Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/28

4 Himalayas to the Alps and Atlas mountains which were then in the equatorial zone.

The previously mentioned separation from the Australian block of the former coastal ranges of New Zealand, forming later a festoon of islands, leads us up to the phenomenon that smaller portions of the blocks are left behind by the westward wandering of the larger blocks. In this manner the marginal ranges of the East Asiatic continental coast separated as festoons of islands. The Lesser and Greater Antilles lag behind the movement of the Central American block, and similarly the so-called arc of the South Antilles between Patagonia and West Antarctica. Indeed all blocks tapering in a meridional direction show a curve of their points towards the east on account of this lag. The latter is well shown in the south point of Greenland, the submarine shelf of Florida, Tierra del Fuego and Graham Land, and the manner in which Ceylon has broken away from India.

It will easily be seen that this complete and extensive conception of the displacement theory must emanate from a definite acceptance of the relation of the oceans to the continental blocks. In fact, it is assumed that these two phenomena are fundamentally distinct, that the continental blocks with a thickness of about 100 km. swim in a magma out which they only project about 5 km. and which is uncovered in the floor of the oceans.

Thus the outermost lithosphere no longer completely covers the entire earth (whether it ever did can be left undecided), but has become smaller and smaller by continued folding and compression during the course of geological time, thereby increasing in thickness and splitting ultimately into more and more separated smaller continental blocks. The latter to-day cover but a quarter of the earth. The floors of the