph1

37.65 

22.91

39.55

100.11 

75.5

mph3

40.3 

12.1 

9.04 

20.5 

.07 

.98 

8.90 

5.48 

.16

97.53

grd grd2 xen1

38.14 36.19 38.27 

25.75 34.27 17.99 

.45 .45 —— 

35.45 29.50 43.30 

.09 .02 —— 

.31 .45 ——

100.19 100.88 99.56 

71.1 60.9 81.1

Apatita :

Occur- mph3 

rence .

Fe (as FeO)- 0.75

MgO ——————— .48 

CaO ——————— 53.88 

MnO ——————— .10

Total ————— 96.13

Ilmanita :

grd grd3

0.47 

8.95 

40.34 

1.21 

48.34 

.91

100.22

0.10 

7.30 

39.76 

1.98 

49.07 

.82

99.03

and others (1988). 

2Perdue (1982).

3Used in mass-balance calculations in tables 22 and 23. 

*Frey and others (1990); same as cpxl of table 22. 

5Fodor and Vandermeyden (1988, table 3, No. 9); same as cpx2 of table 22.

tion among Laupahoehoe lavas. However, we believe that 

the evidence does not support polybaric crystallization as a 

control on compositional variation. The data plotted in figures 59 and 60, which should show the effects of any polybaric crystallization, display no such effect. The most mafic 

Laupahoehoe hawaiite, sample HR-67, plots within the 

tight cluster of data points (fig. 59) between the 8- to 30- 

kbar and 1-bar cotectics on the DI-OL-NEPH plane of 

Sack and others (1987); there is no spreading away from 

this cluster toward the 1-bar cotectic of data points representing the more evolved Laupahoehoe lavas. Similarly, 

data points representing the full Laupahoehoe compositional range (fig. 60) are approximately equidistant from the 

1-bar cotectic in the CS-MS-A plane of O'Hara (1968).

An additional line of reasoning also argues against 

polybaric crystallization as a significant cause of the compositional variation among Laupahoehoe lavas. As shown in 

figure 62, the most mafic hawaiitic liquid had reached a 

cotectic where it was in equilibrium with plagioclase, clinopyroxene, and olivine. This is, in fact, a quaternary cotectic involving magnetite as well. Decompression would 

displace the cotectic composition such that the liquid composition would lie in the plagioclase field, and increasingly 

greater amounts of plagioclase would have to be fractionated for the liquid to reach the lower-pressure cotectic composition. The calculations summarized in table 23, however, 

suggest that the ratios among the four major phases remain 

nearly constant as the liquid evolves; there is no indication
110 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

Table 21. Major-oxide and normative-mineral compositions of representative lavas of the 

Laupahoehoe Volcanics

[Major-oxide compositions and Cross, Iddings, Pirsson, and Washington (CIPW) norms in weight percent; major oxides adjusted to 100 percent dry weight after partitioning of Fe to FeO and Fe2O3 in the 

ratio 88:12. See table 1 for original analyses and analysts]

Sample• HP-11 HQ-4 HR-55 HR-67 HR-72 JQ-10

Major oxides

SiO2 ———

AX2U3

Fe203 —— 

FeO-- - —

MgO — ---

PaO

Na2O ----

K

r\

T-i O

P

r\

MnO — ——

—— 50.

—— 1.

—— 1.

.53

.11

dp

.70

o c.

o c.

• £* £*

1.

p

3.

6.

5,

1,

.79

.60

n P

.03

1 ft

.19

.36

.07

16,

1,

1, 

3,

.44

.92

.48

ftO

.55

.39

.50

n c.

DP

P 1?

16.

1.

10.

5.

1.

3.

.75

.51

.00

.01

,65

.20

.65

R1

51

1,

3

6

4

1

"7 C.

1 P

• —> £t

.71

.59

.74

.91

.06

.50

0?

55

17

1

7

4

5

2

1

1

o c.

.71

"3. P

O C.

.54

.70

.79

.41

.00

CIPW norms

or -----

ab ——— -

an -----

ne -----

di — ——

hy — ——

ol —— --

mt- - — -

il — ——

ap-- ——

——— 0,

——— 10,

——— 35,

——— 20

——— 2,

- —— 7,

——— 13,

——— 2,

——— 5.

——— 2.

.00

.99

.86

.29

.12

.47

.00

.69

.09

.43

.13

0,

13,

43,

17

3,

12,

1.

3,

2,

.00

.95

.13

.76

.43

.97

.00

.18

.77

.93

.96

0,

10.

33.

20.

2.

8.

14.

2.

5.

2.

.00

.40

.95

.77

.23

.46

.00

.17

.15

.85

.06

0,

9,

32.

22,

1,

8,

15,

2.

6.

1.

.00

.75

.22

.63

.80

.29

.00

.11

.19

.13

.92

0,

12.

40.

18,

6,

12.

1.

4.

2.

.00

.17

.19

.75

.74

.69

.00

.43

.91

.75

.42

0,

16,

48,

14,

1,

4,

8,

1,

2.

2.

.00

.49

.23

.50

.00

.26

.58

.33

.62

.68

.37

Samples:

HP-11. Hawaiite flow from Puu Ka Pele (see pi. 4).

HQ-4. Mugearite scoria block from Puu Pohakuloa (see pi. 

3) .

HR-55. Hawaiite flow from Puu Makanaka (see pi.3). 

HR-67. Hawaiite flow from Puu Kaiwiiwi (see pi. 3). 

HR-72. Mugearite flow from Puu Poliahu (see pi. 3). 

JQ-10. Benmoreite flow from Kaluamakani (see pi. 4).

of the enhanced plagioclase fractionation that should have 

occurred as a result of decompression. Therefore, we suggest that all the Laupahoehoe magmas originated at similar 

depth, in a deep magma chamber(s) in which the magmas 

evolved to varying extents. Little or no fractionation 

occurred upon ascent, although some of the magmas began 

to crystallize plagioclase before eruption.

The slight increase in silica saturation throughout the 

fractionation sequence of Laupahoehoe lavas (table 21) 

results from the 1.5- to 3-percent removal of magnetite and 

ilmenite for each step summarized in table 23.

MAFIC AND ULTRAMAFIC XENOLITHS

Useful evidence to help locate the magma chamber(s) 

in which the hawaiitic magmas evolved comes from the 

suite of mafic and ultramafic xenoliths contained in 20 to 30 

percent of the Laupahoehoe flows and cinder cones. Xenoliths in Hawaiian lavas have been the subject of numerous 

studies (see review by Clague and Dalrymple, 1987, p. 24- 

27, and references therein). Those in Mauna Kea lavas were 

investigated by Fodor and Vandermeyden (1988), who 

made a careful study of gabbroic xenoliths from the summit
PETROLOGY 111

57

54

LLJ

18

17

16

12

11

SiO,

AUO2^3

O

O

LLJ

Q

X 10

O

FeO + 0.9 Fe2O3

CaO

4 

3.0

2.5

2.0

1.5 

4

Na?O

1.5

1.3

1.1

0.9

0.7

KoO

TiO,

PoO2^5

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

MgO CONTENT, IN WEIGHT PERCENT

Figure 58. MgO-variation diagrams for lavas of the Laupahoehoe Volcanics. Circled data points represent lava compositions 

used for modeling in mass-balance calculations (see table 23); connecting line, viewed from right to left, approximates fractionation-controlled liquid-descent line.
112 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

NEPH

Figure 59. Compositions of lavas of the Laupahoehoe Volcanics (crosses), projected from plagioclase onto DI-OLNEPH plane of Sack and others (1987). See figure 50 for algorithm used to derive components of triangular projection. 

Curves show cotectic lines at different pressures.

cone; by Jackson and others (1982), who reported field 

modes of occurrences from more than 35 cones and flows; 

and by H.G. Wilshire and I.E. Nielson (written commun., 

1987), who made a careful study of xenoliths from Puu 

Haiwahine.

