Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/177

Rh folding. Biological facts also appear to verify the fact that the deep-sea basins were first formed during the course of the earth’s history. Walther writes: “The general facts of biology, the stratigraphical position of the present-day deep-sea fauna, as well as tectonic investigations, force us to the conviction that the deep-sea basins are, as biological regions, no primitive property of the earth, dating from the most ancient periods, and that their first establishment occurred at the same time as that in which in all parts of the present continents, tectonic folding movements set in and essentially transformed the relief of the earth’s surface.” The earliest rifts in the sialsphere, in which the simasphere was exposed for the first time, may well have been similar to those which to-day form the East African rift-valleys. They opened more and more as the folding of the sial made greater progress. It was a process which we can compare to some extent with the folding of a round paper lantern—on one side opening, on the other compression. It is extremely probable that the area of the Pacific Ocean, which is universally regarded as very old, was first deprived of its sial mantle in this manner. Small pieces broke off from the margin of the sial covering in the tearing-open, as well as during the widening of the rift, and perhaps also later in the course of the western drift of the entire continental masses, and remained fast in the sima, and now rest on the deep-sea floor as islands or submarine elevations. The rows of the Pacific islands show a remarkable parallelism. Arldt has measured 19 lines which all strike very nearly N. 62° west. It might possibly