Volcanic Islands
Although in some respects more technical in their subjects and style than Darwin’s “Journal,” the books here reprinted will never lose their value and interest for the originality of the observations they contain. Many parts of them are admirably adapted for giving an insight into problems regarding the structure and changes of the earth’s surface, and in fact they form a charming introduction to physical geology and physiography in their application to special domains. The books themselves cannot be obtained for many times the price of the present volume, and both the general reader, who desires to know more of Darwin’s work, and the student of geology, who naturally wishes to know how a master mind reasoned on most important geological subjects, will be glad of the opportunity of possessing them in a convenient and cheap form.
The three introductions, which my friend Professor Judd has kindly furnished, give critical and historical information which makes this edition of special value.
Rocks of the lowest series.—A calcareous sedimentary deposit, with recent shells, altered by the contact of superincumbent lava, its horizontality and extent.—Subsequent volcanic eruptions, associated with calcareous matter in an earthy and fibrous form, and often enclosed within the separate cells of the scoriae.—Ancient and obliterated orifices of eruption of small size.—Difficulty of tracing over a bare plain recent streams of lava.—Inland hills of more ancient volcanic rock.—Decomposed olivine in large masses.—Feldspathic rocks beneath the upper crystalline basaltic strata.—Uniform structure and form of the more ancient volcanic hills.—Form of the valleys near the coast.—Conglomerate now forming on the sea beach.
FERNANDO NORONHA.—Precipitous hill of phonolite.
TERCEIRA.—Trachytic rocks: their singular decomposition by steam of high temperature.
TAHITI.—Passage from wacke into trap; singular volcanic rock with the vesicles half-filled with mesotype.
Charles Darwin
Geological Observations on the Volcanic Islands
Contents
G.T.B.
VOLCANIC ISLANDS.
GEOLOGICAL OBSERVATIONS ON VOLCANIC ISLANDS.
JOHN W. JUDD.
(FIGURE 1: MAP 1: PART OF ST. JAGO, ONE OF THE CAPE DE VERDE ISLANDS.)
MINERALOGICAL DESCRIPTION OF THE ROCKS OF THE LOWEST SERIES.
THE EXTENT AND HORIZONTALITY OF THE CALCAREOUS STRATUM.
THE BASALTIC LAVA, SUPERINCUMBENT ON THE CALCAREOUS DEPOSIT.
SIGNAL POST HILL.
INLAND HILLS OF MORE ANCIENT VOLCANIC ROCKS.
VALLEYS NEAR THE COAST.
RECENT CONGLOMERATE.
FERNANDO NORONHA.
TERCEIRA IN THE AZORES.
EFFECTS OF STEAM ON THE TRACHYTIC ROCKS.
TAHITI (OTAHEITE).
MAURITIUS.
ST. PAUL’S ROCKS.
A GLOSSY INCRUSTATION.
(MAP 2: THE ISLAND OF ASCENSION.)
BASALTIC ROCKS.
VOLCANIC BOMBS.
AERIFORM EXPLOSIONS.
EJECTED GRANITIC FRAGMENTS.
TRACHYTIC SERIES OF ROCKS.
VEINS IN THE EARTHY TRACHYTIC MASSES.
SILICEOUS SINTER AND JASPER.
CONCRETIONS IN PUMICEOUS TUFF.
FORMATION OF CALCAREOUS ROCKS ON THE SEA-COAST.
A FRONDESCENT CALCAREOUS INCRUSTATION.
SINGULAR LAMINATED BEDS ALTERNATING WITH AND PASSING INTO OBSIDIAN.
FIRST.
SECONDLY.
THIRDLY.
FOURTHLY.
FIFTHLY.
LAMINATION OF VOLCANIC ROCKS OF THE TRACHYTIC SERIES.
BASALTIC SERIES.
BASAL SUBMARINE LAVAS.
FLAGSTAFF HILL AND THE BARN.
TURK’S CAP AND PROSPEROUS BAYS.
BASALTIC RING.
THE CENTRAL CURVED RIDGE.
SUPERFICIAL DEPOSITS.
BEDS OF EXTINCT LAND-SHELLS.
ELEVATION OF THE LAND.
COAST DENUDATION.
CRATERS OF ELEVATION.
(FIGURE 11. MAP 3. GALAPAGOS ARCHIPELAGO.
CHATHAM ISLAND. CRATERS COMPOSED OF A SINGULAR KIND OF TUFF.
(FIGURE 12. THE KICKER ROCK, 400 FEET HIGH.)
SMALL BASALTIC CRATERS.
ALBEMARLE ISLAND.
FLUIDITY OF DIFFERENT LAVAS.
CRATERS OF TUFF.
BANKS’ COVE.
JAMES ISLAND.
SEGMENT OF A BASALTIC CRATER.
PSEUDO-EXTRANEOUS, EJECTED FRAGMENTS.
CONCLUDING REMARKS ON THE TUFF-CRATERS.
MINERALOGICAL COMPOSITION OF THE ROCKS.
ELEVATION OF THE LAND.
DIRECTION OF THE FISSURES OF ERUPTION.
ON THE DISTRIBUTION OF VOLCANIC ISLANDS.
NEW SOUTH WALES.
STRATIFICATION OF THE ESCARPMENT.
CURRENT-CLEAVAGE.
VALLEYS IN THE SANDSTONE PLATFORMS.
VAN DIEMEN’S LAND.
TRAVERTIN WITH EXTINCT PLANTS.
ELEVATION OF THE LAND.
KING GEORGE’S SOUND.
SUPERFICIAL FERRUGINOUS BEDS.
SUPERFICIAL CALCAREOUS DEPOSIT.
CAPE OF GOOD HOPE.
SANDSTONE FORMATION.