Beagle Expedition (1831-1836); Coral reefs and islands; Geology -- South America; Islands; Volcanoes
Turning now to the red colour; as on our map, the areas which have sunk
slowly downwards to great depths are many and large, we might naturally
have been led to conjecture, that with such great changes of level in
progress, the coasts which have been fringed probably for ages (for we
have no reason to believe that coral-reefs are of short duration),
would not have remained all this time stationary, but would frequently
have undergone movements of elevation. This supposition, we shall
immediately see, holds good to a remarkable extent; and although a
stationary condition of the land can hardly ever be open to proof, from
the evidence being only negative, we are, in some degree, enabled to
ascertain the correctness of the parts coloured red on the map, by the
direct testimony of upraised organic remains of a modern date. Before
going into the details on this head (printed in small type), I may
mention, that when reading a memoir on coral formations by MM. Quoy and
Gaimard[6] I was astonished to find, for I knew that they had crossed
both the Pacific and Indian Oceans, that their descriptions were
applicable only to reefs of the fringing class; but my astonishment
ended satisfactorily, when I discovered that, by a strange chance, all
the islands which these eminent naturalists had visited, though several
in number, namely, the Mauritius, Timor, New Guinea, the Mariana, and
Sandwich Archipelagoes, could be shown by their own statements to have
been elevated within a recent geological era.
[6] “Annales des Sciences Nat.” tom. vi., page 279, etc.
In the eastern half of the Pacific, the _Sandwich Islands_ are all
fringed, and almost every naturalist who has visited them, has remarked
on the abundance of elevated corals and shells, apparently identical
with living species. The Rev. W. Ellis informs me, that he has noticed
round several parts of Hawaii, beds of coral-detritus, about twenty
feet above the level of the sea, and where the coast is low they extend
far inland. Upraised coral-rock forms a considerable part of the
borders of Oahu; and at Elizabeth Island[7] it composes three strata,
each about ten feet thick. Nihau, which forms the northern, as Hawaii
does the southern end of the group (350 miles in length), likewise
seems to consist of coral and volcanic rocks. Mr. Couthouy[8] has
lately described with interesting details, several upraised beaches,
ancient reefs with their surfaces perfectly preserved, and beds of
recent shells and corals, at the islands of Maui, Morokai, Oahu, and
Tauai (or Kauai) in this group. Mr. Pierce, an intelligent resident at
Oahu, is convinced, from changes which have taken place within his
memory, during the last sixteen years, “that the elevation is at
present going forward at a very perceptible rate.” The natives at Kauai
state that the land is there gaining rapidly on the sea, and Mr.
Couthouy has no doubt, from the nature of the strata, that this has
been effected by an elevation of the land.
Public-domain text, read in full here on John Shaqi.
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