Slump Blocks in the 

Atlantic Highlands 

of New Jersey

GEOLOGICAL SURVEY PROFESSIONAL PAPER 898

Slump Blocks in the 

Atlantic Highlands 

of New Jersey

By JAMES P. MINARD

GEOLOGICAL SURVEY PROFESSIONAL PAPER 898

A description of slump blocks and slumping 

in the hills of the northeastern 

New Jersey Coastal Plain, and a 

discussion of their potential 

as geologic hazards

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1974
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress catalog-card No. 74-600183

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

Washington, D.C. 20402 Price 95 cents (paper cover)

Stock Number 2401-02585
CONTENTS

Abstract _______________________________

Introduction ____________________________

Acknowledgments _______________________

Physical setting ______________________

Characteristics of the formations ____

Mount Laurel Sand __________________

Navesink Formation ________________

Red Bank Sand _____________________

Tinton Sand ________________________

Hornerstown Sand __________________

Vincemtown Formation ______________

Cohansey Sand _____________________

Younger sediments _________

Indurated layers ________________ 

Structure __________________

Historical notes _____________

Summary of characteristics of slump blocks

Page

1

1

4

4

4

5

5

5

5

6

6

6

6

6

6

7

10

Page

Descriptions of individual slump blocks 11

Block A ____________________ _ 11

Block B _______________ - 12

Block C ________________________ 12

Block D ____________ - - 12

Block E ______________________ 12

Block F _____________________ 12

Blocks G and H ______________ _ 12

Block I ________________________ 12

Other possible slumps or zones of weakness __ 12

Lineaments ___________ 13

Recent erosion _ _ __ 13

Current slumping _ _______ ___ _ 14

Causes _ _ _ 16

Additional considerations _____ _ _ 18

Summary ___________ _ __ 22

Conclusions and recommendations __ _ ____ 23

Glossary ____________________________ 23

References cited _ _ _ __ 24

ILLUSTRATIONS

FIGURE 1. Index map showing area of report ____________________________

2. Map of the Atlantic Highlands area showing location of slump blocks and lineaments

3. Stratigraphic column showing formations of Late Cretaceous and early Tertiary age _

4. Map showing changes in shoreline of Sandy Hook spit, 1685-1961 ____________ 

5. Section showing slump block B as a terrace _________________-_____.

6. Diagrammatic cross sections showing history of slump block A _________________

7. Cross section of slump block A ________________________________-

8. Block diagram showing parts of a landslide _________________________

9. Block diagram showing tilted beds in slump blocks __________ ______ 

10-22. Photographs:

10. Vertical drainage hole in pit floor, slump block A __________ _ __.

11. Stereoscopic pair of vertical aerial photographs of slump blocks A and B __.

12. Oblique aerial photograph of bluff, 1966 ______________________-

13. Oblique aerial photograph of bluff, 1974 ______________________.

14. House showing slump damage, block B _______________________.

15. House showing slump damage, block B __________________ ____ .

16. Breakage in concrete steps, block B_____________________________

17. Slump scarp 4-5 m high, block B 3 _________________________-

18. House minus rear porch, block B 3 ________________________-__

19. Cracks in pavement and wall, block B 1 ________________________

20. Fissure between blocks B 3 and B 4 _.________________________-

21. Small scarp between blocks B 3 and B 4 ______________________.

22. Tilted surface and trees on block B 4 ___________________--__-

Page

1

2

4

7

8

10

11

11

12

13

14

15

16

17

17

17

18

19

19

20

20

21

TABLE

TABLE 1. Average grain size of the material constituting each formation

Page

5

ill

SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

By JAMES P. MINARD

ABSTRACT

Many slump blocks are present in the bluffs of the Atlantic 

Highlands along the south side of Sandy Hook Bay and the 

north side of Navesink River, N.J. At present, slumping is 

taking place in parts of the bluffs that are as much as 60 m 

(200 ft) high. The formations in the bluffs are largely unconsolidated nearly fiat-lying silty and clayey marine sands 

of Late Cretaceous and early Tertiary age. Blocks range in 

size from about 30 m (100 ft) to 180 m (590 ft) in width, 

by about 150 m (490 ft) to 900 m (2,950 ft)in length; vertical displacement is as much as 26 m (85 ft). The larger 

blocks may contain as much as several million tons of 

material.

Most former slumps probably occurred when tidal currents 

and open ocean waves eroded the bluffs, possibly centuries 

ago to as recently as about 100 years ago. Since 1972, slumping has been reactivated in former slump blocks and initiated in steep slopes adjacent to older blocks. In addition to 

undercutting the toe of the slope, other factors such as an 

unusually high water table and, conceivably, earthquake 

tremors, may have contributed to the slumping. The entire 

bluff along Sandy Hook Bay appears to have a history of 

slumping and should thus be considered an area of possible 

geologic hazards. Slumping is currently causing considerable 

damage to houses and properties. Careful investigations 

should be made and precautions exercised before any construction is done at the base, on the slope, or on top of the 

bluff.

INTRODUCTION

The statutory charter of the United States Geological Survey is to make examinations of and report 

upon "the geological structure, mineral resources 

and products of the national domain." USGS neither 

approves nor disapproves land-use plans for privately owned land or the siting and design of any 

structure on privately owned land. Accordingly, no 

attempt has been made in this report to evaluate 

land-use or construction siting and design and nothing herein should be construed as a conclusion or 

recommendation concerning these subjects.

Several years ago, slump blocks were mapped and 

described in the bluffs along the southern shore of 

Sandy Hook Bay and along Navesink River (Minard, 

1969). The slump blocks were observed and identified during routine geologic mapping of the Sandy 

Hook quadrangle (fig. 1).

Although many slump features were recognized, 

only three slump blocks were shown. Two of these

74°

41

SANDY HOOK 

QUADRANGLE

39°

O 10 20 30 40 50 MILES

I i I I i___i

0 10 20 30 4O 50 KILOMETRES

FIGURE 1. Index map of New Jersey showing location of Sandy Hook quadrangle (stippled) and the 

area referred to in this report as the Atlantic 

Highlands (solid black area in the south-central 

part of quadrangle).

are the largest and most distinct blocks and clearly 

show the characteristic features of such slump 

blocks concave upper scarp, bulged convex lower 

profile, and a rotation normal to the scarp face 

(Minard, 1969, p. 36-41).

From about the summer of 1972 to the present 

(summer 1974), slumping has recurred in former 

slump blocks and has begun in steep slopes adjacent 

to older blocks. In this report, all slump blocks identified as definite, probable, and possible are outlined 

on a large-scale map (fig. 2) ; the physical settings
SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

74 C 02'3D"

EXPLANATION

Line along which slumping has 

occurred

Line along which slumping probably 

has occurred

_T ? 7- -?- -? ? ?- -? 7-- 

Line along which slumping possibly 

has occurred

Lineament 

Joint or possible zone of weakness

Upthrown side of slump block

Downthrown side of slump block

Al, A2, Bl, B2, etc. 

Designate slump blocks described 

in text

V2 MILE

I I 1 I I

5 KILOMETRE

CONTOUR INTERVAL 20 FEET

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. ,.,

'

Base from U.S. Geological Survey, Sandy Hook Quadrangle, 1943-54

FIGURE 2. Map of the Atlantic Highlands
INTRODUCTION

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Geology mapped in 1963-74

showing location of slump blocks and lineaments.
SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

of the blocks and the characteristics of the material 

in them are described, and their past, present, and 

potential instability is discussed. A glossary (p. 23) 

gives the meanings of certain words in this report.

ACKNOWLEDGMENTS

Appreciation is extended to the many people who 

helped in gathering the material for this report. 

Property owners generously gave permission to 

enter and cross their properties and volunteered 

pertinent information. Included were Mr. and Mrs. 

Robert T. Abrams, Mr. and Mrs. John R. Sundin, 

Mr. and Mrs. Martin Finan, Mr. Martin Jensen, Mr. 

Edward Weiler, and Mr. Clifford Brooks to name 

a few. Engineers with Woodward, Moorhouse & Associates generously supplied oral information on 

their test borings. The assistance of many others not 

mentioned is equally appreciated. Frank Markewicz, 

Principal Geologist, New Jersey Bureau of Geology 

and Topography, supplied valuable information and 

stimulated further investigation.

PHYSICAL SETTING

The location, form, and nature of the material in 

the Atlantic Highlands all contribute to the process 

or combine to increase the probability of slumping. 

In this report, the name "Atlantic Highlands" does 

not have a political subdivision connotation (except 

where the borough of Atlantic Highlands is specifically mentioned) but encompasses the area of hills 

between Sandy Hook Bay on the north and the Navesink River on the south.

The topography of the Atlantic Highlands and 

surrounding hills is equaled in relief and dissection 

in the entire Coastal Plain of New Jersey only by 

the Clarksburg Hills, 48 km (30 mi) to the southwest (fig. 1). The Atlantic Highlands area is unique 

in that it is the only area in the entire Coastal Plain 

of New Jersey (which includes about 10,360 km2 or 

4,000 sq mi) in which hills higher than 60 m (200 

ft) and precipitous bluffs practically border the 

ocean. The mass of hills apparently inspired early 

settlers to use the name Neversink.1

This name was later modified to Navesink. The 

bluffs are protected from the open ocean only by 

Sandy Hook and a narrower barrier bar. Similar 

conditions are present on Long Island, N.Y., to the 

northeast, where many landslides have occurred in 

coastal-plain sediments (Fuller, 1914, p. 54-56), and 

along Chesapeake Bay, Md., to the southwest, where 

slumping is common. The rugged topography in the 

Atlantic Highlands is caused by the sandy permeable nature of the sediments and the resistant layers 

of rock locally present. The permeability of the unconsolidated materials allows water to pass through 

the sediments instead of eroding the surface, and 

the layers of rock resist erosion by water and create 

steep slopes.

