Memoirs of Bulletin of Museum of Comparative Zoology 28

MEMOIRS
OF THE

MUSEUM OF COMPARATIVE ZOOLOGY
AT

HARVARD

COLLEGE.

VOL. XXVIII.

^CAMBRIDGE, U.S.A.
PRINTED FOR THE MUSEUM.
1903.


University Press

:

John Wilson and Son, Cambridge, U.

S.

A.


CONTENTS.
REPORTS ON THE SCIENTIFIC RESULTS OF THE EXPEDITION TO THE
TROPICAL PACIFIC, in charge of Alexander Agassiz, by tlie U. S. Fish Commission

Steamer

Jefferson

F.

"Albatross,"

Moser, U.

Tropical Pacific.

B3'

S.

from

August, 1899, to

N., Commanding.

Alexander

Agassiz.

IV.

March,

pp. xxxiii., 410.

ary, 1903.

One Volume Text.

1900,

Commander

The Coral Reefs of the

Three Volujies Plates.

238 Plates.

Febru-



Itmoirs of tbc

Museum

Compratitre ^oologn

of

AT HARVARD COLLEGE.

Vol. XXVIII.

REPORTS ON THE SCIENTIFIC RESULTS OF THE EXPEDITIOM
THE
TROPICAL PACIFIC, IN CHARGE OF ALEXANDER AGASSt0, BY TIHE
U. S. FISH COMMISSION STEAMER " ALBATROSS," FROM AX^GUST,
1899, TO MARCH, 1900, COMMANDER JEFFERSON F. MOSER, U. S. N.,
COMMANDING.
ii-Gi

IV.

THE CORAL REEFS
OF THE

TEOPICAL PACIFIC.
By

ALEXANDER AGASSIZ.

WITH TWO HUNDRED AND THIRTY-EIGHT PLATES.

TEXT.

[Published by permission of

George M. Bowers, U.

CAMBRIDGE,
Prtntcti

for

tlje

February,

S.

U.

Commissioner of Fish and Fisheries.]

S.

A.

:

fHuseum.
1903.



;;

;

TABLE OF CONTENTS.
Introduction

XI

Page

The Marquesas,
Fig.

Plates 2, 3, 200, and

Page

Marokau and Ravahere, Plates

1

70,

figs. 1, 2; 201, 203; 204, fig. 5
Hao, Plates 67, 201, 203; 205, fig. 2
.

The Paumotds,

Plates 4-83, 201-207

The Paumotu

Plateau, Plates

.

Aki-Aki, Plates 68, 69, 201, 203

201,

234, and Figs. 1-12

Nukutavake, Plates

Rangiroa, Plates 4-19, 201, 202; 204,
figs. 3,

4; 205,

fig.

3

and Figs.

;

fig-

118
206,

;

120

3

The Duke

2-4; 201,

of Gloucester Islands

.

.

52

Nukutipipi, Plates 76, 77, 201, 203

54

Anu-Anuninga, Plates

Makatea, Plates 21-32; 201, 202;
and Figs. 7, 8
205, fig. 1

56

Anu-Anuraro, Plates 201, 203; 206,

64

202

;

204,

Matahiva,

4

fig.

Plates

202; 204,

fig.

20,

.

.

Niau, Plates 33-36, 201, 202

.

.

Apataki, Plates 37, 39

fig.

;

;

40,

.

.

1

68

Tikei, Plates 40,

2^;

figs.

71

Kauehi, Plates 45, 201, 203

Fakarava, Plates 46-50; 51,
fig.

1

;

201, 203; 204,

Anaa, Plates 51,

fig. 1

.

.

fig.

Tahanea, Plates 54, 55, 201, 203

.

The Raveskoi Islands

56, 57

;

....

58,

2

fig.

Raroia, Plates 201, 203

;

....
75,

Hikueru, Plates 201, 203

.

.

....

;

95,

fig. 1

;

140

fig.

1

208-210
91

;

;

.

156

6

210,

;

94,

fig.

4

;

202

;

157

fig. 1

90
90

Bora Bora, Plates 96,

91

Maupiti, Plates 104,

.

103, 202; 210,

98

202; 210,

Motu

109

Iti,

110

fig. 1

141

208,

Raiatea and Tahaa, Plates 93; 94,
figs. 1-3; 96, fig. 2; 210, fig. 2

99
'

2

202

fig-

85

131

135

fig.

fig.

fig.

;

The Cook

fig.

3

161

figs. 3,

4

;

105,

164
figs. 1,

figs.

2,

2; 202

165

3; 96,

202

166

Islands, Plates 106,

211; 212,

159

97-

3;

4

Plates 104,

Tetiaroa, Plates 95,

201, 203, 204

Tekokota, Plates 66, 201, 203

Mehetia, Plates 90,

Huaheine, Plates 92

4

fig.

130

2

Hereheretue, Pl.ates 79-83, 201, 203
The Society Islands, Plates 84-105,

84

94

Taenga, Plates 201, 203
Makemo, Plates 59-65

203
128

Murea, Plates 90,

;

201, 203, 205

78, 202,

fig. 1

76

90

Tepoto
Tuanake, Plates 201, 203

125

4

Tahiti, Plates 84-89. 202,

52, 53, 201,

;

203

Takume, Plates

74

2;
1,7

figs.

fig-

125

;

201, 202, 208-210

41-44,

201, 203

fig.

206,

;

201. 202

68,

206,

201,

1;

fig.

4

113
116

4

3,

Pinaki, Plates 72-75, 201, 203

33
figs.

.

71, 201, 203

2,

3, 5

Tikahau, Plates 20,

70, figs.

.

111

figs. 2,

5

fig.

1

;

1G8


CONTENTS.

Vlll

Page
Plates

Aitutaki,
212,

fig.

106,

211; 212.

1

fig.

