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I.—Subsidence and Elevation, and on the Permanence of Oceans

Published online by Cambridge University Press:  01 May 2009

Extract

The theory of permanent Continents and Oceanic basins, opposed as it is to the general teaching of text-books, seems to have given rise to comparatively little discussion. In the latest edition, for instance, of Lyell's Principles, we read: “It is not too much to say that every spot which is now dry land has been sea at some former period, and every part of the space now covered by the deepest ocean has been land.” The new theory has been upheld chiefly by Sir Wyville Thomson, Prof. Geikie and Mr. Wallace. The latter especially has collected every kind of evidence together that seems to support it in his latest, and most admirable work, “Island Life.” By a process of reasoning, supported by a large array of facts of different kinds, he arrives at the conclusion that the distribution of life upon the land, as we now see it, has been accomplished without the aid of important changes in the relative positions of continents and seas. Yet if we accept his views, we must believe that Asia and Africa, Madagascar and Africa, New Zealand and Australia, Europe and America, have been united at some period not remote geologically, and that seas to the depth of 1000 fathoms have been bridged over; but we must treat as “utterly gratuitous, and entirely opposed to all the evidences at our command,” the supposition that temperate Europe and temperate America, Australia and South America, have ever been connected, except by way of the Arctic or Antarctic Circles, and that—lands now separated by seas of more than 1000 fathoms depth have ever been united.

Type
Original Articles
Copyright
Copyright © Cambridge University Press 1881

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References

page 242 note 1 According to Lyell, all known rocks would fuse under a pressure of from 20 to 25 miles, whilst greater pressure would reconvert them to solids with a high specific gravity.

page 242 note 2 Geol. Mag. 1872, Vol. IX. p. 119.

page 242 note 3 See Permanence of Continents, J. S. Gardner, Popular Science Eeview, 1881, p. 125.

page 243 note 1 Sir J. Hersehel was of opinion that the weight of sediment displaced by the sea produced elevation and depression along coast-lines (Phys. Geogr. p. 116).

page 243 note 2 This would deposit, if replenished annually, one inch of sediment in 8,000 years. If life extended equally to 2,000 fathoms, one inch would be produced in 400 years. If 12 generations were produced per annum, one inch would result in 33 years, and this might be more than doubled by the decay of life at the bottom.