CHARACTERISTICS OF THE FORMATIONS

The Atlantic Highlands are underlain by different 

formations of marine and beach-complex origin (fig. 

3). These layers range in thickness from a metre

SERIES

Cohansey Sand

Vincentown Formation

Hornerstown Sand

Tinton Sand

Shrewsbury Member

Sandy Hook Member

Navesink Formation

Mount Laurel Sand

SCHEMATIC

COLUMNAR

SECTION

THICKNESS IN 

METRES (FEET)

UNCONFORMITY

0-10.7 

(0-35)

e.i

(20)

27.4-32 

(90-105)

4.6-9.1 

(15-30)

7.6 

(25)

UNCONFORMITY

7.6 

(25)

EXPLANATION

Fossils Cross- Borings and 

stratification siderite 

concretions

FIGURE 3. Stratigraphic column showing formations of Late 

Cretaceous and early Tertiary age underlying the Atlantic 

Highlands.

1 So shown on a map entitled "The province of New Jersey, commonly 

called the Jerseys." This map was published nearly 200 years iago on 

December 1, 1777, by William Faden, Charing Cross, London, England. 

It was based on a survey made in 1769.
CHARACTERISTICS OF THE FORMATIONS

(several feet) to slightly more than 30 m (100 ft). 

The formations are largely unconsolidated sands 

containing varying amounts of silt and clay. A detailed description of the stratigraphy has been given

by Minard (1969). The significant characteristics of 

the formations are discussed below. Grain sizes are 

given in table 1.

TABLE 1. Average grain size of the material constituting each formation (in weight percent of the total sample)

[Figures represent the average of five sieve analyses of channel samples of each unit]

Red Bank Sand

Grain 

size

Mount Laurel 

Sand

Navesink 

Formation

Sandy Hook 

Member

Shrewsbury 

Member

Tinton 

Sand

Hornerstown 

Sand

Vincentown 

Formation

Cohansey 

Sand

'Z % & p

'$%'$ $

> £ ft JS ft

i O Pi Q Pi h5 p * p

Lower PI 

PI 

P

fc PI

Q ft 2 P

14 5

13 Coarse to very coarse _ 

§ Medium _ _ _ _ _

02 Very fine to fine _ _

Clay to silt _ ___ _

2

4

54

40

2 

32

32

31

10 

32

32

26

35 

25

10

30

3 

9

52

36

2 

18

53

27

10 

50

30

10

16 *&

24

18

12 

18

38

32

5

25

27

43

10 

53

23

14

26 

46

13

1

48 

33

11

1

MOUNT LAUREL SAND

The oldest unit cropping out in the Atlantic Highlands is the Mount Laurel Sand. It crops out along 

the base of the bluff west of slump block B (fig. 2), 

where nearly the entire thickness of 7.6 m (25 ft) is 

exposed. The lower two-thirds of the formation is 

mostly thin-bedded very fine to medium-grained 

glauconitic quartz sand containing thin layers of 

clay and silt which constitute about 40 percent of 

this part of the formation (table 1). The formation 

is greenish gray to dark greenish gray; much lignite and mica are present. The upper third of the 

formation is thick-bedded coarse grained to pebbly 

sand containing about 31 percent clay and silt (table 

1). Glauconite may constitute nearly half the formation in the upper metre (few feet), and fossils and 

fossil fragments are common there.

NAVESINK FORMATION

The Navesink Formation overlies the Mount 

Laurel Sand; it is a massive to thick-bedded clayey 

glauconite sand about 7.6 m (25 ft) thick. Clay and 

silt constitute about 26 to 30 percent of the formation (table 1). The rest consists almost entirely of 

fine- to coarse-grained glauconite sand. The formation is largely dusky green to greenish black and 

olive black. A small amount of quartz sand is present as a trace of fine grains throughout, but is especially plentiful in the base and near the middle. The 

formation underlies the lower and middle slopes of 

hills along Sandy Hook Bay.

RED BANK SAND

Overlying the Navesink Formation is the Red 

Bank Sand which is divided into two members, the

lower Sandy Hook Member and the upper Shrewsbury Member (Minard, 1969, p. 16). The Sandy 

Hook is a compact dark-gray massive-bedded silty, 

clayey feldspathic quartz sand about 4.6 m (15 ft) 

to 9.1 m (30 ft) thick. The sand is fine to very fine 

and contains abundant mica, carbonaceous matter, 

and pyrite; glauconite is abundant in the basal metre 

(few feet). Fossils are abundant, and concretionary 

masses of siderite are present locally. Clay-silt content ranges from about 27-36 percent. The unit 

underlies middle slopes along Sandy Hook Bay and 

lower slopes along Navesink River. The Shrewsbury 

is a massive-bedded silty and clayey, fine to medium 

feldspathic quartz sand about 27.4-32 m (90-105 ft) 

thick. Many coarse grains and some very coarse 

grains are present, especially in the upper half of 

the member (table 1). Much of the member consists 

of fairly loose sand, except locally where crusted or 

cemented by iron oxide. Clay-silt content ranges 

from about 10-18 percent. The unit underlies middle to upper slopes along Sandy Hook Bay and along 

Navesink River.

TINTON SAND

The Tinton Sand overlies the Red Bank Sand and 

is the uppermost unit of Cretaceous age in the area. 

It is massive-bedded clayey, medium to very coarse 

feldspathic quartz-glauconite sand to glauconitic 

quartz sand. It is stained, crusted, and cemented by 

iron oxide and is mostly shades of brown. The sand 

is poorly sorted; grain size ranges from clay and silt 

to very coarse (table 1). Granules are locally abundant, and some pebbles are present in the upper 

metre (few feet). Glauconite also is more abundant
SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

in the upper part. Clay-silt content is about 32 percent. The unit underlies steep middle to upper slopes 

of the highest hills.

HORNERSTOWN SAND

Unconformably above the Tinton is the Hornerstown Sand, the lowermost unit of Tertiary age. 

Typically it is dusky green and grayish olive, 

massive-bedded, poorly sorted clayey glauconite 

sand. Locally the upper metre (few feet) is oxidized 

to dusky red and may contain thin layers of ironstone. Several percent quartz sand is present 

throughout, and as much as 30 percent occurs in the 

basal half metre. Grain size ranges from clay to 

coarse sand; clay constitutes one-third to one-half 

the formation locally (table 1). The formation underlies middle to upper slopes of the highest hills. 

It is well exposed at Waterwitch on Sandy Hook 

Bay, along the north side of Navesink River, and 

near the top of several other bluffs at various 

localities.

VINCENTOWN FORMATION

The Vincentown Formation is thick to massivebedded medium glauconitic quartz sand. Typically it 

is light greenish to yellowish gray, but locally it is 

moderate red and brown and is cemented by iron 

oxide. Glauconite content is nearly half the sand 

fraction in the basal metre (few feet). Grain size 

ranges from clay to coarse sand, but generally more 

than half the unit is medium sand (table 1). Much 

of the sand is clean and loose, but in some outcrops 

as much as 25 percent clay and silt are present. The 

formation does not appear to be fossiliferous in the 

Atlantic Highlands area, but it is very fossiliferous 

elsewhere (Minard, 1969, p. 24). It underlies steep 

middle and upper slopes in the hills.

COHANSEY SAND

The Cohansey Sand is composed chiefly of clean, 

somewhat pebbly, medium to coarse quartz sand; 

however, much fine and very coarse sand and granules also are present (table 1). The distinctive characteristic of the sand is the well-formed cross 

stratification. The sand typically is yellowish gray 

and grayish to pale yellowish orange, except where 

stained grayish red to moderate brown by iron 

oxide.

The basal contact is distinct and unconformable. 

In most outcrops it overlies the massive glauconitic 

sand of the Vincentown. Locally, the basal contact is 

irregular and cuts down through the Hornerstown 

to the Tinton (Minard, 1969, p. 28). Locally, basal 

beds are micaceous fine sand and silt and resemble

the Kirkwood Formation. The Cohansey underlies 

the upper slopes and caps the highest hills in the 

area.

YOUNGER SEDIMENTS

In addition to the previously described units, thin 

bands of alluvial and tidal-flat material are present 

along drainage and waterways, and a thick mass of 

beach sand constitutes Sandy Hook, the barrier bar, 

and the flat beach area at Waterwitch and Highlands.

INDURATED LAYERS

Some layers of the sediments locally are cemented 

to varying degrees from weakly to firmly indurated. The cementing agent is chiefly iron oxide and 

some iron carbonate. These cemented layers range in 

thickness from about a centimetre to a metre ( y% in. 

to a few feet) and are locally discontinuous and 

highly irregular. Typically, the cemented layers are 

in the coarser material. The layers appear to result 

from precipitation of excess iron from the ground 

water where the water becomes sufficiently aerated 

to oxidize iron, which coats and cements sand grains 

or pebbles. This process commonly occurs where 

sand layers intersect a slope and ground water flows 

outward and down the slope. It also occurs where 

upward-flowing ground water reaches the surface 

beneath a stream, and the iron oxide-cemented gravel 

armors the streambed (Lang, 1961). Although indurated layers are common in sediments of the Atlantic 

Highlands, they probably constitute only several 

percent of the total volume of the sediments. The 

formations containing the most ironstone are the 

Shrewsbury Member of the Red Bank Sand, the Tinton Sand, and the Cohansey Sand.