Xenoliths in Laupahoehoe lavas and cinder cones represent three lithologic groups, in order of abundance: 

gabbro, peridotite, and pyroxenite. The gabbros vary in 

grain size and modal composition, but they are uniformly 

composed of plagioclase (An81 _86), clinopyroxene 

(Wo44En46Fs 10), and olivine (Fo80) (Fodor and Vandermeyden,-1988). Gabbro, two-pyroxene gabbro, and troctolite are 

the most common rock types. Grain size ranges from 0.5 to 

5 mm, and many samples appear banded from inhomogeneous distribution of pyroxene and plagioclase. Microgabbros with very fine grained to fine-grained, equigranular 

textures commonly are compositionally banded. Some of 

these microgabbros contain crosscutting dikes and veins 

with similar minerals that differ from those of the host in 

grain size.

Dunite and wehrlite are the most common of the 

Mauna Kea ultramafic xenoliths (see Jackson and others, 

1982); Cr-diopside Iherzolites are comparatively rare, and 

some or them occur as composites with dunite. Many to 

most peridotites are deformed; the rocks are sheared, and 

grains exhibit kink bands. In most of the literature on 

Hawaiian xenoliths, such peridotites are termed "metamorphic"; they form significant proportions of the total xenolith 

assemblages. H.G. Wilshire and I.E. Nielson (oral commun., 1988) reported that some xenoliths of this type, 

including some dunites, have veins and dikes of gabbro and 

microgabbro, as much as about 1 cm thick; the finer grained

dunites commonly contain net veins of microgabbro, 1 to 3 

mm thick. Such textures suggest that the dunites could be 

from melt-extraction zones, possibly for midoceanic-ridge 

basaltic (MORE) magmas, and so are not "cumulates." 

The larger dikes cutting these dunites could be very 

much younger, possibly related to Mauna Kea shield-stage 

volcanism.

Fodor and Vandermeyden (1988) showed that the compositions of plagioclase in the gabbros are unlikely for plagioclase that crystallized from MORB-like magma. They 

suggested, instead, that the gabbroic xenoliths represent 

crystallization residues from Hamakua alkaline basalts 

which yielded evolved Hamakua hawaiites (our high-Ti 

basalts) or Laupahoehoe hawaiites. They hypothesized the 

crystallization of a large magma chamber in the superstructure of the volcano to account for the various types of xenoliths found in their study. Although we cannot rule out such 

a possible source of some xenoliths, the persistence of peridotite in the xenolith assemblage argues for an alternative 

source. Most xenoliths are bounded by planar surfaces, with 

as many as six differently oriented surfaces on a single fragment. The source of these xenoliths must be complexly 

jointed. Well-rounded xenoliths, possibly from loosely compacted accumulates, are fairly rare.

We agree with H.G. Wilshire and I.E. Nielson (oral 

commun., 1988) that the source for most, if not all, of the 

xenoliths is likely to be a zone of intensely injected and 

jointed peridotite at or somewhat below the base of the oceanic crust. An alternative suggestion to the view that the 

gabbro xenoliths represent residues from fractionating 

Hamakua basaltic magma (Fodor and Vandermeyden, 1988) 

is that most of these xenoliths, especially those with two 

pyroxenes, could represent tholeiitic dikes injected during 

building of the shield. Mineral compositions alone, however, are insufficient to distinguish whether a pyroxene and 

plagioclase assemblage was derived from tholeiitic magma 

or from transitional- to alkali-basalt magma.

ORIGIN OF LAUPAHOEHOE HAWAIITIC LAVAS

Interpretations of the major-element compositions of 

the hawaiitic lavas require extensive fractionation of an 

alkali-basalt parental magma. The first stage of this fractionation must have been dominated by removal of clinopyroxene at pressures of at least 5 to 7 kbars. This removal 

produced a hawaiitic liquid at a quaternary cotectic (olivine, 

clinopyroxene, plagioclase, magnetite). Varying degrees of 

fractionation of this cotectic assemblage produced more 

evolved magmas, ranging in composition to benmoreite.

These hawaiitic, mugearitic, and benmoreitic magmas 

apparently ascended to the surface without interruption, 

passing through the source region(s) of xenolith assemblages and entraining fragments. The spatial relations of the 

magma chamber, xenolith source, and ascent paths are illustrated in figure 64D.
PETROLOGY 113

30 30

20

10

\

-HR-67(H)

V

20

10

Figure 60. Selected compositions of lavas of the Laupahoehoe Volcanics projected from olivine onto CS-MS-A 

plane of C-M-S-A tetrahedron of O'Hara (1968). See figure 40 for algorithm used to derive components of tetrahedron. Heavy lines, 1-bar phase boundaries of O'Hara (1968); light lines, 30-kbar phase boundaries of O'Hara (1968). 

Circles, Laupahoehoe lavas, showing sample number and, in parentheses, lava type (B, benmoreite; H, hawaiite; M, 

mugearite); see table 21 for chemical analyses and normative-mineral compositions, and figure 58 for approximations 

of fractionation-controlled liquid-descent lines. Square, composition of sample Mu-5 (basalt of the Hamakua Volcanics), which is modeled as parental magma of sample HR-67 (most mafic hawaiite); see table 22 for mass-balance 

calculations. Sample HR-67 is modeled as parental magma of other Laupahoehoe lavas depicted here; see table 23 for 

mass-balance calculations.
114 GEOLOGY AND PETROLOGY, MAUN A KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

1400 

O

=! 1200 

^

cca! 1000

CO

< 800

600

O 

O

CO

400

200

v.

6> 

°o o

Diopside

0.0 0.2 0.4 0.6 0.8 1.0 1.2 

P2O5 CONTENT, IN WEIGHT PERCENT

1.4

Figure 61. Sr versus P2O5 contents of lavas of the Hamakua 

Volcanics and the Laupahoehoe Volcanics (from Frey and others, 

1990). Circles, Hamakua Volcanics; dots, Laupahoehoe Volcanics.

DEVELOPMENT OF

MAUNA KEA VOLCANO—

AN INTERPRETATIVE SUMMARY

INTRODUCTION

The geology and petrology of Mauna Kea Volcano provide a rich detail of activity during a particularly extensive 

postshield stage. That detail, combined with inferences on 

shield-stage activity, enables us to write a history of mantle 

melting and surface eruptions for this large Hawaiian volcano. In the following review of the development of Mauna 

Kea Volcano, we describe its growth through the first three 

stages—preshield, shield, and postshield—that are now recognized in the evolution of a typical Hawaiian volcano 

(Clague and Dalrymple, 1987).

The growth and evolution of Hawaiian volcanoes 

apparently results from continuous passage of the Pacific 

Plate over the Hawaiian hotspot, a relatively fixed source of 

ascending primitive mantle material (Clague and Dalrymple, 1987). However, volcano growth along the Hawaiian 

Chain is a discontinuous process. As indicated by Mauna 

Kea, once a conduit system is established as a pathway for 

ascending magma, it persists for possibly a million years 

(see fig. 4). During this time, production of tholeiitic 

magma increases to a rate as high as about 0.1 knvVyr but 

averages somewhat less (Dvorak and Dzurisin, 1993). 

While eruptions and intrusions are completing construction 

of a shield with a volume of approximately 30,000 km3 , 

another, apparently independent conduit system is established 40 to 50 km to the southeast (fig. 64C). Eventually, 

magma production decreases by an order of magnitude, and 

the volcano enters the postshield stage.

Anorthite Forsterite

Figure 62. Liquidus boundaries in diopside-anorthite-forsterite 

system (from Presnall and others, 1978), showing effect of pressure on crystallization of alkali basalt to produce hawaiitic liquid. 