213

;

171

The Tonga Archipelago,

3; 212,

180

.

.

Tongat ibii, Pl.ati's 115-118; 213-215
The Nomiika GroiiiJ, Plates 119, 214,
216

The Haapai Group,

The

The Ellice
212,

6-8;

222;

221,

204

flg.

129,

fig.

1

210

8; 221

Funafuti, Plates 129,
137, 221, 222; 224,'

212,

fig.

223;

figs.

212
229

2-6;

figs.

226,

307

fig.

Arbno, Plates 180,

figs.
fig.

1

3,

4;

figs.

182, figs. 1, 2; 225;

228,

Namorik, Plates 225; 226,
3,

232

Islands,

.

fig.

4

fig.

10

225,

229-

333
figs.

2-4; 225;

340

5

Ponapi, Plates

183,

342

188-190,

figs.

1

;

fig.

Nama, Plate 232
The Royalist Islands, Plates

223

226,

;

fig.

237

1

Plates 138,

1-3; 223; 226,

figs.

Maiana,
flg.

1

Plates
;

223

Tarawa, Plates 140,
144; 145,

fig.

fig.

6

figs.

figs.

240

140,

...

.

245

2-4; 141-

4; 223; 224,

Apaiaug, Plates 145,
224,

4;

fig.

fig.

...

fig.

5

.

247
252

Maraki, Plates 146-150, 223; 224,
flg.

253

3

Taritari, Plates
fig.

151-160, 223

;

224,

258

4

The Marshall
182,

figs.

2;

225;

226,

4-10; 227, 228
Jaluit, Plates 161-166; 167,
.

225;

226,

1-3; 228,

figs.
fig.

2

.

.

4-10;

.

.

fig.

227,

.

.

.

351

352
.

.

Namonuito, Plates 232
233, fig. 1
The Laurones, Plates 194-199; 232;
;

233,

figs. 4,

Guam,

Plates

fig.

271

353
363
365

5

194-198;

232;

233,

366

4
fig.

5

.

376

List of the Stations occupied by the

"Albatross"
San Francisco, Cal.,
Marquesas Islands
Marquesas Islands to
via

379
to

Nukuhiva,
379

Tahiti, Society

Northwestern

Pau380

Stations in vicinity of the Marquesas

Islands

2;

351

190,

moUis

figs.

.

3

4; 231, 232

Islands,

161-

Islands, Plates
1,

233,

fig.

Rota, Plates 199, 232; 233,

1-3; 223;

2

fig.

;

Truk, Plates 191-193, 231, 232

139,

;

2

fig.

139,

224,

;

4

fig.

;

350

236
1-3;

4

225, 230

Onoatoa, Plate 223

Apamama,

1-3;

342

Islands, Plates 182,

fig.

329

330

225, 229

fig.

321

3; 184-187,

fig.

Losap, Plates 232

figs.

.

1-3

figs,

236

138,

.

182,

Arorai, Plate 223

Plates

315

.

181;

225, 230

232

Tapeteuea,

2;

1,

Plates

183-193,

4;

233,

;

227,

303

228,

3

Andema

figs.

1-3

225;

The Seniavina Islands

Islands, Plates 138-160,

224,

...

8

fig.

3;

2,

figs.

174-177,

Pingelap, Plates 183,

3;

2,

221

6;

The Gilbert

...

fig. 1

Nukufetau, Plates 129,

130-

4;

fig.

171,

Kusaie, Plates 182,

212,

;

225;

296

Plates

172, 173, 225; 226,

figs.

210

170,

2

The Caroline

224,

fig. 1

Nurakita, Plates

fig.

4; 228,

Islands, Plates 129-137;

figs.

227,

169,

225; 227,

206

227,

295
Plates

178-180,

.

225;

fig. 1

fig.

220
.

;

Wotje, Plates

197

126, 127, 220

293

fig. 1

192
195

1;

fig.

5

fig.

Likieb, Plates

...

Fiji Islands, Plates 126-128,

Kambara, Plates

171,

188

Plates 217, 218

Vavau, Plates 120-125, 219

168;

Plates 167,

Rongelab,

122,

4: 213, 214

fig.

226,

;

Kwajalong,
175

111-114;

Plates

Island,

fig.

Plates 111-

213-219

125,

225

Namu,

3; 107-110;

figs. 2,

Page
Ailinglap, Plates

1G9

2

NiuK, Plates 106,

Eua

211;

1;

fig.

380

Stations from the Marquesas to Ran-

figs.

279

Siroa

380


CONTENTS.

IX

Page

Rangiroa to Tikahau and

to

Mata-

hiva

Matahiva

Hereheretue

381
to

Makatea and

382

Islands, the

.

383

Island

.

.

383

.

.

Tahiti Island

Through the Paumotu Archii^elago
Tahiti to Makatea, via Tetiaroa
Makatea to Apataki, via Niau
Apataki to Tikei
Ngarue Pass, Fakarava, to Takume,

via Anaa and Talianea
Takume to Makemo, via Raioia and
Taenga
Makemo to Hikueru, via Tekokota
Hikueru to Hao, via Marokau and
Ravahere
Hao to Aki-Aki
Aki-Aki to Piuaki, via Nukutavake

....
.

.

Pinapi to Nukutipipi

383
383
383
385

385

From

388

Tahiti to the

Leeward Society

Islands

388

From Aitutaki to Niue
From Niue to Eua (Touga)
Vavau to Fiji
Fiji

388

....

388
389

to Jaluit, Marshall

Archipelago

.

385

Through the Marshall Archipelago

Marshall Islands through the Caro-

387

lines to

Guam, Ladroues, and

Yokohama, Japan
Through the Carolines
Namouuito to Guam

389

390

Taritari to .Jaluit

386
386

388

through Ellice and Gilbert Islands

From

Nukutipipi to Ilereheretue, via Anu.