STRUCTURE

The layers of sediments in the Atlantic Highlands 

hill mass resemble those in a layer cake tilted at a 

low angle towards the southeast, so that the layers 

dip in that direction from about 1.8 to 7.3 m per 

kilometre (10 to 40 ft per mile). The top several 

layers have been dissected by erosion, so that a 

rugged hilly surface remains.

There are local anomalies to this general picture, 

especially in the younger (upper) formations. For 

instance, as described by the author (Minard, 1969, 

p. 35) :

The base of the Hornerstown Sand is nearly horizontal near 

Hilton (pi. 1), but the dip increases sharply southeastward, 

in the hills south of Highlands. The base of the formation 

near the Hart horizontal control station is 100 feet (30 m)
STRUCTURE

lower than it is 1 mile (1.6 km) northwest. This relationship 

may be due to an increase in dip, or it may be the result of 

displacement along faults or slumps. Several northeast-trending lines in the groups of hills south of Highlands, as seen on 

aerial photographs, strongly suggest the presence of faults 

or slumps. Because of the scarcity of outcrops and the highly 

dissected topography, which prevents augering in critical 

areas, it was not possible to demonstrate the existence of 

faults or slumps there.

HISTORICAL NOTES

During geologic mapping of the Sandy Hook quadrangle in 1963 and 1964, the author speculated on 

the age of the slump blocks (Minard, 1969, p. 40). 

It was thought that slumping was caused by wave 

action from the open ocean undercutting the bluffs, 

as was believed by Fuller (1914, p. 55) for the slump 

blocks on Long Island. Because Sandy Hook spit protects the bluff between the boroughs of Atlantic 

Highlands and Highlands (fig. 2) from the open 

ocean, the author believed that the slumping predated the hook which was thought to be, at least in 

part, several thousand years old (Minard, 1969, p. 

40). A search through the literature, however, reveals some interesting information. There was an 

early awareness of the changing shape and ephemeral nature of parts of Sandy Hook spit. Although 

parts of the spit may be several thousand years old, 

the narrow southern part, south of Plum Island 

(Island Beach in fig. 4), is younger. Merrill (in 

Cook, 1885, p. 59, 60, 75-79) discussed the changing 

shape of Sandy Hook spit. According to Merrill (p. 

60), "the Hook has increased in length and breadth 

so as to include more than four times the area it 

covered in 1685" (a period of 200 years at Men-ill's 

writing). A map in the front of the Annual Report 

of the State Geologist for 1885 (Cook, 1885) shows 

various surveys of the Hook from 1685 through 

1853, as well as the 1885 shoreline (fig. 4). It is of 

interest to note that in Keith's survey of 1685, the 

Hook did not appear to be connected with the mainland. Merrill (p. 77) stated:

From a point about one and one-third miles [2.1 km] north 

of Highlands to about one mile [1.6 km] south of it, near 

Bellevue, on the N. J. S. R. R., the beach has been washed 

away and remade again and again since the settlement of the 

country, and doubtless previously by Shrewsbury inlets, once 

important to navigators. The dates of the inlets, which have 

been handed down mainly by tradition, are as follows * * * * 

Previous to 1778 Sandy Hook was connected to The Highlands of Navesink by a narrow isthmus or bar [Lawrence's 

survey, fig. 4] and the Navesink or North Shrewsbury river 

was open to the ocean on the east, there being no beach for 

about three miles [4.8 km] north of the present Seabright 

[fig. 2]. In 1777-8 a passage was broken through the isthmus, 

and the tidal currents flowing through this channel allowed 

the waves to build up gradually a bar or sand reef which

74'

40° 

27' 

30"

40° 

25'

EXPLANATION

Keith's survey 

(1685)

Lawrence's survey 

(Prior to 1764)

Original surveys 

(1885)

Aerial photographs 

(1940 and 1961)

1000

10OO

40* 

22' 

30"

FIGURE 4. Map of Sandy Hook spit showing progressive 

changes in shoreline during the period 1685-1961 (modified from Cook, 1885).
8 SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

closed the eastern passage [through the present bar near 

Bellevue, fig. 4] or old Shrewsbury inlet in 1810. From this 

time on the outer beach continued and the Navesink River 

flowed through its present outlet [north and northwest, fig. 

4] until 1830 or 1831, when a breach was made in the sand 

reef and the second Shrewsbury inlet was formed. Shortly 

after a bar formed across the present mouth of the river and 

connected Sandy Hook with the mainland, just north of 

Highlands, by way of Island Beach [fig. 4]. About 1835 the 

residents of the vicinity undertook to open a channel through 

the bar, and after much labor cut a ditch through it, which 

was gradually widened and deepened by the tides until it 

became navigable. The second inlet opened in 1830 or 1831, 

and closed about 1840. The third opened in 1837 or 1838, and 

for a time there were two navigable inlets the second or 

more southerly being most used. The east inlet closed in the 

latter part of 1848. Within the past 35 years the sea has 

made occasional breaches in the strip of beach under discussion [the offshore bar that presently (1974) connects Sandy 

Hook with the mainland in the vicinity of Long Branch adjacent to the south of the map area [fig. 4], but the efforts of 

property owners, and especially of the railroad company, 

since the building of the road, have prevented them from 

attaining any magnitude.

An earlier report by Barber and Howe (1844) 

gave several dates approximately agreeing with 

MerrilPs observations. They stated (p. 361) that 

"Sandy Hook * * * changed its character from a 

promontory to an island in 1778, by an opening 

forced by the sea, termed the old Shrewsbury Inlet. 

In 1800 the inlet was closed, and the Hook again 

became a promontory until 1830, when it was reopened and now is an island."

The point of this discussion of the frequent 

breaching of the barrier bar connecting Sandy 

Hook with the mainland is to show that the open 

ocean apparently did have access to the bluffs of

Highlands through breaches in the bar as much as 

4.8 km (3 mi) wide. The sandy flats at Waterwitch 

and Highlands probably were at maximum width 

when the bar to the east was intact and the Navesink-Shrewsbury River flowed north into Sandy 

Hook Bay. This is suggested because these sandy 

flats are similar to a point bar. During this time the 

bluffs would be protected. However, when the bar 

was breached, the sand load carried by the rivers 

would be carried east, and open ocean waves and 

tidal currents could erode the "point bar," possibly 

enough to expose the base of the bluffs to active 

wave and tidal current erosion. If this breaching 

were typical for hundreds of years before recorded 

history of the events, slumping may have taken 

place more recently than originally thought. Some 

of it may have occurred within the past few centuries.

The different physical characteristics of what appears to be slump block B (fig. 2) was recognized 

by Merrill (in Cook, 1885, p. 76). In the figure titled 

"Section across Navesink Highlands and Sandy 

Hook," slump block B is shown as a terrace at Hilton 

Park, of different lithology than the bluff behind it 

(fig. 5). Shown in section with vertical exaggeration, 

the terrace seems to occupy a precarious position.

Documentation for slumping was sought in the 

literature, and two references were found. One of 

these is in Cook (1868, p. 348) ; he discussed the 

wear of beaches and shorelines by water and waves, 

stating that:

At Long Branch, which is hard upland, the wear is very 

serious. The spot where the first boarding house was located,

METRES 50-,

Slump block B

-150 FEET

1 MILE 

J

i KILOMETRE

Spermaceti Cove

Section across Navesink Highlands and Sandy Hook, showing 

terrace at Hilton Park

FIGURE 5. Section showing what probably is slump block B as "a terrace at Hilton Park." From Cook, 1885, page 76.
HISTORICAL NOTES

thirty years since, together with road which ran behind it, 

is now all worn away, and the shoreline' is west of it. The 

wear is irregular; last year it was from 12 feet [3.7 m] to 

20 feet [6.1 m]. Along the shores of Sandy Hook and Raritan 

Bay the wear is equally rapid. At the Highlands enormous 

slides have been the result of this wear [italics added].

Cook does not say when these slides occurred, but 

there seems a suggestion of recency. It also seems 

to indicate agreement with wave cutting or water 

erosion of shorelines as the mechanism causing the 

slides. Perhaps there were slides in the bluffs east 

and southeast from slump block A, including the 

bluff at the east end of the hills bordering the present north-flowing segment of the Navesink-Shrewsbury River. If so, the slides have been removed by 

water currents and probably deposited as the sandy 

flats at Highlands and along the west side of Sandy 

Hook spit.

The second reference to slumping is more revealing. Barber and Howe (1844, p. 357) reported that: 

In the spring of 1782 a slide of earth happened at Greenland 

bank, the highest point of the highlands, situated two miles 

north of Beacon hill. The noise was heard for a distance of 

several miles. The annexed account was published at the 

time: On the ridge of mountains, commonly called Navisink 

hills, in Monmouth co., East Jersey, a considerable quantity 

of land, some say 40 acres, gave way, in April last, and sunk 

directly down a considerable depth; forming a cavity equal 

in circumference, at bottom, to the void space above. The 

tops of the trees, that sunk with the soil, and which were 

mostly of considerable bulk, are now nearly level with the 

edges of the remaining ground. Round this again the earth 

opens, in one continuous fissure, a foot or more in breadth, 

for a considerable distance; and, as is conjectured, from its 

present appearance, will shortly go down also the foundation being perhaps but a loose quicksand. It is supposed, by 

the country people thereabouts, to have been occasioned by 

the washing and undermining of the sea, to which it is 

contiguous.

