Some Physical Constants for 

the Marshall Islands Area

GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-AA
Some Physical Constants for 

the Marshall Islands Area

By J. H. SWARTZ

BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-AA

Data for IJ groups of physical properties and 

discussion of the methods used in their measurement

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1962
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington 25, D.C.
CONTENTS

Abstract_ ________________________________________

Introduction _______________________________________

Method of arrangement and presentation of data_______

Acknowledgments—_____ ____________________________

Physical constants __________________________________

Absorption of water_____________________________

Attenuation constants___________________________

Coefficient of absorption___-_._______________

Specific damping capacity____________________

Density and specific gravity____________________

Elastic constants-______________________________

The elastic moduli for tension or compression: 

Young's modulus _________________________

Poisson's ratio____________________________

Modulus of rigidity_________________________

Bulk modulus (modulus of incompressibility)___ 

Units used for elastic constants-..____________

Determination of the elastic constants.--______

Static methods-______________^_________

Dynamic methods ______________________

Hardness-___________________________________

Impact toughness_ — _________________

Page 

953 

953

953

954

954

954

955

955

957

958

961

962

962

963

964

964

964

964

965

969

970

Page 

Physical constants—Continued

Magnetic constants________-___________._____-__ 971

Susceptibility.---___----_--- — ____________ 971

Permeability (magnetic)_____________________ 972

Remanent magnetization____________________ 972

Permeability (hydraulic)_______________________ 975

Porosity____________________________ 976

Radioactivity (natural)_____________________-_-__ 978

Seismic speeds; speeds of transmission of seismic 

waves-_____----_--------------_---_-_------- 979

Strength,.. ___________._.__.__________._. 981

Compressive strength- __________-_-____---__ 981

Triaxial compressive strength (shearing

strength)...____________________ 981 

Flexural strength (modulus of rupture)________ 982

Thermal data....--___________________ 983

Temperature profiles__________________---___ 983

Thermal conductivity-_.________-____-__-_-_ 983

Thermal flux (heat flow)___________-__ 986

Thermal gradients_____-_-___----___-------_ 987

References.--.-__-_---_-__-----------_--_—_--_-__ 987

ILLUSTRATIONS

Page

FIGURE 290. Map of west Pacific Ocean_________________________________________________________________________ 954

291. Map of northwestern Marshall Islands._-__--________-_________-__-_-__________--______---__------__- 955

292. Map of Eniwetok AtolL________._______________________________________________________ 956

293. Map of Bikini Atoll------____.______________________________________________ 957

294. Variation of relative amplitudes of first arrivals with distance___________________________________________ 957

295. Stress-strain curve and elastic moduli___________________________________________________________-____ 962

296. Shearing strains____________________________________________________________________________________ 963

297. Shifting stress-strain cycles. _--__--_-______-_________________-______-_-__-___-_-________-____-__---- 964

298. Narrowing of stress-strain cycles._____________________________________________________________________ 965

299. Diagram of U.S. Bureau of Mines sonic equipment____________________-_____-______-__-_--_____--_--_ 966

300. Young's modulus plotted against specific gravity-___-__________-_______________---______-_-_---_----_- 967

301. Diagram of Michelsen susceptibility bridge_--_________________________________________-_-_-___-_--__- 971

302. Diagram of Michelsen remanent magnetometer___________________________________-_______-_____---_--- 973

303. Variable head permeameter______________________________________________________________________-_- 975

304. Mohr's circles and envelope for core MU-5___________________________________________________________ 982

305. Thermal-conductivity apparatus.____________________________________________________________________ 984

TABLES

Page 

TABLE 1. Percent absorption of water in limestone drill cores from Eniwetok Atoll, Marshall Islands________________ 955

2. Mean values of the coefficient of absorption for refracted waves in layers 2 and 3 in Bikini Atoll_____________ 958

3. Specific damping capacity for some drill cores from Eniwetok Atoll, Marshall Islands______________________ 958

4. Densities and specific gravities of drill cores from Eniwetok Atoll, Marshall Islands________________________ 961

5. Bulk specific gravity computed from porosity and mean value of true specific gravity._____________________ 961

in
IV CONTENTS

Page 

TABLE 6. Densities of some Mid-Pacific ocean-bottom sediments, Scripps Institution of Oceanography Mid-Pacific

Expedition of 1950_____________________________________________________. 961

7. Observed static-test data for the seventh stress-strain cycle for four drill cores from Eniwetok Atoll__________ 968

8. Mean elastic constants, observed and derived, for some Eniwetok drill cores______________________________ 969

9. Hardness of some Eniwetok drill cores in arbitrary "scleroscope units"-_________________-___--_______---- 970

10. Comparison hardness measurements on a series of U.S. Bureau of Mines standards_______________________ 970

11. Impact toughness of some Eniwetok Atoll drill cores_______--__-___-_-_---_-_-_-_-_--------_-_-_------- 971

12. Acid-bottle surveys of Eniwetok drill holes____________________________________-_--__---_---_-_-__ 974

13. Magnetic constants for both induced and remanent magnetization of some Eniwetok drill cores____________ 974

14. Coefficient of permeability (hydraulic) for Eniwetok cores._________-__--_-_-_--_--_-----_-_---_---_---- 976

15. Porosities of Eniwetok drill cores, percent by volume_________________________________________________ 977

16. Natural radioactivity of coral limestone in drill hole E-l, Parry Island, Eniwetok Atoll, December 1952______ 978

17. Natural radioactivity of the basalt_________________________---_-__------------_-_---__------___------ 978

18. Helium content of the basalt_______________________-_____-______--__-__-_-______--------_-_--------- 978

19. Speeds of seismic-wave transmission: laboratory measurements.__________________-______-__-_---__--_- 979

20. Speeds of seismic-wave transmission: ground surface refraction surveys, Eniwetok Atoll ____________________ 980

21. Speeds of seismic-wave transmission: in-hole measurements in drill hole 2B, Bikini island, Bikini Atoll_______ 980

22. Speeds of seismic-wave transmission: marine-refraction surveys. A, Bikini Atoll; B, Bikini and Kwajalein

Atolls and Sylvania Guyot; C, Eniwetok Atoll--------___-____----_--_-_-_--__--— _ — __--___-_-_ 980

23. Compressive, triaxial-compression, and flexural strengths of some Eniwetok drill cores__-_-_-_-_______-_--_- 982

24. Temperature profiles in Eniwetok and Bikini drill holes, and in the Pacific Ocean, Marshall Islands area____ 983

25. Thermal conductivity of drill cores from Eniwetok Atoll, Marshall Islands-_____________-___-__-__-___---- 985

26. Thermal conductivity of sea-floor sediments collected by the 1950 Mid-Pacific Expedition of the Scripps Institution of Oceanography.____________________________-_______-___-______--_----------------_---- 986

27. Heat flow. A, Heat flow in Eniwetok Atoll; B, Heat flow through the ocean floor in the Mid-Pacific area— 986

28. Thermal gradients in Eniwetok and Bikini Atolls and for the Pacific Ocean in the Marshall Islands area: gradients for linear segments fitted to the data by least squares._________________________________________ 987

29. Thermal gradients in Eniwetok and Bikini Atolls and for the Pacific Ocean in the Marshall Islands area: actual

gradients for each measured interval-___________________________________________--_-----_---__----- 987
BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA

By J. H. SWARTZ

ABSTRACT

Measured values of physical properties of some geologic 

materials in the west Pacific Ocean and the Marshall Islands 

area, particularly Eniwetok and Bikini Atolls, and including 

sea-bottom muds, loose coral sands, coral limestone, dolomite, 

and olivine basalt are as follows: absorption, 6.0 to 20.05 percent; 

density (grams per cm3) and specific gravity, 1.18 to 2.97; 

coefficient of absorption for seismic waves, 0.003 to 0.2 per 1,000 

feet; elasticity, Young's modulus 0.084 to 10.72 million psi, 

modulus of rigidity 0.35 to 5.29 million psi, bulk modulus 0.44 to 

57.58 million psi, compressibility 0.25 to 33.0 millionths reciprocal 

bars, Poisson's ratio 0.01 to 0.53; hardness, 13 to 71 scleroscope 

units; heat flow, 0.74 to 1.4 microcalories per square centimeter 

per second; impact toughness, 1.01 to 2.86 inches per square 

inch; magnetic constants, volume susceptibility from less than 

2X10~5 to 0.85 X10-3 cgs, magnetic permeability 1.0048 to 

1.0107 cgs, intensity of remanent magnetization 0.0044 to 0.0183 

cgs, Koenigsberger Q factor 21 to 120, inclination 11° to 69°, 

north end down (no inverse magnetization was observed); 

hydraulic permeability, 0.00004 to 12.7 meinzers; porosity, 0 to 

56.0 percent; mean radioactivity, 0.01 to 0.04 milliroentgens per 

hour for the upper 924 feet of drill hole E-l, 0.575X 10~12 grams 

of equivalent radium per gram of basalt; seismic speeds, 1,000 

to 27,250 fps or 0.3 to 8.3 kmps; specific damping capacity, 0.007 

to 0.03; strength, compressive strength 240 to 28,200 psi, modulus 

of rupture 850 to 4,100 psi; temperatures, 29.1° to 6.4°C in the 

drill holes, 27.8° to 4.4°C in the ocean; thermal conductivity 

0.00168 to 0.0065°C cal per cm sec °C; and thermal gradients, 

thermocline —0.030° to — 0.124°C per meter, asthenocline 

-0.003° to -0.018°C per meter, epeirocline +0.021°C per 

meter.

INTRODUCTION

During the years 1951-52 several geophysical investigations were conducted in the Marshall Islands area of 

the western Pacific Ocean (figs. 290-293). In connection with these studies physical constants of some 

geologic materials were evaluated, both in the field and 

in the laboratory. As there are very few data on 

physical properties available for this part of the world 

it has seemed worth while to gather these data together 

for easy reference.

The measurements presented were made both in the 

field and in the laboratory and represent the work or 

assistance of numerous individuals. Some are the

work of the writer and his associates; some are measurements made through the cooperation of others on 

materials furnished by the writer; some, especially the 

field measurements, were made by others who have 

very kindly placed their results at the writer's disposal.

The cores used in the measurements came from drill 

holes on Parry Island, and Elugelab, Engebi, and 

Mujinkarikku islands, Eniwetok Atoll, and on Bikini 

island, Bikini Atoll. (See figs. 1-4 for locations.) In 

some of the measurements, portions of the original 

cores were used; in others, smaller cores cut from the 

original cores were used, usually in the form of right 

circular cylinders 1 inch in diameter and 1 inch long, 

with ends accurately squared and ground.

As detailed descriptions of the lithology and petrography of the various cores are given in other chapters 

of Professional Paper 260 (Ladd and Schlanger, 1960; 

Schlanger, 1962; Macdonald, 1962) only the most 

generalized statement of rock type is given for the 

various specimens cited in the present discussion. The 

reader is referred to the more detailed descriptions for 

additional petrographic data.

METHOD OF ARRANGEMENT AND 

PRESENTATION OF DATA

To facilitate reference the physical properties discussed are listed in alphabetical order.

The physical constants are presented in 29 tables. 

Each table is placed at the end of its appropriate section. 

It is preceded by a discussion in which the property is 

defined to avoid any question as to its meaning, particularly where a term may be used in the literature in 

different senses; methods of measurement are discussed, 

units of measurement given, and both instruments and 

measurement techniques described to permit judgments 

as to the adequacy of procedures and the accuracy and 

precision of results. Introductory discussions have 

been made somewhat detailed for the sake of those 

readers who have not previously had occasion to familiarize themselves with the particular property under

953
954 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

Sea-floor heaf-flow station of the 

1950 mid-Pacific cruise of the 

Scripps Institution of Oceanography

500 0

FIGURE 290.—Map of the west Pacific Ocean showing the location of the Marshall Islands and of Mid-Pacific Expedition stations.

discussion or its methods of measurement, or who do 

not have ready access to reference literature.

ACKNOWLEDGMENTS

It is not possible to acknowledge individually the 

assistance of the many persons who aided in the 

collection of the data and the determination of the 

constants. The writer is greatly indebted to the 

Office of Naval Research and to the Atomic Energy 

Commission for their support of the field projects; to 

C. T. Cooper and H. H. Lewis, of the Atomic Energy 

Commission; to C. L. Coray, S. P. Howell, J. P. Ryan, 

and others, of the Holmes and Narver Co., for assistance with field logistics and field measurements; to the 

Bureau of Reclamation, and the Bureau of Mines; and 

especially to Leonard Obert and Byron E. Blair, of 

the Bureau of Mines, and Arnold I. Johnson, of the 

Geological Survey, for laboratory measurements on 

field specimens and drill cores. Particular acknowledgment is due Rudolph Raspet, W. L. Smith, and 

C. J. Spengler, Jr., for assistance with field measurements; to M. E. Lilliard, W. J. Huff, E. D. Saunders, 

A. L. Baldwin, and S. A. H. Goldstein for laboratory

measurements; to G. E. Manger for numerous helpful 

discussions; and to H. S. Ladd, who placed at his 

disposal the drill cores from the various Marshall 

Islands drill holes.

The writer is indebted also to Professor Francis 

Birch, of Harvard University, for permission to present 

his data on heat flux; to Dr. P. M. Hurley, of the 

Massachusetts Institute of Technology, for permission 

to present his measurements of radioactivity; and to 

Drs. Roger Revelle, Arthur E. Maxwell, Russell W. 

Raitt, and Walter Munk, of Scripps Institution of 

Oceanography, for sea-floor heat-flow, seismic, and 

ocean-temperature profile data.

PHYSICAL CONSTANTS 

ABSORPTION OF WATER

Absorption of water may be defined as the percentage 

increase in weight of a dry body when saturated with 

water. Methods of determining the dry and saturated 

weights and of drying and saturating specimens are 

discussed hi detail in the section on "Density and 

specific gravity".
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 955

EXPLANATION

o

Capricorn Expedition. Scripps 

Institution of Oceanography 

therrnal station 

oB 

Bathythermograph station

oN 

Nansen-bottle station

0 E-1 

Drill hole

10-14-52 

Date

Y. TAONGI 

I/ ATOLL

N ?0-15-52

B 10-14-52

. BIKAR 

ATOLL

E-li Parry Island 

Eniwetok Island 

o 

B11-12-52

BIKINI ATOLL

Blkmi 

Island RONGELAP 

ATOLL

AILINGINAE 

ATOLL

RONGERIK 

ATOLL

UTIRIK 

ATOLL

ATOLL

pi WOTHO 

N) ATOLL

AILUK 

ATOLL

Mejit 

Island

LIKIEP 

ATOLL

KWAJALEIN ATOLL

LAE 

ATOLL

WOTJE 

ATOLL

Kwajalein Island

ERIKUB 

k ATOLL

MALOELAP 

ATOLL

FIGUBE 291.—Map of northwestern Marshall Mands showing the location of Eniwetok and Bikini Atolls and of ocean-temperature observation stations.

If a is the percent absorption, w0 the oven-dried 

weight, wa the air-dried weight, and ws the saturated, 

surface-dried weight,

(1)

The use of the air-dried instead of the oven-dried 

weights introduces negligible error. Experiments by 

the Bureau of Mines (Obert, Windes, and Duvall, 1946, 

p. 47) have indicated that the two weights rarely differ 

by more than about 0.02 percent.

Values of the absorption of water by drill cores from 

Eniwetok Atoll, Marshall Islands, are given in table 1.

TABLE 1.—Percent absorption of water in limestone drill cores

from Eniwetok Atoll, Marshall Islands

[Measured by U.S. Bureau of Reclamation]

Core

EN-8. — — -

EN-9...—-.

EN-10————

Depth 

(feet)

90. 5-91. 0

95. 0-96. 0

81. 0-82. 0

Absorption 

(percent 

by 

weight)

7.12

20.05

20.05

Core

EN-11- — ——

MU-5— —— .

MU-7-. -----

Depth

(feet)

8.0- 9.0

38. 1-70. 5

81. 5-82. 0

Absorption 

(percent 

by 

weight)

6.0

17.8

20.05

ATTENUATION CONSTANTS

Two types of attenuation constants were measured 

in the present investigation: the coefficient of absorption and the specific damping capacity, the former in 

the field, and the latter in the laboratory.

COEFFICIENT OF ABSORPTION

Perkins (1952) has derived values of the absorption 

coefficient for the refracted seismic waves in the 

second and third layers (Dobrin, Perkins, and Snavely, 

1949) in Bikini Atoll on the assumption that, for the 

shot-detector distances involved, the refracted waves 

along the layers may be represented adequately by a 

cylindrical wave whose equation is

-

(2)

where AI and A2 are the amplitudes of the waves at 

distances r\ and r2 respectively from the shot point, 

and a is the coefficient of absorption. Solving for a,

logi iri— logip A2r2 

Z— ri)logi0 e

(3)
956 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

162°00' 162° 10' 162°20'

162°10' 162°20'

FIGURE 292.—Map of Eniwetok Atoll showing locations of Elugelab, Engebi, and Mujinkarikku islands and of Parry Island, and of drill holes E-1, F-1, EN-8, EN-9, EN-10,

EN-11, MU-5, and MU-7.
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 957

165° 30'

I65°30'

FIGURE 293.—Map of Bikini Atoll showing location of Bikini and of drill hole 2B.

The observed values of A and r are shown in figure 

294, after Perkins (1952) and Dobrin and Perkins 

(1954), where the relative amplitudes of the first 

arrivals, whose frequencies ranged from 9 to 10.5 cycles 

per second, are plotted against the corresponding 

distances from the shot, using logarithmic scales. 

Solution of equation (3) for these points has yielded the 

mean values of a given in table 2.

SPECIFIC DAMPING CAPACITY

The specific damping capacity is defined as the ratio 

of the energy dissipated per cycle to the total vibrational energy of the wave (Obert, Windes, and Duvall, 

1946, p. 7). It is determined by a small additional 

step in the procedure for determining seismic speeds 

dynamically by the sonic method. (See p. 965 to 966, 

979 of this report.) After the maximum amplitude (Am) 

has been attained and the corresponding resonant 

frequency (fr) determined, the frequency of oscillation 

is altered until the amplitude of vibration (^4.) drops to 

K V^m- Two such points will be found, one at a higher 

and one at a lower frequency than the resonant frequency. If A/ is the difference in frequency between 

these two points, 5 the specific damping capacity, AC7 

the wave energy dissipated per cycle, and U the total 

vibrational energy of the wave,

U fr

(4)

The values of the specific damping capacity for 

Eniwetok drill cores, as determined by the Applied 

Physics Branch of the U.S. Bureau of Mines, are given 

in table 3. As seen in equation (4), 8 is a dimensionless 

quantity.