Solid black lines, 1-bar phase boundaries; solid red lines, 7-kbar 

phase boundaries. Circle indicates composition of alkali basalt, 

hypothetical parental magma of hawaiitic liquid. Dashed black line 

shows path of parental liquid during crystallization at 7 kbars; 

dashed red line shows trace of three-phase cotectic point (E to E') 

as magma is decompressed.

The types of lava and length of activity of the postshield stage vary from volcano to volcano (Wright and 

Clague, 1989). The characteristic lava is hawaiite, an 

evolved alkalic basalt, but some volcanoes (such as Mauna 

Kea) pass through a transitional period during which the 

shield-stage tholeiitic lavas give way to transitional and 

alkali basalts before the appearance of hawaiite.

Comparison of basalt compositions with those of liquids obtained through high-pressure, dry-melting experiments by O'Hara (1968) (see fig. 40) and Falloon and others 

(1988) show that the range of lava compositions erupted 

during the preshield, shield, and postshield stages can originate from parental magmas generated by differing degrees 

of partial melting of garnet-bearing peridotite at pressures 

near 30 kbars. Although the precise cause of this melting is 

still unknown, the general view is that hot primitive mantle 

material ascends beneath the oceanic lithosphere underlying 

Hawaii and reacts with the lithosphere to produce the 

Hawaiian parental magmas (Clague and Dalrymple, 1987). 

Isotopic compositions of Hawaiian lavas (for example, 

Chen and Frey, 1985) indicate that the dominant contribution comes from undepleted primitive mantle, with smaller 

amounts from depleted lithospheric mantle. The magmaproduction history (rate, volume, and composition) of
DEVELOPMENT OF MAUNA KEA VOLCANO—AN INTERPRETATIVE SUMMARY 115

Table 22. Mass-balance calculations to derive the compositions of the most mafic hawaiites of the Laupahoehoe Volcanics

[Major oxides and mineral compositions in weight percent, calculated to 100 percent dry weight; trace-element contents in parts per million (from Frey and 

others, 1990). Clinopyroxene compositions: cpxl, Wo38En47Fs 15 , 8.56 weight percent A12O3 , and 2.24 weight percent TiO2 (Frey and others, 1990) (see table 

20 for microprobe analysis); cpx2. Wo43En51Fs6 , 4.10 weight percent A12O3 , and 1.10 weight percent TiO2 (Fodor and Vandermeyden, 1988, table 3, no. 9) 

(see table 20 for microprobe analysis); cpx3, Wo40En48Fs)2, 3.62 weight percent A12O3 , and 1.61 weight percent TiO2 (see table 8 for microprobe analysis)]

Parental magma 

(sample Mu-5)

Daughter 

(sample HR-67)

Observed 

(a)

Modeled Residual 

(b) (a-b)

Modeled Residual 

(c) (a-c)

Modeled 

(d)

Residual 

(a-d)

Major oxides

Si02 —

AJ.2 U3

Fe (as

MgO —— -

Na2 0 — -

2°5

MnO —— -

————— 46

FeO) — 12

————— 10 

————— 2

•j

.78 

.59 

.37 

.08 

.36 

.85 

.90 

.34 

.42 

.17

48.82 

17.02 

11.38 

5.02 

7.66 

4.21 

1.65 

3.24 

.81 

.20

48.91 

17.06 

11.43 

5.04 

7.66 

4.15 

1.53 

3.30 

.74 

.19

-0.09

-.04 

-.05 

-.02 

.00 

.06 

.12 

-.06

.07 

.01

48 

17 

11 

5 

7 

4 

1 

3

.97 

.08 

.47 

.05 

.66 

.19 

.48 

.33 

.71 

.18

-0.15

-.06 

-.09 

-.03

.00 

.02 

.17 

-.09 

.10 

.02

48 

17 

11 

5 

7 

4 

1 

3

.97 

.07 

.47 

.04 

.66 

.20 

.47 

.33 

.71 

.19

-0.15

-.05

-.09 

.02 

.00 

.00 

.18 

-.09 

.10 

.01

Trace elements

Rb ————

tj JBa ———— • **f\*

1 £ Q

C.f\ Q

——— 61

30

1,300

570

100

27.9

500

100

2.1

305

70

0

_ n/io

o c c

Q A C.

475

3 *J

3.5

354

95

5

i no

o c c

944

475

96

3.5

356

95

4

i nn

(major oxides only). 

Phases removed from or added to parental magma in calculating modeled composition:

Olivine————— 

Plagioclase—— 

ClinopyroxeneMagnetite1 ——— 

Ilmenite1 ———

•<Fo74 ) 

(An79 ) 

(cpxl)

-5.12

-10.40

-19.80

-3.11

-.51

-4.49

-4.72

(cpx2) -23.27

-3.31

+ .28

-5.02

-8.42

(cpx3) -18.16

-3.58

-.23

Total -38.94 -35.51 -35.41

table 20 for composition.

Mauna Kea places significant limiting constraints on this 

melting process.

PRESHIELD STAGE

Hawaiian preshield lavas are known only from Loihi 

Volcano (see fig. 1). Dredge samples from Loihi include 

tholeiitic and alkali basalts. Moore and others (1982) suggested that Loihi is in transition from production of early 

alkali basalts, reflecting low degrees of partial melting of 

the source rocks, to production of tholeiitic basalt, reflecting 

greater partial melting as shield building develops.

Preshield lavas, if present on Mauna Kea Volcano, are 

not exposed. Figure 3 shows an approximate volume of 500 

km3 of preshield lava, equivalent to the volume of Loihi as 

estimated from bathymetry (fig. 1). However, neither the

ultimate volume of Mauna Kea preshield lava nor the duration of its production is known. We simply infer that a relatively small volume of alkali basalt was produced by low 

degrees of partial melting from the Mauna Kea source rocks 

during the earliest period of magma production.

SHIELD STAGE

Shield-stage lavas are not exposed on the subaerial part 

of Mauna Kea. Hilo Ridge, however, which has strong topographic definition at depths below 1.5 km (fig. 1), closely 

resembles in form the submarine extension of Kilauea's east 

rift zone. By analogy with Kilauea (see Decker, 1987, for a 

review of its structure and dynamics), we interpret Hilo 

Ridge as the east rift zone of Mauna Kea Volcano during the 

shield stage. We presume that, as at Kilauea, the rift-zone
116 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

70 60 50 

REMAINING MELT, IN WEIGHT PERCENT

40 30

Figure 63. Schematic diagram illustrating stepwise fractionation of hawaiitic lavas of the Laupahoehoe Volcanics, showing 

evolution from most mafic hawaiite to benmoreite. Sample HR67 (most mafic hawaiite) is modeled in successive mass-balance 

calculations as parental magma of sample JQ-10 (benmoreite); 

other sample numbers shown are modeled intermediate daughters 

(see table 23). Vertical lines represent individual samples; amount

of each mineral removed is shown by vertical separation of mineral boundaries. Percentages of both crystals removed and melt 

remaining for each step are determined with respect to composition of sample HR-67. "An" (anorthite content, in weight percent) 

indicates calculated composition of plagioclase removed in each 

modeled step. See Spengler and Garcia (1988) for similar fractionation diagram for hawaiitic lavas of Kohala Volcano.

lavas of Mauna Kea were erupted along the ridge axis from 

shallow conduits supplied from a shallow central reservoir 

beneath the summit region of the volcano.