From the above information it is difficult to pinpoint the location of the slide. Barber and Howe 

(1844) located it 3.2 km (2 mi) north of Beacon 

Hill. According to them (p. 356, 357), Beacon Hill 

is the hill on which Navesink Lighthouse is situated 

(fig. 2). They referred to the lighthouse as Highlands Lighthouses (p. 356) on Navisink Hills (p. 

357). A location 3.2 km (2 mi) north of their Beacon Hill is presently in the east part of Spermaceti 

Cove, 1.6 km (1 mi) north of Plum Island (figs. 2 

and 4) ; a location 3.2 km (2 mi) northwest is on the 

wide east end of slump block B (Bl, B2). Slump 

block A is 2.4 km (1.5 mi) northwest of Beacon Hill.

If Greenland bank is at the highest point of the 

highlands, this suggests that the slide is slump block 

A or in the near vicinity. Other than the current

slumping (1972-74), slump block A is the most 

youthful-appearing major block. The highest altitude presently shown (81 m (266 ft)) is at the 

water tower about 183 m (600 ft) directly behind 

block A. An altitude of 80 m (263 ft) is shown only 

91 m (300 ft) from the top of the scarp at the 

southwest part of block A. If the writers meant at 

the highest part of the bluff face, it could be any 

place from Navesink Lighthouse all the way west 

nearly to Atlantic Highlands. It is interesting to 

note that the slide of earth "is supposed, by the 

country people thereabouts, to have been occasioned 

by the washing and undermining of the sea, to 

which it was contiguous." If it were contiguous to 

the sea, then Sandy Hook probably was an island 

(fig. 4), and open-ocean and tidal currents scoured 

the bases of the bluffs, as postulated by Minard in 

1969 (p. 40). Not being aware, at that writing, of 

the absence of the bar at different times in the 18th 

and 19th centuries, a much older date was proposed 

than is now believed. The slide of April 1782 may 

be one of those mentioned by Cook, or his slides 

may have been subsequent ones, possibly associated 

with lines of weakness developed by the slide of 

April 1782. If this slide is not the one I map as 

slump block A (or one of those shown in fig. 2), 

it may have been completely eroded by waves and 

currents.

It seems then that an awareness of the instability 

of parts of the shoreline in question was, in part, 

recorded at least in geologic literature. However, if 

there has been no more recent mention (other than 

that by Minard, 1969) of slump blocks in the area 

than those by Cook (1868, p. 348 and Barber and 

Howe, 1844, p. 357), it is easy to understand the 

apparent lack of public awareness of these few lines 

of reference in communications not widely read by 

builders or members of the community and planning 

committees.

This seems to point out the desirability of better 

dissemination and use of pertinent geologic information among officials of political subdivisions concerned with zoning and land use. An awareness of 

the benefits of such information is presently being 

realized, particularly in certain metropolitan and 

suburban areas, through the preparation and use of 

geologic hazard or constraints maps. Maps and studies by knowledgeable engineers and geologists, who 

probably are more likely to recognize geologic hazards such as landslides, faults, and flood-prone areas, 

can result in information that can be used by local
10 SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

officials to plan and regulate land use so that natural 

catastrophies will less likely be initiated or hastened 

by human activity and so that damage can be 

averted.

SUMMARY OF CHARACTERISTICS OF 

SLUMP BLOCKS

The slump blocks described in this report are 

typical of the landslides of Fuller (1914, p. 55, 56), 

the Toreva block of Reiche (1937, p. 538), the 

slump blocks described by Sharpe (1938, p. 68) and 

Strahler (1940, p. 288, 289), and those mapped by 

Minard in Arizona (1956 a, b).

Several features and events are characteristic of 

the slump or Toreva blocks. These features and 

events are:

1. Downward movement of a mass of rock and (or) 

earth.

2. A rotational movement of the block normal to 

the scarp face of detachment.

3. Inward tilting of the upper surface of the block 

and an upward drag of the beds in contact 

with the scarp face down along which the 

block is sliding.

4. An elongate depression on the scarp side of the 

surface of the block resulting from the tilt and 

drag.

5. A concave scarp from which the inner convex 

surface of the block detaches, and a convex 

bulge at the outer base or toe of the block.

The history of slumping of a block is illustrated 

diagrammatically in figure 6. Also typical of many 

slump blocks is the secondary slumping that shears 

the primary block approximately in two and results 

in farther downward movement of the resultant 

outer block and additional rotation and tilting of 

beds in this block (fig. 7). More shearing and slumping in the secondary block is possible, particularly 

in unconsolidated sediments (Sharpe, 1938, figs. 8, 

11, pis. IV B, VII A). Secondary shearing, however, 

is not characteristic of Reiche's Toreva block, which 

is considered a single large mass of unjostled material (Reiche, 1937, p. 538). A block diagram of a 

typical slump block, with names of the various parts, 

is shown in figure 8.

The degree of tilt of the upper surface of a slump 

block towards the scarp of detachment varies considerably. Dips of the upper tilted beds may range 

from a few degrees to at least as much as 79° 

(Minard, 1956 a, b; Reiche, 1937, fig. 5). It appears 

that the farther away from the point of detachment,

Land surface before 

slumping

Primary slumping of 

block A

Secondary slumping showing secondary block (A2) 

sheared from front of 

primary block A, leaving 

block Al.

Secondary slumping 

probably occurred with 

and immediately after 

primary slumping

Sea

level

Present surface (solid line) 

of slump block A (A14- 

A2) in relation to preerosion surface, as it 

existed immediately 

after slumping of block 

A2

Sea 

level

Present erosion-modified 

surface of slump block 

A (Al +A2) and bluff 

from which block detached

Sea

level

FIGURE 6. Diagrammatic cross sections through the bluff at 

the location of slump block A (fig. 2), showing progressive 

steps in the history of the slumping.

the steeper the tilt (Minard, 1956, a, b; Reiche, 1937, 

fig. 2, 6). Also, the upper beds in the outer block or
SUMMARY OF CHARACTERISTICS OF SLUMP BLOCKS 11

EXPLANATION 

Qbs. Beach sand

Tvt. Vincentown Forma 

Tht, Hornerstown Sand 

Kt. Tinton Sand

Krs. Shrewsbury Member! . _ . , Krsh. Sandy Hook Member / Red Bank Sand

Kw Wenonah Formation

FIGURE 7. Cross section (looking west) of slump block A in 

the bluff just west of Waterwitch (fig. 2). Vertical displacement of the small secondary block is about 85 feet. 

Vertical exaggeration X 4. See figure 3 for explanation of 

lithologic symbols. Modified from Minard, 1969, figure 13.

blocks, which are farther from the point of detachment, usually have a steeper dip than similar beds 

in the inner or primary block (fig. 9).

DESCRIPTIONS OF

INDIVIDUAL SLUMP BLOCKS

BLOCK A

Block A is a complete block, about 137 m (450 ft) 

wide by 425 m (1,400 ft) long a classic example of 

a definite rotationally slumped earth mass. It has 

the convex inner face nestled into the concave scarp 

along which it slumped downward; the top of the 

concave scarp is outlined by the road on top. The 

block has a very prominent bulge at the toe where 

it has moved a considerable distance away from the 

bluff. It has a conspicuous sag or depression on the 

inner upper surface. The sag is about 3 to 3.7 m (10 

to 12 ft) deep, 46 to 61 m (150 to 200 ft) long, and 

12.2 m (40 ft) wide in the middle, tapering to closure at each end.

The block has a secondary line of failure and 

slump block (A 2) near the middle of its cross section (fig. 7). The beds in block A 2, which originally 

were continuous with the beds at the top of the bluff 

26 m (85 ft) above, have rotated from a nearly horiTIP The point on the toe most distant from the top of 

the slide

FLANK The side of the landslide

CROWN The material that is still in place, practically 

undisturbed, and adjacent to the highest parts of the 

main scarp

ORIGINAL GROUND SURFACE The slope that existed 

before the movement which is being considered took 

place. If this is the surface of an older landslide, 

that fact should be stated

LEFT AND RIGHT Compass directions are preferable 

in describing a slide, but if right and left are used 

they refer to the slide as viewed from the crown

MAIN SCARP A steep surface on the undisturbed 

ground around the periphery of the slide, caused by 

movement of slide material away from the undisturbed ground. The projection of the scarp surface 

under the disturbed material becomes the surface 

rupture

MINOR SCARP A steep surface on the disturbed material produced by differential movements within the 

sliding mass

HEAD The upper parts of the slide material along the 

contact between the disturbed material and the main 

scarp

TOP The highest point of contact between the disturbed material and the main scarp

FOOT The line of intersection (sometimes buried) between the lower part of the surface of rupture and the 

original ground surface

TOE The margin of disturbed material most distant 

from the main scarp

FIGURE 8. Block diagram showing names for various parts 

of a landslide or slump block (from Varnes, 1958, pi. 1).

zontal attitude to about 40° inward and have been 

dragged on the inner surface to nearly 40° outward
12 SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

ROTATIONAL

SLUMP

(EARTHFLOW)

FIGURE 9. Block diagram showing steeper scarpward tilt 

of upper beds in outer blocks (from Varnes, 1958, pi. 1).

(fig. 7). The primary (inner) slumping apparently 

was bottomed in the basal member of the Red Bank 

Sand and Navesink Formation. Secondary slumping 

was largely in the upper member of the Red Bank 

Sand. As can be seen in figure 2, several houses have 

been constructed on the block. A sand pit is present, 

from which much material has been removed in the 

past decade. This probably is beneficial in that it 

has taken much load off the block. It was in the 

sand pit that excellent exposures of the different 

lithic units made it easily possible to correlate these 

units with those from which they were separated in 

the bluff 26 m (85 ft) above.