It may be noted (Obert, Windes, and Duvall, 1946, 

p. 7) that in the sonic method of the Bureau of Mines

63130&—162———2

the signs 

vibratior 

Duvall ( 

such as 

resonanc 

curve in

1000- 

800-

600- 

500-

300-

150-

100-

C/5 DU

UJ

D 

l5 40-

a. 

^ 

< 30 .

UJ 

!> oc

<

UJ *U

or

10-

6- 

5-

4-

2-

1-

u

il amplitude is a function of the velocity of 

i, not of its amplitude. However, Obert and 

1941) have shown that for small values of A/, 

are here involved, the use of the velocitye curve instead of the amplitude-resonance 

troduces negligible error.

i 1 »

•

•

e

j

•

)

X

X X

X

>

DO OO O OOO OOO OO

8

00 o ooo ooo oo OO O OOO OOO OO

•) 10 co Q in o m" o o o o" o o"

-H -H Cvj CJ CO ^^Jfi~ (O 00 O

SHOT-DETECTOR DISTANCE, IN FEET

FIGURE 294.—Variation of relative amplitudes of first arrivals with detector-shot 

distance. The relative amplitudes of the waves refracted along the second 

(11,000 fps) layer are shown by circles; those along the third (17,000 fps) layer 

shown by crosses.
958 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

TABLE 2.—Mean values of the coefficient of absorption for 

refracted waves in seismic layers 2 and S, Bikini Atoll

[Data by Beauregard Perkins, Jr. Computed from measurements made in a marine 

refraction seismic survey by Dobrin, Perkins, and Snavely (1949)]

Assumed rock

Limestone. _________________

Igneous, probably basalt __

Seismic speed 

(fps)

11, 000

17, 000

Coefficient of 

absorption: fractional 

energy dissipated 

per 1,000 feet

0.2

.003

TABLE 3.—Specific damping capacity (5) for three drill cores from 

Elugelab island, Eniwetok Atoll, Marshall Islands

[Measurements by Applied Physics Branch, U.S. Bureau of Mines]

Rock

Dolomite. ____

Core

F-l-5-4______

F-l-6-2______

F-l-12-6 _ .

Depth (feet)

1, 978-2, 003

2, 662-2, 687

4, 316-4, 341

Specific damping 

capacity: fractional 

energy dissipated 

per cycle

0.01

.007

.03

DENSITY AND SPECIFIC GRAVITY

Two types of density are customarily determined: 

bulk density and true or grain density. Bulk density 

is the mass of the body divided by its external volume. 

It is thus the density of the specimen rather than of 

the material composing it. It includes within its 

volume not only the volume of the solid portion of the 

specimen but also of its voids and pores, both permeable and impermeable. True or grain density is the 

density of the material composing the body. It equals 

the mass of the solid portion of the body divided by the 

volume of the solid portion, that is, by the external or 

bulk volume minus the volume of the permeable and 

impermeable voids and pores.

Specific gravity is the ratio of the weight of the 

body to the weight of an equal volume of distilled 

water. The weights should be determined in vacuo and 

the distilled water should be air-free, but for practical 

reasons these conditions are rarely met. Weights are 

usually measured in air, and the water usually contains 

the volume of air that can be dissolved at the ambient 

temperature and pressure. For most purposes this 

procedure is adequate. When it is not adequate, airfree water must be used and weighing done in vacuo as 

required.

The American Society for Testing Materials recognizes four types of specific gravity: absolute specific 

gravity, specific gravity, apparent specific gravity, and 

bulk specific gravity. Absolute specific gravity is defined (ASTM, 1952c, p. 1594-1595) as the "ratio of 

the weight referred to vacuum of a given volume of 

the material at a stated temperature to the weight

referred to vacuum of an equal volume of gas-free 

distilled water at a stated temperature." Specific gravity is defined as the "ratio of the weight in air of a 

given volume of the material at a stated temperature 

to the weight in air of an equal volume of distilled 

water at a stated temperature". Apparent specific 

gravity is defined as the "ratio of the weight in air of 

a given volume of the impermeable portion of a permeable material—that is, the solid matter including 

its impermeable pores or voids—at a stated temperature to the weight in air of an equal volume of distilled water at a stated temperature". Bulk specific 

gravity is defined as the "ratio of the weight in air of 

a given volume of a permeable material (including 

both permeable and impermeable voids normal to the 

material) at a stated temperature to the weight in air 

of an equal volume of distilled water at a stated temperature". The "material" in the terms "absolute specific gravity" and "specific gravity" refers to the solid 

material of which the body is composed, excluding any 

voids or pores, permeable or impermeable. The ASTM 

term "specific gravity" is frequently referred to in the 

literature as "true specific gravity". The term "bulk specific gravity" is frequently referred to in the literature 

as "apparent specific gravity". To avoid confusion, 

in the present discussion the term ''true specific gravity" will be used for the specific gravity of the solid 

material excluding voids and pores, both permeable 

and impermeable, and the term "bulk specific gravity" 

will be used for the specific gravity of the specimen 

including all voids and pores, both permeable and 

impermeable.

The weight of the body should be, strictly speaking, 

the weight of the specimen minus its included moisture. This is difficult to obtain as all bodies contain 

both adsorbed and capillary water, and frequently free 

moisture as well. It is standard practice to use the 

oven-dried weight, (w0 ) as the weight of the body. To 

obtain this the body is dried for 24 hours or more in 

an oven at a temperature of 105° to 110°C, then cooled 

to room temperature, preferably in a dessicator, and 

then weighed on a balance in air.

In the present investigation, because of the danger 

of altering other and more critical properties by heating, the specimens investigated by the Bureau of Mines 

and by the Geological Survey could not be oven-dried, 

and the air-dried weight (wa ) of the specimen was used. 

In determining the air-dried weight the specimen was 

dried, actually for a period of several months, in the 

laboratory under normal atmospheric conditions of 

temperature, pressure, and humidity. This would remove free water and part of the capillary water but 

would still leave the adsorbed water and part of the 

capillary water, especially that in the finer pore spaces.
SOME PHYSICAL CONSTANTS FOB THE MARSHALL ISLANDS AREA 959

The air-dried weight is thus slightly greater than the 

oven-dried weight. However, as previously noted on 

page 955, error from this source is negligible for most 

practical purposes.

The volume of the specimen or material for density 

measurements, or the weight of an equivalent volume 

of distilled water for specific gravity measurements may 

be obtained in several ways, depending upon the particular volume or weight desired, and the particular 

technique most convenient. The external or bulk volUEi6 (Vi>) of the specimen, that is the volume including 

the volume of its voids and pores, both permeable and 

impermeable, may be gotten geometrically, or by 

weighing. In the present investigation the specimens 

were all carefully prepared right circular cylinders, with 

accurately squared and ground ends. After carefully 

measuring the length of the cylinder and making a 

number of micrometer measurements of the diameter 

of the cylinder the bulk volume may be calculated from 

the equation

F6=I^ (5)

where D is the mean diameter and h is the height of the 

cylinder. Because the micrometer will not fit into reentrants in the sides of the cylinder, the external volume 

so determined will be slightly too large, but the difference for most practical purposes may be regarded as 

negligible.

The external volume may also be obtained by weighing in a fluid of known density. In one method, the 

method used by the U.S. Geological Survey, the specimen 

is dipped in melted paraffin to seal the external pores. 

The coated specimen is first weighed in air, and then 

completely immersed in water. If wa is the weight in 

air before being coated with paraffin, wpe the weight in 

air after being coated with paraffin, wpi the weight completely immersed in water after being coated with 

paraffin, pw and pP the densities of the water and paraffin at the temperature of the measurements, and F6 is 

the bulk volume, we have

_Wvc — UJpj t 

Pw

(6)

All quantities must, of course, be measured in the same 

system of units.

If the units are all in the cgs system the equation 

may be still further simplified. At room temperature 

the cgs density for water differs by only three parts per 

thousand from unity. It is usually adequate therefore 

to accept its value as pw=l. The density of paraffin is 

0.9 gm per cm3 at room temperatures. Inserting these 

values, equation (6) reduces to

=1.11 Wa — 0.11 Wpe— (7)

In a second method, employed by the Bureau of 

Mines, the Bureau of Reclamation, the Geological 

Survey, and others, the specimen is not coated. Instead the air-dried specimen is first thoroughly saturated with water. This may be done in a number of 

ways with varying degrees of completeness. It may 

simply be soaked for several days completely immersed 

in water. It may be similarly soaked but under a 

partial vacuum (usually 20 inches or less of mercury), 

or under pressure (on the order of 500 psi). Or, while 

completely immersed in water, it may be heated or 

boiled under vacuum, pressure, or both alternately.

After the specimen has been saturated, all surface 

water must be removed, but none of the pore water. 

This may be done by rolling the specimen on a piece 

of linen or cotton cloth which has first been saturated 

with water and then squeezed until it barely stops 

dripping. If the cloth is too dry it will remove some 

of the pore water; if it is too wet it will not remove 

all the free surface water. The saturated specimen— 

usually referred to in the literature as "saturated, 

surface-dried"—is then weighed in air in a balance and 

its saturated surface-dried weight, w3, recorded. It 

is then suspended completely immersed in water and 

its weight when so immersed, wi} recorded. The loss 

of weight on immersion is, of course, the weight of the 

water displaced by the external or bulk volume of the 

specimen. From this

(8)

P«r

Or, if all measurements are in cgs units, and if pw at 

room temperature is accepted as effectively equal to 1,

Vb=wt-Wi (9)

It is immediately apparent that the bulk density, p6 , 

of the specimen is then given by the equation

Wapa,

or, if ptc=l and cgs units are used,

(10)

(11)

Similarly, if 76 is the bulk specific gravity, we have

76= (12)

which holds for any system of units.

The true density and true specific gravity require 

the elimination of the effects of the pores and voids, 

both permeable and impermeable. This may be 

accomplished by pulverizing a portion of the specimen 

to break down the septa between the communicating
960 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

and noncommunicating pores, thus making all the 

voids permeable, and then weighing the powdered 

sample first dry and then completely immersed in 

water in a pycnometer (ASTM, 1942e, p. 281-282). 

In this method the sample is pulverized to pass a 

100-mesh screen. An empty pycnometer, together 

with its capillary stopper, is weighed. Let this weight 

be WP . A small portion of the pulverized sample is 

placed in the pycnometer and both are weighed, together with the capillary stopper. Let the weight of 

pycnometer, stopper, and sample be wps. The pycnometer is then partly filled with distilled water and the 

sample stirred until thoroughly mixed with the water. 

It is then placed under a vacuum of 0.5 to 1.0 inch 

of mercury long enough to remove all the entrapped 

air. The pycnometer is then filled to the top of the 

stopper with distilled water at room temperature 

and any excess water at the tip of the capillary removed 

by filter paper. Let its weight so filled be wpsw. Let 

the pycnometer then be completely emptied and 

refilled with distilled water alone, again to the top of 

the stopper, with any excess water being removed by 

a piece of filter paper. Let wpw be the weight of the 

water-filled pycnometer. If wg is the weight of the 

pulverized sample placed in the pycnometer, often 

called the grain weight, and Vg the volume of its solid 

portion, often called the grain volume, wd the weight 

of the water displaced by the solid portion of the 

sample, ww the weight of the water required to fill 

the empty pycnometer, and p t and jt the true density 

and true specific gravity, respectively, of the specimen, 

we have

v *~— (13)

from which

7(=^= _ MM-"* _ (14)

Pt=ytPw (15)

The densities and specific gravities determined for 

drill cores from the Marshall Islands are given in table 4.

Additional values of the bulk specific gravity were 

obtained indirectly by computation from the porosities. 

If Pt is the total porosity in percent of volume,

Pt

_vb -vt xioo

or

Vb 100

It may be shown that

76.

so that, from equation (17)

>=« *—165,

(16)

(17)

(18)

(19)

Determinations by the Bureau of Keclaniation of the 

true specific gravities of 13 specimens of coral limestone 

from Eniwetok Atoll gave an average value of 2.77. 

This value was used in computing the bulk specific 

gravities given in table 5.

The wet densities of a series of sea-bottom samples 

collected by the Scripps Institution of Oceanography 

during the Mid-Pacific Expedition of 1950 (fig. 290) 

are given through the courtesy of Drs. Roger Revelle 

and Arthur E. Maxwell in table 6. Densities and 

moisture content were determined by D. W. Butler, of 

the National Physical Laboratory of England.
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 

TABLE 4.—Densities and specific gravities of drill cores from Eniwetok Atoll, Marshall Islands

Measured by USBM=Applied Physics Branch, U.S. Bureau of Mines

USBR=Concrete Laboratory, U.S. Bureau of Reclamation 

USQS=U.S. Geological Survey

961

Rock

Basalt. _ _______ _

Core

E-l-1-13 __ _ ..

E-l-3-21.— __-._

E-l-4-3 A__— .._

E-1-4-3B-— _--.

E-1-4-9-- _-__ __

E-l-5-l_.________

E-l-5-2— .-._._.

E-l-5-5__________

E-l-5-6-___-_.___

E-l-5-ll__..__.._

E-l-6-2A________

E-1-6-2B-— _.__

F-l-3-6--_--_-___

F-l-4-l__________

F-l-5-4____ ______

F-l-6-2__________

F-l-ll-31.____.__

F-l-12-6- ______

F-l-14-18— _____

F-l-14-19 _ _ _ _

EN-8—— —————

EN-9____._-_____

EN-10——— ————

EN-11___________

MU-5__---___.__

MU 7_. _________

Depth (feet)

2, 003-2, 128 

4, 078-4, 100 

4, 208-4, 211 

4, 208-4, 211 

4, 208-4, 211 

4, 211-4, 216 

4, 211-4, 216 

4, 211-4, 216 

4, 211-4, 216 

4, 211-4, 216 

4, 216-4, 222 

4, 216-4, 222

1, 232-1, 248 

1, 718-1, 740 

1, 978-2, 003 

2, 662-2, 687 

4, 197-4, 222 

4, 316-4, 341 

4, 500-4, 525 

4, 500-4, 525

90. 5-91. 0 

95. 0-96. 0 

81. 0-82. 0 

8. 0- 9. 0

38. 1-70. 5 

81. 5-82. 0

Location

———do———— ————— —

——— do———— ———— ——— —— .do— — ——— _. ———

——— do—— ——— ———— —

———do.——— ———— — —

do _. .

——— do————— —— ————

———do——— —— —————— .....do— . _ _ — ._ — _.._

———do—————— —————

———do— ——— ——————

.....do.. .-_-__ -----------

——— do———— ————— .—

——— do———— ——— ————

_.___do— ____ — .._- ———

.....do— . — --_ — . — .

———do——— —— ——— ———

..__. do... — ———— ————

.....do— ————— _ ————

_____do__--_--_--_--__--_-

——— do——— ——— —————

Specific gravity

Bulk

1. 21

2. 31

2. 25

1. 83

2. 51

2.39

1.84

2. 53

1. 89

1 RQ

2.25 

1. 79 

1.79 

2.35

1.82 

1. 79

True

2. 75 

2.82 

2.82 

2.75

2.76 

2.82

Density

Bulk 

(gper cm3)

2.83

2.97

2. 86

2. 84

2. 96

2.93

2. 75

2. 69

2. 56

2. 66

True 

(gper cms)

Measured byUSBM 

USBM

USGS 

USGS 

USBM

USGS 

USGS 

USGS 

USGS 

USGS 

USGS 

USGS

USBM 

USBM 

USBM 

USBM 

USBM 

USBM 

USBM 

USBM

USER 

USER 

USER 

USER

USER 

USER

TABLE 5.—Additional values of bulk specific gravity computed from 

total porosity and mean value of true specific gravity

Rock

LimestoneCoreE-l-2... 

F-l-1... 

F-l-9... 

F-l-10.. F-1-13-.

Depth 

(feet)

2,802-2,808 

170-191 

3, 655-3, 665 

3,963-3,988 

4, 406-4, 431

Location

Parry Island __ 

Elugelab island ...

.....do _ ........

—— _do— — .... .

Specific gravity

Bulk

1.98 

1.58 

1.78 

1.74 

2.24

True

2.77 

2.77 

2.77 

2.77 

2.77

Total 

porosity 

(percent)

28.7 

43.0 

35.9 

37.1 

19.1

TABLE 6.—Densities of some mid-Pacific ocean-bottom sediments, 

Scripps Institution of Oceanography, Mid-Pacific Expedition of 

1950

[Measurements by D. W. Butler, National Physical Laboratory of England. 

Courtesy of Eevelle and Maxwell]

Station

21-1.———————— 32.. ——— . —— — — ———

35-2._ _ ....... ___ ...

35-2......-..-- ....... —

36. — — .—

36—————— ——— —— —

38.——————— ——— —

38 .. .. „

Location

Lat. N.

20°48' 

18°18' 

19°28' 

19°28' 

16°45' 

16°45' 

19°2' 

19°2'

Long. W.

159°42' 

173°23' 

174°35' 

174°35' 

176°24' 

176°24' 

177° 19' 

177°19'

Depth 

below sea 

floor 

(inches)

38^-42^ 

24-28 

24-27 

76-79^ 

53-57 

79-84^ 

271-2-31^ 

75}|-79^

Moisture 

content 

(percent 

wet weight)

52 -56.5 

50 

42. 5-43. 5 

58 

52.5 

52 

67. 5-71. 5 

61 -62.5

Wet 

density 

(g per ml)

1.43-1.38 

1.47 

1. 58-1. 57 

1.35 

1.41 

1.40 

1. 22-1. 18 

1.27

ELASTIC CONSTANTS

When an elastic body is subjected to an external force 

it is changed in size or shape, or both. When the force 

is relieved, the body will return to its original size or 

shape, provided the force is less than a certain critical 

value. If it is greater than that value, the body 

receives a permanent set. The external force exerted 

on the body is termed the load. It is resisted by internal 

elastic forces which at equilibrium are equal and opposite to the external force and thus determine and limit the 

amount of the distortion. The intensity, or force per 

unit area, of the external force and of the equal but 

opposite internal elastic reaction are called the stress. 

The stress at which the first permanent set appears is 

termed the elastic limit of the body.

The amount of change under load in the size or shape 

of the body per unit original dimension is called the 

strain. It may be a change in a lineal direction, in the 

angle between lineal dimensions, or a change in volume. 

Whatever its type it is always expressed as the amount 

of change per unit original quantity.

Hooke in 1676 discovered experimentally that as 

long as stresses did not exceed (or closely approach) the
962 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

elastic limit the strain or elongation in a given wire 

under tension from different suspended weights was 

proportional to the applied load; in other words, 

inversely,

stress

strain= constant (20)

Later investigators have extended this from the case of 

tension to any type of elastic stress and strain. The 

constant so determined is referred to as the elastic 

constant or modulus for that type of stress.