Page
387

Cook Group, and Nine

In Fiji Archipelago

386

.

.

Archipelago, via Leeward Society

to Papiete,

Anuruuga and Auu-Auuraro

Mehetia
Society Islands to Tongatabu, Tonga
to Tahiti, via

.

390

to

391
391

392

INTHODUCTION.
While

in charge of the expedition of the United States Fish

Steamer "Albatross" during the winter of 1899-1900 we

Commission

visited tlie coral

reef districts of the tropical Pacific, with the exception of the Sandwich, the

Samoan

Islands,

The Hawaiian Islands

and the Galapagos.

I

had explored

on former occasions, and had also obtained a bird's-eye view of the reefs of

Samoa on my way

has thus been

It

examine the Great Barrier Reef

to

my

of Australia.

good fortune

to observe the structure of the great

and

coral islands of the tropical Pacific,

majority of the coral reefs,

atolls,

and to have the benefit of the excellent charts published since the days of

Darwin and Dana.
derived from

One cannot overestimate

recent surveys in studying groups of coral islands like the

The

Fiji or the Society Islands.

amount
and

of information

charts and " Sailing Directions " contain an

which no one individual could hope

publication

their

the great advantages to be

has made

it

to bring together,

possible for an observer

immense area and obtain within a reasonable time an

'

to cover

insight

an

into the

structure of the coral reefs of an oceanic realm like the Pacific.

In this, as in preceding Reports, I have limited myself to an
sition

and explanation

districts

of the observations

made

examined, and have only made such

various groups

as

seemed

essential

expo-

in each of the coral reef

comparisons between the

to the proper

understanding of the

Report.

These investigations on coral reefs date back to 1877; they have

now

covered the principal coral reefs and islands of the Pacific, the West Indies,

and the Indian Ocean.
limited

to

The

earlier

reports were mainly descriptive, and

statements that the facts observed

did not seem to confirm

Darwin's theory of the structure and formation of coral

reefs.

As

the

work


INTRODUCTION.

xii

was extended the subject proved
pected by previous investigators.

far

more complicated than had been

The

sus-

explorations were not continued for

the sake of proving Darwin to be wrong, as seems to be the impression of

some

my

of

critics.

engrossing, and

own

it

Year

after year the subject of coral reefs

was studied

for its

own

sake.

had no theory of

I

as a guiding star, nor did I attempt to uphold

became more

any one

my

of the theories

on coral reefs advanced since the publication of Darwin's " Structure and
Distribution of Coral Reefs."

An immense amount of information regarding the coral reefs and islands
of the Pacific may be found in the journals of missionaries, who have often
spent years at certain localities.
Some of the descriptions by Williams,
Whitmee, Gill, and Turner are remarkably accurate, and many of their illusmost interesting

trations

;

especially

instructive

are

voyages of English, French, and Russian navigators

the

reports

in the last

of

the

part of the

eighteenth and beginning of the nineteenth century, containing the

first

accurate charts of atolls, barrier and fringing reefs published.

A

number

journeys.

of independent travellers

The voyage

of the

'•

have also published sketches of their

Blossom " under Beechey,^ of the

Beagle,"

'.'

and the United States Exploring Expedition under Wilkes, are memorable
Darwin's and Dana's reports on coral reefs and the geology of the

for

islands of the Pacific.

These expeditions have been supplemented by the surveys of the British

Admiralty and the French Hydrographic Bureau, as well as by several

minor expeditions

sent

out by the

United

States

Government.

Their

results include the publication of a series of excellent charts covering nearly
all

the oceanic island groups of the tropical Pacific, like those of

Tonga, of the Society Islands, and of many of the Line Islands
surpass

in accuracy the

;

and give us a very

earlier publications

Fiji, of

they far
different

idea of the structure of atolls, of coral reefs, both fringing and barrier,

from that obtained from data available

fifty

years ago.

Since the " Challenger " expedition, dating with the appearance of Murray's " Structure

An

and Origin of Coral Reefs

Darwin's theory of

excellent analysis of the results of Beechey's voyages by Ainsworth will be found in the

Journal of the Royal Geographical Society of London, Vol.
'^

" in 1880,'^

I.,

Proceedings of the Royal Society of Edinburgh, X., p. 508.

1831,

p.

193.


INTKODUCTIOX.

xiii

the formation of barrier reefs and atolls has been subjected to prolonged

Following Rein and Semper, recent investigators have, w^ith

criticism.

few exceptions, regarded

Pelew Archipelago have
far back as

it

Semper's investigations in the

As

hardl_y received the recognition they deserve.

1861 he spent nearly ten months

attention to the fact that

in the Pelews,*

and called

kinds of reefs (atolls, barrier and fringing

all

found in the Pelews, within a comparatively short distance,

are

reefs)

as untenable.

a region considered by Darwin as one of subsidence, and that at the

in

southern extremity of the group an elevated coralliferous limestone island

(Ngaur) rose to a height of over 300

man,

feet,

Semper

fossils of late tertiary age.

containing, according to Wich-

lays great stress on the effects of

currents between the land rim and the barrier reef in widening barrier reef

lagoons

He

;

further suggests that marine animals

growth

have described

reef platform lagoons such as I

of reef corals,

may

build

illustrate this well.

up a foundation

for the

from far greater depths than those at which corals

can thrive.

Semper
rial

fii'st

from an

ments

called attention to the effect of solution in

atoll,

but

it is

to determine the

to Sir

amount

tion of its importance as

John Murray

of lime

-

that

removing mate-

we owe

careful experi-

removed by solution and the sugges-

a factor in the formation of lagoons.

Semper

considers the effect of solution in removing lime from the lagoon of an

corals

in

To

by the growth

of

Dana was undoubtedly due the general acceptance

of

balancing

as

atoll

the

constructive

agencies

it.

