Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/207

Rh in this fashion tectonically by the former structure of the coastal mountain systems.

The remarkable similarity of the festoons in their geological structure has been already mentioned. The concave side always bears a row of volcanoes, obviously a result of the pressure, which results from the bending and forces out the inclusions of sima. On the other hand, the convex sides bear Tertiary sediments, whilst these are usually absent on the corresponding shore of the mainland. This signifies that the separation first took place in very late geological time, and that the festoons still formed the margin of the continents at the time of the deposition of these sediments. These Tertiary deposits everywhere show great disturbances of the strata as a result of the tension that occurs here on account of the bending, and leads to fissuring and vertical faulting. Nippon (Hondo or Honshiu), Japan, has been broken up, in the “Fossa Magna,” by the excessively strong bending. That this outer margin of the festoon appears to be elevated, in spite of the depression connected everywhere else with extension, indicates a tilting movement of the festoon, which one can believe to be caused by the fact that it is dragged along at its ends by the westerly drift of the continental blocks, while deep down it is held back by the sima. The ocean deep that usually accompanies the outer margin of the festoons is apparently connected with the same process. Attention has already been drawn to the fact that these ocean deeps never form on the freshly exposed surface of the sima between the continent and festoon, but always only on the outer margin of the latter, and therefore on the margin of the old ocean-floor. It appears as a rift, one side of which