If the stress is plotted against the strain, equation 

(20) shows that the graph should be a straight line 

whose slope equals the elastic constant or modulus 

involved. Such curves, however, prove in general to 

be curvilinear at the beginning and end, although they 

usually have a middle approximately linear segment 

which is called the "proportional part" of the curve. 

They may occasionally be curvilinear throughout. 

Part of the difficulty appears to be due to minute 

permanent sets or creep which occur during the process 

of loading (see Pao and Marin, 1952, p. 951).

The slope of the stress-strain curve may be determined in several different ways, as shown in figure 295.

UJ 

DC

ce

UJ

Q.

en Q

z

o

CL

600

500

400

300

5 200

en 

en

UJ

a:

100

100 200 300 400 

LONGITUDINAL STRAIN, 1Q-6INCHES PER INCH

500

FIGURE 295.—Stress-strain curve showing relation of the various elastic moduli 

determined from the curve to it and to each other.

The slope of the proportional part of the curve may be 

determined by computation, or if it does not pass 

through the origin, a line parallel to the proportiona 

part may be drawn through the origin and its slope 

determined. If the stress-strain curve is curvilinear

•angents may be drawn to the curve at any point and 

the slope of the tangent determined. This is the 

angent modulus. The tangent drawn at the beginning 

of the curve is called the initial tangent and its slope the 

initial-tangent modulus. Or a line may be drawn from 

the origin to any point on the curve. Such a line is 

called a secant, and its slope the secant modulus for 

jhat point. Or a line may be drawn between any two 

points on the curve; such a line is called a chord, and 

ts slope the chord modulus for the stress range between 

lihe two points.

The load applied to produce the elastic deformation 

may be one of several types. It may be a tensional, 

a compressional, or a shearing load, or a hydrostatic 

pressure. In a tensional or compressional load the 

force is unidirectional, normal to the surface of application, and tends to elongate or shorten the body in the 

lineal direction along which it operates. In a shearing 

load the force is tangential to the surface of application 

and tends to change the shape of the body. In a 

hydrostatic load the force is everywhere perpendicular 

to the surface or surfaces of the body and tends to 

decrease its volume. Conversely when the hydrostatic 

load is released the body will undergo an expansion or 

dilatation.

THE ELASTIC MODULI FOR TENSION OB COMPRESSION: 

YOUNG'S MODULUS

Each type of stress will be related to its resultant 

strain by its own modulus of elasticity. Both tension 

and compression will change the lineal dimensions 

along which they operate. If L is the original length 

of this dimension of the body prior to the application 

of the load, and Ai its change in length under a tensional or compressional load (F) applied over an area, 

A, we have for the elastic modulus, E,

_steess__FM_.fX_ 

"strain A.L/L A -A (21)

since the stress equals the force per unit area, and the 

strain is the change in length per unit length. The 

elastic modulus (E) for tensional or compressional 

stresses is called Young's modulus, because it was first 

investigated by Sir Thomas Young. Both the elastic 

modulus for tension and that for compression are called 

Young's modulus, although the value for compression 

may at times differ slightly from that for tension.

POISSON'S RATIO

If a body is lengthened under tension, its width or 

diameter is shortened. The change in length is referred 

to as the longitudinal strain, the change in lateral 

dimensions as the lateral strain. The ratio of the 

lateral strain to the longitudinal strain is a constant
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 963

known as Poisson's ratio (/*). Its value usually approximates 0.25, although it may depart widely from that 

value. For the core cylinders used in the present 

investigation,

AD

where L and D are the original length and diameter of 

the cylinder and AL and AZ> are their respective changes 

under the applied load.

MODULUS OP RIGIDITY— SHEAR OR TORSIONAL LOADS

If a cube is pushed askew by an applied force, or a 

cylinder twisted by a torque, the body is distorted by 

the motion of one plane over another, either translational, rotational, or both. Such a displacement is 

said to be a shear and the stresses so developed are 

referred to as shearing stresses. The elastic resistance 

of the body to such shearing forces is called its rigidity 

and the ratio of shearing stress to shearing strain is a 

constant called the modulus of rigidity, usually represented by the letter G.

The shearing strain is measured by the displacement 

in the shear plane per unit length of the body. Thus 

if the displacement is translational, as in figure 296A, 

a line perpendicular to the shear plane is rotated through 

an angle 8 and the displacement, s, in the shear plane 

is given by

s=L tan 0 (23)

As the angle 0 is small it may replace the tan 8 with 

negligible error. From this, recalling that the strain is 

the displacement per unit length,

strain=9 

and G, the modulus of rigidity, is given by

~ F

(24)

(25)

where A is the area over which the force F is applied.

If a torque, r, is applied to a cylindrical core, such 

as those investigated in the present study, a rotational 

displacement or twist, s, is produced in the cylinder, 

figure 2965; a longitudinal line is rotated through the 

angle 8, as before, and the top of the cylinder is rotated 

through the angle <£. If R is the radius of the cylinder,

Strain = (26)

As the stress is proportional to the strain, which in 

turn is proportional to the distance from the center of 

the cylinder, it is obvious that the stress is not a constant throughout the cylinder. However, it will be a 

constant for an incremental cylindrical tube of mean

A. TRANSLATIONAL SHEAR

B. ROTATIONAL SHEAR

FIGURE 296.—Strains produced by (A) translational and (B) rotational shearing

radius, r, and thickness dr. If the increment of stress 

on this tube is d<r we have, as G is a constant for the 

material

d<r=G r-£ (27) LI

Also, if dr is the torque on the incremental tube, we 

have

dr dawhence, combining equations (27) and (28),

(28)

(29)
964 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

Integrating in r from 0 to R, and rearranging,

„ 2Lr (30)

BULK MODULUS (MODULUS OF INCOMPRESSIBILITY)

If an elastic body is placed under hydrostatic pressure, its volume will decrease with increasing pressure. 

The elastic constant that represents the ratio of volumetric stress to volumetric strain is called the bulk 

modulus or modulus oj incompressibUity, and may be 

represented by the letter B. We then have

B=

AV/V (31)

where AF" is the change in volume under pressure P, 

and Vis the original volume before compression. Note 

that if V is not the volume at zero pressure, this equation must be modified to

B=- P2 -Pi (32)

where PI and V\ are the initial pressure and volume, 

and V2 is the volume at a different pressure, P2 .

The reciprocal of the bulk modulus is called the 

compressibility or coefficient of compressibility, often designated by the letter k.

UNITS USED FOR ELASTIC CONSTANTS

The strain factor is dirnensionless, as both numerator 

and denominator of the strain are in the same units. 

The elastic moduli, therefore, which represent the ratio 

of stress to strain, have the dimensions of the stress, 

that is of force per unit area. In the English system 

of units used in engineering practice they are given in 

pounds per square inch (psi), whereas in the metric 

system they are usually expressed in kilograms per 

square centimeter (kg per cm2). Conversion factors 

are

1 psi=0.070307 kg per cm2= 68947 d per cm2= 

0.068947 bar

1 kg per cm2=14.223 psi.

Poisson's ratio is of course dirnensionless, as both 

numerator and denominator are in the same units.

The coefficient of compressibility is the reciprocal of 

the bulk modulus and as such is expressed in reciprocal 

units. In the cgs system it is usually given in terms 

of reciprocal bars (bar" 1).

DETERMINATION OF THE ELASTIC CONSTANTS

STATIC METHODS

The elastic constants can be determined either by 

static or dynamic methods. Under static methods the

core is placed in a testing machine and subjected to a 

load that is slowly increased at a definite rate. The 

strain developed is measured, usually at regular intervals, either directly by a dial indicator sensitive to 

changes as small as 0.0001 inch, or electrically by means 

of suitably mounted strain gauges.

In making such tests the time element is important, 

since creep may occur and invalidate the measurements 

if too long a time is allowed to elapse during a run. 

Other factors such as temperature, moisture content, 

and core dimensions, may also affect the measured 

values. For these reasons the rate of loading is kept 

fixed at a standard value, the measurements are carried 

out at as nearly a constant temperature, usually room 

temperature, as is possible and convenient, and the 

core dimensions are either kept to a standard size or 

are corrected to such a size.

As seen in figure 297 the stress-strain curve, because 

of elastic hysteresis, is different under decreasing 

pressure from that under increasing pressure, and that 

for a second increase-decrease cycle is different from 

that for the first. In other words, the values of the 

elastic moduli vary with the stress histories. It is 

therefore necessary, in presenting results of static tests, 

to define the preceding stress conditions. It is usually 

assumed that the core, after having been in storage for 

some months, has released the stresses and strains from 

the drilling process and is initially in an unstressed

2000

1600

O- 1200

800

400

0

EXPLANATION

———— First cycle

• — — — Second cycle

0 100 200 300 400 500

STRAIN, 10 ~6 INCHES PER INCH

FIGURE 297.—Changes in the stress-strain curve for core EN-8 during successive 

load-unload cycles.
SOME PHYSICAL CONSTANTS FOE THE MARSHALL ISLANDS AREA 965

condition. In any particular case this may or may 

not be true, but in general it is probably not too 

seriously in error.

As seen in figures 297 and 298, the width of the stressstrain loop decreases with later cycles. Normally most 

of the narrowing of the loop occurs between the first 

and second cycles, with much less change for the later 

cycles. However, the beginning and end of successive 

curves as well as of successive cycles will rarely coincide. 

For this reason the elastic constants are seldom determined from the first cycle, but usually are read after 

a certain standard number of cycles have been run. 

The Bureau of Mines used measurements from the 

seventh cycle.

Static measurements in the present study were 

limited to determinations of Young's modulus and of 

Poisson's ratio. Young's modulus was determined from 

the stress-strain curves. Where the curve was essentially linear the slope of the best straight-line fit was 

used. Where it was curvilinear, the secant values for 

the particular stress range noted were used. In the 

Bureau of Reclamation measurements only the proportional part of the curve was used and it is stated that 

the modulus can be regarded equally well as either 

a secant or a tangent determination. Poisson's ratio 

was determined from simultaneous measurements of 

the lateral and longitudinal strains.

Measurements were made in standard compressiontesting machines. The specimen ends were carefully

600

EXPLANATION

—— First cycle

— — Second cycle

100 200 300 400 

STRAIN, 10 ~6 INCHES PER INCH

500

"FIGURE 298.—Stress-strain curve for core MU-^5 showing narrowing of second loadunload cyde.

931305—-62——3

squared by diamond saw. In the Bureau of Reclamation tests the ends were capped with plaster of paris to 

provide an even bearing for the longitudinal load. In 

the Bureau of Mines tests they were made smooth and 

flat by polishing. The compression machine was 

provided with spherically-seated joints so that the 

specimens, which were carefully centered in mounting, 

would be self-alining. The specimens were mounted 

under a small initial pressure to insure proper seating. 

In the Bureau of Mines measurements compression was 

initiated at a pressure of 100 psi and the load then 

increased at a rate of 100 psi per second. In the 

Bureau of Reclamation tests the pressure was increased 

at a rate of approximately 2,000 psi per minute until 

the specimen showed a strain of 500X10"6 inches per 

inch, after which the cycle was reversed.

In table 7 are shown the observed values of stress, 

longitudinal and transverse strain, and the corresponding values of Young's modulus (£"), and Poisson's 

ratio, (/z) for the seventh compressional cycle on four 

cores measured by the Bureau of Mines: (1) a dense 

coralline limestone, F-l-6-2; (2) a moderately hard 

porous limestone, F-l-11-13; (3) a foraminiferal limestone, F-l-14-18; and (4) an olivine basalt, E-l-4-9. 

The strain values are the mean for both the ascending 

and descending limbs of the cycle.

It may be shown that if any two of the four elastic 

constants, E, p, G, and B are known, the other two can 

be computed (see, for example, Macelwane, 1932, 

p. 82-88) from the relationships

E

E

B=

'2(1 + M>

B 

3(1-2M)

(33)

(34)

(35)

Table 8 summarizes the observed data from all the 

static tests in the present investigation, together with 

computed values derived from them for the other 

constants.

DYNAMIC METHODS

The elastic moduli may be determined dynamically 

by setting up sonic vibrations in the core and measuring 

the resonant frequencies for both compressional and 

torsional vibrations. From these data the various 

elastic constants may be computed, as discussed by 

Obert, Windes, and Duvall (1946), Pickett (1945), 

the American Society for Testing Materials (1952a), 

Teller (1956), and Whitehurst and Parker (1956).

The procedures and equipment (figure 299) described 

by Obert, Windes, and Duvall (1946) were used in the 

dynamic measurements made by the Bureau of Mines.
966 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

Oscillaior amplifier 1

^

Pole

piece

Driver 3 q

/

Central 

mount

V

Core

,///////////////i U,L,HH

Zero

control

Pole

piec

•>

5

e

Pickup 1

• —— High-gain — a-c

j amplifier ,,,.,. voltmeter

FIGUEE 299.—Block diagram of sonic equipment used by the U.S. Bureau of Mines for dynamic determinations of the elastic constants (after Obert, WIndes, and Duvall).

In summary, both ends of a core were carefully squared. 

Soft-iron pole pieces were cemented to the ends and 

allowed to set for 24 hours. The core was then mounted 

in a clamp and accurately centered to give single-point 

central support and symmetrically placed between 

an electro-mechanical driver at one end, whose function 

it was to set the core into vibration, and a magnetic 

pickup of identical construction at the other end, whose 

function it was to convert the vibration at that end 

into an electrical signal for measurement and recording. 

The design of the driver, which differed for compressional and torsional vibrations, determined the type of 

vibration set up in the core. Power to operate the 

driver was furnished by a beat-frequency oscillator 

with a range of from 20 to 17,000 cycles per second. 

The oscillator was provided with an incremental dial 

for the measurement of small changes in frequency, and 

fed into a 15-watt linear power amplifier whose output 

was delivered to the driver. The voltage from the 

magnetic pickup was fed into a linear high-gain amplifier 

whose output was then read on a high-impedance voltmeter.

The output voltage was proportional to the velocity 

rather than to the amplitude of vibration. This, however, caused no difficulty since the velocity was also a 

maximum at resonance.

Stray radiation between the driver and the pickup 

was reduced by shielding and by feedback of an out-ofphase component from the power amplifier into the 

high-gain amplifier.

The soft-iron pole pieces, because of added inertia, 

decrease both the longitudinal and transverse frequencies. This may be corrected by means of equations 

(36) and (37) below. If fre and frt are resonant frequencies for compressional and torsional vibrations 

respectively without the pole pieces, fref and /,/ the 

corresponding resonant frequencies with the pole 

pieces, kg the ratio of the radius of gyration of the pole 

pieces to that of the core, and M and M' the weights

respectively of the core and of the two pole pieces, 

we have (Obert, WIndes, and Duvall, 1946, p. 9)

'TT)

(36)

(37)

If L is the length of the core, and ve and v t the velocities 

of compressional and torsional vibrations through the 

core, respectively, we have, from the resonant frequencies,

ve=2frcL (38)

v t=2frtL 

whence, if p is the density of the core,

(39)

(40)

(41)

(42)

If the ratio of length to radius of the core is less than 

approximately 10:1, it becomes necessary to make a 

correction to ve for a cross-section effect. If ve is the 

true compressional velocity, and ve ' the apparent 

velocity, as given by equation (38),

(43)

Dynamic measurements made by the Bureau of 

Keclamation employed flexural vibrations, using the 

equipment and procedures described by the American 

Society for Testing Materials (1952a). •. Flexural 

vibrations are induced in a core supported on sponge 

rubber by applying "a driving probe near one end of 

the specimen. The driving probe is powered by a 

variable oscillator and resonance is determined by 

means of an amplitude meter connected to a vibration
SOME PHYSICAL CONSTANTS FOB THE MARSHALL ISLANDS AREA 967

pickup near the center or near one end of the specimen. 

The type and mode of vibration are determined by 

checking the number and location of nodes and the 

direction of vibration.

If frf is the resonant frequency of the first mode of 

flexural vibration, w the weight of the core, and Cf a 

flexural constant whose value is dependent on the shape 

and physical dimensions of the specunen, the mode of 

vibration, and on Poisson's ratio,

E= Cfwffj3 (44)

If frt is the resonant torsional frequency, and Ct a 

similar torsional constant,

G=Ctwfr t* (45)

The evaluation of C/ and Ct is discussed by Pickett 

(1945, p. 850-853). From these equations and the

values of E and 0 so obtained, the values of Poisson's 

ratio and of the bulk modulus may be computed from 

equations (33) and (35), or Poisson's ratio may be 

computed from the equation

_Cffrj*

(46)

Table 8 lists the mean elastic moduli, both observed 

and derived, as determined by static and dynamic 

methods.

In figure 11 the values of Young's modulus are 

plotted against the bulk specific gravities. There is a 

general increase in E with increase in the bulk specific 

gravity. However, the points show so much scatter 

as to make difficult the recognition of a specific 

relationship.

12.0

11.0

10.0

o

? 9.0

E>

USBM sta 

i it

USBN

USE 

. USBR

+

CPLANATIO 

o

tic, limestone or 

a 

3BM static, basa

X

1 dynamic, limes 

A 

R static, limesti 

+ 

dynamic, limes

O

^o—

N

dolomite 

It - ————

tone

ane 

tone

A

X

0

+

A

X

X

Q

-

I

<r

UJ 

CL

V) 

Q

Z

1

8.0

7.0

6.0

5.0

4.0

3.0

2.0

1.0

1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0

SPECIFIC GRAVITY 

FIGURE 300.—Qraph of Young's modulus plotted against specific gravity.
968 BIKINI AND NEAEBY ATOLLS, MARSHALL ISLANDS

TABLE 7.—Observed static-test data for the seventh stress-strain cycle for four drill cores from Eniwetok Atoll

Conversion factors:

1 psi=0.070307 kg per cm*=68947 dynes per em*=0.068947 bar 

1 bar-'=1 reciprocal bar=0.068947 reciprocal—psi

[Measurements by the Applied Physics Branch, U.S. Bureau of Mines]

Stress (psi)

Strain (10-« in. per in.)

Longitudinal Transverse,

Measured constants

Young's 

Poisson's modulus 

ratio 

E

** (10 « psi)

Derived constants

Modulus of Bulk 

rigidity modulus

O B

(10 « psi) (10 « psi)

Compressibility

k 

(10-« bar-J)

Dense recrystallized coral limestone, core F-l-6-2, Elugelab island

427.... _ ..... _ ..... __ . _ ..... __ ........... ...

855.. ........... __ . _ ........ __ . _ ......... _ ..

1,282....................................................

1,709....................................................

2,137... _________________________________________________

2,564....................................................

2,991....................................................

3,419— __..__.___._..„__.___._.._______._._____________

3,846....................................................

4,274....................................................

4,701— .................................................

5,128.... _______ .......