Professor

Darwin's theory of the formation of coral
reefs

proved

reefs.

Dana's views on coral

were based upon the study of the coral reefs of Samoa, the Hawaiian

Islands, Tahiti, the larger Fiji Islands, seven of the islands in the

motus, of Tongatjibu, of Tapeteuea and Apaiang
of

in

Pau-

the Gilbert Islands,

Gente Herniosa, Fakaofu, Oatafu, Hull, and Enderbury among the Line

The publication

Islands.

Darwin's theory could not

of his results in
fail

to supply a

1849^ supporting

in the

mass of evidence wanting

main
in the

Report of Darwin's researches, based as they were upon the survey of the
^

2
^

Die Natiirlichen Existenzbedingungen d. Tliiere, Leipzig, II., 1880, p. 39.
Proceedings of the Royal Society of Edinburgh, XVII., 1889-90, p. 79.
Geology of the United States Exploring Expedition under Commodore Wilkes.


INTRODUCTION.

xiv

comparatively limited

of Keeling,

and Jukes thus seemed to include

demands

of

was

that

all

field

covered

that

since

time have greatly modified

A number

instances been opposed to Darwin's theory.

the

them

in the field,

of material

It is

and who have added

which has done

views so gener-

of explorers in recent years

have in nearly

unfortunate that so

has been written on the subject of coral reefs by persons

mass

by Dana

essential to satisfy the

have attacked limited areas, and their conclusions

reefs a

survey

which have arisen from a more extended study of the

ally held regarding their origin.

studied

Darwin's

Darwin's theory.

Tlie problems
reefs

and Mauritius.

The

Great Barrier Reef of Australia.

the

coral

Tahiti,

adopted by Jukes, who had just completed a

theory was also
of

field

all

much

who have never

to the bibliography of coral

little or

nothing towards the solu-

tion of the questions at issue.

may

It

not be out of place to sketch rapidly the characteristics of the

coral reef groups of the Pacific.

The Galapagos and Marquesas are not
^

In both groups corals are limited to restricted shore

reefs are concerned.

areas

;

of special interest as far as coral

they do not even form fringing reefs

shallow bays cut into volcanic
In the Sandwich and

;

they are mere patches in the

bluffs.

Samoan

Islands occur fringing reefs limited

certain parts of the larger volcanic islands

;

to

on the shores of other islands

they are either absent or reduced to mere patches.
In the Sandwich Islands, Lysan, Lisianski, French Frigate Shoal, Maro,

Hermes, Cure, and Midway Islands are

atolls

and coral

reefs scattered along

the chain of volcanic islets extending to the westward of Kauai.
coralliferous limestones occur along the southern

face of

Oahu.

Elevated

On

the

northern side ajolian rocks attain a height of twenty to twenty-five feet

and the fringing

reefs are underlaid

from which a reef
In

Samoa

flat

platform has been eroded.

extensive fringing reefs and barrier reefs occur on Upolu.

Savaii the east face
'

by a base of elevated tertiary limestone

is

flanked by barrier reefs.

At the Galapagos, during a deep sea expedition

importance regarding coral

reefs.

off

the

In

In Tutuila, as in the islands
Panamic

See also Darwin, Coral Reefs, p. 197.

district,

we found nothing

of


;

xv

INTRODUCTIOlSr.

named

above,

stretches

Rose IsLand

southern shores.
it

described

is

rock

such

as

is

by Wilkes

32, PI.

p.

along the

Samoan

Islands

he states that outliers of volcanic

;

An

reef.

given in Graeffe's Samoa, " Journ.

atoll is

occur

reefs

the only atoll of the

found upon the encircling

are

1873,

disconnected fringing

of

d.

sketch

excellent

Museum

Godeffroy," Heft

more than seventy

consists of

atolls,

many

great size and of elevated islands composed of coralliferous limestone.

of

The

have been cut down from the denudation and submarine erosion

atolls

of higher islands,

forming sounds or sinks surrounded at

subsequently cut into islands or

stages

successive

the

to

and

denudation

of

first

level

they

now

the

of

Pinaki, Nukutipipi,

Paumotu

atolls

The

occupy.

submarine erosion are represented

by such islands as Makatea, Niau, Rangiroa, Hao, and others.
easternmost

by high rims

with passes leading into the sounds,

islets

were reduced

the land rims

until

I.,

1.

The Paumotu Archipelago
low

the

of

diminutive,

are

Some

and such

of the

atolls

as

Anu-Anurunga, Anu-Anuraro are admirable epitomes

of the structure of the larger ones.

Some

of

the smaller of the

Paumotu

Islands have a central sink or

apparent depression formed by the closing in of a part of the summit of a
reef flat
flat

is

by beaches thrown up on the sea faces of the

somewhat below low-water mark a shallow lagoon

according to the height of the reef

be

filled

flat

If the island

islands.

a dry sink

may

is

formed, and

be enclosed, to

only during the rainy season.

The Paumotus

are flanked on

the east by

Manga Rev^,

a cluster of

volcanic islands encircled by a barrier reef, and on the west by the Society

This group

Islands.

volcanic

islands

barrier reef

flat,

is,

with

may

reefs,

of

Tetiaroa,

composed

The fringing

noted for their great breadth

;

and western coast show admirably how a wide fring-

gradually become gouged out into a barrier reef edging a

of the Society Islands the islands

continuous

reefs

on Tahiti the

shallow lagoon, and ultimately a wide and deep barrier reef lagoon.

some

of

edging often a very wide

enclosing a lagoon of moderate depth.

reefs of the northwest

reef

exception

surrounded by barrier

of the Society Islands are also

ing

the

belt,

On

on the barrier reef form a nearly

covered with a luxuriant growth of cocoanut trees and


INTKODUCTIOlSr.

xvi
of

low bushes, separating the barrier reef lagoon from the

and denudation have been great factors

Erosion

sea.

in shaping the volcanic slopes of

the islands of the group, and the wide platform on which the encircling
reefs

have obtained a foothold has been cut by submarine erosion.