The inward tilt of the upper surface, characteristic of the rotated block, is clearly evident on block A.

BLOCK B

Block B, a definite slump block, is shown in four 

segments in figure 2. Blocks B 1 and B 2 were 

mapped by the author (1969) as block B. The wider 

eastern part of the block is again the classic convex shape fitting into the concave scarp of detachment (outlined by the road). The upper surface is 

depressed near the inner part, parallel to the long 

axis, as it is on block A. The overall length of the 

entire block (B 1-B 4) is nearly 900 m (2,950 ft) ; 

the widest part is about 120 m (390 ft). There are 

no good exposures on the block. Some large (1.2 by 

3.6 m (4 by 12 ft)) blocks of ironstone are present 

and have given confidence to some home owners that 

their houses are on good solid rock. A detracting 

aspect, however, is the fact that these blocks are 

tilted scarpward as a result of rotation during the 

downward movement of the block.

Block B 2 forms a ramplike feature from west 

to east; this surface expression reflects the vertical 

displacement along a secondary line of rupture.

Blocks B 3 and B 4 are new slump blocks that

apparently have formed since the summer of 1972. 

They will be described in more detail in a following section on current slumping.

BLOCK C

Block C is the third and last block shown on plate 1 

of Minard (1969). The highest part of this probable 

slump-block surface is at an altitude of about 30 m 

(100 ft). The top of the slope above is about 60 m 

(200 ft) in altitude. The block's maximum dimensions are about 120 m (390 ft) wide and 610 m 

(2,000 ft) long. From aerial photographs it appears 

that a secondary outer block may be present. The 

upper surface of the southern half of this block tilts 

inward towards the scarp, as would be expected of 

a rotational block. Except for a narrow strip of 

beach, the basal part of this block is in direct contact with the water, possibly a serious situation.

BLOCK D

Block D, as outlined in figure 2 is a probable 

slump block. It is fairly large, about 180 m (590 ft) 

wide by about 450 m (1,475 ft) long and has several 

features of a typical slump block. It has a convex 

inner bulge fitting into a concave scarp which is 

modified considerably by erosion, except at the 

west end. The surface of the block noticeably tilts 

or slants inward. It may be wise to avoid building 

large structures on this block.

BLOCK E

Block E is a possible small slump block. There has 

been considerable surface modification by man, but 

a small concave scarp is characteristic.

BLOCK F

The significant feature here is not a slump block, 

but the concave scarp that suggests that a slump 

once occurred, the block having been almost completely eroded, leaving only the typical scarp.

BLOCKS G AND H

Blocks G and H are possible small slumps of 

minor downward displacement in the bluff between 

and above blocks A and B. Block H particularly 

shows a typical convex inner outline, fitted into the 

concave scarp behind it.

BLOCK I

Block I, near the west end of the bluff not far 

from Atlantic Highlands Yacht Harbor, has the 

typical convex-concave profile from above. It is 

about 45 m (150 ft) wide and 225 m (740 ft) long.

OTHER POSSIBLE SLUMPS OR ZONES OF WEAKNESS

A possible line or zone of weakness may extend 

westward from block I, but it is not clearly defined.
DESCRIPTIONS OF INDIVIDUAL SLUMP BLOCKS 13

A line of weakness also may be in the slope just 

southeast from Navesink (Twin Light) Lighthouse. 

The slope has a concavity, and material at the base 

appears jumbled and disturbed. A possible slump 

block may be at the point of land at triangulation 

station Lower, southeast from the Air Force Reservation. The bluff east of block C to the bridge is 

steep and appears to be the product of active erosion and slumping. This also is true for the steep 

bluff along the north side of Navesink River just 

northwest from triangulation station Hart.

LINEAMENTS

Short dashed line in figure 2 represents linear features apparent on the aerial photographs. A cluster 

of such features is evident in the wooded hills southeast from Navesink Avenue. A few other lineaments 

are northwest of Navesink Avenue and south of 

Locust. These lineaments may be a reflection of 

joints or fractures, possibly in the iron-oxidecemented layers in the upper Red Bank, Tinton, and 

Cohansey Sands. They may indicate zones of relative weakness.

RECENT EROSION

Surface erosion is active in many places along the 

bluffs. Many gullies groove the face of the bluff east 

from near Atlantic Highlands Yacht Harbor to the 

west ends of blocks B3 and B4. This erosion is 

largely the result of rainwater runoff, plus groundwater seepage and sapping towards the lower parts 

of the slopes. Much of the material eroded is loose 

soil mantle resulting from weathering processes. 

However, many of the gullies bottom in more compact less weathered in-place material. The combination of surface wasting, solifluction, and sheet and 

gully erosion constantly removes appreciable volumes of material from the bluff face. This material 

is carried to the toe of the slope, where it may form 

temporary small alluvial fans. Much of the material 

eventually reaches the bay shore and is removed and 

redistributed by wave and tidal action.

A deep gully cuts into the scarp above the east 

end of slump block B. Another gully is being extended upward in the headwall above the west end 

of block A. The vertical headwall is 4.6 m (15 ft) 

high at present in this gully. A quantity of eroded 

material forms a heap just above the road near the 

base of the slope.

Probably the largest area of surface erosion is in 

the scarp at the east end of block A. A large area of 

the bluff face is bare, and erosion has migrated headward to the road at the top edge of the bluff.

Erosion is apparent in the scarp of block D, 

mainly as surface wash. Surface wasting is evident 

in the upper face of the high bluff on Navesink; 

River, just northwest from triangulation station 

Hart.

Many small gullies are present elsewhere, such as 

on the face of block C and nearby. None of the gullying in the bluffs along Navesink River is as severe 

as that in the bluffs along the south side of Sandy 

Hook Bay.

On January 23, 1974, a natural vertical drainage 

hole (fig. 10) was in the floor of the borrow pit on

FIGURE 10. A natural vertical drainage hole in the floor of 

the borrow pit on slump block A 1. As observed on January 23, 1974, the hole appeared to be the drain for hundreds of square metres of pit floor. This would suggest a 

permeable zone or "pipe" that might result in piping of 

underlying sand and caving of the surface. The formation 

is the upper member (Shrewsbury) of the Red Bank Sand.

block A (A 1 plus A 2). The hole was near the middle of block A 1. Drainage lines from all over the 

pit indicated that rainwater from hundreds of square 

rretres had drained into the hole. This suggests a 

permeable zone or "pipe" that might result in piping 

of underlying sand and caving of the surface.

It is interesting to compare the stages of erosion 

shown on photographs of different years. Photographs taken after the aerial photographs of 1961 

(fig. 11) show that erosion is farther advanced. 

These differences can be seen on the photograph 

taken in March 1966 (fig. 12) and that taken in
14 SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

FIGURE 11. Stereoscopic pair of vertical aerial photographs showing slump blocks A and B on the bluffs along the south 

side of Sandy Hook Bay. Scale 1:17,500. Photograph by Aero Service Corp., April 1961.

February 1974 (fig. 13). The gully in the scarp 

above and near the west end of block A is much 

deeper and wider at present than it appeared on the 

stereoscopic pair of aerial photographs taken in 1961 

(fig. 11).

CURRENT SLUMPING

Noticeable slumping was reported by local residents to have begun sometime during the summer 

of 1972. The area affected is slump block B (as 

mapped by the author in 1969) and the area adjacent to the west of it. These blocks are now labeled 

B 1, B 2, B 3, and B 4 (fig. 2). At present, B 1 is 

the least active. No appreciable movement is noticeable on most of it, but cracks in the road pavement 

and rock wall at the west end of the inner rupture 

zone of the block indicate some reactivation here or 

an extension of a line of rupture westward from the 

previous curved west end of slump block B as shown 

by Minard (1969, pi. 1).

On January 24, 1974, 22 houses and 8 garages 

were on, or mostly on, block B 1. Block B 2 has been 

noticeably reactivated; near the longitudinal middle of this block, several houses and properties are 

being adversely affected by the slumping. Two 

houses have been damaged (figs. 14, 15), largely 

through vertical displacement of as much as 0.3 m 

(1 ft). An open crack passes in back of two more 

houses. This crack has been open as much as 20 cm 

(8 in.) wide and 1 to 1.3 m (3 to 4 ft) deep. At least 

one stone wall has been cracked completely through. 

West of here, concrete steps leading down to the 

shore are conspicuously cracked all the way across; 

the upper more pronounced crack is shown in figure 

16. According to Mr. Edward Weiler (oral commun., 

January 25, 1974), the steps were not cracked in 

the fall of 1973.

Blocks B 3 and B 4 appear to be new blocks. No 

visible evidence of them appears on the aerial photographs of 1961. The movement on block B was first 

noticed by the local residents in the summer of 

1972 (Mr. Martin Jensen, oral commun., June 7, 

1973). A new scarp about 4 to 5 m (13 to 16 ft) 

high is present at the top of the slumping area immediately in back of the line of houses on top of 

the bank (fig. 17). One house lost its back porch
CURRENT SLUMPING 15

FIGURE 12. Oblique aerial (helicopter) photograph (looking west) showing extent of surface erosion on the bluff face (center of photograph) on March 16, 1966. Vertical distance from road on top of bluff to road at base of bluff is about 60 m 

(200 ft). Slump block A is on right part of photograph. Compare extent of slope erosion with that shown in figure 13. 