5,556... _ ........... _ .......... ___ ___ _ .. ...

5,983....................................................

6,410— .—....—......................................

6,838... __________ . _____ .... . _ . _ . ...

7,265....................................................

55 

115 

175 

230 

290 

350 

407.5 

467.5 

527.5 

595 

655 

717.5 

780 

830 

895 

990 

Failure

12.5 

27.5 

40 

55 

67.5 

81 

«5 

109 

121.5 

135 

145 

165 

180 

257.5 

312.5 

475 

Failure

0.23 

.24 

.23 

.24 

.23 

.23 

.23 

.23 

.23 

.23 

.22 

.23 

.23 

.31 

.35 

.48

7.76 

7.43 

7.33 

7.43 

7.37 

7.33 

7.34 

7.31 

7.29 

7.18 

7.18 

7.15 

7.12 

7.21 

7.16 

6.91

3.15 

3.00 

2.98 

3.00 

3.00 

2.98 

2.98 

2.97 

2.96 

2.92 

2.94 

2.91 

2.89 

2.75 

2.65 

2.33

4.79 

4.76 

4.52 

4.76 

4.55 

4.52 

4.53 

4.51 

4.50 

4.43 

4.27 

4.41 

4.40 

6.32 

7.96 

57.58

3.03 

3.05 

3.21 

3.05 

3.19 

3.21 

3.20 

3.22 

3.22 

3.27 

3.40 

3.29 

3.30 

2.29 

1.82 

.25

Moderately hard porous limestone, core F-l-11-13, Elugelab island

85......................................................

256 ___ . ___ . _ . ___ . ____ . ___ ...... ......... ...

427...., _____ . _____ ... . ... ..... . .... ...

598.....................................................

769.....................................................

940............. ..................... ...................

1,111....................................................

1,282.— ................................................

1,453—— __ . ___ . _ . _ __ .. _ _ . ... . ..

1,624....................................................

1,795— -.—.-...........,..............................

2,137— -,-.-...—.._..—...___.._._._.__..._........„

2,564....................................................

2,752....................................................

100 

305 

475 

667.5 

845 

1,015 

1, 177. 5 

1, 327. 5 

1,465 

1, 587. 5 

1, 727. 5 

2,010 

2,420 

Failure

20 

60 

105 

150 

197.5 

252.5 

295 

345 

395 

445 

507.5 

662.5 

1,005 

Failure

0.20 

.20 

.22 

.22 

.23 

.25 

.25 

.26 

.27 

.28 

.29 

.33 

.42

0.85 

.84 

.90 

.90 

.91 

.93 

.94 

.97 

.99 

1.02 

1.04 

1.06 

1.06

0.35 

.35 

.37 

.37 

.37 

.37 

.38 

.38 

.39 

.40 

.40 

.40 

.37

0.47 

.47 

.54 

.54 

.56 

.62 

.63 

.67 

.72 

.77 

.83 

1.04 

2.21

30.9 

30.9 

26.9 

26.9 

25.9 

23.4 

23.0 

21.6 

20.1 

18.8 

17.5 

14.0 

6.6

Foraminlferal limestone, core F-l-14-18, Elugelab island

885.....................................................

1,770— .................................................

2,655...................................................

3,540....................................................

4,425— ____ . ___ .. ___ _ . ___ ___ __ ..

5,265.. ___ . _____________________________

422.5 

862.5 

1,272.5 

1,625 

1, 972. 5 

Failure

80 

170 

270 

365 

475 

Failure

0.19 

.20 

.21 

.22 

.24

2.09 

2.05 

2.09 

2.18 

2.24

0.88 

.85 

.86 

.89 

.90

1.12 

1.14 

1.20 

1.30 

1.44

13.0 

12.7 

12.1 

11.2 

10.1

Olivine basalt, core E-l-4-9, Parry Island

855.. ____ . ___ . _____ . ______ _______ ...

1,709— .................................................

2,564....................................................

3,419... .................................................

4,274... ____________ . ____________ .........

5,128— __ .. _____ _____ _ . .. .. ...

5,983— ___________ . _________ .. .............

6,838....................................................

7,692. __________ _ ...

8,547— .................................................

85 

175 

262.5 

345 

430 

510 

600 

682.5 

787.5 

Failure

15 

31

45 

67.5 

85 

100 

120 

132.5 

150 

Failure

0.18 

.20 

.17 

.20 

.20 

.20 

.20 

.19 

.19

10.05 

9.77 

9.77 

9.91 

9.94 

10.05 

9.97 

10.02 

9.77

4.26 

4.07 

4.18 

4.13 

4.14 

4.19 

4.15 

4.21 

4.11

5.23 

5.43 

4.93 

5.51 

5.52 

5.58 

5.54 

5.39 

5.25

2.77 

2,67 

2.94 

2.63 

2.63 

2.60 

2.62 

2.69 

2.76
SOME PHYSICAL CONSTANTS FOE THE MARSHALL ISLANDS AREA 969

TABLE 8.—Mean elastic constants, observed and derived, for some Eniwetok drill cores

Measured by:

USBM=Applied Physios Branch, U.S. Bureau of Mines 

USB R = Concrete Laboratory, U.S. Bureau of Reclamation

Rock

Basalt _________ . _ . __

Dolomite.. _________ . .......

Core

E-1-4-9.. _._______.._.______

F-l-5-4.. .............. ..

F-l-fr-2.. ...................

F-l-11-31-.-.— - ..........

F-1-12-6.. ________ ..

F-l-14-18--- — - ... ... ......

EN-8— ................ ....

EN-9.......................

EN-10.. _ ............ . ..

EN-11......... .............

MU-5—————————. ...

MU-5..... ................ ..

MU-7.. _ .............

Rock

Depth (feet)

4, 208-4, 222

1, 978-2, 003 

2, 662-2, 687 

4, 197-4, 222

4, 316^, 341

4, 528-4, 553

90. 5-91. 0 

95. 0-96. 0 

81. 0-82. 0

8. 0-9. 0

} 59. 0-70. 5 

81. 5-82. 0

Location

Parry Island

Elugelab islar 

do

id..——— ..... ..... .....

——do-———————————— __ -

—— do_.__— ....... ... _ .....———

do

Engebi island 

do

——.do..——.. ..... —— — — ... ——

do — - ——

fMujinkarlkki 

1 do ::::: d0:::::: :::;: ::: ::: ::: ::: ;::: ::: :::

Core

E-1-4-9.............,.......— _ .... __ ..

F-l-5-4..-.. _ ................. __ .......

F-l-6-2.. __ .. _ ............. __ —.....

F-l-11-31———————————————————

F-1-12-6--.———...—.—.- _ ........

F-l-14-18---— _ .——....—— _

EN-8———————————————————

EN-9... .......... ———— ————— ————— .

EN-10—————————————————————

EN-11—————— ............ ........ .... ....

MU-5.————... —————— ————— ————

MU-5-....—. ... — - — —— ... —— ..... ..

MU-7...... ..——. ... ....... —— ... ......

Depth (feet)

4, 208-4, 222

1,978-2,003 

2, 662-2, 687 

4, 197-4, 222 

4, 316-4, 341 

4, 528-4, 553

90. 5-91. 0 

95. 0-96. 0 

81. 0-82. 0

8.0-9.0

} 59.0-70.5 

81. 5-82. 0

Static tests

Measured

JCT

(10« pSi)

9.92

7.28 

.95

2.13

4.44 

2.50 

2.54 

5.91

1.10 

.95 

2.38

M

0.19

.26 

.26

.21

.12 

.29 

.17 

.16

.14 

.07 

.17

Derived

G

(10« psi)

4.17

2.89 

.38

.88

1.98 

.97 

1.09 

2.55

.48 

.44 

1.02

B

(108 psi)

5.33

5.06 

.66

1.22

1.95 

1.98 

1.28 

2.90

.51 

.37 

1.20

fc (10-« bar-1)

2.72

2.87 

21.98

11.85

7.45 

7.33 

11.30 

5.00

28.48 

39.39 

12.07

Dynamic tests

Measured

E1

(106 psi)

9.18 

7.51

10.72

2.82

6.96

{---

G

(10« psi)

4.10 

3.32

5.29

.92

2.75

Derived

M

0.12 

.13

.01

.53

.27

B

(106 psi)

4.03 

3.38

3.67

4.94

ft (10-6 bar-i)

3.60 

4.29

3.95

2.94

Measured by —

USBM

USBM 

USBM 

USBM 

USBM 

USBM

USER

USER 

USER 

USER

USER 

USER 

USER

HARDNESS

There is no generally accepted definition of hardness. 

In a general way, hardness may be described as the 

resistance of a body to penetration by another body 

(see Williams, 1942). This definition is not entirely 

satisfactory quantitatively, since it depends on the body 

doing the penetrating as well as on the body being 

penetrated, and depends also on the type of equipment 

being used and on its method of application. Because 

an absolute method of hardness measurement is not 

available, and measurements are relative in character, 

hardness cannot be expressed in terms of a definite 

and established quantitative unit, but will in general 

be measured in terms of an arbitrary unit established 

for a particular method and piece of equipment.

One widely used method of measuring hardness is 

the rebound method. In this method a hammer with 

a sharp point of definite dimensions and radius of 

curvature is dropped from a given height onto the 

body to be tested and the height of rebound measured. 

The height of rebound, other factors being constant,

631305—62———4

will depend on the amount of energy used up by the 

hammer point in penetrating the test body. This in 

turn will depend on the hardness of the body. Although the relationship is not a simple one, the height 

of rebound may thus be used as a measure of the 

hardness.

The Shore Scleroscope, used by the Applied Physics 

Branch of the U.S. Bureau of Mines in making the 

present measurements, employs a hammer with a 

diamond tip which is dropped from a standard height 

onto the test body. The height of rebound is measured 

by a dial graduated in "scleroscope units" found by 

dividing the average rebound from quenched pure 

high-carbon steel into 100 equal parts. This will then 

normally range from 95 to 105 scale divisions, and the 

scale may be recalibrated at any time by the use of a 

standard block of such high-carbon steel.

Because hardness may vary from point to point in 

a rock sample, a series of scleroscope readings were 

made at different points on each specimen, and their 

arithmetic mean accepted as the hardness value for
970 BIKINI AND NEAKBY ATOHLS, MARSHALL ISLANDS

the specimen. The degree of variability of the readings 

was determined by means of the standard deviation * 

of the measurements. The standard deviation so 

given is not a measure of the precision of the measurements but of the variability of the rock hardness from 

one point to another, as the latter is in general very 

much greater than the random errors of the equipment. 

In table 9 the hardness of the various cores tested 

is presented in "scleroscope units" and the variability 

(u) in terms of the percent standard deviation

lOOo- v=—=— 

H

(47)

where a is the standard deviation of the series and H is 

the arithmetic mean of the scleroscope readings.

For purposes of comparison, table 10 lists hardnesses 

determined with the same scleroscope on a number 

of hardness standards used by the Bureau of Mines.

TABLE 9.—Hardness of some Eniwetok drill cores in arbitrary 

"scleroscope units"

[Measurements by the Applied Physics Branch, U.S. Bureau of Mines]

Rock Core Depth 

(feet)

Hardness 

(scleroscope 

units)

Variability 

(percent 

standard deviation)

Number 

of observations

Elugelab island

F-l-3-6......—

F-l-4-1 „_.___ ...

F-l-5-4.-— . ...

F-l-6-2-.-— ..

F-l-12-6. .......

F-l-14-18-.-—

1, 232-1, 248 

1, 718-1, 740 

1,978-2,003 

2, 662-2, 687 

4,316-4,314 

4, 528-1, 553

52 

14 

64 

52 

52 

13

9 

45 

14 

11 

15 

17

10 

30 

60 

30 

40 

10

Parry Island

Basalt— _____

E-l-3-21.. _ ...

E-l-4-9.-— ... .

4, 078-4, 100 

4, 208-4, 222

42 

71

15 

11

30 

30

TABLE 10.—Comparison hardness measurements on a series of 

U.S. Bureau of Mines standards

[Measurements by Applied Physics Branch, U.S. Bureau of Mines]

Rock standard

Rhyolite: a very fine-grained dark-green rock, presumably a devitrified rhyolite___._--_________--____-.

Orthoclase: a large pink orthoclase phenocryst from 

granite from Amelia, Va,----.----------------------

Greenstone: composed primarily of tremolite-actinolite 

laths and fine-grained lathlike albite; some chlorite and 

a little epidote; from Mount Weather, Va_________

Lithographic limestone: Solenhofen, Germany________

Marble: White marble from Lynchburg, Va.; grains approximately 1 mm in diameter, but with numerous 

crush-bands of finer grain-size_-____-_______________

Fpssiliferous limestone: Bedford, Ind________________

Limestone: Bedford, Ind.; less fossiliferous, more marl 

matrix________________________________________

Talc: Fine-grained massive block talc from South India. _

Average

hardness

(sderoscope

units)

105

104

52

49

26

18

IMPACT TOUGHNESS

Impact toughness is the resistance of the specimen to 

fracture under impact. It is determined by dropping 

a weight of given mass onto a hammer or plunger of 

given size in contact with the surface of the specimen 

and increasing the height of drop until the specimen 

fractures.

A study by the Bureau of Mines (Obert, Windes, and 

Duvall, 1946, p. 41-43) of factors affecting impact 

toughness has shown that: (1) the cross-sectional area 

of the impact surface affects the values, but the ratio 

of height of drop at fracture to the cross-sectional area 

of the impact surface is a constant, and (2) the ratio of 

core diameter (D) to core length (L) affects the value 

of the impact toughness. If a ratio of D/L equal to 

unity is selected as standard for specimens, the observed 

impact toughness, k0, for a core of other dimensions, 

can be corrected to that for a core of standard 1:1 

dimensions by the equation

(48)

1.23- -0.23^ LI

1 The standard deviation is the root mean square of the departures of the individual readings from the arithmetic mean of the series.

where ks is the impact toughness for a core whose 

length equals its diameter. (3) Moisture reduces impact toughness slightly so that impact toughness is 

greatest for oven-dried cores and least for saturated 

cores. For convenience the air-dried state was selected 

as standard and used in the present investigation.

The machine used for these tests comprised a 50 kg 

anvil on which the specimen was placed, a 1 kg plunger 

with a 1 cm radius of curvature placed in contact with 

the top of the core or specimen, and a 2 kg hammer constrained by guides which, however, permitted a free fall 

of the hammer onto the plunger. The height of fall 

was measured each time and was increased, usually by 

1 cm steps, until fracture occurred.

Because the ratio of the height of drop to the crosssectional area of the core is a constant, impact toughness 

is expressed in terms of this ratio for a standard specimen as computed from equation (48) above. The unit 

for impact toughness used by the Bureau of Mines is 

"inches per square inch."

Table 11 gives the values of impact toughness for 

several Eniwetok drill cores. All measurements were 

made by the Applied Physics Branch of the U.S. Bureau 

of Mines.
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 971

TABLE 11. — Impact toughness of some Eniwetok Atoll drill cores 

[Measured by the Applied Physics Branch, U.S. Bureau of Mines]

Rock Core Depth 

(feet)

Impact 

toughness 

(in. per 

in.*)

Number of 

observations

Elugelab island

F-l-4-1. __

F-l-5-4 _ .—.—..

F-1-6-2-— — — —

F-l-12-6. _ ._...—

1, 718-1, 740 

1,978-2,003 

2,662-2,687 

4,316-4,341

1.18 

1.68 

1.01 

2.86

2 

3 

1 

2

Parry Island

E-l-3-21.. ..........

E-l-4-9 _ -—.....

4,078-4,100 

4,208-4,222

1.51 

1.35

2 

1

MAGNETIC CONSTANTS

Three primary magnetic quantities were determined 

in the present investigation: the susceptibility of the 

cores studied and the intensity and inclination of their 

remanent magnetization. The azimuth of the remanent 

magnetization could not be determined as the cores 

could not, of course, be oriented in their horizontal 

plane.

SUSCEPTIBILITY

Susceptibility was determined by the use of a Michelsen susceptibility bridge (Michelsen, 1952). The 

Michelsen bridge is basically a Maxwell resistanceinductance bridge equipped with a Wagner ground to 

minimize the effect of ground admittances. It is provided with three identical resistances and three identical 

inductance coils, as shown in figure 301. Two of the 

inductance coils and two of the resistances form the 

four arms of the bridge; the third inductance coil and 

resistance form the arms of the Wagner ground.

The inductance coils are wound as modified Helmholtz coils to assure uniformity of field over the sample 

volume (1X1X1 inches). The inductance coil in one 

arm of the bridge, the search coil, accepts the sample to 

be measured. The inductance coil in the other arm, 

the balance coil, is provided with a cone of ferrite admixed with enough permalloy to match the resistive 

component of magnetite and mounted on a lucite screw 

moving axially through the coil. Both the balance 

coil and the inductance coil of the Wagner ground are 

provided with small adjacent ferrite slugs and resistance

.Reference voltage channel

Preamplifier

Voltmeter Phase meter

FIGURE 301. -Block diagram of Michelsen susceptibility bridge.
972 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

elements which can be adjusted prior to the insertion 

of the specimen to insure an accurate bridge null before 

measurements are begun.

To determine the susceptibility of a specimen, it is 

placed in the search coil and the ferrite cone advanced 

axially into the balance coil until balance is achieved. 

The position of the ferrite cone at balance is noted on 

a^scale which has been carefully calibrated in advance 

in terms of specimen susceptibility by the use of a series 

of standard ferric chloride solutions introduced into the 

search coil.

Because the inductive and resistive components are 

90° out of phase, they may be adjusted independently 

and the two variables separated by the use of phase 

detection.

Figure 301 gives a block diagram of the instrument 

setup. Detection of unbalance is accomplished by 

means of an oscilloscope and a phasemeter. The oscilloscope detects clipping and thus helps adjust proper 

amplifier amplification. Its primary function, however, 

is in the coarse adjustment of bridge balance, as the 

phasemeter quickly goes off scale with a small unbalance. When the bridge is unbalanced the oscilloscope shows a typical Lissajous loop. Adjustment of 

the resistive component narrows this loop to a straight 

line. Adjustment of the inductive component rotates 

the straight line into a horizontal position. Final adjustment is then made by the phasemeter. The limit 

of reliable sensitivity is on the order of 1X10~6 cgs 

units 2 of susceptibility per cm3 of sample.

Two values of the susceptibility are given in table 13: 

K the volume susceptibility and x the mass susceptibility. The volume susceptibility represents the strength 

of the magnetic poles generated at any point of the 

body per unit area perpendicular to the field. If / 

is the intensity of magnetization per unit volume, or 

magnetic moment of the material per unit volume (per 

cm3 in the cgs system), and H the intensity of the 

magnetic field producing the magnetization,

I=KH (49)

If J is the intensity of magn etization per unit mass (per 

gram in the cgs system),

(50)

If p is the density of the material, it is obvious that

and

(51)

(52)

a The unit of susceptibility has no name. It has the dimensions of p in the electromagnetic system of units.