We view the shield stage as representing that period in 

the growth of the volcano characterized by voluminous

eruption of fluid lava, much of which was pahoehoe. As 

noted above in the subsection entitled "Geologic Setting," 

surface slopes on actively growing Hawaiian shields are 

much steeper below sea level than above; a sharply defined 

break in slope occurs at the shoreline (Moore and Fiske,
DEVELOPMENT OF MAUNA KEA VOLCANO—AN INTERPRETATIVE SUMMARY 117

Table 23. Mass-balance calculations illustrating fractionation in hawaiitic lavas of the Laupahoehoe Volcanics 

[All values in weight percent, calculated to 100 percent dry weight]

A1203 - 

Fe (as

MgO —— •

Na20 — • K2 0 —— • Ti02 — •

2 us — 

MnO —— •

Parental magma 

(sample HR-67)

Fed) ———— 11.40

————————— 5.01

4

*5 f\

__ _ _, __ .____ 7 07

————————— .20

Daughter (sample HR-55), 

using sample HR-67 as parent

Observed 

(a)

49.51 

16.95 

11.15 

4.56 

7.40 

4.51 

1.76 

3.09 

.87 

.21

Modeled 

(b)

49.53 

16.95 

11.16 

4.56 

7.39 

4.44 

1.76 

3.10 

.90 

.20

Residual 

(a-b)

-0.02 

.0 

-.01 

.0 

.01 

.07 

.0 

-.01 

-.03 

.01

Daughter (sample HP-11), 

using sample HR-55 as parent

Observed 

(a)

50.18 

17.20 

10.86 

4.11 

7.09 

4.71 

1.86 

2.87 

.91 

.22

Modeled 

(b)

50.18 

17.20 

10.86 

4.11 

7.09 

4.71 

1.86 

2.87 

.91 

.21

Residual 

(a-b)

0.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.01

. nnrv

Phases removed from or added to parental magma in calculating modeled composition:

Magnetite1 ————————————— •

Apatite1 ——————————————— •

rri_.|- a 1 «..»»

Original melt

———— ———— tro70 > -x.03

—————————— -2.45

1 OT

——————————— -0.24

——————————— -1.11

f\ c

• U O

\ru70 / u.30 

(An 50 ) -3.38 

-2.61 

-.76 

-.40

-.50 

-.10 

-8.68

79.38

Daughter (sample HR-72), 

using sample HP-11 as parent

Daughter (sample HQ-4), 

using sample HR-72 as parent

Daughter (sample JQ-10), 

using sample HQ-4 as parent

01

C •! ft 1

Fe (as FeO) —

MgO ————————

2 U5 ————————————

MnO ————————

>served 

(a)

31.80

L7.20 

9.92 

3.59

4.92

2.50

1.02 

.22

Modeled 

(b)

17.19 

9.91 

3.59

5.00

2.07

2.49

.99 

.22

Residual 

(a-b)

0.02

.01 

.01

.0

-.01

• u o

-.01

.01

.03

.0

Observed ; 

(a)

•J £. . O O

9.19

3.03

6.19

5.20

2.07

Modeled I 

(b)

J £. m O O

9.19

3.03

5.22

2.07

1.24

.23

tesidual 

(a-b)

0.0

.0 

.0

.0

.0

-.02

.0

.0

.01

.0

Observed 

(a)

55.92

17.72

8.40

2

0 £

4.54

5.70

2.79

1.42

1.00

Modeled I 

(b)

55.93

17.73

8.40 

29 a

4.54

5.68

2.79 

1.42

1.00

o /:

Residual 

(a-b)

-0.01

-.01

.0 

.0

.0

.02

.0

.0

.0 

-.03

Sum of the squares of residuals— .0099 .0007

Phases removed from or added to parental magma in calculating modeled composition:

.0017

Ilmenite 1 ----- —— ——

Total —— —— —— — ——

Original melt

-10.42 

-2.30 

-2.75 

-.15 

-1.15 

-.26

-18.75 

64.49

(An,0 ) -7.15 

-4.83

-L.59 

-.60 

.94 

.09

-14.63 

55.06

Vro70 / u.oj.

(An40 ) -17.54 

5.62 

-3.01

.62

-4.71 

-1.33

-30.78 

38.11

lSee table 20 for composition.

1969). As long as the rate of upward growth due to volcanic 

resurfacing exceeds the rate of subsidence, the slope break 

is maintained at sea level. However, when production of 

voluminous fluid lava is curtailed, subsidence carries the 

fossil slope break below sea level. Figure 1 shows three successive slope breaks along the northeast flank of Hawaii: 

the first at approximately 1-km depth on Kohala Volcano; 

the second at approximately 0.4-km depth on Mauna Kea 

Volcano; and the third, south of Hilo, at sea level on Mauna 

Loa and Kilauea Volcanoes.
118 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

The submarine surface above the Mauna Kea slope 

break slopes 2.8° in the area of the cross section shown in 

figures 1 and 2. An identical slope occurs along the northeastern part of Kilauea's subaerial southeast flank; Kilauea's 

subaerial flank farther southwest has been steepened by 

faulting. Even gentler slopes (generally less than 2° and 

locally less than 1°) characterize the lower northeast sector 

of the combined Mauna Loa and Kilauea shields between 

Hilo and Cape Kumukahi. Thus, we believe that the gentle 

submarine slope between sea level and 400-m depth along 

the northeast flank of Mauna Kea approximately represents 

the fossil surface of the shield.

The subaerially exposed postshield lavas on the lower 

flank of Mauna Kea underlie appreciably steeper slopes, 

ranging from approximately 4° to 9°. However, the postshield flows have been truncated in the seacliffs of Mauna 

Kea's northeast coast, indicating that they at least partly 

bury shield-stage lavas on the nearshore submarine slope. 

Nevertheless, we conclude that the approximate boundary 

between shield and postshield flows is close below sea level 

at the shoreline.

K-Ar ages for some of the oldest visible basalts of 

Mauna Kea, exposed near sea level in deep gulches on the 

northeast flank of the volcano (figs. 12, 13), indicate that the 

shield stage had terminated by about 250 ka. We estimate 

the volume of the shield, including the large volume that has 

subsided beneath the level of the adjacent ocean floor (fig. 

IB), at 32,000 km3 . Applying Swanson's (1972) estimate of 

0.1 kmVyr for Kilauea's magma-supply rate, we calculate a 

minimum duration of 320,000 yr for the shield stage. However, as indicated by Dvorak and Dzurisin (1993), that rate 

probably represents a maximum value, and Kilauea's average magma-supply rate is more likely between 0.01 and 0.1 

knrVyr. In addition, Mauna Kea's magma-supply rate probably accelerated during the early part of the shield stage and 

waned during the later part. Thus, appreciable uncertainty 

exists about the duration of the shield stage. A median average magma-supply rate, approximately 0.5 kmVyr, gives a 

650,000-yr duration for the shield stage, which we provisionally accept as a reasonable estimate (see fig. 4).

Figure 1 shows that Hilo Ridge loses its strong topographic definition at depths above 1,500 m and has no topographic expression above the slope break at 400-m depth or 

on the subaerial part of the volcano. The lavas on the crest 

of Hilo Ridge represent the youngest flows erupted during 

the active life of the east rift zone. Moore and Peck (1966) 

noted that the vesicularity of samples of pillow basalt 

dredged from Hilo Ridge was comparable to that of basalt at 

much shallower depths on the currently active rift zones of 

Kilauea and Mauna Loa. They concluded that approximately 1,000 m of subsidence had occurred since these 

dredged basalts were erupted on Hilo Ridge. At a subsidence rate of approximately 2.6 mm/yr, which Ludwig and 

others (1991) determined to have been fairly uniform since 

475 ka for this part of Hawaii, this much subsidence would

Figure 64. Schematic cross sections of Mauna Kea, showing —> 

its growth history and its relation to adjacent volcanoes along 

Kea locus (Jackson and others, 1972). Sections run approximately northwest to southeast (left to right). Interleaved lavas 

of Mauna Loa, to southwest along Loa locus (Jackson and others, 1972), are not shown. A, Middle shield stage, approximately 600 ka. Magma-supply rate is high, averaging 0.01 to 

0.1 km3/yr. Tholeiitic-basalt magma rises from upper-mantle 

source region through a central conduit to shallow reservoir 

beneath Mauna Kea's summit. Volcano develops active east 

rift zone (not shown), which is also supplied with magma from 

summit reservoir. Summit-reservoir drawdown that results 

from large rift-zone eruptions or intrusions causes formation 

and episodic rejuvenation of caldera (see Holcomb, 1987). 