The present front of block A lies about 100 m (several hundred feet) bayward (to the right) from its pre-slump position in the bluff.

(fig. 18), one house has been moved back, another 

has had its foundation footing exposed, and two 

more are only a metre or two from the line of 

failure. This line of failure, at least in the upper 

exposed part, is in the loose-bedded sand of the 

upper Red Bank Sand. It may be an extension of the 

line of failure behind slump block B 1, which was 

mapped by the author in 1963-64 (Minard, 1969, 

pi. 1) as crossing Bayside Drive near the curve 

where the road abruptly turns south and uphill. No 

cracking was visible in the pavement at the time 

of that mapping. On June 7, 1973, however, cracking was visible in the edge of the road and through 

the stone wall. By January 25, 1974, this cracking 

in the pavement had multiplied and extended across

the road and widened considerably in the stone wall 

(fig. 19); vertical displacement in the road pavement 

was 6 to 8 cm (3 in.).

The surface of the slope on blocks B 3 and B 4 

is irregular and unstable, a truly jumbled mass. 

Actually, more than two blocks are present; several 

fissures have opened below the main upper scarp at 

the rear of the houses, dividing the main blocks into 

smaller blocks (figs. 20, 21). As a result, trees have 

been tilted at considerable angles from vertical (fig. 

22), vines have been stretched taut between blocks. 

Most movement is down on lower blocks relative to 

upper blocks, but in some instances upper blocks 

have slid down and wedged beneath lower blocks so 

that the upper edges of the lower blocks actually
16 SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

FIGURE 13. Oblique aerial (helicopter) photograph (looking west) showing extent of surface erosion on the bluif face (center of photograph) on February 13, 1974. Vertical distance from road at top of bluif to road at base of bluff is about 

60 m (200 ft). Inner part of slump block A is at far right; scarp is above and left of it. Compare extent of slope 

erosion with that shown on figure 12, nearly 8 years earlier. Erosion has extended upward, nearly undercutting the 

road, and laterally. Erosion has cut back into the face of the bluif, as is indicated by the steeper banks bordering the 

edges of the scar.

project about a metre above the lower edge of the 

upper block, illustrating the relative greater downward movement of the upper blocks.

It appears that initial movement in blocks B 3 and 

B 4 probably was in the toe of the slope, possibly as 

a base failure (at least below the base of the old railroad bed). As material at the toe moved towards the 

bay, support was removed from material above, 

which followed in possibly several stages of slope 

failure before the present uppermost block began 

the slumping that has produced the 4- to 5-m (13- 

to 16-ft) scarp behind the houses.

The lower slumped material may or may not have 

included other than surface waste and soil material. 

The upper block (B 3) has, at least in part, failed 

in material in place, carrying this and surface waste 

downward.

CAUSES

Processes leading to slides have been nicely 

summed up by Jones (1973, p. 10).

An examination of the processes leading to the slides suggests that the physical agents at work to produce slides are 

principally water, the weight of the slope-forming material, 

and gravity stresses * * * The events or processes that bring 

the agents into action are rains and construction operations. 

The modes of action of the rain are raising the piezometric 

surface in the slope-forming material, seepage toward the 

slope, removal of soluble binders in joints, subsurface erosion, 

rearrangement of grains, chemical weathering, and displacement of air in voids and joints. The modes of action of construction operations are high-frequency vibrations and an 

acceleration of creep by undermining and locally overloading 

the slope. The modes of action combine to produce changes 

in the stress of the slope-forming material, thus causing 

damage to intergranular bonds, rearrangement of grains, 

opening of new joints and closing of old ones, an increase in 

pore water pressure, and elimination of surface tension.
CURRENT SLUMPING 17

FIGURE 14. House on wide eastern part of slump block B, 

straddling line of failure between subsidiary blocks B 1 

and B 2, looking west. Settlement since summer 1972 has 

been more than 25 cm (1 ft). Note two jacks (arrows) 

holding up rear part of house. Photograph taken June 7, 

1973.

FIGURE 15. Next house west of one shown in figure 14. Major structural damage to house results from its position 

astride the line of failure between slump blocks B 1 and 

B 2. Settlement and breakage goes all the way through the 

house. Photograph taken June 7, 1973.

When some of the various elements of the processes combine 

to increase shearing stresses and to decrease cohesion and 

frictional resistance to a sufficient degree, a slide is activated.

Several factors may have been involved in the

FIGURE 16. Breakage in concrete steps (see arrows) on the 

western part of slump blocks B 1 and B 2 (fig. 2). The 

steps were reported unbroken in late fall 1973. Photograph 

taken January 25, 1974. First slumping and ground breakage on the blocks were reported during the summer of 

1972. This indicates observable movement continuing over 

a period of 15 or 16 months.

movement of all the B blocks weight on top, removal of material at the toe, and excess water, both 

in the surface waste and material in place. Some 

residents speculated on a possible weakening effect 

resulting from the driving of piling for the new 

concrete bridge nearby. It appears that no additional 

weight was added to the top. Prolonged heavy rains 

took place before the first noticeable failures. This 

would tend to saturate the surface waste and soil, 

thereby increasing the weight and also increasing 

pore water pressure which can effectively reduce 

intergranular contact, hence internal friction.

A higher water table in the material in place 

beneath surface waste and soil also could cause an 

increase in pore water pressure and decrease in internal friction in this material. This alone may have 

been enough to initiate movement. Local residents 

attribute initiation of movement to the excavation of 

a sewer trench near the toe of the slope.

An additional danger in the area is that if the 

outer blocks (B 2 and B 4) move downward and 

outward the loss of support may be enough to allow 

the inner or upper blocks (B 1 and B 3) to move 

more. This in turn could remove support from unslumped areas farther back in the bluff.
18 SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

FIGURE 17. Looking east from the west end of slump block B 3. Scarp on right is rupture zone at top and rear of the block. 

Total vertical displacement is about 4 to 5 m (13 to 16 ft), most of which is reported to have occurred during a 3-month 

period in the summer and fall of 1972. The flat grassy area at bottom left was level with the lawn at upper right before failure. Photograph taken January 24, 1974. House in background is shown in figure 18.

An interesting facet of the reactivation of old 

slumping and the initiation of apparently new slumping (other than settling) is the fact that the block 

seems to have been relatively inactive for a long 

time before, suddenly, very observable movement 

became evident. Such areas apparently can become 

critical by the addition of one or more ordinary factors.

ADDITIONAL CONSIDERATIONS

Because of the lithic nature of some of the formations involved, it is important to consider another 

set of physical and chemical factors. The lithic nature specifically is the glauconite and calcareous material in certain formations; the physical and chemical factors are the interaction of all the elements, 

particularly as a result of the role and effect of the 

glauconite and calcareous material.

During informal discussions with colleagues and 

other workers in the geologic, hydrologic, and engineering disciplines, it was interesting to learn 

opinions on the stability of the formations underlying the lower parts of the bluffs. Because in-place 

material of these formations is compact and firm as 

compared with surface waste, colluvium, and parts 

of the overlying formations, many consider these 

formations stable and not liable to slide.

The formations in question are the upper part of 

the Mount Laurel, the entire Navesink, and the basal 

part of the Red Bank (Sandy Hook Member) . These 

formations have several things in common: They 

underlie the lower parts of the bluffs in the area under discussion; they are largely firm and compactappearing in place; they are relatively unweathered; 

and, perhaps most important, in part, they all contain abundant glauconite and calcareous fossil re-
CURRENT SLUMPING 19

FIGURE 18. House near east end of bank above block B 3, 

looking east. This is the house in the background of figure 

17. The rear porch, which was attached to the house, collapsed when block B 3 dropped. Note position of door 

(watch that step!). Photograph taken January 24, 1974.

mains. The upper part of the Mount Laurel Sand 

contains as much as 50 percent glauconite, the 

Navesink Formation contains as much as 70 percent 

glauconite and many calcareous shells, and the 

Sandy Hook Member of the Red Bank contains 

about 15 percent glauconite near the base and calcareous shells in great abundance. It apparently is 

because these formations appear largely as firm 

compact masses of material, subject, superficially, 

only to surface sloughing, that many consider them 

stable and not likely to slump. A search through the 

literature, however, reveals some interesting observations and interpretations in several papers.

Benson (1946, p. 328) noted that rocks in an area 

of landslides in the Dunedin District of New Zealand were divided by bands of incoherent sand or

FIGURE 19. 'Cracks in pavement of road and in wall at west 

end of block B 1 (block B as mapped in 1963 64 (Minard, 

1969, pi. 1)). No cracking was visible when field mapped. 

Cracking was visible June 7, 1973, in parts of the pavement and wall. When this photograph was taken on January 25, 1974, cracking had multiplied and extended across 

the road, and the cracks were wider in the wall. Vertical 

displacement was as much as 6 to 8 cm (3 in.) in the pavement near the far side of the road.

glauconite. He further noted (p. 340) that a railway 

tunnel passes through a ridge of Caversham Sandstone and that every feature favorable to landsliding
20 SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

FIGURE 20. View towards west of a fissure 1 m (several 

feet) and more deep, separating blocks B 3 and B 4. The 

fissure is several tens of metres long. Note tilt of tree 

caused by collapse into fissure.

is present moderate rainfall, jointed porous sandstone resting on a thin layer of incoherent greensand (glauconite), seaward slope of beds, and frequent vibrations caused by railway traffic and wave

FIGURE 21. View towards east showing one of the small 

scarps typical of those on slumps blocks B 3 and B 4. 