In the Paumotus there

coralliferous limestone

the reef

flat

;

is

a great development of buttresses of tertiary

they run across the beaches of the sea face and of

platforms, and are the last remnants of the former elevated

land once covering a large area of the

atolls.

In the Ellice and the Marshall Islands, and some of the Gilbert Islands,

we

modern

find similar buttresses of

In the Gilbert Islands we find buttresses of both

an elevation

of a

modern and

tertiary limestone, as

We

few

feet.

and conglomerate indicating

reef rock

we

also do in the

should remember the existence of

many

Paumotus and

Fiji.

reefs, elevated to a

few

feet

only, where the elevated mass consists of recent reef rock material or of

These reefs are not to be confounded with

recent conglomerate or breccia.

elevated coralliferous limestones

been

lifted to

a moderate height only and

may have

age, though they

tertiary

of

may

also constitute the under-

lying base of the elevated modern reef rock.

In the Paumotus, as in other groups like the Marshall, Ellice, and Gilbert, the

We may

width of the land rim varies greatly.

that a part of the land rim
larly be built
to be swept

is

built

up from the lagoon

up on the sea

side

where the

state in general

face, a part

may

simi-

enough

atolls are large

by the trades, or the land rim may be increased simultaneously

both on the lagoon side and the sea face.

may

Finally the land rim

widened by the material blown or swept over

it

be

from the sea face towards

the lagoon side, the latter process rapidly filling small lagoons, or in larger
atolls shoaling the lagoons

extensive

flats

and restricting their area by the formation

on the lagoon side of the land rim

;

or, as in

some

of

of the

Marshall Islands, the sand dunes of the lagoon face are blown over the land

rim and encroach upon the outer reef

due to the solvent action of the
the land rim, and

we

sea,

flat

platform.

Add

to this the changes

both on the sea face and lagoon side of

get an idea of the complicated factors at

work

in

maintaining an equilibrium between the destructive or constructive agencies
acting on the land rim of an atoll.

Any one

of these factors

may

obtain


;

mTRODUCTION.
the preponderance

according

xvii

thus in adjoining atolls different results

;

to the conditions

which

may

take place,

The above

mastery.

oljtain the

factors

are at work in the Paurnotus upon plateaus of elevated coralliferous lime-

stone cut

down towards

the level of the sea, while in other groups where

nature of the underlying plateau

the

known, they are at work

not

is

upon a land rim of modern reef rock, or modern conglomerate or breccia.

The bottom deposits on the deep parts
or

atolls

groups of atolls in

of

the

great

of

the

northern

clay belt, covering

red

Paurnotus and

and

the

central

the

ill

Gloucester Islands line,

the extension

surrounds

Pteropod

the

and

of

this

and

Marquesas
coral

finally

There

clay into

red

passage

its

sand

ooze

char-

in

islands are extensions

the

main

the

of

belt

and a similar trough sepahowever, a marked

is,

differ-

volcanic bottom

the

the

into

developed

is

the

trough lying to the southeast

Paurnotus between

rating the Paurnotus and Marquesas.

ence

separating

Paurnotus are truly oceanic

the

The many and wide passages dividing the

acter.

ocean

the

of

which

globigerina-ooze

round

the

Paumotu

Islands in shallower water.

of

The Cook Archipelago

consists of volcanic islands with encircling reefs,

elevated

limestone islands and of

coralliferous

lying base of which

is

The elevated

not known.

platforms formed by submarine erosion

flat

rises

some

under-

the

narrow

reef

of the elevated islands

a small independent plateau between the Cook Islands and

Tonga

the island of Nine, also composed of elevated coralliferous limestone.

The
row

atolls,

islands have

and partly limestone.

are partly volcanic

On

;

low

Tonga and

elevated limestone islands of

reef platforms

;

its

by nar-

these are not continuous and occur only on parts of

the islands where the sloughing

platform which in

Fiji are flanked

of the

off

terraces has formed a shore

turn has been subject to submarine erosion.

On

this

platform corals have established themselves, usually as fringing reefs.

The Tonga Archipelago
liferous limestone, greatly

consists of an extensive area of elevated coral-

denuded and eroded.

At the two extremes

plateau land masses of considerable extent have been elevated

mass, Tongatabu,

is

greatly indented at

its

;

the southern

northern face and forms the

The northern land mass, Vavau,

southern face of an ill-defined lagoon.
b

of the

is

cut


INTRODUCTION.

xviii

Both the northern and southern

numerous islands and sounds.

into

The Haapai group

are terraced.

low islands on the east

Tongatabu

to the north of

flanked with

is

Noinuka group we

face, while in the

islands

find elevated

coralliferous limestone islands as well as volcanic or limestone islands

where

volcanic outbursts have pushed through the limestone mass.

The bank

of which

Eua

Island

height of over 1000 feet and

is

is

summit has been elevated

the

separated from Tongatabu by a channel

a greatest depth of not more than 108 fathoms

of

marine plateau

to

the south of

to a

;

a part of

the

sub-

Tongatttbu extends as far as Pylstaart.

The banks forming the greater Tonga Plateau

are sepai'ated by water of

a considerable depth, from 200 to 300 fathoms.