Mauna Kea's volcanic edifice progressively subsides as its 

mass increases. Lava flows interfinger with those of Kohala, 

which is near end of its shield stage (Wolfe and Morris, 1996). 

B, Late shield stage, approximately 350 ka. Tholeiitic-basalt 

magma and, possibly, transitional-basalt magma continues to 

rise, although diminishing magma production had resulted in 

termination of rift-zone activity, and so caldera fills with lava 

and is not rejuvenated. Central conduit and summit reservoir 

are still active; shield lavas erupt at summit or, possibly, from 

radial vents supplied from summit reservoir. Flows interfinger 

with postshield lavas of Kohala. C, Postshield stage (basaltic 

substage), approximately 150 ka. Melting rate and, thus, degree 

of partial melting in source region are diminished, and so production of tholeiitic-basalt magma has ceased. Transitionalbasalt magma from central part of source region maintains supply to central conduit and summit reservoir. Alkali-basalt 

magma from outer parts of source region rises in small batches 

into flanks of volcano, where it commonly fractionates in isolated ephemeral chambers before erupting at surface. Southeastward along Kea locus, Kilauea is in preshield stage, 

erupting alkalic-basalt lavas. D, Postshield stage (hawaiitic 

substage), approximately 30 ka. Alkali-basalt magma, generated in response to slow melting rate and, thus, low degree of 

partial melting in source region, collects in reservoirs in upper 

mantle near base of crust, where it fractionates into evolved 

magma (hawaiite, mugearite, or benmoreite) that rises to surface without undergoing further fractionation. Some evolved 

magma entrains gabbro, peridotite, and pyroxenite xenoliths 

either from upper mantle or from intrusive bodies within oceanic crust or volcanic edifice of Mauna Kea. To southeast, full 

tholeiitic-basalt magma production is now under way at 

Kilauea.

have required about 400,000 yr. Evidently, Mauna Kea's 

east rift zone was inactive during a later part of the shield 

stage. Apparently, rift-zone eruptions ceased, possibly as a 

result of waning magma production (see fig. 4), and shield 

lavas issued from the summit area or, possibly, from radial 

vents like those on the northwest flank of Mauna Loa 

(Lockwood and Lipman, 1987). Thus, subaerial Mauna Kea 

lacks the elongate-ridge form that, on its neighbors, reflects 

the influence of recurrent rift-zone eruptions.
DEVELOPMENT OF MAUNA KEA VOLCANO- AN INTERPRETATIVE SUMMARY 119

KILOMETERS 

5 -]

KILOMETERS

5 -i
120 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

KILOMETERS

Figure 64 Continued.
DEVELOPMENT OF MAUNA KEA VOLCANO—AN INTERPRETATIVE SUMMARY 121

EXPLANATION

Postshield lava flows of Mauna Kea 

Hawaiitic substage

Balsaltic substage 

Magma in reservoirs or conduits 

Hawaiitic

Alkalic basalt 

Transitional basalt

Tholeiitic basalt 

Solidified magma reservoir

Dikes

Contact

— - — - — Contact between subaerial and submarine deposits

\v\v\V- General orientation of lava flows and fragmental 

materials—Steeper dip indicates deposition on 

steep submarine flank

Figure 64. Continued.

Our compositional data set (table 1) for the Mauna Kea 

shield stage consists of analyses of three pillow-basalt samples dredged from Hilo Ridge, the same samples from 

which Moore and Peck (1966) inferred ridge subsidence. 

Two of the dredged samples, ER-20 and ER-21, are of 

picritic tholeiitic basalt collected from 1,650- and 2,750-m 

depth, respectively; the third sample, ER-22, is of transitional olivine basalt, collected from 3,200-m depth. As 

shown in figure 36, Kilauea lavas, though predominantly 

tholeiitic, include a few basalts similar in composition to the 

transitional basalts of Mauna Kea. This similarity indicates 

that such basalts are erupted at times during the shield stage, 

and sample ER-22 may represent an apparently similar 

occurrence in the shield stage of Mauna Kea. An alternative 

view is that sample ER-22 represents a period of transition, 

late in the shield stage, during which tholeiitic and alkalic 

basalt were both erupted. In support of such a view, Moore 

and Clague (1992) interpreted samples collected from the 

sea floor west of Hawaii as representative of Mauna Kea 

flows of both tholeiitic and transitional basalt that drape 

reefs with ages of 245 and 340 ka. They concluded from 

these observations that the transition from tholeiite to alkalic basalt was underway by 340 ka and was still incomplete 

by 245 ka.

POSTSHIELD STAGE 

BASALTIC SUBSTAGE

The postshield, basaltic-substage lavas, which compose the Hamakua Volcanics, capped the entire subaerial

surface of Mauna Kea (fig. 64C) before the hawaiitic capping lavas (Laupahoehoe Volcanics) were erupted. Nearly 

all of the Hamakua lavas are transitional or alkali basalt. We 

estimate the total volume of these postshield basalts at 

approximately 850 km3 . They were erupted from approximately 250 to 70 ka, giving an average lava-supply rate of 

about 0.005 km3/yr, about a tenth of the median estimated 

supply rate during the shield stage. The decrease in production rate and silica saturation, in comparison with those of 

the tholeiitic shield lavas, reflects lower melt production 

and lower degree of partial melting in the mantle source 

region.

Hamakua basalts cover a broad compositional range, 

reflecting two separate controls: differing degrees of partial 

melting of the mantle source rocks to generate parental 

magmas of varying alkalinity (fig. 40) and subsequent crystal fractionation to produce various evolved daughter magmas from the parents. The Hamakua lavas include many 

evolved basalts (fig. 36) representing magmas fractionated 

by crystallization and separation of approximately 10 to 40 

percent crystals of olivine, clinopyroxene, and plagioclase. 

Except for the small group of CaO-poor, high-Ti basalts 

that apparently fractionated relatively deep within the volcano, the evolved basalts fractionated at shallow levels, 

probably at pressures of about 1 to 2 kbars. Thus, we expect 

that many small plutons composed of these separated crystals plus crystallized unerupted magma are scattered 

beneath much of the volcano surface at about 3- to 6-km 

depth (fig. 64C).

Many of the Hamakua surface flows are no more than 

150,000 yr old. The oldest flows, for which K-Ar data sug-
122 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

2000 —

— 3000

— 2000

1000 1000

VERTICAL EXAGGERATION X 2.5

Figure 65. Comparison of topographic profiles of Mauna Loa 

and Mauna Kea Volcanoes. Base maps from U.S. Geological Survey 1:100,000, Hawaii County, Hawaii, Sheets 1 and 2, 1980; contour interval, 40 m. A, Profile of Mauna Loa, showing normal 

faults that bound or occur near summit caldera. Faults are dashed 

in cross section to indicate uncertainty about style and depth of 

downward projection. Ball and bar on downthrown block; arrows

indicate directions of relative movement. B, Profile of Mauna Kea 

showing superimposed profile of Mauna Loa (dot-dashed line), 

which represents inferred contact between the postshield-stage 

Hamakua Volcanics and underlying shield-stage lavas. Contact 

with overlying Laupahoehoe Volcanics dashed where approximately located, queried where uncertain.

gest an age of approximately 200,000 to 250,000 yr, are 

exposed only in deep gulches that cut the northeast flank of 

the volcano (fig. 12). Two tholeiitic basalt flows interleaved 

with transitional basalt occur among these oldest lavas in 

Laupahoehoe Gulch, between sea level and 50-m elevation 

(fig. 13). We know of no other tholeiites exposed on the 

subaerial part of Mauna Kea. These relatively old lavas, 

with minor interlayered tholeiitic basalts and picrites, seem 

to represent the uppermost part of a transition zone between 

the tholeiitic shield and the overlying transitional and alkaline postshield basalts.

