The structure and distribution of coral reefs. Being the first part of the Geology of the voyage of the Beagle, under the command of Capt. Fitzroy, R.N. during the years 1832 to 1836 / [Charles Darwin].
- Charles Darwin
- Date:
- 1842
Licence: Public Domain Mark
Credit: The structure and distribution of coral reefs. Being the first part of the Geology of the voyage of the Beagle, under the command of Capt. Fitzroy, R.N. during the years 1832 to 1836 / [Charles Darwin]. Source: Wellcome Collection.
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![the island underwent a movement of subsidence, during the earthquakes lately felt there. The facts stand thus;—there are many large tracts of ocean, without any high land, interspersed with reefs and islets, formed by the growth of those kinds of corals, which cannot live at great depths ; and the existence of these reefs and low islets, in such numbers and at such distant points, is quite inexplicable, excepting on the theory,- that the bases on which the reefs first became attached, slowly and successively sank beneath the level of the sea, whilst the corals continued to grow upwards. No positive facts are opposed to this view, and some general considerations render it probable. There is evidence of change in form, whether or not from subsi- dence, on some of these coral-islands; and there is evidence of subterranean disturbances beneath them. Will then the theory, to which we have thus been led, solve the curious problem,—what has given to each class of reef its peculiar form? Let us in imagination place within one of the subsiding areas, an island surrounded by a fringing reef,”—that kind, which alone offers no difficulty in the explanation of its origin. Let the unbroken lines and the oblique shading in the woodcut [No. 4] A A—Outer edge of the reef at the level of the sea. B B—Shores of the island. A'A'—Outer edge of the reef, after its upward growth during a period of subsidence. C C—The lagoon-channel between the reef and the shores of the now encircled land. B' B'—The shores of the encircled island. N.B. In this, and the following wood-cut, the subsidence of the land could only be represented by an apparent rise in the level of the sea.](https://iiif.wellcomecollection.org/image/b29331213_0116.jp2/full/800%2C/0/default.jpg)