The flux density (B) within the body is related to the 

intensity, H, of the field and the intensity (7) of magnetization per unit volume of the material by the equation

(53)

PERMEABILITY (MAGNETIC)

The ratio of the flux density (B) of the field inside 

the body to the intensity (H} of the field in which the 

body is placed is called the magnetic permeability (j«), 

often referred to as the magnetic conductivity of the 

body:

M =|=l + 4,« (54)

The magnetic permeabilities of the cores are listed in 

table 13.

REMANENT MAGNETIZATION

Most ferromagnetic materials when subjected to a 

magnetic field become permanently magnetized to a 

greater or lesser extent, that is, they retain a measurable 

intensity of magnetization when the magnetizing field 

has been removed. Such residual, permanent magnetization is called "remanent magnetization." If the 

magnetizing field has been the earth's field, it is called 

natural remanent magnetization.

Two types of remanent magnetization are observed 

in rocks: (1) isothermal remanent magnetization, where 

the permanent magnetization has occurred at ordinary 

temperatures; and (2) thermoremanent magnetization 

where the magnetization of the rock has occurred during 

cooling from a high temperature, usually from a melt 

or from a temperature higher than the Curie point. 

Thermoremanent magnetization is usually more permanent as well as more intense than isothermal remanent 

magnetization.

To express quantitatively the relationship between 

remanent and induced magnetization, Koenigsberger 

(1938) has introduced the quantity Q, whose value is 

given by the relationship

(55)

where He is the total intensity of the earth's magnetic 

field; IT and Jr are the intensities of the remanent 

magnetization per unit volume and per unit mass, 

respectively; and K.He and xHe are the intensities of 

induced magnetization per unit volume and per unit 

mass, respectively, in the same field. Q might be called 

the coefficient of remanent magnetization. The value 

of Q usually ranges between 2 and 10: occasionally it 

exceeds 100, and rarely is less than unity.
SOME PHYSICAL CONSTANTS FOB THE MARSHALL ISLANDS AREA 973

Equation (55) may be written

Ir=QKH, and Jr=QxH. (56)

from which it is seen that the intensity of remanent 

magnetization is equivalent to induced magnetization 

under an effective susceptibility of either QK or Qx, as 

the case may be.

The orientation of the remanent magnetization vector 

may or may not agree with the earth's present magnetic 

field. Its relationship to the earth's present field 

becomes a matter of great interest since it must represent the integrated effects of the magnetic, thermal, and 

geologic history of the specimen. Unfortunately, in 

the present investigation only the inclination, i, and 

polarity of the down end of the magnetic remanence 

vector can be given, as the cores cannot be oriented as 

to azimuth.

The remanent magnetizations of the cores in the 

present investigations have been measured by the U.S.

Geological Survey, using the Michelsen remanent 

magnetometer (Michelsen, 1951). This instrument 

(figure 302), which was developed through the efforts 

of the Department of Terrestrial Magnetism of the 

Carnegie Institution of Washington, measures both 

the intensity and direction of the magnetization vector 

in a rock specimen. If the sample is an oriented specimen on which the position of the horizontal plane and 

the direction of either true or magnetic north have 

been marked, the orientation of the remanence vector 

with reference to the earth's present field, and to 

geographic coordinates is determined.

The remanent magnetometer consists of two coaxial 

coils, one larger in diameter than the other, connected in opposition and balanced to cancel out the 

effects of stray a-c fields. This balance means that 

magnetic shielding can be omitted, except for materials 

of very low susceptibility, as the effect of a strong stray 

a-c field is reduced to about 0.001 of its value by the 

balanced coils. The sample to be tested is mounted,

Reference voltage channel

Balanced coils

L. \~f

filter

Frequency 

meter I

Amplifier

Band

pass

filter

Amplifier

Attenuator

Voltmeter 

FIGURE 302.—Block diagram of Michelsen remanent magnetometer.

Phase rneter Frequency 

meter
974 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

either as a cube or as a cylinder whose length equals its 

diameter, in a sample holder in the axis of the coils 

and spun by an air turbine at a speed of 280 rps, this 

speed being selected so that the electronic units of the 

susceptibility bridge can also be used with the remanent magnetometer. The coupling of the remanent 

field of the specimen with the inner coil is much greater 

than with the outer coil, so that the signal from the 

bridge is effectively that due to the remanent magnetization alone.

In operation the sample is spun in both direct and 

reversed rotation about three mutually perpendicular 

axes in the specimen. The intensity of the field thus 

induced and the orientation of the reman ence vector 

with respect to the three axes of rotation are determined 

and combined vectorially, usually with the use of an 

equiangular projection net, to give both the intensity 

and orientation of the remanent magnetization vector.

The drill holes from which the present cores came were 

satisfactorily vertical as seen in table 12 below, which 

gives the deviations from the vertical for different 

depths in the drill holes as determined by an acid-bottle 

survey.

The inclination of the remanence vector as determined by the measurements is therefore of significance, 

even though the azimuth cannot be determined.

TABLE 12.—Acid-bottle surveys of Eniwetok drill holes

Depth (feet)

Deviation from 

the vertical 

(degrees)

Drill hole E-l, Parry Island

146

2,000 ___ ._ _.

2,802-.-. _-__.

4,078—— —— -. 1

Drill hole F-l, Elugelab island

160.- ____ .-

1,232.— ______

1,650. _________

K

I

Depth (feet)

Deviation from 

the vertical 

(degrees)

Drill hole F-l, Elugelab island— Con.

1968

1*975

2,470—— ______

2,900—— ______

3,350—— ____

3 963

4*182

4,197— ___ -.

A Aflfi

4,500—--.- ___

5% 

3% 

4 

4

3

3/4

The direction of the magnetic-north end of the remanence vector in the core can be determined by means of 

an astatic magnetometer. However, there is no 

certainty concerning its relationship to geographic 

north or to present magnetic north. Moreover, the 

intensity of magnetization is apt to be altered by 

proximity to the magents of the magnetometer. It 

was, therefore, felt desirable not to make this test. 

Table 13 lists the various magnetic constants for both 

induced and remanent magnetization determined during 

the present study.

TABLE 13.—Magnetic constants for both induced and remanent magnetisation of some Parry Island, Eniwetok Atoll drill cores

NOTE.—Susceptibility («) "very weak": less than 2X10-' cgs units, the smallest susceptibility for which the bridge was calibrated.

Values of Q are based on the assumption that the intensity of the magnetic field on Eniwetok Atoll was approximately the same at the time of remanent magnetiza- tion as now; that is, 0.341 gauss. 

Polarity: N, north-seeking pole. 

Position: Small 1- by 1-in. cylinders were cut out of a large drill core: T from the top; B from the bottom; and M, from the middle of the large core.

[Measurements by the U.S. Geological Survey]

Rock

Limestone ____________

Basalt. ——— . —— __ ... __ .. ...

Core

S-l-1.. .........................

E-l-2.. „_„__„ _ . __ .......

E-l-3 _____ .... ..............

E-1-4-3-. -„.„...._..._.. __ .

E-1-5-1-. ___ . _ ..... ........

E-1-5-2-- .......................

E-l-5-5... _______ . .........

E-1-5-6.. ___ . _ .... ........

E-l-6-11..... __________ .

E-1-6-2-. ___ .... __ . ........

Depth (feet)

170-191 

2, 802-2, 808 

4, 078-4, 100

4,208-4,211

4,211-4,216 

4,211-4,216 

4,211-4,216

4,211-4,216

4, 211-4, 216 

4,216-4,222

Induced magnetization

(HHcgs)

Very weak 

Very weak 

Very weak

0.60 

.79 

.85

.45 

.46

.38 

.66

.70 

.65 

.64 

.63 

.63 

.71 

.71

.58 

.52 

.52 

.60 

.48

.48 

.52 

.49

(10-»cgs)

0.21 

.28 

.30

.16 

.16

.13 

.22

.24 

.22 

.22 

.22 

.22 

.24 

.24

.21 

.19 

.19 

.22 

.17

.18 

.20 

.19

M

1.0075 

1.0099 

1. 0107

1.0057 

1.0058

1.0048 

1.0083

1.0088 

1.0082 

1.0080 

1.0079 

1.0079 

1.0089 

1.0089

1.0073 

1.0065 

1.0065 

1.0075 

1.0060

1.0060 

1.0065 

1.0062

Remanent magnetization

Ir 

(10-»cgs)

4.4 

10.4 

7.8

8.66 

9.14

15.50 

18.30

16.5 

12.5 

16.0 

14.5 

17.9 

17.9 

17.5

12.9 

8.0 

6.7 

7.0 

9.3

6.01 

12.8 

5.8

Q

21 

39 

27

56 

58

120 

81

69 

56 

73 

67 

83 

74 

72

65 

45 

38 

34 

57

37 

72 

35

i 

(degrees)

44 

69

58 

37

53 

53

60 

62 

63 

67 

55 

62

68 

60 

48 

48 

48

30 

29 

11

Polarity 

(end 

down)

N 

N

N 

N

N 

N

N 

N 

N 

N 

N 

N 

N

N 

N 

N 

N 

N

N 

N 

N

Core 

position

T 

B

M

T 

B

T 

B

T 

B 

T 

M 

B 

T 

M

T 

B 

T 

M 

B

T 

T 

B
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 975

PERMEABILITY (HYDRAULIC)

The hydraulic permeability, often called the coefficient of permeability, is the capacity of rocks or soils to 

transmit water under pressure. It is determined hi the 

laboratory by measuring the rate at which water will 

percolate through a specimen or sample of given 

cross-sectional area and length under a given gravity 

head.

If V is the volume of water passed through the 

specimen, h the hydraulic head—that is, the difference 

in the water levels at input and output points—A the 

cross-sectional area of water flow, and L the length of 

the flow path, we have, after Darcy,

KAh

dt (57)

where dV/dt, often denoted by g, is the volume rate of 

flow, t is time, and K is the coefficient of permeability. 

In the determination of the permeability of relatively 

impermeable samples it is often more convenient to use 

a variable head, that is, to start out with a given volume 

of water and allow the head to decrease as the water 

percolates through the sample. If the change, dh, hi 

water level is measured in a graduated manometer 

(fig. 303) whose area of cross-section is a, it follows that

Time

FIGURE 303.—Variable head permeameter used by the U.S. Geological Survey in 

measuring the hydraulic permeability of Eniwetok cores. (After A. I. Johnson, 

1953, written communication.)

dV 

dt

dh (58)

the minus sign indicating that h decreases as y increases. 

Combining this with equation (57) we have

dh ~dt~~ KAh 

a,L

whence, integrating from 2=0 to t=t,

hp_KAt 

h aL

(59)

(60)

where ho is the water level at the start of the measurements (t=0) and h is the level at time t. Solving for K,

=— In ^ 

At 1 h

(61)

The value of K will of course be affected by the viscosity of the water, the rate of flow being greater the 

smaller the viscosity. For this reason the value of K 

is specified for a standard viscosity. The standard viscosity may be directly specified in viscosity units, or it 

may be indirectly established by specifying a certain 

temperature for the water. If rjs is the standard viscosity or the viscosity at the standard temperature, 

i\T the viscosity at the temperature of the measurements, 

and Ks the permeability at the standard viscosity or 

temperature, equation (61) becomes

aL ijT. •-*-, • — «" ^r (62) At its h

Converting natural to Briggs logarithms, equation 

(62) becomes

(63) -j- — 

At its

i logioj

It has been found convenient in the laboratory to 

measure L, ho, and h in centimeters, a and A hi square 

centimeters, and t in seconds. It is obvious dimensionally that a/A, i)Tfris, and ho/h are numerics. It 

therefore follows that jK"has the dimensions of a velocity, 

L/t, which in equation (63) is centimeters per second. 

For engineering reasons it has been found convenient 

in the U.S. Geological Survey to express K hi Meinzer 

units. A Meinzer unit, or more simply, a meinzer, is a 

flow, when fully saturated, of 1 gal of water per day 

through a cross-sectional area of 1 sq ft under a hydraulic 

gradient of 1 ft per ft at a temperature of 60°F. Converting to meinzers, equation (63) becomes

9J8Q

(64)

where KM is the permeability in meinzers, L is in 

centimeters, t is in'seconds, and ^90 is the viscosity of the 

water at 60°F.
976 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANPS

A more widely used unit of permeability is the darcy, 

which is defined as a flow of 1 cm3 per sec through a 

cross-sectional area of 1 cm2 of a fluid of 1 centipoise 

viscosity under a pressure differential of 1 atm per cm.

To convert meinzers into darcies it may be noted that

1 meinzer=4.877X10~2 darcies=48.77 millidarcies 

1 darcy=20.50 meinzers

The variable head permeameter used by the U.S. 

Geological Survey in measuring the hydraulic permeability of Eniwetok cores is shown in figure 303. A 

graduated-tube manometer of internal cross-sectional 

area a, filled with water, is connected by a length of 

rubber hose to a sample holder, s. From the sample 

holder the water flows past a thermometer, T, and 

through a rubber hose to an overflow tank, 0, in which 

the water level is regulated by the position of a glass 

funnel, F. The height of the water head, h, driving the 

water through the specimen, is measured above the 

water level in the overflow tank. From the overflow 

tank the water flows out through the funnel and hose 

into a waste drain.

The sample holder is a cylinder of acrylic plastic 

seated against gaskets in two end plates. A seamless 

rubber tube is mounted inside the cylinder and overlapped over its ends. Through a valve in the side of the 

cylinder a vacuum is created between the rubber tube 

and the cylinder walls, drawing the tube against the 

walls and permitting the insertion of the core sample.

TABLE 14.—Coefficient of permeability (hydraulic) for Eniwetok 

cores

[Measurements by the U.S. Geological Survey, Denver, Colo.]

Bock Core Depth

(feet)

Coefficient of

permeability

(meinzers)(millidarcies)

Remarks

Parry Island

Limestone..

Basalt.. _ ._

E-l-1.....

E-l-2.....

E-l-3.. „_

E-l-3 _ ..

E-l-4.....

E-l-6.....

E-l-6-.—

2,003-2.028

2, 802-2, 808

4,078-4,100

4,078-4,100

4,208-4,211

4,211-4,216

4,216-4,222

9.3

12.7

.12

.0032

.013

.00004

.09

454

619

5.9

.16

.63

.002

4.4

Bottom of sample 5 ft

above base of core.

Bottom of sample 6 in.

above base of core.

Top of sample 10 in.

below top of core.

Top of sample 2 ft

below top of core.

Top of sample 1 ft 8 in

below top of -core.

Elugelab island

Limestone..

Dolomite--

Limestone . -

F-l-1-1 _

F-l-3-5 ...

F-l-4-6...

F-l-5-4...

F-l-6-20..

F-l-9-3...

F-1-10-6-.

F-l-11-31.

F-l-12-6..

F-l-13-5..

F-l-14-19.

170-191

1,232-1.248

1, 718-1. 740

1,978-2.003

2,862-2,687

3,665-3,665

3, 963-3. 988

4,197-4,222

4,318-4,341

4,406-4,431

4, 600-4. 525

5.1

.042

3.2

.00013

.00022

9.7

10.0

2.3

.00046

1.0

.073

249

2.0

156

.006

.011

473

488

112

.022

48.8

3.6

The vacuum is then released and the tube allowed to 

snap back against the specimen to seal off the sides of 

the core. A porous bronze filter is then placed at each 

end of the cylinder to seal in the core and the whole 

assembly is tightly clamped together by three brass 

rods. Air pressure is then introduced between the 

cylinder walls and the rubber tube to make certain that 

the core sides are sealed off and that the water flows 

through the length of the core.

Several runs are made on each core for several time 

intervals and the maximum value of K obtained is 

accepted as the correct value for the saturated permeability. These values are given in table 14.

POROSITY

Two types of porosity are recognized: permeable and 

impermeable or occluded. The permeable porosity 

comprises those pores and other voids which are intercommunicating and open either directly or indirectly 

to the exterior of the specimen. The impermeable or 

occluded porosity comprises those pores and other voids 

which are sealed off from each other and from the 

exterior of the specimen. Pores differ greatly in size, 

ranging from large open lacunae to microscopic pores 

only a few angstroms in diameter.

Porosities of a series of Eniwetok drill cores have 

been determined by two different laboratories of the 

U.S. Geological Survey, by the Applied Physics Branch 

of the U.S. Bureau of Mines, and by the Concrete 

Laboratory of the U.S. Bureau of Reclamation in 

Denver, Colo. The method employed by the Hydrologic Laboratory of the U.S. Geological Survey is as 

follows: The true specific gravity is first determined 

for a part of the core by the pycnometer method 

described under "Density and Specific Gravity." A 

section of the core dried at 105°C is next weighed 3 

and then given a very thin paraffin seal by dipping 

it in a bath of melted paraffin. It is next reweighed 

and the weight of the paraffin coat thus determined. 

It is then completely immersed in water in a wire 

cradle attached to the arm of a balance and again 

weighed while so immersed. The loss in weight is the 

weight of the water displaced by the core and its 

paraffin coat. The external or bulk volume, F6, of the 

core alone is then obtained from the equation

PP

(65)

where w0 is the weight in grams of the dry sample in

»Although the terms, "weight" and "weighed" are here used in accordance with 

standard custom, it is to be understood that the balance or other weighing equipment used is so calibrated as to give the mass of the body in grams rather than the 

gravitational attraction on the body in dynes. The "weights" wa, wpe, wfi, and so on, 

are thus the masses rather than the weights, and are so treated in stating and solving 

the equations here used.
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 977

air, Wpc is the weight in grams of the coated sample in 

air, wpi is the weight in grams of the coated sample 

when suspended completely immersed in water, pw and 

pp are the densities of water and paraffin respectively 

at the temperature of the measurements. If the 

density of water at room temperature is assumed to be 

unity, and the density of paraffin is taken as 0.9, this 

reduces to

Vb =(wve —wpj) — 0.9 (66)

If wd is the weight of the water displaced by the uncoated core, we have

if pw is regarded as unity. The bulk specific gravity, 

76 , of the core is then obtained from the equation

76=— (68)

If y t is the true specific gravity and Pt is the total 

porosity hi percent, that is the percent of the volume 

occupied by both permeable and impermeable voids,

t==T«-76x 100 (69)

The values so determined for the Eniwetok cores are 

listed in table 15.