Hamakua basalt, which forms much of the present surface of the volcano, was erupted from vents near the summit 

and on the flanks of Mauna Kea. Lower-flank flows are predominantly elongate aa flows that issued during individual

eruptions from scattered vents. Where not buried by 

younger lavas, these vents are generally marked by cinder 

cones. Three-quarters or more of the exposed Hamakua 

cones are on the northwest flank (fig. 12). This asymmetry 

partly reflects burial by younger lavas; Laupahoehoe lavas 

are more extensive over the east than the west half of the 

volcano. However, it also reflects a high concentration of 

plagioclase basalt cinder cones on the lower west flank (pi. 

1), where repeated Hamakua eruptions built a prominent 

topographic bulge. Generally, each isolated cinder cone on 

the lower flanks probably represents the rise from the mantle of an individual magma batch. However, the abundance 

of numerous cones and flows of similar plagioclase basalt 

on the lower west flank leads us to speculate that these fea-
DEVELOPMENT OF MAUNA KEA VOLCANO—AN INTERPRETATIVE SUMMARY 123

19°45'

20°00'

155°30'

Interlayered flows of Mauna Loa 

and Laupahoehoe Volcanics

2000 —

1000

VERTICAL EXAGGERATION X 2.5

-2000

1000

Figure 65. Continued.

tures could have been erupted from a common fractionating 

magma reservoir.

Upper-flank lavas of the Hamakua Volcanics record a 

somewhat different eruptive style from those on the lower 

flanks. Several lines of circumstantial evidence, which we 

review below, suggest to us that these upper-flank lavas may 

have been erupted from a long-lived, shallow magma-reservoir complex beneath the summit of Mauna Kea. Actively 

inflating and deflating summit reservoirs are fundamental 

elements in the dynamics of such shield-stage volcanoes as 

Kilauea and Mauna Loa (Decker, 1987).

In their limited gulch exposures, the older (approx 

150,000-200,000 yr) upper-flank basalts, which compose 

the Hopukani Springs Volcanic Member, consist largely of 

thin-layered pahoehoe. Thus, morphologically they resemble the fluid basalts of the active shield volcanoes Kilauea

and Mauna Loa more than they do the elongate aa flows on 

the lower flanks.

The younger (approx 70,000-150,000 yr) upper-flank 

basalts, which compose the Liloe Spring Volcanic Member, 

consist predominantly of stacked, thin aa flows of evolved 

basalt of fairly constant, phenocryst-poor lithology. Kipukas 

in the overlying Laupahoehoe Volcanics reveal that these 

Liloe Spring flows veneered at least the upper north, northwest, and south flanks of the pre-Laupahoehoe volcano (fig. 

12). Repeated eruption of numerous flows of lithologically 

similar, evolved basalt from vents concentrated in a limited 

area near the summit of the volcano suggests that the Liloe 

Spring basalts fractionated in and were erupted from a longlived, shallow, near-summit reservoir. Crystal zoning in 

these basalts, formed by rounding of phenocrysts by resorption, followed by development of overgrowths of differing
124 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

composition, provides evidence that the lavas were erupted 

from a reservoir periodically recharged by hotter, less 

evolved magma.

Exposures in the south-flank kipuka show that some of 

these Liloe Spring basalts were fed by dikes or erupted from 

fissure vents. The fissure vents and some of the dikes form a 

120° arc (pi. 2) high on the upper south flank, centered near 

the summit, with a 1.5- to 2-km radius of curvature. We 

speculate that this arcuate feeder system represents Liloe 

Spring dikes emplaced along circumferential fractures 

related to cross-summit extension and summit subsidence.

Flows of Liloe Spring basalt on the north, northwest, 

and south flanks disappear upslope beneath a cover of 

younger lavas of the Laupahoehoe Volcanics. Although a 

few scattered basaltic cinder cones occur within the kipukas 

of Liloe Spring basalt on the north and south flanks, no 

basaltic cinder cones project upward as kipukas through the 

veneer of near-summit Laupahoehoe lavas. This observation suggests that the buried Liloe Spring vents may have 

been fissure vents which built only low spatter ramparts— 

as predominate on Kilauea and Mauna Loa—rather than 

point-source vents which built large cinder cones.

Comparison of the flank and summit topography of 

Mauna Kea with that of Mauna Loa may bear on the 

hypothesis that a shallow summit reservoir persisted at 

Mauna Kea throughout the postshield, basaltic substage. 

Profiles and topographic maps of the two volcanoes (fig. 

65) show that (1) the summit area of each volcano includes 

a plateaulike surface which slopes less steeply than the 

flanks and (2) the upper flanks of Mauna Kea are approximately twice as steep as those of Mauna Loa.

A plateaulike surface surmounted by a veneer of 

Laupahoehoe cinder cones and lava flows forms the summit 

of Mauna Kea, contrasting markedly with the steep (approx 

20°) upper flanks (figs. 65B). Extrapolation from outcrops 

of Liloe Spring basalt along or near the profile line (see pi. 

2) indicates that the slope of the summit plateau before 

addition of the Laupahoehoe lavas was about 3°. The summit plateau, the slope break at its edge, and the steep upper 

flanks, therefore, predate the hawaiitic substage.

A remarkable analog of the buried Mauna Kea summit 

plateau is at the summit of Mauna Loa. Mokuaweoweo 

Caldera and a gently sloping (approx 3°) surface to the 

southeast form a summit plateau that is 5 km wide along the 

profile line (fig. 65A), contrasting sharply with the steeper 

slopes (approx 10°) of the upper flanks. The gently sloping 

lavas southeast of the caldera, as well as those underlying 

the steeper upper southeast and northwest flanks of Mauna 

Loa, are all part of a 750- to 1,500-yr-old, tube-fed pahoehoe complex erupted from a shield centered in the area of 

the present caldera (Lockwood and Lipman, 1987), which is 

a younger feature. Because the caldera walls are essentially 

the footwalls of high-angle normal faults, this Mauna Loa 

summit plateau is bounded by normal faults. We suggest 

that its low slopes and bounding faults are the surface

expressions of extension and subsidence of the summit of 

Mauna Loa above a magma reservoir at about 3-km depth 

(Decker, 1987). Extending the analogy to Mauna Kea, we 

suggest that the gently sloping summit plateau of the basaltic substage, which is bounded by abruptly steepening 

slopes, is the now-buried surface expression of extension 

and subsidence of the summit of Mauna Kea above a shallow magma reservoir.

The arcuate fracture system indicated by dikes and fissure vents of the Liloe Spring Volcanic Member suggests 

that normal faults may have bounded the summit plateau at 

times during the basaltic substage. However, we have no 

evidence of a deep caldera like those, several hundred 

meters deep, that have existed in fairly recent times on 

Mauna Loa and Kilauea (Holcomb, 1987; Lockwood and 

Lipman, 1987). Holcomb suggested that large caldera-collapse events on Kilauea result from voluminous rift-zone 

eruptions. Extending that view to Mauna Kea, we believe 

that large caldera-forming summit collapses were unlikely 

on Mauna Kea during the basaltic substage or even during 

the later part of the shield stage after the termination of 

eruptive activity in the east rift zone.