A

line of volcanic islands runs parallel

Two

with the Tonga Plateau.

of

summits, Falcon Island and Metis Shoal, are of great interest, as they

its

may

both perhaps indicate the depths to which the action of the sea

shaping platforms of submarine erosion.'

in

attained a height of 250 feet

;

it

now forms

Falcon Island at one time

a breaking shoal

Metis Shoal,

;

with a depth of fifteen fathoms, was once an island, reputed at

first,

in

which the action

of

1875, to be twenty-nine feet high, subsequently raised to 150

Admiral Wharton^ has suggested that the depth
the waves reaches

may

extend

to

feet.

be indicated by the change of slope generally taking

place off shore, below a depth of eighty to one hundred fathoms,

and further

that the existence of banks in the open sea at a depth of thirty to forty

fathoms

may

upon which they

act.^

He

an opportunity of testing
former

the

down a mass

be the limit of depth to which oceanic waves cut

site

of

we may have

also suggests that
this

in the future

by sounding the banks now forming on

Falcon and of

Metis Islands in Tonga since their

disappearance.

That such extensive submarine denunation takes place seems
1

^

Wharton, Sir J. W., " Nature," VI.,
Address to the Geographical Section

to

me

p. 611.

of the British Association, Oxford, 1896

;

" Nature," Feb-

ruary 25, 1897.
3

known that the effect
At the straits of Bernini

It is

depth.

of great oceanic currents like the Gulf
in

439 fathoms the bottom

is

Stream

swept clean, as

it

is

felt at consideral)le

also is to the north of

Jupiter Inlet along the east coast of the United States as far north as Cape Hatteras, and along this
stretch

tlie

Gulf Stream carries a certain amount of

wear the bottom very perceptibly. This is seen
" Tlirec Cruises of the Blake," Vol. I. p. 258.

in

sill

;

this

must act

the sections

and
Stream given in

like a hydraulic flume

across the Gulf


INTRODUCTION.

xix

abundantly proved from the great variety of submarine platforms formed

and of elevated limestone masses throughout

at the base of volcanic islands

platforms being fairly indicated by that

the depth of these

the Pacific,

by the encircling reefs or by that of the barrier

of the lagoons enclosed

reef lagoons.

The formation

huge masses of limestone

of

in

layers of corals or beds of reef-building corals

areas of subsidence,

— the

were

laid

down

more rapid

at a

at a depth greater

This process has nothing in

But when these

atolls.

I'ate

coralliferous masses of lime-

more than 1000

feet,

the resulting islands in the

must have represented either a bed deposited near the surface
liferous

and

— enclosing

comparatively modern

in

forming a capping of moderate thickness.

—

if

case

coral-

times, with

beds were subject to denudation

by the action of the

If

depth at which

sea.

corals

recent corals

In the second case, during each

stage of rest the elevated

the

first

perhaps a lagoon, or a sound, or a basin of solution

formed

erosion,

common

thickness were elevated either suddenly or intermittently

stone of great
to heights of

in

were deposited, and while the non-coral-

than that at which corals could grow.
with the formation of

must have taken place

subsidence taking place at a comparatively slow

rate while the coralliferous belts
liferous limestones

which occur at intervals

and erosion

each stage was an elevation greater than

can grow, the denudation and erosion

may

have continued long enough to cut the elevated limestone down, or nearly

down

to,

the

which marks the uprising of the mass.

terrace

may merely have gone

denudation and erosion
circumscribed

area

the action

to

of

far

thus connect what was the lagoon or basin at the

One can

readily see

when we take

how

enough to open the

some points only, and

the sea at

lagoon or basin or sound of the second stage of

Or the

first

sea-level with the

rest.

complicated the resultant action

may become

into account the varying height of the different stages of

elevation, the condition of the limestone

stones after the elevation,

and the action

mass and

of the coralliferous lime-

of denudation

and

of erosion

upon

such an elevated mass, as well as the solvent action taking place on the

summit and

sides,

basin, should

it

and

finally the eroding action of the sea

upon the interior

once break through the outer rim of the elevated basin or


INTRODUCTION.

XX
sink,

when

its

would thus form an entrance
to

This break

lowest point has reached the level of the sea.

much

as

is

formed the entrance

Should this mass be elevated a second, a third,

any lagoon or sound.

or a fourth time,

to the lagoon,

we may

find one, or two, or

more entrances

to the old

lagoons and sounds according to the rate of denudation and of erosion of
the elevated mass during the periods of rest.
Tlie coralliferous limestone rings

would be

a slow rate of denudation and erosion

and with a rapid rate

of the sea

more or

former ring

;

exterior

tlie

numerous, according

less

and

and

finally,

;

if

fairly

continuous in case of

broken through by the action

of denudation, only disconnected patches,

would indicate the

to the rate of erosion,

with a very rapid denudation and erosion, both of

interior face of the lagoon, or sound, nothing

left of the elevated

mass except the submerged

This becomes

reef-ring.

more complicated when the limestone mass, while

still

would be

elevated, has been

broken through by the underlying volcanic rocks, and they have displaced
portions

of

the coralliferous limestone beds and left

to the effects of

them more exposed

denudation and of erosion, especially when this action has

taken place on the outer face of the elevated mass, and
openings connecting the outer sea and

left

and

cuts

the interior basins, which would

The

thus soon be transformed into great sounds or lagoons.

erosive as

well as the solvent action of the sea would soon level the outer rim

to

the plane of the sea, the further disintegration being stopped by the growth
of recent corals or of coralline Alga3

upon the surface

of the coralliferous

or massive limestone eroded to the level of the sea or

more rapid

the

limestones

erosion

below

it.^

With

and denudation, both atmospheric and marine, the

would rapidly disappear, and there would be

left

only

the

volcanic mass which had uplifted them, with here and there a remnant of

the limestones to indicate the probable course of events.
the volcanic masses
conditions

are

much

Of

course,

when

come up without elevating any limestone beds the
simpler,

and

it

becomes only a question of the

According to Dana's views the existence of such foundations " only prove that, in coral seas,
grow over any basis of rock that may offer where the water is right in depth, and do not
nullify any of the evidence of subsidence" (Am. Jour. Scien., XXX., September, 1885, p. 181); yet
these very instances are advanced as supporting the theory of subsidence, and we may justly reply that
^

corals will

they have great interest as they arc opposed to the application of the theory of subsidence as explanatory of the formation of coral reefs in the areas where these rock bases occur.