The Bureau of Mines, the Bureau of Reclamation, 

and the Geological Survey laboratory determined the 

volume of the permeable voids and pores and from this 

determined the permeable or effective porosity, that is, 

the percentage of the specimen volume occupied by permeable pores and voids. As essentially the same procedure was followed by all three, their methods will be 

described together. The specimen is first oven dried for 

a period of 24 hours or longer at a temperature of 105° 

to 110°C, and then cooled and weighed. It is next 

saturated with water, surface-dried as described under 

"Density and Specific Gravity," and reweighed in air. 

If w0 is the oven-dried weight and ws the saturated 

surface-dried weight, the volume Vp of the permeable 

pores is given by ,

,, _WS — W 0

Pw

(70)

where pu is the density of the water filling the pores of 

the specimen. As the density of water at room temperature departs from unity by only 3 parts hi 1,000, it is 

usually regarded as unity, with negligible error, and 

equation (70) can be written

Vp=wg —w0 (71)

If the external volume, V6 , of the specimen is determined by the paraffin method described above, or by 

any of the methods discussed under "Density and

Specific Gravity," we have

(72)

where Pe is the permeable or effective porosity—that is, 

the percent of the volume occupied by permeable voids 

and pores.

If wt is the weight of the saturated specimen when 

completely immersed in water, we have, from equations 

(8), (70), and (72)

(73)

The values of the permeable or effective porosity for 

the Eniwetok cores are given in table 15.

TABLE 15.—Porosities of Eniwetok drill cores, percent by volume

Porosity: Values in parentheses have been computed by the writer from the bulk 

specific gravities. All others are measured values.

Measured by—

USBM=Applied Physics Branch, U.S. Bureau of Mines 

USBB=Concrete Laboratory, U.S. Bureau of Reclamation 

USGS=U.S. Geological Survey

Bock Core Depth 

(feet)

Porosity (percent)

Total Effective

Bulk 

specific 

gravity

Measured byParry Island

Limestone _ E-l-1...... E-l-1-13— 

E-l-2...... E-l-3.——

E-l-3——

E-l-3-21— 

E-l-4—— __

E-l-4-3 A-.

E-l-4-3 B_- 

E-l-4-3 C_. 

E-l-4-9— _ 

E-1-5- — - 

E-l-6......

E-l-6-2 BE-l-6-2 C-.

2,003-2,028 

2,003-2,028 

2, 802-2, 808 

4, 078-4, 100 

4, 078-4, 100 

4, 078-4, 100 

4, 208-4, 211 

4, 208-4, 211

4, 208-4, 211 

4,208-4,211 

4, 208-4, 211 

4, 211-4, 216 

4, 216-4, 222 

4, 216-4, 222

4,216-4,222 

4, 216-4, 222

47.6 

(56. 3) 

28.7 

111.7 

2 15.0 

(16. 6) 

33.0

(3.7) 

«7. 5 

« 8.1

.06 

.00 

.04

2.94 

1.50 

2.50

1.21

2.31

2.96 

2.97 

2.99 

2.86

2.61 

2.68 

2.62

USGS 

USBM 

USGS 

USGS 

USGS 

USBM 

USGS 

USGS 

USGS 

USGS 

USBM 

USGS 

USGS 

USGS 

USGS 

USGS

Elugelab island

Limestone- ...

Dolomite ..... 

Limestone. . ..

F-l-1-1 — _ 

F-l-3-5—— 

F-l-3-6 — . 

F-l-4-1 —— 

F-l-4-6—— 

F-l-5-4 ——

F-l-5-4 ——

F-l-6-2— . . 

F-l-6-20 — 

F-1-9-3-.

F-l-10-6--. 

F-l-11-31 — 

F-l-11-31 —

F 1 19— fi

F-l-12-6— 

F-l-13-5 — 

F-1-14-18-.

F-l-14-19.-

170- 191 

1, 232-1, 248 

1, 232-1, 248 

1, 718-1, 740 

1, 718-1, 740 

1, 978-2, 003 

1,978-2,003 

2, 662-2, 687

3, 655-3, 665 

3, 963-3, 988 

4, 197-4, 222 

4, 197-4, 222 

4, 316-4, 341 

4, 316-4, 341 

4, 406-4, 431 

4, 500-4, 525 

4, 500-4, 525

43.0 

12.1 

(18.8) 

(33. 9) 

9.9 

7.4 

(5.8) 

(13. 7) 

7.6 

35.9 

37.1 

31.1 

(33. 6) 

(8.7) 

12.0 

19.1 

(31.8) 

32.7

4.0

2.25

1.83

2.61 

2.39

1.84 

2.53

1.89

USGS 

USGS 

USBM 

USBM 

USGS 

USGS 

USBM 

USBM 

USGS 

USGS 

USGS 

USGS 

USBM 

USBM 

USGS 

USGS 

USBM 

USGS

Engebi island

EN-8-— ..

EN-9- ..... 

EN-10.——

EN-11——.

90. 5-91. 0

95. 0-96. 0 

81.0-82.0

8. 0-9. 0

16.04 

36.0 

36.0 

14.09

2.25 

1.79 

1.79 

2.35

USER 

USER 

USER 

USER

Mnjinkarikkn island

Limestone .... MU-5- ——

MU-7_ ——

38. 1-70. 5

81. 5-82. 0

32.71 

36.0

1.82 

1.79

USER 

USER

i Bottom of sample 5 ft above base of core. 

2 Bottom of sample 6 in. above base of core. 

3 Top of sample 10 in. below top of core. 

* Top of sample 2 ft below top of core. 

6 Top of sample 1 ft 8 in. below top of core.
978 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

RADIOACTIVITY (NATURAL)

An attempt was made to measure the radioactivity 

of the sediments in drill hole E-l on Parry Island, 

Eniwetok Atoll. An in-hole Geiger-Mueller tube was 

lowered into the drill hole by means of an electric 

cable connecting it to a counter at the surface. The 

counter was provided with three ranges: 0 to 0.2, 

0 to 2.0, and 0 to 20.0 mr per hr.4 Prior to its use 

at the drill hole the counter was carefully calibrated 

against radiation standards in the Radiation Laboratory on Eniwetok. All readings in the drill hole were 

taken on the 0.2-mr-per-hour scale, which was found 

to be accurately calibrated. Before and after each 

run in the drill hole the operational functioning of 

tube and counter was tested by a pair of radioactive 

standards carried with the equipment.

The drill hole was filled with water almost to ground 

level. The Geiger-Mueller tube was protected by a 

thin-walled brass cylinder which was closed by a brass 

ferrule at the base and by a threaded cap and a packing 

gland at the top. Several types of packing and packing 

glands were tried at the top, but great difficulty was 

experienced, particularly with increasing depth, in 

keeping minute traces of moisture from getting inside 

the tube and interfering with counter operation. 

Eventually the ferrule was silver-soldered to the case 

at the base and a plastic coating sprayed over the outside of the tube and cable after reassembly to seal all 

possible leaks. Before its effect could be established, 

however, the protecting brass cylinder imploded at a 

depth of 924 feet below the water surface of the well, 

928 feet below the top of the well casing. Table 16 

shows the counter readings down to the depth of 

implosion.

The background radioactivity in the air at the top 

of the drill hole was measured at intervals of 5 seconds 

during two runs of 2 minutes each with the GeigerMueller tube held just above the top of the casing in 

the well. Individual readings ranged from 0.02 to 

0.065 mr per hr. The average for the two runs was 

0.041 mr per hr.

Measurements were made in the laboratory by P. M. 

Hurley of the radioactivity of the basalt from the 

bottom of drill core E-l-5-5 from a depth of 4,216 

feet in drill hole E-l on Parry Island. (Written 

communication, to H. S. Ladd, January 12, 1954.) 

The specimen was described as an "unusually fresh 

olivine basalt, very hard, with a conchoidal fracture."

4 The abbreviation mr=milliroentgen. A roentgen was denned by the International Commission on Eadiological Units hi 1950 (U.S. Bureau of Standards, 

1951, p. 24) as "... the quantity of X- or gamma radiation such that the associated corpuscular emission per 0.001293 g of air produces, hi air, ions carrying 1 

electrostatic unit of quantity of electricity of either sign." It may be noted that 

0.001293 g is the mass of 1 cm' of dry atmospheric air at 0°C and 760 mm of mercury 

pressure.

The radioactivity was determined by two methods: 

thick-source alpha count in an ionization chamber 

with a source area of 160 cm2 and in a proportional 

counter with a source area of 24 cm2. As seen in table 

17, the ionization chamber gave a value of 0.57 X10~12 

grams of equivalent radium per gram of basalt, and 

the proportional counter gave a value of 0.58 X10"~12 

grams of equivalent radium per gram of basalt.

Hurley also made volumetric measurements of the 

pure helium extracted from two samples of the basalt, 

one sample of 10.255 grams, the other of 9.467 grams. 

The first sample gave 0.35 X10~5 and the second 0.36 X 

10~5 cubic centimeters of helium per gram of basalt, as 

shown in table 18.

These values of helium content and radioactivity 

permit an estimate of the age of the basalt. The 

value of the age depends upon the value of helium 

retentivity assigned to the rock. Retention values

TABLE 16.—Natural radioactivity of the coral limestone in drill

hole E-l, Parry Island, Eniwetok Atoll, December 1952

[Measured by the author with an in-hole Geiger-Mueller counter]

Depth below top of 

casing (feet)

0_-._-_ _ .....

4 _________

0-100_. ________

100-200 ________

200-300 ________

300-400 ____ _

400-525 .____._.

525-725 ________

725-795.-- _ -_

795-825 ________

825-925 ____ .-

Radioactivity 

(mr per hr)

Maximum 

observed

0 065 

030

04 

028 

025 

025 

03 

035 

04 

04 

043

Average

0 041 

020

013 

012 

010 

012 

014 

Oil 

015 

023 

022

Remarks

In air above top of casing. 

At top of water in drill 

hole.

TABLE 17.—Natural radioactivity of the basalt 

[Measured in the laboratory by P. M. Hurley]

Description of rock

Unusually fresh olivine 

basalt, very hard, with 

conchoidal fracture.

Core

E-l-5-5...

Depth 

(feet)

4,216

Method of measurement

Ionization chamber. 

Proportional alpha 

counter.

Radioactivity 

(grams of 

equivalent 

radium per 

gram of 

basalt)

0. 57X10-" 

0. 58X10-"

TABLE 18.—Helium content of the basalt 

[Measured in the laboratory by P. M. Hurley]

Description of rock

Unusually fresh olivine

basalt, very hard, with

conchoidal fracture.

Core

E-l-5-5...

Depth 

(feet)

4,216

Sample

A

B

Weight 

(grams)

10. 255

9.467

Helium content (cm' 

per gram of

basalt)

0.35X10-'

0.36X10-S
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 979

of 40 to 60 percent are found in the literature. If a 

retentivity of 50 percent is assumed, the age of 

the basalt would be 40,000,000 ±10,000,000 years. 

Dr. Hurley regards this value as very uncertain, 

however.

SEISMIC SPEEDS: SPEEDS OF TRANSMISSION OF 

SEISMIC WAVES

The speeds of transmission of sonic waves, both 

compressional and torsional, through a few of the 

Eniwetok cores have been measured by the U.S. 

Bureau of Mines using the dynamic method described 

earlier in the section on "Elastic Constants." As 

there noted, the resonant frequencies, /rc and /rt, for 

compressional and torsional vibrations are determined. 

From these the corresponding speeds of transmission, 

vc and ®t respectively, are computed from equations 

(38) and (39), given on p. 966,

where L is the length of the core being tested. The 

results of these measurements, made on air-dried cores, 

are listed in table 19.

The torsional waves generated in the Bureau of 

Mines measurements represent a rotational shear. 

The speeds so determined, however, apply equally 

well to waves involving translational shear, and thus to 

the general class of distortional waves — also called 

transverse, shear, equivoluminal, or rotational waves. 

(See Ewing, Jardetsky, and Press, 1957, p. 10.)

Speeds computed from equations (38) and (39) are 

"bar speeds", since they represent transmission in only 

one direction, along the axis of the core. Threedimensional transmission in the earth would give rise 

to slightly higher speeds. Thus if vc is the bar speed 

for the compressional wave

(74)

where E is Young's modulus and p is the density.

The speed of transmission, vt, of a compressional 

wave in three dimensions in an isotropic medium is 

given by the equation (see Macelwane, 1932, p. 105),

(1-M) (75)

where p is Poisson's ratio. The computed values of vt 

found from the measured values of vc and n for the 

three cores tested dynamically by the Bureau of Mines 

are given in table 19. It may be noted that the 

change from bar speed to isotropic speed for these 

three cores is small because of the low values of their 

Poisson's ratios. Normal values of ju, around 0.25, 

would lead to a correction factor of 1.2, or an isotropic 

speed 20 percent higher than the bar speed.

Joesting, Swartz, and Farnham made a series of 

seismic-refraction surveys on a number of islands in 

Eniwetok Atoll. Their results, which are for shallow 

depths, are listed in table 20. Except for materials 

exposed at the surface, identifications of lithological 

units are based on extrapolation from nearby drill holes. 

They are, therefore, to be regarded as approximate 

only, particularly in view of the many local and rapid 

variations known to occur.

Perkins with Dobrin and Lill (Perkins and Lill, 1948; 

Dobrin and Perkins, 1954) made a series of in-hole 

velocity measurements in drill hole 2B on Bikini island, 

Bikini Atoll. Their results, together with the geologic 

column for the drill hole (Emery, Tracey, and Ladd, 

1954) are given in table 21.

Perkins with Lill, Dobrin, and Snavely (Perkins and 

Lill, 1948; Dobrin, Perkins and Snavely, 1949; Dobrin, 

1950; Dobrin and Perkins, 1954; Perkins, 1954) and 

Raitt (1951, 1954, 1956, 1957) made a series of marine 

seismic refraction surveys at and near Bikini, Eniwetok, 

and Kwajalein Atolls, and Sylvania Guyot. Data 

from these surveys are presented in table 22. The 

marine measurements were made and interpreted by 

standard seismic refraction methods, with some modiTABLE 19.—Speeds of seismic-wave transmission: laboratory measurements 

[Measurements by Applied Physics Branch, U.S. Bureau of Mines]

Rock

Dolomite _______

Core

F-l-5-4.. ...........

F-l-6-2. ________

F-l-12-6.. ..„.„.„„

Depth 

(feet)

1,978-2,003 

2,662-2,687 

4,316-4,341

Measured

Speeds of transmission in core

Compressional waves

PC

Feet per 

sec.

16,400 

15,100 

17,500

Kilometers 

per sec.

5.00 

4.60 

5.33

Torsional waves 

PI

Feet per

sec.

11,000 

10,100 

12,300

Kilometers 

per sec.

3.35 

3.08 

3.75

Computed

Speeds of transmission of compressional 

wave in isotropic earth of same material 

as core

M

0.12 

.13 

.01

J 1-M

V (l+ji)(l-%)

1.03 

1.04 

1.00

Feet 

per

sec.

16,900 

15,700 

17,500

Kilometers 

per 

sec.

5.15 

4.78 

5.33

Method

Sonic. 

Sonic. 

Sonic.
980 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

fications in equipment and techniques to meet marine 

conditions. They are discussed in detail in papers by 

Raitt (1954, 1957) and by Dobrin and Perkins (1954), to 

which the reader is referred for additional details.

TABLE 20.—Speeds of seismic-wave transmission: ground-surface 

seismic refraction surveys

[Measurements by Joesting, Swartz, and Farnham]

Rock

Sand and gravel, unconsolidated to 

partly cemented. 

Limestone, weakly to well consolidated.

Reef rock ___ . _________ ..

Compressional speeds

Feet per 

second

1,000- 1,350 

4, 900- 5, 600 

3, 800- 6, 600

6, 700-10, 500 

7, 400-12, 000

11,400-11,800 

13, 000-14, 000

Kilometers 

per 

second

0. 31-0. 41 

1. 49-1. 71 

1. 16-2. 01

2. 04-3. 20 

2. 26-3. 66

3. 47-3. 60 

3. 96-4. 27

Remarks

Average approximately 8,500 

fps=2.59 kmps. 

Measured on reef.

TABLE 21.—Speeds of seismic-wave transmission: in-hole measurements, drill hole 2B, Bikini island, Bikini Atoll

[Measurements by Dobrin, Perkins, and Lill. Lithologic units from log of drill 

hole 2B (Emery, Tracey, and Ladd, 1954, p. 82-83 and fig. 35)]

Depth interval 

(feet)

150-200.... .....

200-300.........

300-400————

400-450—— __

450-500.—- _

500-550.—- __

550-600—— __

600-650—————

650-700————

700-750—— ———

750-800.—————

800-900——— —

900-1,100——..

1,100-1, 400.... _ 

1,400-1,600---- 

1,600-1,800-.--

Compressional 

speed

Feet per 

second

6,320 

7,590

10, 100

11, 670 

7,100 

9,090 

7,620 

14,240 

7,380 

10, 450 

10,000 

6,400 

8,430 

7,250

9,080 

10,200

Kilometers 

per 

second

1.93 

2.31

3.08

3.56 

2.16 

2.77 

2.32 

4.34 

2.25 

3.19 

3.05 

1.95 

2.57 

2.21

2.77 

3.11

Lithologic unit

Description

Chalky poorly consolidated detritus. 

Moderately consolidated recrystallized white limestone.

Porous friable, but recrystallized 

white to buff limestone.

Porous friable tan to light-brown 

limestone; crystalline calcitefllled cavities.

Light- to medium-brown unconsolidated unsorted sand; wellpreserved shells and corals.

Consolidated brown foraminiferal limestone. 

JTJnconsolidated brown sand .....

Depth 

interval 

(feet)

100-187 

187-290

290-425

425-550 

550-715

715-1,120

1,120-1,155 

1,155-2,556

TABLE 22.—Speeds of seismic-wave transmission: marine seismic refraction-surveys

Zone Layer

Compressional-wave speed

Kilometers per 

second

Feet per second

Estimated depth to top of layer

Kilometers Feet

Remarks

A. Bikini Atoll

[Measurements by Dobrin, Perkins, and Snavely]

1

2'

2

3

2. 1

2.7

3. 4

5. 2

7,000

9,000

11, 000

17, 000

0

0.6

0.8

2. 1-4. 0

(Mean 3. 0)

0

2,000

2,500

7, 000-13, 000

(Mean 10, 000)

Observed only near Enyu

island.

Assumed calcareous.

Probably igneous.

B. Bikini and Kwajalein Atolls and Sylvania Guyot

[Measurements by Raitt]

Crust__ _________

Mohorovidid discontinuity .

Mantle. __ _ __. ___ _

1

2

3

4

4'

5

6

2.45

3. 10

3. 84-4. 74

5. 54

6. 15

6. 53

8. 3±0. 21

8,000

10, 200

12, 600-15, 500

18, 200

20, 200

21, 400

27, 250

0

0.7

1. 3

3

3.6

7-9

13

0

2,300

4,300

9,800

12, 000

23, 000-30, 000

43, 000

Assumed calcareous.