The upper flanks of Mauna Kea are twice as steep 

(approx 20°) as those of Mauna Loa (approx 10°). Basalts 

of the Liloe Spring Volcanic Member dip essentially parallel 

to the surface slopes. Because there is no direct evidence of 

deformation of these flows, most probably they mantle 

slopes that were already steep when the Liloe Spring basalts 

were erupted. We suggest two mechanisms for steepening of 

the upper flanks: (1) emplacement of voluminous shallow 

intrusions that would steepen the upper flanks by deforming 

the volcanic edifice during the later part of the shield stage 

or early part of the postshield stage; and (2) greater viscosity of postshield lava flows than of shield-stage tholeiitic 

basalt, and thicker accumulation of vent deposits and lava 

flows on the upper than on the lower flanks. We know of no 

evidence other than steepening of the upper flanks for massive intrusion (mechanism 1). Increased viscosity, in combination with preferred concentration of vents on the upper 

flanks (mechanism 2), probably contributed to upper-flank 

steepening during the basaltic substage. Projection of the 

Mauna Loa profile shown in figure 65A into figure 65B 

illustrates a hypothetical cross section in which upper-flank 

steepening of Mauna Kea reflects only greater upper-flank 

thickness of the Hamakua Volcanics.

The K-Ar ages of postshield basalts from the upper and 

lower flanks indicate that the Liloe Spring and Hopukani 

Springs Volcanic Members on the upper flanks of Mauna 

Kea Volcano consist of flows which (1) may have been 

erupted from a long-lived summit reservoir and (2) accumulated during the same interval as the lower-flank flows 

which were erupted from scattered individual vents marked 

by cinder cones. A compositional difference accompanies 

the difference in eruptive styles between the broadly coeval 

upper- and lower-flank flows. The upper-flank flows are
DEVELOPMENT OF MAUNA KEA VOLCANO—AN INTERPRETATIVE SUMMARY 125

almost all transitional basalt (silica saturated) and include 

some of the most silica saturated lavas of the postshield 

stage; only 4 of 63 analyzed samples (approx 6 percent) of 

Hamakua basalt from above 2,000-m (6,560 ft) elevation 

are alkalic (ne normative). The lower-flank flows are generally more alkaline, and alkali basalt (silica undersaturated) 

is common; 29 of 155 analyzed samples (approx 19 percent) 

of Hamakua basalt from below 2,000-m (6,560 ft) elevation 

are alkalic. Thus, transitional basalt, generated by higher 

degrees of partial melting in the upper-mantle source, sustained and was erupted from the summit reservoir, whereas 

alkali basalt, generated by lesser degrees of partial melting, 

was more commonly erupted from scattered individual 

vents on the lower flanks of the volcano. This compositional 

zoning of the volcano suggests that the source region was 

zoned with respect to degree of partial melting: Greater partial melting occurred in the central part of the source area, 

and lesser partial melting near its perimeter. Furthermore, 

this scenario implies that magma batches supplying the 

lavas of the volcano's flanks rose along individual vertical 

paths from the mantle source (fig. 64Q.

HAWAIITIC SUBSTAGE

The postshield, hawaiitic-substage lavas, which compose the Laupahoehoe Volcanics, form a discontinuous, 

magmatically evolved cap on Mauna Kea Volcano (fig. 22). 

Approximately 10 percent of the lava is benmoreite, and 90 

percent is hawaiite and mugearite. The volume of Laupahoehoe flows and pyroclastic deposits is about 25 km3 

(dense-rock equivalent). These lavas were erupted from 

approximately 65 to 4 ka, giving an average lava-supply 

rate of about 0.0004 km3/yr. This rate, which is one-tenth 

the lava-supply rate for the basaltic substage, presumably 

reflects greatly diminished melting rates in the mantle 

source.

Most Laupahoehoe eruptions formed prominent cinder 

cones and elongate, rugged lava flows composed predominantly of aa. The vents are largely concentrated near the 

summit and on the upper flanks of the volcano. Laupahoehoe cones and flows provide the rugged local topographic 

irregularities that make the upper slopes and summit of 

Mauna Kea contrast so markedly with the much smoother 

slopes of the Mauna Loa shield.

Concentrations of Laupahoehoe cinder cones occur in 

sectors west, northeast, and south to southeast of the volcano's summit. Cone alignments and elongation of these 

clusters radial to the summit are distinct in the western cluster, less certain in the northeastern cluster, and unrecognizable in the south-to-southeastern cluster. Although Macdonald (1945) and Porter (1972b) referred to these clusters 

as having erupted along rift zones radial to the summit, we 

see no connection between the clusters and the rift-zone 

structure of the underlying tholeiitic shield. However, the

cone distribution apparently reflects radial stress inhomogeneities in the volcanic edifice.

The Holocene record provides some evidence that 

Laupahoehoe eruptions may have occurred in sporadic 

bursts of activity, rather than being more or less evenly 

spaced over the past 65,000 yr. Radiometric dating (table 6) 

and field relations indicate that the line of cinder cones, representing at least seven separate vents (pi. 2) extending 

northeastward from Kalaieha through Puu Kole (south 

flank), formed between 6 and 4 ka. Virtually identical lava 

compositions along this alignment suggest that the group of 

aligned cones and their flows represent a single magma 

batch. 14C ages indicate that at least three other flows were 

erupted elsewhere on the volcano during the same time 

interval; these eruptions occurred on the northeast flank at 

Puu Lehu and Puu Kanakaleonui and on the south flank 

near Hale Pohaku. Apparently, Mauna Kea has been quiescent during the past 4,000 yr. We have found no Laupahoehoe lavas younger than those erupted during this burst of 

eruptive activity between 6 and 4 ka.

Laupahoehoe eruptions produced voluminous ash that 

was distributed beyond the cinder cones and the local airfall deposits near some of the cinder cones. This ash is the 

dominant component of a host of eolian, fluvial, and colluvial deposits that now mantle parts of Mauna Kea's flanks.

Mass-balance modeling and consideration of phase 

equilibria at elevated pressure suggest that the hawaiitic 

Laupahoehoe magma was generated by fractionation of an 

alkali basalt parent at a pressure of at least 5 to 7 kbars. Production of the most mafic hawaiitic lava requires removal of 

40 to 50 percent of the parent as a crystal assemblage dominated by clinopyroxene (approx 50 weight percent), with 

lesser amounts of plagioclase, olivine, and Fe-Ti oxides. 

Dominance of clinopyroxene in the assemblage reflects 

the expanded stability field of clinopyroxene at elevated 

pressure. Generation of more evolved Laupahoehoe lavas, 

ranging to benmoreite, requires increasing plagioclase 

fractionation.

Compositions of Laupahoehoe lavas plot between the 

trends of liquids on the olivine+orthopyroxene+clinopyroxene cotectic at 8 to 30 kbars and 1 bar on the DI-OL-NEPH 

diagram (fig. 59) of Sack and others (1987), as well as in a 

restricted cluster offset from the low-pressure cotectic projected onto the CS-MS-A plane (fig. 60) of O'Hara (1968). 

These results suggest that the Laupahoehoe magmas were 

all generated by fractionation at elevated pressure and that 

no additional low-pressure fractionation occurred. Furthermore, the essentially constant proportions of silicate phases 

fractionated during the evolution from the most mafic 

hawaiite to benmoreite (table 23) suggest that the liquids 

represented by this compositional range were produced by 

cotectic crystallization at similar pressures and did not fractionate further during ascent.

About 20 to 30 percent of Laupahoehoe lavas contain 

gabbroic and ultramafic xenoliths entrained in the ascend-
126 GEOLOGY AND PETROLOGY, MAUNA KEA VOLCANO, HAWAII—A STUDY OF POSTSHIELD VOLCANISM

ing evolved magma. Mineralogies, structures, and fabrics of 

these xenoliths indicate that they probably came from a 

zone of injected and intensely jointed peridotite at and 

somewhat below the base of the oceanic crust. In accord 

with this observation and with the evidence from phase 

equilibria discussed above, we conclude that the suite of 

hawaiitic magmas originated by varying degrees of fractionation of alkali basalt magma in a reservoir(s) in the 

upper mantle near the base of the oceanic crust (fig. (AD). 