Vertical displacement is about 1 m (several feet).

attack on the closely adjacent shore. He noted that 

cracking of the tunnel lining with lateral and downward movement of the railroad were a constant 

source of trouble. He stated (p. 342) that the most 

rapidly moving point is nearest the north portal and 

that it probably moved on the greensand below "as 

if on ball bearings."

In the same year, Proix-Noe (1946) presented a 

paper with the interesting title "Etude de'un glissement de terrain du a la presence de glauconie" 

(Study of a landslide due to the presence of glauconite), in which she discussed landslides in the cliffs 

forming the amphitheater of Algiers Bay. She noted 

that (p. 1) "Since 1896, the amplitude of these accidents keeps increasing due to deforestation of the 

slopes that result from building development."

Throughout the paper, it appears that the author 

is emphasizing the importance of the combination of 

glauconite and calcareous material in the rocks. 

This is confirmed in the last paragraphs which are 

quoted here:

The geochemlcal action of water is determined by the presence of glauconite. Glauconite is essentially a hydrated 

alumino-silicate with heavy potassium contents, the structure 

of which is suited to base-exchange.

When crossing the molasse or calcareous formations, the 

water becomes charged with electrolytes, particularly calcium salts. In contact with the glauconite, the fixation of 

Ca++ ion and the liberation of alkaline ions occur, which fix 

the water at pH9. The alkalinized water acts as a peptising 

agent on the collodial micelles and hydrolyses [hydrolyzes]
CURRENT SLUMPING 21

FIGURE 22. View toward east showing tilted inner surfaces 

of block B 4 where slumped down from block B 3. (right 

of photograph). Notice that trees are tilted scarpward, 

illustrating rotational nature of the block; some vines 

appear to be stretched taut.

the alumino-silicates, so that the permeability increases by 

putting back in suspension particles which are carried along 

by the water, and by the solubilization of the silicic ion. The 

marl bed gradually loses its rigidity and then slides. The 

undercutting at the base of the cliff provokes its periodic 

collapse.

The same area was discussed 2 years later by 

Drouhin, Gautier, and Dervieux (1948). These 

authors reached a conclusion similar to that reached 

by Proix-Noe, but perhaps stated more clearly and

explained in greater detail. They outlined the stratigraphy (p. 104) as an ancient massif of shale and 

gneiss overlain by sandstone, which in turn is overlain by marl containing glauconite and capped by a 

calcareous molasse, containing "extensive cracks or 

pockets due to dissolution, and generally filled with 

red clay, resulting from decalcification." The history 

of the landsliding is described (p. 105) as "segregation of huge blocks of mollasse [cap rock] as a consequence of dissolution, perforation of the [underlying] altered marl by these blocks which then drift 

away very slowly without toppling over."

The authors further noted (p. 105) that "the 

origin of the phenomena, namely the progressive destruction of the mollasse, had not been explained up 

to now. Why did the marl not support the mollasse 

and why did the blocks, once segregated from the 

cliffs, drive [down] through the marl?" They found 

(p. 105) near the front of the cliff "a decompression 

of the marl beneath the mollassic table," and that 

only 500 to 700 m back from the front of the cliff 

was the "marl in its normal state of consolidation 

with a compaction in keeping with the load of the 

supported soils [molasse cap].

The decrease of the pressure [decompression] is 

due first to the water supply of the marl resulting 

from the mollassic infiltration and direct runoff."

Glauconite plays an important part in accelerating the 

process. Glauconite is found in the upper layers of the marl, 

underlying the mollasse. This mineral, iron and potash disilicaite of variable composition, is an actual permutite which 

replaces in the ground water the ion Ca [calcium] by the 

ion K [potassium] through simple contact, and with a strong 

increase in pH * * *

Water, thus alcalinized results in the defloc[c]ulation of 

the marl, which is partially put into suspension in the shape 

of a colloidal gel passing the filters, and which is progressively carried away.

* * * Washed away substances are replaced by water. 

The water content of the marl increases and its mechanical 

characteristics decrease steadily and eventually reach those 

of a highly viscous liquid.

Thus transformed the marl slides * * * *

In conclusion, the authors of these three papers 

appear to believe that glauconite directly contributes 

to landsliding. Benson emphasized physical characteristics, the others chemical. Stated concisely, the 

two papers on Algiers Bay suggest that because 

of the chemical nature and action of glauconite in 

the ground water, dissolution and removal of solid 

material in the marl layer occurs with an increase in 

water content, hence a marked decrease in ability 

to support the overlying rock strata.

Abundant glauconite is present in the formations 

in the bluffs along Sandy Hook Bay, not only in the
22 SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

lower formations cited in the first part of this section, but also in the upper strata, particularly the 

Hornerstown and Vincentown. Emphasis, however, 

is on the lower formations because of the greater 

static load on them. Drouhin, Gautier, and Dervieux 

(1948, p. 106) noted that where the soil was saturated in the area of their report, the stress limit [of 

apparently the marl] was exceeded if the height of 

the cliff [overlying molasse] reached about 20 m.

The bluffs along Sandy Hook Bay near Waterwitch are about 60 m high above the Navesink 

glauconite. Also, abundant ground water seeps from 

the bluff at and above this level, after having passed 

through thick beds of calcareous shell material. If a 

major rotational slump should occur here, houses on 

the flat area at the base could be endangered by 

thousands of tons of material moving a considerable 

distance out from the base of the bluff, as occurred 

when block A slumped.

Drouhin, Gautier, and Dervieux (1948, p. 104) 

suggested that if a large block (4,000 m3 ) that broke 

from the cliff at Algiers Bay had tilted and slid, instead of driving itself down into the underlying material, an entire residential area would have been 

destroyed.

SUMMARY

Slump blocks were mapped in the bluffs along the 

south side of Sandy Hook Bay and along the north 

side of Navesink River by the author in 1963-64.

Since about the summer of 1972, renewed slumping has been observed in former slump blocks and in 

adjacent areas. In the present study, I have attempted to map not only all definite slump blocks, 

but also probable and possible slump blocks and to 

indicate other related features such as possible 

joints and zones of weakness. As many as 9 to 12 

slump blocks may be present, and several of these 

have 1 to possibly 5 subsidiary blocks.

Slumping in this area is to be expected because 

hills are high, bluffs are steep and commonly border 

bodies of water, material is chiefly unconsolidated, 

the water table is well above adjacent sea level, and 

lateral seepage and sapping are common along the 

lower slopes of the bluffs. Slumping here appears 

similar to that along the north shore of Long Island, 

except that much of it may be older than that visible 

on Long Island where scarps are still fresh. This 

apparently is because the bluffs in the Atlantic 

Highlands area presently are more protected from 

erosion by open ocean waves than the bluffs along 

the north shore of Long Island.

Much slumping on Long Island occurred in or 

involved clays of Cretaceous age (Fuller, 1914, p. 

67, 71), probably equivalent to the Magothy Formation (Minard, 1969, pi. 1) and older. Slumping in the 

bluffs along Sandy Hook Bay appears to have occurred or originated mostly in the clayey lithologic 

units such as the Mount Laurel Sand, Navesink 

Formation, and Sandy Hook Member of the Red 

Bank Sand (Minard, 1969, p. 36). All these units 

have 20-40 percent clay (table 2) and 15-70 percent glauconite (Minard, 1969, p. 12, 14, 17).

Ideal conditions are present for slumping in the 

Mount Laurel, Navesink, and Sandy Hook Member 

because of the thick Cohansey and Shrewsbury sands 

above to allow rapid infiltration of water during excess rainfall, the clayey sediments below to impede 

infiltration and migration at depth and cause the 

water table to rise above its normal level, a high 

water table to increase pore water pressure and decrease intergranular friction, and a thick stratigraph: c section to provide a heavy static load.

Although probably slump susceptible, the Hornerstown has much less static load than the Mount 

Laurel, Navesink, or Sandy Hook Member, thus reducing its slide potential in much of its outcrop.

Present slumping is causing considerable damage 

to private homes and property and, as a result, is 

of much concern to these people and other residents 

liable to be effected by any additional slumping.

In addition to slumping, erosion along the faces 

of the bluffs has removed quantities of material, 

leaving bare soil material and formations exposed, 

'llustrating the steepness and unstable nature of the 

slopes. This surface erosion is visible as many gullies 

and sheet-erosion scars.

The current slumping apparently came as a surprise to many people. Although erosion was known, 

few realized the slump history of the bluffs, partly 

because they had not read the limited amount of 

literature on the subject (Barber and Howe, 1844? 

Cook, 1868; and Minard, 1969.) and partly because 

there has not been much recent slumping. Evidence 

for much of the slumping has to be interpreted from 

the present form of the land.

The cause for the present slumping has been variously attributed to prolonged heavy rains, driving 

of pilings, and excavating for a sewerline near the 

toe of the bluff. Certainly the prolonged heavy ra^ns 

and resultant rise in the water table and pore pressure are cogent factors to consider. The pile driving 

apparently predated noticed movement by some time. 

Studies were and are being made by engineers to 

determine whether, construction of the sewerline
SUMMARY 23

may have had any effect on the slumping.

First cracking of the ground and structures seems 

to have been noticed during the summer of 1972. 

The concrete steps (fig. 16) were reported to have 

cracked sometime between late fall 1973 and January 1974. Woodward, Moorhouse, and Associates, 

who are monitoring lateral movement of the sewerline, have reported continued movement towards the 

bay (oral commun., June 7, 1974).

