Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/84

60 Our reconstruction of North America shows a deviation from the present map in that Labrador appears to have been pushed far to the north-west. It is assumed that the great drag, which finally led to the breaking away of Newfoundland from Ireland, caused a stretching and superficial tearing of the adjoining parts of the two blocks before the break. On the American side, not only was the Newfoundland block (including the Newfoundland Bank) broken off and rotated about 30°, but the whole of Labrador seized the opportunity to give way to the south-east, so that the previously straight rift-valley of the St. Lawrence and Belle Isle Straits acquired its present S-shaped curvature. The shallow seas of the Hudson Bay and the North Sea may have been formed or enlarged by this rupture. Thus the Newfoundland shelf undergoes by this restoration, a double change of position, namely, a rotation and a north-westward displacement, and adapts itself to the line of the shelf near Nova Scotia, over which it now juts out very far.

Iceland is assumed to lie between a double rift, a supposition to which the present depth charts of its surroundings appear to hint. Perhaps a fissure (rift-valley) was first formed between the gneiss massives of Greenland and Norway, which was then partly filled with molten sial from underneath the blocks. But since this was, for the rest, filled with sima, as the Red Sea is to-day, a renewed compression of the blocks would have the effect that this sima would be cut off from its connection with the lower regions and would be forced to the surface, thus causing the great basalt flows. That this took place in the Tertiary appears to be very plausible; the westwardly drift of South America at this time must have transmitted a moment of torsion to North America, which, as long as the anchor formed by the chains stretching from Ireland