Beagle Expedition (1831-1836); Coral reefs and islands; Geology -- South America; Islands; Volcanoes
SAMOA or NAVIGATOR GROUP.—Kotzebue, in his “Second Voyage,” contrasts
the structure of these islands with many others in the Pacific, in not
being furnished with harbours for ships, formed by distant coral-reefs.
The Rev. J. Williams, however, informs me, that coral-reefs do occur in
irregular patches on the shores of these islands; but that they do not
form a continuous band, as round Mangaia, and other such perfect cases
of fringed islands. From the charts accompanying La Peyrouse’s
“Voyage,” it appears that the north shore of _Savaii_, _Maouna_,
_Orosenga_, and _Mannua_, are fringed by reefs. La Peyrouse, speaking
of Maouna (page 126), says that the coral-reef surrounding its shores,
almost touches the beach; and is breached in front of the little coves
and streams, forming passages for canoes, and probably even for boats.
Further on (page 159), he extends the same observation to all the
islands which he visited. Mr. Williams in his “Narrative,” speaks of a
reef going round a small island attached to _Oyolava_, and returning
again to it: all these islands have been coloured red.—A chart of
_Rose_ Island, at the extreme west end of the group, is given by
Freycinet, from which I should have thought that it had been an atoll;
but according to Mr. Couthouy (“Remarks,” page 43), it consists of a
reef, only a league in circuit, surmounted by a very few low islets;
the lagoon is very shallow, and is strewed with numerous large boulders
of volcanic rock. This island, therefore, probably consists of a bank
of rock, a few feet submerged, with the outer margin of its upper
surface fringed with reefs; hence it cannot be properly classed with
atolls, in which the foundations are always supposed to lie at a depth,
greater than that at which the reef-constructing polypifers can live;
not coloured.
_Beveridge Reef_, 20° S., 167° W., is described in the “Naut. Mag.”
(May 1833, page 442) as ten miles long in a N. and S. line, and eight
wide; “in the inside of the reef there appears deep water;” there is a
passage near the S.W. corner: this therefore seems to be a submerged
atoll, and is coloured blue.
_Savage_ Island, 19° S., 170° W., has been described by Cook and
Forster. The younger Forster (volume ii., page 163) says it is about
forty feet high: he suspects that it contains a low plain, which
formerly was the lagoon. The Rev. J. Williams informs me that the reef
fringing its shores, resembles that round Mangaia; coloured red.
Public-domain text, read in full here on John Shaqi.
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