CONCLUSIONS AND RECOMMENDATIONS

It appears that the entire bluff along the south 

side of Sandy Hook Bay for a distance of about 

6.5 km (4 mi) 5 from near Atlant'c Highlands Yacht 

Harbor, and south into the mouth of Navesink River, 

is an area of possible geologic hazards, principally 

in the form of slump blocks and landslides. The fact 

that slumping and large-scale earth movement have 

begun again, after many years (perhaps centuries) 

of comparative or seenrng inactivity, should be a 

matter of concern to all in the area affected or 

liable to be affected.

It seems evident that careful thought, planning, 

investigations, tests, and analyses should be undertaken before construction is begun in any areas on 

definite slump blocks, probable or possible slump 

blocks, along zones of weakness, or near the edges 

of the tops of any of the high, steep bluffs. Included 

in such precautionary measures should be avoidance 

of the removal of material from the toes of possibly 

critical slopes, prevention of excessive water infiltration in the ground in critical areas, and avoidance of excessive loading on upper surfaces in these 

areas.

Several slump blocks have depressions on their 

inner upper surfaces. The absence of standing water 

or appreciable quantities of aquatic vegetation indicates fairly rapid percolation into the ground.

During heavy rains such areas could serve as conduits for excess water entering the ground, thereby 

raising the water table to possibly critical heights 

(and pore water pressures) as the lower less permeable strata force some water to migrate laterally and 

seep from the ground in zones along the lower 

slopes. The open vertical conduit (fig. 10) observed 

on block A indicates the high permeability and caving characteristics of the upper loose sandy material.

The possibility of earthquake tremors triggering 

slumping was considered. If a tremor of sufficient 

intensity coincided with a condition of high pore 

water pressure and loss of intergranular contact 

through liquefaction large masses of sand could 

"go quick" (lose strength), resulting in rapid downdropping of blocks or masses of earth. No quakes 

were recorded in the area during 1972. Quakes of 

noticeable intensity were recorded near Long 

Branch, N.J., in 1927, about 30 miles northwest of 

New York City during 1953-66, and near Camden, 

N.J., in February 1973. The last quake had an intensity of V (MM) at Asbury Park, N.J., about 20 

km (12 mi) south of Atlantic Highlands.

Besides the precautions suggested earlier in this 

report to prevent slumping, additional act'on may 

be taken, primarily to remedy an already critical 

situation that exists on blocks B 1, B 2, B 3, and B 4. 

If adequate berms or seawalls were constructed at 

the toes of the slopes, much material eroded from 

above could be held at the toe to provide additional 

support. Buttressing the toe with much additional 

earthfill and riprap would help provide further support, especially if the material were placed in back 

of the protective wall. Adequate surface and subsurface drainage should be provided to prevent a rise 

in the water table.

These measures should be considered not only 

for the areas slumping at present, but also for present and intended sites of heavy construction.

GLOSSARY

Alkaline. Having basic properties, as opposed to acidic. 

Barrier bar. Elongate sand ridge rising above high-tide level

and generally parallel to the coast, but separated from it

by a lagoon or marsh. 

Base failure. A landslide or slump in which failure occurs

along a surface that passes at some distance below the toe

of the slope.

Colloidal. Any substance in a certain state of fine division in 

which the particles range in diameter from about 0.2 to 

about 0.0005 micron.

Decalcification. The lack or removal of calcareous material.

Deflocculation. To break up clumps and aggregates into fine

particles synonym of peptize. 

Electrolyte. A substance in which the conduction of electricity

is accompanied by chemical decomposition. 

Feldspathic. Containing feldspar as a principal ingredient;

feldspar is a group of rock-forming minerals basically

potassium, calcium, sodium, aluminum silicates. 

Glauconite. A generally green mineral essentially a hydrous

potassium iron silicate. 

Hydrolysis. Chemical decomposition involving the addition of

the elements of water.
24 SLUMP BLOCKS IN THE ATLANTIC HIGHLANDS OF NEW JERSEY

Hydrolyze. To subject to, or undergo, hydrolysis.

Intensity of V (MM). Earthquake tremors strong enough to 

be felt outdoors. Some liquids spilled. Small unstable articles displaced or upset. Doors swing, Sleepers awakened.

Ion. An electrically charged atom or group of atoms. In 

electrolysis, the negative ions (anions, containing an excess of one or more electrons) move toward the anode, 

whereas the positive ions (cations, deficient in electrons) 

move toward the cathode.

Joint. A fracture or parting in a rock or rock mass.

Lineament. A line or linear feature especially visible on 

aerial photographs, that reveals the hidden architecture of 

underlying rocks.

Liquefaction. The process of liquefying or reducing to a 

liquid or near-liquid state.

Marl. Calcareous clay.

Massif. A mountainous mass more or less clearly marked off 

by valleys and having relatively uniform characteristics.

Micelle. A unit of structure built up from complex molecules 

in colloids. It may have crystalline properties and can 

change size without chemical change.

Micron. A unit of length equal to one one-millionth of a 

metre.

Molasse. Soft green sandstone with marl and conglomerates. 

Detritus worn from elevated ranges during and immediately after the major diastrophism and deposited in the 

foredeep.

Peptize. To bring into colloidal solution; to convert to a sol.

Permutite. Capable of being changed.

Piezometric surface. An imaginary surface that everywhere 

coincides with the static level of the water in the aquifer.

Point bar. A bar formed by sediment dropped on the inside of 

a growing meander loop or the slip-off slope of a river bend.

Pore water pressure. Pressure exerted by water in the pore 

spaces of the rock or sediment; the higher the water table, 

the greater the pore water pressure below.

Quick. Where grains become coated and separated by water 

and buoyed up by water pressure, hence semiliquid and 

easily moved.

Sag. Shallow basin; downwarping of beds near a fault caused 

by frictional drag and rotation.

Sapping. To undermine by removal of material such as sand.

Scarp. A steep surface on the undisturbed ground around the 

periphery of a landslide, caused by the movement of slide 

material away from the undisturbed ground.

Shearing. An action resulting from applied force which causes 

contiguous parts of a body or mass to slide relative to each 

other parallel to their plane of contact.

Silicate. A compound of any of the silicic acids.

Silicic. Containing silicon dioxide (such as quartz).

Slope failure. A landslide or slump in which failure occurs 

along a surface that intersects the slope at or above its toe.

Solifluction. Slow downslope flowage of masses of soil and 

waste saturated with water.

Solubilization. Causing to pass into solution.

Waste. Material derived from rocks or sediments by chemical

and mechanical weathering. 

Wasting. The process that produces waste.

REFERENCES CITED

Barber, J. W., and Howe, Henry, 1844, Historical collections 

of the State of New Jersey * * *: New York, S. Tuttle, 

624 p.

Benson, W. N., 1946, Landslides and their relation to engineering in the Dunedin District, New Zealand: Econ. 

Geology, v. 41, no. 4, pt, 1, p. 328-347.

Cook, G. H., 1868, Geology of New Jersey: Newark, N.J., New 

Jersey Geol. Survey, 900 p.

 1885, Annual report of the State Geologist for the

year 1885; Trenton, N.J., New Jersey Geol. Survey,

228 p. 

Drouhin, G., Gautier, M., and Dervieux, F., 1948, Slide and

subsidence of the hills of St. Baphael-Telemly: Internat.

Conf. Soil Mechanics and Foundation Engineering, 2d,

Rotterdam, 1948, Proc., v. 5, p. 104-106. 

Fuller, M. L., 1914, The geology of Long Island, New York:

U.S. Geol. Survey Prof. Paper 82, 231 p. 

Jones, F. 0., 1973, Landslides of Rio de Janeiro and the

Serra das Araras escarpment, Brazil: U.S. Geol. Survey

Prof. Paper 697, 42 p. 

Lang, S. M., 1961, Natural movement of ground water at a

site on the Mullica River in the Wharton Tract, southern

New Jersey: U.S. Geol. Survey Prof. Paper 424-D, p.

D52-D54. 

Minard, J. P., 1956a, Photogeologic map of the Emmett Wash

NW quadrangle, Coconino County, Arizona: U.S. Geol.

Survey Misc. Geol. Inv. Map, 1-192.

 1956b, Photogeologic map of the Tanner Wash NW 

quadrangle, Coconino County, Arizona: U.S. Geol. Survey 

Misc. Geol. Inv. Map, 1-193.

1969, Geology of the Sandy Hook quadrangle in Monmouth County, New Jersey: U.S. Geol. Survey Bull. 1276,

43 p. 

Proix-Noe, Marthe, 1946, Etude d'un glissement de terrain

du a la presence de glauconie: Acad. Sci. Comptes Rendus, v. 222, no. 7, p. 403-405. (Translated by S. H. Britt,

1949, Study of a landslide due to the presence of glauconite: U.S. Geol. Survey open-file rept., 4 p.) 

Reiche, Parry, 1937, The Toreva-blo<ck, a distinctive landslide

type: Jour. Geology, v. 45, no. 5, p. 538-548. 

Sharpe, C. F. S., 1938, Landslides and related phenomena; a

study of mass-movements of soil and rock: New York,

Columbia Univ. Press, 136 p. 

Strahler, A. N., 1940, Landslides of the Vermilion and Echo

Cliffs, northern Arizona: Jour. Geomorphology, v. 3, no.

4, p. 285-300. 

Varnes, D. J., 1958, Landslide types and processes, in Eckel,

E. B., ed., Landslides and engineering practice: Natl.

Research Council, Highway Research Board Spec. Rept.

29, p. 20-47.

* U.S. GOVERNMENT PRINTING OFFICE: 1974 O 583 469/43