Batches of this magma then rose directly to the surface, 

passing through the crust and the volcanic edifice with no 

further fractionation.

Our mapping shows no interleaving of basalt 

(Hamakua Volcanics) and hawaiitic lava (Laupahoehoe Volcanics). Thus, an abrupt change from production of basalt to 

production of hawaiite, mugearite, and benmoreite occurred 

before approximately 65 ka. Laupahoehoe melt-production 

rates were greatly diminished from those associated with 

Hamakua volcanism, as indicated by the diminished average lava-supply rate. Furthermore, evidence suggests that 

only alkali basaltic magma was produced in the source 

region, indicating a lower degree of partial melting than that 

which produced transitional basaltic magma during 

Hamakua volcanism. The most remarkable—and enigmatic—change was that the basaltic parental magma of the 

Laupahoehoe Volcanics ponded and fractionated extensively in the upper mantle before ascending to the surface 

without further interruption. In marked contrast, basaltic 

parental magma of the Hamakua Volcanics was erupted 

without undergoing such extreme fractionation—it was still 

basalt—and most of it shows the petrologic imprint of lowpressure fractionation in either ephemeral or long-lived reservoirs within the volcano superstructure.

GLACIATION

The glacial record on Mauna Kea was a major focus of 

attention for S.C. Porter (for example, Porter, 1979a, b, c, 

d), and we accept many of his interpretations as authoritative. However, our mapping, stratigraphic interpretations, 

and new K-Ar dating have led to some important revisions, 

foremost among which is recognition that the glacial record 

extends back no more than to 200-150 ka, rather to nearly 

300 ka, as indicated to Porter (1979c, d) by the K-Ar ages 

available to him. Two separate glacial episodes were 

recorded during the postshield, basaltic substage, and their 

deposits are mapped as the Pohakuloa and Waihu Glacial 

Members of the Hamakua Volcanics. The older, Pohakuloa 

Glacial Member overlies basalt dated at approximately 150 

to 200 ka and is overlain by basalt flows dated within the 

range 100-150 ka. K-Ar results indicate that the age of the 

younger, Waihu Glacial Member is within the range of 70- 

150 ka; Dorn and others (1991) reported an exposure age of 

60 to 70 ka.

We recognize a single additional glacial unit, the 

Makanaka Glacial Member, which was deposited between 

approximately 40 and 13 ka, during the hawaiitic substage. 

Accordingly, these deposits are mapped as a glacial member 

within the Laupahoehoe Volcanics. Although Porter (1979a, 

c) described deposits of two separate Makanaka glacial episodes, we have found the deposits largely indistinguishable 

and the separate units unmappable. Field evidence suggests 

that the Makanaka deposits represent a single glacial episode unbroken by an interglacial hiatus.

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North America: Boulder, Colo., Geological Society of America, p. 218-237.

U.S. GOVERNMENT PRINTING OFFICE: 1997 - 573-046 / 20071 REGION NO. 8



SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS

Periodicals

Earthquakes & Volcanoes (issued bimonthly). 

Preliminary Determination of Epicenters (issued monthly).

Technical Books and Reports

Professional Papers are mainly comprehensive scientific reports 

of wide and lasting interest and importance to professional scientists and 

engineers. Included are reports on the results of resource studies and of 

topographic, hydrologic, and geologic investigations. They also include 

collections of related papers addressing different aspects of a single scientific topic.

Bulletins contain significant data and interpretations that are of 

lasting scientific interest but are generally more limited in scope or geographic coverage than Professional Papers. They include the results of resource studies and of geologic and topographic investigations; as well as 

collections of short papers related to a specific topic.

Water-Supply Papers are comprehensive reports that present significant interpretive results of hydrologic investigations of wide interest 

to professional geologists, hydrologists, and engineers. The series covers 

investigations in all phases of hydrology, including hydrology, availability of water, quality of water, and use of water.

Circulars present administrative information or important scientific information of wide popular interest in a format designed for distribution at no cost to the public. Information is usually of short-term interest.

Water-Resources Investigations Reports are papers of an interpretive nature made available to the public outside the formal USGS publications series. Copies are reproduced on request unlike formal USGS 

publications, and they are also available for public inspection at depositories indicated in USGS catalogs.

Open-File Reports include unpublished manuscript reports, maps, 

and other material that are made available for public consultation at depositories. They are a nonpermanent form of publication that may be cited in other publications as sources of information.

Maps

Geologic Quadrangle Maps are multicolor geologic maps on topographic bases in 7 1/2- or 15-minute quadrangle formats (scales mainly 1:24,000 or 1:62,500) showing bedrock, surficial, or engineering 

geology. Maps generally include brief texts; some maps include structure 

and columnar sections only.

Geophysical Investigations Maps are on topographic or planimetric bases at various scales, they show results of surveys using geophysical 

techniques, such as gravity, magnetic, seismic, or radioactivity, which reflect subsurface structures that are of economic or geologic significance. 

Many maps include correlations with the geology.

Miscellaneous Investigations Series Maps are on planimetric or 

topographic bases of regular and irregular areas at various scales; they 

present a wide variety of format and subject matter. The series also includes 7 1/2-minute quadrangle photogeologic maps on planimetric 

bases which show geology as interpreted from aerial photographs. The 

series also includes maps of Mars and the Moon.

Coal Investigations Maps are geologic maps on topographic or 

planimetric bases at various scales showing bedrock or surficial geology, 

stratigraphy, and structural relations in certain coal-resource areas.

Oil and Gas Investigations Charts show stratigraphic information for certain oil and gas fields and other areas having petroleum potential.

Miscellaneous Field Studies Maps are multicolor or black-andwhite maps on topographic or planimetric bases on quadrangle or irregular areas at various scales. Pre-1971 maps show bedrock geology in relation to specific mining or mineral-deposit problems; post-1971 maps 

are primarily black-and-white maps on various subjects such as environmental studies or wilderness mineral investigations.

Hydrologic Investigations Atlases are multicolored or black-andwhite maps on topographic or planimetric bases presenting a wide range 

of geohydrologic data of both regular and irregular areas; the principal 

scale is 1:24,000, and regional studies are at 1:250,000 scale or smaller.

Catalogs

Permanent catalogs, as well as some others, giving comprehensive 

listings of U.S. Geological Survey publications are available under the 

conditions indicated below from USGS Map Distribution, Box 25286, 

Building 810, Denver Federal Center, Denver, CO 80225. (See latest 

Price and Availability List.)

"Publications of the Geological Survey, 1879-1961" may be purchased by mail and over the counter in paperback book form and as a set 

microfiche.

"Publications of the Geological Survey, 1962-1970" may be purchased by mail and over the counter in paperback book form and as a set 

of microfiche.

"Publications of the U.S. Geological Survey, 1971-1981" may be 

purchased by mail and over the counter in paperback book form (two volumes, publications listing and index) and as a set of microfiche.

Supplements for 1982, 1983, 1984, 1985, 1986, and for subsequent years since the last permanent catalog may be purchased by mail 

and over the counter in paperback book form.

State catalogs, "List of U.S. Geological Survey Geologic and Water-Supply Reports and Maps For (State)," may be purchased by mail and 

over the counter in paperback booklet form only.

"Price and Availability List of U.S. Geological Survey Publications," issued annually, is available free of charge in paperback booklet 

form only.

Selected copies of a monthly catalog "New Publications of the 

U.S. Geological Survey" is available free of charge by mail or may be obtained over the counter in paperback booklet form only. Those wishing a 

free subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 National Center, Reston, VA 22092.

Note.-Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect. Therefore, the prices 

charged may differ from the prices in catalogs, announcements, and publications.