INTRODUCTION.

mode

of

XXI

formation of the recent corals around the base of the elevated

volcanic mass.

Paumotus, of the

of continuity of the atolls of the eastern

The want

EUice, Gilbert, and Marshall Islands, their separation by considerable

dis-

tances and great depths, would seem to preclude the idea of the formation

The

over great areas.

tertiary limestones

of

existence of these discon-

nected and isolated limestone islands would suggest their formation upon
ridges elevated to very different heights below the surface of

mounds or

— the

the ocean,

elevated

ridges consisting of volcanic or other rocks

mounds and

by the

we know

agencies

volcanic

to

have been active over

very extensive areas of the Pacific from tertiary times to the present
In some of the Pacific archipelagoes the areas covered by the ter-

day.

tiary limestones are of considerable extent, as, for instance, the plateau of

the northwestern Paumotus, of

Tonga

the

Islands,

the eastern islands of the Fiji Archipelago rise

ward group
range

;

Islands, in

New

Dana very

or

Wind-

New

Hebrides,

Caledonia, in the China Sea, the East Indian

Archipelago, at Christmas Island

West Indian

Lau

were deposited must have been of wide geograph-

they appear in the Philippines, the Loyalty, the

and Solomon

the

the so-called

Conditions similar to those under which the central

of Fiji.

Pacific tertiary limestones
ical

:

and that upon which

the Indian Ocean, the

in

Red

Sea,

and

area.

justly remarks

:

" It

coral-reef era probably covered the

is

important to have in mind that the

whole of the Quaternary and perhaps the

Pleiocene Tertiary also, and hence the local elevations that have taken place
in the

ocean were not crowded events of a short period."

The boring

at Funafuti will

*

show us the character and age

of the rocks

underlying the mass of recent material of which the land rim, not only
of that atoll, but probably also that of the other atolls of the Ellice
of

neighboring groups,

composed

is

by analogy the probable character
the nearest islands where

reached
^

p.

Dana,

173.

1114

feet

;

it

it

though
of

of course

The bore

first

through

the

Reefs and Islands

Am/ Jour.

Scien.,

at

we can

only judge

the underlying base from

has been ascertained.

passed

J. D., Origin of Coral

;

that of

at Funafuti

modern
XXX.,

and

reef

rock

September, 1885,


INTEODUCTION.

XXli

material, and below that

must have, judging by analogy, penetrated

either

an underlying mass of tertiary limestone similar to that of the raised
limestones of

tertiary

Tonga,

Fiji,

Niue, Nauru, and Paanopa, or

have

passed through the mass of recent reef rock forming the outer talus of the
atoll

Funafuti.

of

means

give us the

rims

Groups

like the Ellice, Gilbert,

many modes

of studying the

as clearly the results of the various agencies at
less variations

produced in the islands and

different atolls of these groups

to the incessant handling

or

the

of

material

fresh

;

of formation of tlie land

Nowhere have we been

most satisfactory manner.

in a

and Marshall Islands

work

islets

shaping the end-

in

of the land rims of the

changes due either to slight elevation or

and rehandling of the older material

added from the disintegration

lagoon faces of the land rim, or of the corals on
slopes.

able to follow

of

place,

in

the

sea

or

outer and inner

the

has been most interesting to trace the ever-changing conditions

It

which have produced so many variations

in

the appearance and structure

of the islands, islets, and of the land rims of the different groups.
It

is

most

of course

difficult to

dimensions of an atoll before
the surface
face

and

its

;

spreads laterally after

summit naturally becomes wider

talus

its

it

form an opinion regarding the original

may

as

it

having reached

approaches the sur-

be spread as a thin sheet or disappear entirely in

the deep waters adjoining an atoll.

The

Fiji

group consists of volcanic islands of elevated coralliferous lime-

stone islands and of islands partly volcanic and partly of limestone.

of the volcanic islands are of great size

Two

and flanked by wide barrier and

fringing reefs, as well as by belts of older elevated coralliferous limestone
of tertiary age

number

and by

stratified beds of the so-called soapstone of Fiji.

of the volcanic islands are surrounded

by encircling

A

reefs enclos-

ing lagoons of considerable depths.
In the
of over

shaped.
is

left,

Lau group some

1000

feet

;

of the elevated limestone islands attain a heiglit

they have a wide reef platform and are more or

In others the original limestone mass has disappeared
as in

Argo

for instance, to

show

its

;

less hat-

nothing

existence except a diminutive

limestone island on the outer belt of the encircling reef.

We

find all the intermediate stages

between a

solid

mass

of corallifer-


INTRODUCTION.

xxiu

ous limestone to one cut into separate columns or wedges surrounding a
central sound or
islets of

or less filled with

and

islands

limestone to one where the outer limestone masses or the islands

are reduced to a

minimum forming

by a barrier reef or by a

The

more

basin, or a basin

belt of

low

either an elevated central area encircled
islands.

by encircling reefs show a similar

surrounded

volcanic islands

gradation from islands with a flanking belt of fringing or barrier

reefs

enclosing a narrow lagoon, to islands with an extensive lagoon enclosed by

a barrier reef

or even to an atoll with a volcanic island on the outer

belt,

reef flat.

In the

Fiji as in the Society Islands, the

wider fringing reef

flats

often

pass gradually into barrier reefs with a narrow lagoon between the outer

The rotten condition

edge of the reef platform and the shore

line.

the inner part of a wide fringing reef

most favorable to

by solution or mechanically, and leads
which may, as
lagoons.

is

is

to the formation of

of

removal

its

narrow lagoons,

the case in Tahiti, become wide and deep barrier reef

The small number

of islands

and

in Fiji atolls contrast strongly with the

islets of

the outer barrier reef

well-wooded islands and

on

islets

the encircling belt of the Society Islands.