Assumed volcanic.

Sylvania Guyot. Although

a significantly different

speed, Raitt believes probably same as layer 4.

Raitt identifies with intermediate layer universally

present in deep Pacific.

C. Eniwetok Atoll

[Measurements by Raitt]

Crust _ ___ _ _______

Mohorovicid discontinuity.

Mantle. ___ _ ______ __

0

1 

2 

3 

4 

5

6

1. 92

2. 44 

3.06 

4. 15 

5. 59 

6. 90

8.09

6,300

8,000 

10, 000 

13, 600 

18, 300 

22, 600

26, 500

0

0. 1 

0. 3-0. 7 

1. 5-2. 3-7 

9-10

16-17

0

300 

1, 000-2, 300 

4, 900-6, 600 

9, 800-23, 000 

30, 000-33, 000

52, 000-56, 000

NW of Elugelab.

Calcareous. 

Believed volcanic.
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 981

STRENGTH

By strength is meant the stress at the time of fracture—that is, the maximum stress or maximum load 

per unit area that the specimen can withstand without 

fracture. It is measured by placing a specimen in a 

testing machine and increasing the load until fracture 

occurs. The type of strength determined depends on 

the method of mounting the specimen and applying 

the load. Three major types are obtained: (1) compressive strength, (2) tensile strength, and (3) flexural 

strength. A fourth—triaxial compressive strength—is 

found by applying a fixed hydrostatic pressure to the 

specimen while subjecting it at the same time to an 

increasing uniaxial load.

Factors affecting the result are the shape and relative 

dimensions of the specimen, the rate of application of 

the load, the moisture content of the specimen, and 

the alinement and uniformity of load application. For 

this reason, standard shapes, sizes, and procedures are 

employed. In the present investigation all tests were 

made on cylindrical specimens. Details of procedures 

will be described under the individual strength types 

discussed.

Specimens were tested for compressive strength, triaxial compressive strength, and flexural strength. Because of technical difficulties involved, no measurements 

were made of tensile strengths.

COMPRESSIVE STRENGTH

For these tests the cores were cut to a standard 

length, specified as a fixed ratio of length to diameter. 

For the Bureau of Mines tests this ratio was 1.0; for 

the Bureau of Reclamation tests it was 2.0. If for any 

reason the ratio of length to diameter departed materially from these values, the results were corrected to 

standard dimensions. For the Bureau of Mines tests 

this was done by use of the equation

C=- C0

0.778 + 0.222^ LI

(76)

where G is the compressive strength for the standard 

specimen (D—L), C0 is the observed compressive 

strength, D is the diameter, and L the length of the 

core cylinder. Although the equation was developed 

by the A.S.T.M. for cubic specimens (ASTM, 1942J), 

experiments by the Bureau of Mines (Obert, Windes, 

Duvall, 1946, p. 21-22) showed that it holds also for 

cylindrical specimens, and is subject to an error of 

only a few percent for values of L/D from % to 1%.

For the Bureau of Reclamation tests the correction 

was obtained from a standard curve (U.S. Bur. Reclamation, 1949, p. 456) which agrees within 1 percent 

with equation (76) above.

Experiments by the Bureau of Mines (Obert, Windes, 

Duvall, 1946, p. 22) showed the compressive strength 

to be reduced by moisture. All specimens tested by 

the Bureau of Mines were, therefore, air dried before 

testing. On the other hand, the report accompanying 

the tests made by the Bureau of Reclamation stated 

that the specimens tested "appeared to be nearly 

saturated."

In preparing the cores for testing, the ends were 

accurately squared and ground to a smooth accurately 

flat surface. In the Bureau of Reclamation tests the 

ends of the cores in addition were capped with plaster 

of paris to provide an even bearing surface. The cores 

were then mounted in a testing machine, where they 

were accurately centered between spherical bearing 

segments to assure proper alinement, a slight initial 

pressure applied, and the core positioned with the 

plates accurately parallel with the ends of the specimen. 

Pressure was then applied at a standard rate until 

fracture occurred. In the Bureau of Mines tests a 

120,000-pound hydraulic testing machine was used, 

and pressure was increased at the rate of 100 psi per 

second. In the Bureau of Reclamation tests a 300,000- 

pound testing machine was employed and pressure 

was increased at the rate of 2,000 psi per minute.

If A is the area over which the load is applied, and 

Wf is the load at fracture, the compressive strength, G, 

is computed from the equation

(77)

The values of the compressive strengths measured for 

the Eniwetok drill cores are given in table 23.

TRIAXIAL COMPRESSIVE STRENGTH (SHEARING 

STRENGTH)

In triaxial compression tests the core specimen is 

placed under a lateral hydrostatic load of fixed amount, 

then subjected to an axial compressive load which is 

increased until fracture occurs. The triaxial compression test permits a determination of the shearing 

strength of the specimen, a quantity which it is not 

feasible to measure directly.

The axial and lateral stresses at failure are called 

the "principal stresses". If SA and SL are the axial 

and lateral principal stresses, a series of semicircles 

called "Mohr's semicircles" (Mohr, 1900, 1914; Balmer, 

1952) may be drawn for the different values of SL used. 

Each semicircle has a radius of (SA —SL)/2 and is 

described about a center on the axis of abscissas at a 

distance of x=(SA +SL)!2 from the origin. The envelope tangent to this series of semicircles is known as 

"Mohr's envelope". While actually curvilinear it 

may be approximated by a straight line whose equation 

can be determined by least squares. It may be shown
982 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

(Balmer, 1952) that in the resultant equation, 

y=c+x tan * (78)

y is the shearing stress at fracture parallel to the plane 

of fracture, x is the stress at fracture normal to the 

plane of fracture, c is the unit cohesive strength of the 

specimen, and tan <i> its coefficient of internal friction.

As both x and y are stresses, c must also be expressed 

in the same units—that is, as a force per unit area. 

If x and y are expressed in terms of pounds per square 

inch, c must be expressed in terms of pounds per 

square inch. Tan <i> is of course a numeric.

Triaxial compression tests on the cores were made 

by the Bureau of Reclamation only. In these tests the 

cores, prepared as described under "compressive 

strength", were covered with rubber jackets to exclude 

the hydraulic fluid used to exert the lateral pressure, 

and placed in a small pressure chamber mounted on 

the 300,000-pound testing machine. Hydraulic pressure was then built up through a flexible rubber hose 

by means of a hand pump and the hydraulic pressure 

applied measured by means of a Bourdon-tube pressure 

gauge. After the desired lateral pressure was thus 

established for the particular test being made, the 

axial load was increased by the testing machine ram 

at a uniform rate of 2,000 psi per minute until fracture 

occurred.

In figure 304, Mohr's semicircles and Mohr's envelope 

are shown for cores from drill hole MU-5. The best 

fitting tangent, determined by least squares and shown 

in the figure, has the equation

2/=180+0.6z (79)

where y, the shearing strength, is of course dependent 

on the normal stress, x. The unit cohesive strength 

is 180 psi. The coefficient of internal friction is 0.6. 

The results of the triaxial compression tests on the 

Eniwetok drill cores are given in table 23.

1500

1000

500

500 1000 1500 

NORMAL STRESS, IN POUNDS PER SQUARE INCH

2000

FIGUEE 304.—Mohr's circles and envelope for core MU-5 as determined by the U.S. 

Bureau of Reclamation.

ITLEXURAIj STRENGTH (MODULUS OP RUPTURE)

In testing for flexural strength the core is placed 

horizontally across two knife edges near the ends of 

the specimen. The load is then applied from the top 

by a third knife edge, midway between the supports, 

and the specimen bent until fracture occurs. In this 

test the specimens are subjected to compression above 

and tension below. As has previously been noted under 

elastic constants, such a flexure involves both torsional 

and compressional stresses.

The flexural strength is expressed as a modulus of 

rupture, R, whose value is given by the equation

—8TT/L (80)

where Wf is the load at fracture, L the length of the 

span between the supports, and D the diameter of the 

core. The error in the modulus, due primarily to the 

D3 factor, was estimated by the Bureau of Mines to be 

approximately 6 percent.

Flexural tests were made only by the Bureau of 

Mines. Previous tests by the Bureau (Obert, Windes 

and Duvall, 1946, p. 24) had shown that the modulus of 

rupture is independent of specimen diameter. Because 

of the small diameter of the cores, as well as their 

short length, the separation of the knife edges was 

made less than standard. The vertical load applied at 

the midpoint of the span was increased in the testing 

machine at the rate of 100 psi per minute until rupture 

occurred.

Values of the modulus of rupture so obtained are 

given in table 23.

TABLE 23.—Compressive, triaxial-compression, and flexural 

strengths of some Eniwetok drill cores

Rock Core Depth 

(feet)

Compressive 

strength 

(psi)

Triaxial compression stress at failure (psi)

Lateral Axial

Modulus 

of 

rupture 

(psi)

Elugelab island

[Measurements by Applied Physics Branch, U.S. Bureau of Mines]

Limestone —

Dolomite ....

Limestone ...

F-l-3-6..—

F-l-4-1-- —

F-1-5-4-. ...

F-l-6-2..... 

F-1-12-6-... 

F-14-18-.—

1, 232-1, 248 

1, 718-1, 740 

1, 978-2, 003 

2, 662-2, 687 

4,316-1,341 

4, 500-4, 525

9,400 

2,600 

19,600 

14, 100 

17,700 

5,200

850 

4,100 

2,450 

3,200

Parry Island

[Measurements by Applied Physics Branch, U.S. Bureau of Mines]

LimestoneBasalt ___

E l 1 1Q

E 1-4-fl _ ..

2,003-2,028 

4,078^,100 

4, 208-4, 211

240 

13, 700 

28,200
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 983

TABLE 23. — Compressive, triaxiaLcompression, and flexural 

strengths of some Eniwetok drill cores — Continued

Rock Core Depth 

(feet)

Compressive 

strength 

(P.s.i.)

Triaxial compression stress at failure (p.s.i.)

Lateral Axial

Modulus 

of 

rupture 

(p.s.i.)

Engebi island

[Measurements by the Concrete Laboratory, U.S. Bureau of Reclamation]

Limestone ... EN-8———— 

EN-9 A..... 

EN-9 B—— 

EN-9 C—— 

EN-10———

EN-11 A.— 

EN-11 B..__ 

EN-11 C,...

90.5-91.0 

95. 0-96. 0 

95. 0-96. 0 

95. 0-96. 0 

81. 0-82. 0 

8.0-9.0 

8. 0-9. 0 

8. 0-9. 0

2,750 

2,550 

2,140 

1 3, 630 

3,690 

4,530 

6,830 

5,730

Mujinkarikkn island

[Measurements by the Concrete Laboratory, U.S. Bureau of Reclamation]

Limestone ...

TWTT 7 A

MU-7 B_ — MU-5 2

MU-5...... 

MU-5.......

MU-5— ....

MU-5———.

MU-5— ....

MU-5—.... 

MU-5———

81. 5-82. 0 

81. 5-82. 0 

38.1 

38.6 

41.5 

54.9 

57.5 

69.5 

59.0 

70.5

3,920 

14,140

960

i Sample was oven dried. 

* Equation for Mohr's envelope for MU-5 cores, a 

Reclamation, is #=180+0.6 x, where y= shearing s 

pounds per square inch. For the principal stresse 

is the axial stress and SL the lateral stress in pounds

THERMAL DA'1 

TEMPERATURE PRO

Temperature profiles have been ] 

holes on Eniwetok Atoll (drill 

Island and drill hole F-l on Elugel 

drill hole on Bikini Atoll (drill hole 

The drill-hole temperatures wer 

author using thermistors as the

100 

300 

200 

500 

400 

100 

0 

0

is determir. 

tress, and 

s, SA-610

per squar 

^A

FILES

measur 

hole E 

a,b islan 

2Bon 

e meas 

tempe

600 

2,010 

1,410 

1,780 

1,440 

610 

770 

960

led by the Bureau of 

x= normal stress, in 

4-2.9 SL, where SA 

s inch.

ed in two drill 

i-l on Parry 

d), and in one 

Bikini island), 

sured by the 

rature-sensing

TABLE 24. — Temperature profiles in Eniwetok and Bikini drill 

holes, and in the Pacific Ocean, Marshall Islands area

Depth 

(feet)

Temperature <°0)

Depth 

(feet)

Temperature (°C)

Depth 

(feet)

Temperature 

CO)

Depth 

(feet)

Temperature 

CO)

A. Drill hole E-l, Parry Island, Eniwetok Atoll

[Field measurements (September 10, 1958) by D. L. Reid, Holmes and Narver Co. 

See also Swartz (1958), tables 4 and 5]

3.8..——

27.8———

52.8..—

77.8-—

102.8 __ 

127.8——

152.8—— 

177.8 ....

202.8——

227.8. ...

252.8. ... 

277.8——

28.10 

27.78 

27.54 

27.10 

26.75 

26.32 

25.87 

25.47 

25.11 

24.80 

24.45 

24.16

302.8—— 

327.8 _ . 

352.8——

377.8—— 

402.8 .... 

450.3 _ . 

500.3—— 

600.3 .... 

700.3.... 

800.3 .... 

900.3. ... 

1,000.3—

23.81 

23.57

22.75 

22.40 

21.52 

20.34 

19.26 

18.23 

16.92 

14. 80(?) 

1162

1,100.3... 

1,200.3... 

1,300.3—

1,400.3— 

1,500.3... 

1,600.3... 

1,700.3— 

1,800.3— 

1,900.3— 

2,000.3... 

2,080—— 

2,280——

13.63 

12.81 

11.51 

9.95 

9.92 

9.34 

8.25(?) 

8.99 

8.68 

8.47 

8.27 

7.90

2,380—— 

2,580. ... 

2,680—— 

2,780—— 

2,980—— 

3,180—— 

3,380—— 

3,580.... 

3,780 .... 

3,980——

7.69 

7.35 

7.17 

6.89 

6.41 

6.09 

6.38 

7.12 

8.25 

9.36

B. Drill hole F-l, Elugelab island, Eniwetok Atoll

[Measurements (October 1952) by J. H. Swartz, See also Swartz (1958), table 3]

24.1 __ . 

58.1——

73.1 

98.1— -

123.1... . 

148.1 .... 

173.1—. 

198.1—— 

223.1 _ . 

248.1—— 

273.1—— 

298.1—— 

323.1. ...

29.1 

28.9 

28.5 

28.1 

27.9 

27.7 

27.6 

27.3 

27.3 

27.0 

26.4 

26.0 

25.7

348.1—— 

373.1.... 

398.1 ....

423.1 ....

449.8 .... 

500.5 __

KAQ Q

600.5 .... 

649.8—— 

700.5—— 

749.8.— Qf)A K

849.8 ....

25.3 

24.8 

24.2 

23.6

23.5 

22.0 

20.3

19.0 

17.2 

14.8 

14.0 

13.2

12.8

900.5. ... 

949.8—— 

1.049.8— 

1,100.5—

1,149.8— 

1,249.8— 

1,300——

1,400—— 

1,449.8— 

1,500—— 

1,600—— 1 RAQ Q

1,700 _ .

11.9 

11.5 

10.6 

10.4

10.2 

10.0

9 7

9.6 

9.7 

9.7 

10.0 

10.0

10.1

1,800.... 

1,849.8— 

1,900—— 

2,000——

2,049.8... 

2,100—— 

2,249.8...

2,300.,.. 

2,500—— 

2,700 .... 

2,900—— 

3,100....

3,300——

9.8 

10.4 

9.8 

9.7 

9.6 

9.3 

8.9 

8.6 

8.7 

8.7 

8.9 

8.8 

9.8(?)

C. Drill hole 2B. Bikini island, Bikini Atoll

[Measurements (November 29, 1952) by J. H. Swartz. See also Swartz (1958), table 6]

4— ——

28-——

53— ....

78

103—— 

128 ......

153——

28.7 

28.0 

27.6

27.4

27.2 

27.0 

26.8

178— —

203 __ .

228———

253 ......

278 _ — 

303——— 

328———

26.4 

26.4 

26.2 

25.9

25.9 

25.7 

25.6

353———

378———

403—— . 

500———

600——— 

700 ___

800———

25.5 

25.3 

25.2 

24.6 

23.1 

22.1 

20.5

1,000—— 

1,200 ....

1,400 .... 

1,430 ....

18.0 

17.0 

15.8 

15.7

D. The Pacific Ocean, Marshall Islands area

[Measurements (November 1952) by Scripps Institution of Oceanography, Capricorn 

Expedition. Courtesy of Dr. Walter Munk. See also Swartz (1958), table 7]

0-200— - 

300——. 

400 ......

27.8 

26.7 

23.3

500——. 

600—— 

700———

18.3 

15.6 

11.7

800——— 

1,000—— 

1,500 _ .

10.6 

10.0 

8.6

2,000 _ . 

3,000—— 

4,000——

7.5 

5.8 

4.4

elements (Swartz, 1954, 1958). To avoid introducing 

uncertainties the readings have not been corrected for 

thermistor drift with time. The construction and 

circuitry of the termistor measuring cables, the methods 

of their use, and their precision and accuracy are discussed in detail by Swartz (1958).

The temperature profile in the ocean in the Marshall 

Islands area was measured by the Scripps Institution 

of Oceanography during the Capricorn Expedition in 

1952 (see fig. 291) using bathythermographs for depths 

down to 900 feet and sensitive reversing-thermometers 

for greater depths. The ocean temperatures were 

furnished through the kindness of Dr. Walter Munk.

Table 24 gives the temperature data for the Eniwetok 

and Bikini drill holes and for the ocean in the Marshall 

Islands area.

THERMAL CONDUCTIVITY

Thermal conductivity is the rate of flow of heat 

through a unit cross-section under a unit temperature 

gradient. The unit of heat conductivity will depend 

on the system of units employed. In the fph system 

it is one British thermal unit (Btu) per hour per square 

foot per degree Fahrenheit per foot. In the cgs system 

the unit is one calorie per second per square centimeter 

per degree centigrade per centimeter which may be 

abbreviated to cal per sec cm °C. In the present 

discussion all values will be given in cgs units.

Thermal conductivities of Eniwetok Atoll drill cores 

were measured both in the U.S. Geological Survey, and 

by Prof. Francis Birch in the Dunbar Laboratory at 

Harvard University.
984 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

In the U.S. Geological Survey measurements were 

made by a modification of the Birch divided-bar method 

(Birch, 1950) using the equipment shown in figure 305.

