Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/82

58 The displacement does not exist in the form of a dragging away from each other of the margins of the rift near Smith Sound and Robeson Channel in the north-west of Greenland, but in a lateral displacement of great dimensions, a so-called tear-fault. Grinnell Land has slid along Greenland, producing the striking straight-lined boundaries of both the blocks. This displacement can be detected in the extract given in Fig. 10, from the geological map of North-west Greenland by Lauge-Koch, if the boundary between the Devonian and Silurian, which lies in Grinnell Land at 80° 10′ N. Lat., and in Greenland at 81° 30′, is sought for.

Some reference may be made here to the manner in which the reconstruction of the pre-Atlantic continental connections was worked out. A more detailed discussion of the phenomena considered here, such as the plasticity of the blocks of sial, the melting from beneath, etc., will be given later. It is, however, necessary to mention something about them in the geological comparison of the margins of the rifts in order to prevent misconceptions.

Abrolhos Bank, on the east coast of South America, must be omitted in the fitting together of the blocks.