The

disintegration of the masses of corals growing upon a reef

is

due to

the boring Echini, Mollusks, Annelids, Crustacea, and sponges which infect

the larger masses

;

as these

become weakened they are torn

waves, and rapidly reduced to shingle.

The smaller fragments

off

by the

are then

still

further disintegrated by boring sponges and Algoe, and by attrition on the

wide reef platforms both of the sea face and lagoon side reduced
coarser, then to fine sand

and impalpable

silt

which may be carried

first

to

off in

suspension.

In addition to the mechanical destruction constantly going on, chemical
action takes place and sea water carries off in solution large quantities of

lime from the sea face, where

undercut faces of

smaller fragments of corals.

tion

trace the extent of its action

of masses of corals,

cliffs,

even to a greater extent

we can

;

The same

from the

and the rotten condition

of

action takes place in the lagoon

in every direction

we can

trace the effect of solu-

on the beach rock beaches, the conglomerate or breccia ledges, the


INTRODUCTION.

xxiv

patches of corals, the samples of the bottom, the slopes of the shoals or
ledges within the lagoon, all showing that solution

removing carbonate of lime from the

The

Ellice, Gilbert,

movement

a prominent factor in

interior of a lagoon.

and Marshall Islands represent

of the material

With the exception

is

of a

forming the land rim

few

we

the characteristic feature.

is

the Gilberts where the old tertiary

atolls in

ledge cropped out on the land rim

which the

atolls in

did not observe the structure of the

foundation upon which the material composing the land rim of the Ellice
or of the Marshall Islands rested.

Wliile there

is

every indication that

the modern reef rock conglomerate or breccia which crops out on the islands
in every direction has

been elevated a few

feet,

yet

it

has not been

suffi-

ciently raised to expose the underlying rocks.

The formation

of the extensive Millepore

Taritari represents a stage of land

we

find

slopes

flats

described from

growth somewhat more advanced than

have occasion

are covered with thriving corals (generally

The formation

and Madrepores).

I shall shortly

to describe.

an

to the existence at the Maldives of
flats

flats

on some of the faros of the Maldives where the faces of the

it

and surface of the

Pocillipores

such

and Porites

as the Millepore

and Porites

I

of the flats at the Maldives

need here only

call

attention

earlier stage in the formation of
flats

of the Gilbert

and Marshall

Islands.

The

atolls of the Ellice, Gilbert,

extensive lagoon

flats, for

and Marshall Islands are noted for their

the formation of gaps, of bays, and of secondary

lagoons, where they take a greater development than in any other group of
coral reefs in the Pacific.

There are only a few small coral islands among

these groups which have no lagoons

Marshall Islands.
Gilbert,

The shape

of

and Marshall Islands, and

mythical typical circular atoll
Marshall

;

;

they are more numerous

the atolls varies greatly in
in

no groups

this is especially

is

among

the

the Ellice,

the outline less like the

marked

in the Gilbert

and

atolls.

The land rims

of these groups are narrow, but

nowhere

is

the land rim

reduced to such an insignificant width as in the Marshall Islands.

no important islands in any of the lagoons

;

There are

they contain shoals, ledges, and

sand keys, but no well-wooded islands, as in the Paumotus and

Fiji,

except


mTRODUCTION.

xxv

close to the lagoon edge of the land

rim where they form secondary lagoons.

Nauru and Paanopa

the Gilbert Islands are elevated corallif-

to the west

of.

erous limestone islands, rising to over 250 feet, similar to the elevated islands

Paumotus and

of the

We

Fiji.

noted in the Marshall Islands the large amount of sand blown into

Much

the lagoons from the sea face through gaps.
,

in suspension

part of

A

it

of this sand

and carried out through the passes on the

forms

spits

and

flats

part of the sand goes to

fill

lee side,

is

while a

near the gaps and passes of the weather
the lagoon

a part

;

carried off

is

held

side.

and reduces

the width of the land rim on the sea face.

The

Carolines are divided into high volcanic islands surrounded by fring-

ing, barrier,

and encircling

narrow encircling reef
on the weather

reefs,

flats

face, the

atolls

underlying foundation of which
islets

The southern
ined,

are

partly

not exposed and
flat

platform

In Ponapi the barrier reef fiats

any other volcanic island

in the Pacific.

islands of the Ladrones, the last

volcanic

is

surrounding reef

of the

consist of elevated coralliferous limestone.

are wider than round

with groups of islands reduced to

on which a few islands have been thrown up

where the islands and

atolls

low

group of islands we exam-

and partly composed

of

elevated coralliferous

limestone, while the northern islands are volcanic and have no coral reefs.

Guam or Rota; the reef
at Guam they take their

Coral reefs take but a slight development either in

platforms are narrow, irregularly scattered

flat

;

greatest development at San Luis d'Apra and along parts of the western

At San Luis d'Apra a deep

coast.

elevated coralliferous
of

limestone

Orote Point to Cabras

islands

composed

reef harbor has been eroded

which once jutted out to the north

flat

Island.

from the

Guam

is

one of

in part of coralliferous limestone

and

the

largest of

the

in part of volcanic

material.

We may
islands

approximately classify the

where

reefs are

atolls,

elevated islands, and volcanic

found into the following; categories:

Large volcanic islands with barrier and fringing

and Vanua Levu, the larger Samoan Islands,

New

Hebrides, and Sandwich Islands

;

in

New

reefs, like Tahiti, Viti,

Caledonia, the Solomon,

these the land mass occupies a

large area as compared with that of the reefs.

Viti

Levu and Vanua Levu,