A disc 1% inches in diameter and % inch thick is cut 

from the core whose conductivity is to be determined, 

and the ends accurately squared, ground, and finishAluminum shield 

reflectors

Outer shield

EXPLANATION

Cu = Copper disk 

Th = Thermistor and leads 

D = Ceramic diffuser 

Std = Thermal conductivity standard 

Sp^Specimen being measured

FIGURE 305.—Modified form of Birch thermal-conductivity apparatus used in thermal conductivity determinations by the U.S. Geological Survey.
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 985

lapped to a smooth flat. The disc, mounted in a stack 

of discs of the same size, is placed between two copper 

discs whose temperatures are measured by small beadtype thermistors. On either side of the two copper 

discs are two standard discs of known conductivity. A 

heat source at one end of the stack and a thermostatted 

heat sink at the other end provide a well-regulated heat 

flow through the entire stack. A thin film of silicone 

grease between the discs assures a low thermal contact 

resistance and a cylindrical shield around the stack reduces radial heat flow to a negligible value. The axial 

flow is given by the discs of known thermal conductivity. 

The temperature drop across the disc being tested is 

measured very precisely by the thermistors. From 

these data the thermal conductivity of the test disc is 

quickly computed from the equation

(81)

where k is the thermal conductivity, q is the rate of 

axial heat flow in calories per second, A is the crosssectional area of the disc in square centimeters, L is the 

length of the flow path—that is, the thickness of the 

disc in centimeters—and AT is the temperature difference between the top and bottom of the disc in degrees centigrade as measured by the thermistors in the 

adjacent copper discs, which are assumed to be effectively isothermal. Or more simply, if kx is the unknown thermal conductivity, and ks the known thermal 

conductivity of the standard disc, AT* the temperature 

drop across the unknown disc, and ATS that across the 

known disc,

I. •—. —AT ___* I. f QO\ \°*}

A hydraulic ram permits the application of pressure on 

the stack to insure good thermal contact throughout 

the stack. The measurements were made under a 

pressure of 1,400 psi.

All cores were first measured in their air-dried state. 

Because moisture affects the thermal conductivity, 

some of the cores were later saturated with water and 

remeasured in the saturated state. In the U.S. Geological Survey they were saturated with tap water. 

In the measurements at the Dunbar Laboratory, Prof. 

Birch used a saturated salt solution. Neither condition, 

of course, represents the effect of the saline ocean waters 

actually present in the atoll, but they do give some idea 

of the effect of waters in the core pores.

The resultant thermal-conductivity values are presented in table 25. For comparison, thermal conductivities determined by D. W. Butler in the National 

Physical Laboratory, in England, for a series of seabottom cores collected by the Mid-Pacific Expedition 

of the Scripps Institution of Oceanography and furnished the writer through the kindness of Dr. Roger 

Revelle and Dr. Arthur E. Maxwell, of the Scripps 

Institution, are given in table 26.

Heat conductivity data in cgs units may be converted 

into fph units and vice versa by means of the following 

relationships:

1 cal per sec cm °C=241.9 Btu per hr ft °F 

1 Btu per hr ft °F=0.00413 cal per sec cm °C

TABLE 25.—Thermal conductivities of drill cores from Eniwetok 

Atoll, Marshall Islands

Core Depth 

(feet)

Porosity 

(percent)

Bulk density 

(g per cm3)

AirdriedSaturated

Mean 

temperature (°0)

Thermal 

conductivity 

(10-3 cai per 

sec cm °C)

AirdriedSaturated

A. BASALT DRILL CORES PROM DRILL HOLE E-l, PARRY ISLAND

[Measured under pressure of 1,400 psi by S. A. H. Qoldstein, U.S. Geological Survey. 

Cores saturated with tap water in "saturated" measurements]

E-l-4-3 _ . .-.

E-l-5-1— — __

E-l-5-2— -.—

E-l-5-5 .

E-l-5-6... ......

E-l-6-2.. .......

4, 208-4, 211

4,211-4,216

4,211-4,216

4, 211-4, 216

4, 211-4, 216

4, 216-4, 222

0.06

.00 

.04

2.94

1.50 

2.50

2.96

2.97 

2.99

2.61

2.68 

2.62

2.96

2.97 

2.99

2.64

2.69 

2.65

28.9

29.0 

29.2

28.5

28.7

29.0

29.3

29.5

28.4

29.9

28.1

29.3

29.6 

29.8

4.99

5.06 

5.30

4.59

4.18

4.31

4.57

4.73

4.54

4.00

3.87

3.57

3.63 

3.56

5.10

5.05 

5.28

3.83

3.81 

3.87

B. LIMESTONE DRILL CORES

[Measured by Prof. Francis Birch, Dunbar Laboratory, at Harvard University. 

Cores saturated with a saturated salt solution in "saturated" measurements]

Parry Island

E-1-2-L... ..... .

E-l-2-8— ...... 

E-l-3-1— ... —

E-l-3-20--.-.—

E-l-3-24. .......

E-1-3-26-......

E-l-3-27. .......

2, 802-2, 808 

2, 802-2, 808 

4, 078-4, 100 

4,078-4,100

4, 078-4, 100 

4,078-4,100

4,078-4,100 

4,078-4,100

..........

2.47

2.41

2.47

2.43 

2.48

2.37

- — —

0) 3.5 

4.1 

5.7 

5.3 

5.8

5.4 

6.1 

5.2

~"~~6~6 

6.1

5.8 

6.5 

5.8

Elugelab island

F-l-11-3— .... . 4, 197-4, 222 2.7

1 Boom temperature.
986 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

TABLE 26.—Thermal conductivity of sea-floor sediments collected by the 1950 Mid-Pacific Expedition of the Scripps Institution of

Oceanography

Moisture content and wet density: Values enclosed in parentheses are less certain

Thermal conductivity at 25°0: For all values given, the second decimal is a nonsignificant figure

[Measurements by D. W. Butler, National Physical Laboratory, in England. Data courtesy of Eevelle and Maxwell]

Station

1... _____ . __ ....

21-1—.—.................

32.. ........................

35-2—— ————.._—

35-2.......................

36-........— .............

36———— ..................

38—— .-..—.. .............

38....———— ...............

Location

Latitude

32°25' N— ....................

20°48' N—— ..... ...............

18°18' N.. _————————.__—_

19°28' N...... ...................

19°28' N. .......... ..............

16°45'N__ — ....................

16°45' N. .....................

19°02' N.__..._————— ——— —

19°02' N_.____.——— ——— ———

Longitude

122°30/ W. ......................

159°42' W.......................

170090; TIT

174°35' W... ............. — ....

174°35' W. ......................

176°24' W. ......................

176°24' W. ......................

177°19' W. ........... ........ ...

177°19' W. ......................

Depth to 

sea floor 

(meters)

4,000

4,500

3,900

4,900

4,900 

5,040 

5,040 

4,750

4,750

Depth 

below 

sea 

floor 

(inches)

38^-42Ji

24-28

24-27

76-79J^ 

53-57 

79-84J^ 

27J*_-31^

75J^-79^

Moisture 

content 

(percent 

of wet 

weight)

52 

54 

56.5

50.0 

50.0

42.5 

43.5 

58 

52.5 

52 

(71.5) 

(67. 5)

(61) 

(62. 5)

Wet 

density 

(g per ml)

1.43 

1.39 

1.38

1.47 

1.47

1.58 

1.57 

1.35 

1.41 

1.40 

(1.18) 

(1.22)

(1.27) 

(1.27)

Thermal conductivity 

(10-3 Cal per sec cm °G at—)

25°G

1.93 

1.93 

1.93

2.17 

2.20

2.37 

2.43 

1.82 

1.91 

1.96 

1.68

1.73

4°C

1.9

1.8

2.1

2.0

1.8

1.6

THERMAL FLUX (HEAT FLOW)

Birch (1956) has made an estimate of the upward 

heat flow through Eniwetok Atoll utilizing his measurements of the thermal conductivity of a number of 

Eniwetok cores and the writer's determinations of the 

temperature profiles (Swartz, 1958) in drill hole E-l, 

Parry Island, Eniwetok Atoll. Using a value of 4 to 

6X10"3 cal per sec cm °C for the thermal conductivity 

and 20.5° C per km for the temperature gradient below 

3,380 feet, Birch obtains a heat flux of 0.8 to 1.2X10~6 

cal per cm2 sec. A correction (Birch, 1950, p. 584) for 

the atoll topography increases the temperature at 

3,980 feet by 0.5 to 1.0° C. This increases the gradient

and raises the estimated heat flow to between 0.9 and 

1.4X10"6 cal per cm2 sec as shown in table 27-4.

Revelle and Maxwell (1952) have made measurements 

of the thermal gradient at several points in the North 

Pacific Ocean by driving a probe into the ocean floor 

and measuring the gradient by means of a special 

thermistor bridge built into the probe. At the same 

time samples of the bottom sediments were collected 

and their thermal conductivities later determined by 

D. W. Butler, of the National Physical Laboratory in 

England. The resultant values of heat flow through the 

ocean floor are listed for comparison in table 27B.

TABLE 27.—Heat flow (thermal flux)

Station Latitude 

(north)

Longitude 

(east or west)

Depth below 

surface (ft or m)

Thermal 

gradient 

(°G per m)

Thermal 

conductivity 

(10~3 cal per sec 

cm°G)

Temperature <°C)

Heat flow 

(10~6 cal per cms 

sec)

A. In Eniwetok Atoll

[Birch, 1956]

Drill hole E-l. _______________

11°24' East 162°22' Feet 

3,380-3,980 0.021 4-6 Room 0. 9-1. 4

B. Through the ocean floor in the North Pacific area

[Eevelle and Maxwell, personal communication]

1 _ -__-__.___________.__._.

MP-21___. ___________ _ _.__

MP-32.____. ________________

MP-35-2____________________

MP-36_____________ __ _____

MP-38______________________

32°35'

20°48'

18°18'

19°28'

16°45'

19°02'

West 122°30'

159°42'

173°23'

174°35'

176°24'

177°19'

Meters 

4,000

4,500

3,900

4,900

5,040

4,750

0 067

065

1 035

062

066

069

1.9

1.8

2. 1

2.0

1.8

1.6

4

4

4

4

4

4

1.27

1. 17 i.74

1.24

1. 19

1. 11

Probe apparently did not penetrate completely into sea bottom and both gradient and heat flow are probably too low.
SOME PHYSICAL CONSTANTS FOR THE MARSHALL ISLANDS AREA 987

THERMAL GRADIENTS

Thermal gradients in continental drill holes are 

customarily given in terms of the slope of the best 

straight line that can be fitted to the data by least 

squares. The data for the atoll drill holes and for the 

ocean have several segments of very different slopes. 

For this reason a single straight line would be meaningless. All four curves show a decrease in temperature 

from the surface down to depths of some thousands of 

feet, thus contrasting sharply with continental curves 

which, below a shallow surface zone, show a steady increase of temperature with depth. Four gradient zones 

can be recognized, but not all appear in a single profile. 

In the ocean profile a near-surface zone whose thickness 

varies with the time of year has the same temperature 

throughout and is known as the isothermal zone. Beneath it is a zone of rapid temperature decrease, known 

as the thermocline. Below this lies a zone of continued 

but less rapid decrease in temperature, sometimes 

called the zone of weak gradient, for which the writer 

(Swartz, 1958, p. 728) has suggested the name asthenocline. In profiles from the atoll drill holes the isothermal zone is not recognized. The upper zone represents the thermocline. This in turn is underlain by the 

asthenocline. Below the asthenocline in drill hole E-l, 

at a depth of approximately 3,380 feet, the downward 

trend is reversed and the temperature rises with further 

increase in depth as in the continental drill holes. For 

this section the writer suggests the name "epeirocline" 

from the Greek epeiros, mainland, and klinien, to 

incline. Neither drill hole F-l on Elugelab or 2 B on 

Bikini reached the depth of gradient reversal.

Table 28 lists the gradients of the best straight lines 

fitted to each of the segments. Table 2' 

gradients as actually measured for each interval.

The positive axis is selected vertically downward so 

that an increase of temperature with depth, as in continental drill holes, will give a positive gradient.

TABLK 28.—Thermal gradients in Eniwetok and Bikini Atolls, and 

for the Pacific Ocean in the Marshall Islands arealinear segments fitted to the data by least squares

[See also Swartz (1958), table 14]

Drill hole

E-l-_-___-_.

F-l

2B..____.__.

Ocean ______

Zone

Thermocline _ ___ _

Asthenocline- _________

Epeirocline __ _____ __

Thermocline _ ______

Asthenocline____ _ _ _

Asthenocline (?)____ _

Isothermal ___ __ _ __

Thermocline___ __ _ _

Asthenocline- _______ _

Depth interval 

(feet)

4-1, 400

1, 500-3, 180

3, 580-3, 980

24-1, 050

1, 100-3, 100

4-1, 000

1, 000-1, 430

0-200

300-700

800-4, 000

Thermal 

(°Cperm)

-0. 047

-.007

+ . 021

-.068

-.003

-.030

-. 018

.000

-. 124

-.006

negative gradient will then be one in which the temperature decreases with increasing depth.

The positive gradient near the bottom of drill hole 

E-l is only about half that found for drill holes along 

the California shore. This suggests that the atoll 

gradient may be too low and probably is still affected, 

even at the maximum depth reached, by the cooling 

effect of the adjacent ocean waters.

TABLE 29.—Thermal gradients in Eniwetok and Bikini Atolls and 

for the Pacific Ocean in the Marshall Islands area—actual 

gradient for each measured interval

t zones 

profile, 

ickness 

erature 

e. Beknown 

itinued 

aetimes 

j writer 

sthenohe iso3 repreby the 

leE-1, 

vnward 

further 

s. For 

"ocline" 

ien, to 

2 B on

it lines 

sts the 

il. 

\rard so 

a contiait. A

tolls, and 

iients for

Thermal 

(°Cperm)

-0. 047 

-.007 

+ . 021

-.068

-.003

-.030 

-. 018

.000 

-. 124 

-.006

Depth interval 

(ft)

Gradient 

(°C per 

m)

Depth interval 

(ft)

Gradient 

(°C per 

m)

Depth interval 

(ft)

Gradient 

(°C per 

m)

A. Drill hole E-l, Parry Island, Eniwetok Atoll

[September 10, 1958. See also Swartz (1958), table 15]

3.8-27.8--———

27.8-52.8.-.. __

52.8-77.8. ...... .

77.8-102.8.......

102.8-127.8.-...

127.8-152.8 _ ...

152.8-177.8. ——

177.8-202.8.——. 

202.8-227.8. ——— 

227.8-252.8-——_

252. 8-277.8.——

277.8-302.8. .....

302.8-327.8 _ ... 

327.8-377.8 _ ...

377.8-402.8 __ .-

-0.044 

-.031 

-.058 

-.046 

-.056

-.059 

-.052 

-.047 

-.041 

-.046 

-.038 

-.046 

-.031 

-.054 

-.046

402.8Ht50.3-. 

450.3-500.3——— 

500.3-600.3———

600.3-700.3———

700.3-800.3——.

800.3-900.3———

900.3-1,000.3—. 

1,000.3-1,100.3.- 

1,100.3-1,200.3-. 

1,200.3-1,300.3.. 

1,300.3-1,400.3.. 

1,400.3-1,500.3.. 

1,500.3-1,600.3.. 

1,600.3-1,700.3.. 

1,700.3-1,800.3..

-0.060 

-.077 

-.035 

-.034 

-.043 

-.070 

-.006 

-.032 

-.027 

-.043 

-.051 

-.001 

-.019 

-.036 

-.002

1,800.3-1,900.3. 

1,900.3-2,000.3. 

2,000.3-2,080... 

2,080-2,280—— 

2,280-2,380- ___ 

2,380-2,580. _ . 

2,580-2,680—— 

2,680-2,780—— 

2,780-2,980——. 

2,980-3,180—— 

3,180-3,380—— 

3,380-3,580—— 

3,580-3,780—— 

3,780-3,980——

-0. 010 

-.007 

-.008 

-.006 

-.007 

-.006 

-.006 

-.009 

-.008 

-.005 

+.005 

+.012 

+.019 

+.018

B. Drill hole F-l, Elugelab island, Eniwetok Atoll

[October 29, 1952. See also Swartz (1958), table 15]

24.1-48.1-—— _

48.1-73.1 _ ——

73.1-99.3 ___ ..

99.3-123.1 ___ ..

123.1-148.1 ___ .

148.1-173.1.——.

173.1-199.3 __ ..

199.3-223.1 __ ...

223.1-248.1 __ ..

248.1-273.1 __ ...

273.1-299.3.——.

-0.030

046

-.045

-.039 

-.025 

-.012

-.018 

-.023 

-.041 

-.075 

-.031

299.3-323.1———

323.1-348.1———

348.1-373.1———

373.1-399.3———

399.3-423.1. __ .

423.1-450.3— _

450.3-500.5— _

500.5-550.3 ______ 

550.3-600.5——— 

600.5-650.3——— 

650.3-700.5———

-0.070 

-.047 

-.062 

-.046 

-.120 

-.012 

-.096 

-.113 

-.086

-.118 

-.155

700.5-750.3—— 

750.3-800.5——

800.5-850.3—— 

850.3-900.5—— 

900.5-950.3—— 

950.3-1,050.3— 

1,050.3-1,100.5. 

1,100.5-1,150.3. 

1,150.3-1,250.3. 

1,250.3-1,300.3. 

1,300.3-1,400.0.

-0.053 

-.056 

-.024 

-.059 

-.024 

-.032 

-.010 

-.013 

-.008 

-.011 

-.006

C. Drill hole 2B, Bikini island, Bikini Atoll

[November 29, 1952. See also Swartz (1958), table 15]

4-28—— _ . _ .

28-53... __ ....

53-78—————__

78-103.—— _____

103-128- __ ____

128-153—————

153-178—.——

178-203.—————

-0.090 

-.052 

-.025 

-.032 

-.032 

-.020 

-.050

-.000

203-228 _________

228-253.. _______

253-278—————

278-303—————

303-328 _____ -

328-353. _ .....

353-378 __ _ _

378Ht03_— ___ ..

-0.026 

-.041 

-.004 

-.021 

-.014 

-.012

-.024 

-.014

403-500———

500-600———

600-700. _ ____

700-800. _ ——

800-1,000... _

1,000-1,200——

1,200-1,400—— 

1,400-1,430——

-0.023 

-.049 

-.031

-.053 

-.041 

-.017 

-.019 

-.019

D. The Pacific Ocean in the Marshall Islands area

[November 1952. See also Swartz (1958), table 15]

0-200——————

200-300- __ ——

300-400— __ ..

400-500- ____

0.000 

-.036 

-.112 

-.164

500-600————

600-700—————

700-800—————

800-1,000————

-0. 089 

-.128

-.036

-.010

1,000-1,500—— 

1,500-2,000—— 

2,000-3,000 _._._

3,000-4,000——

-0.009 

-.007 

-.006 

-.005

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T>nK A ft
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O