The Pattern of the Earth's Mobile Belts

Excessive displacement of the earth's crust has been limited, at least since the later Paleozoic, to well-defined belts, here called the earth's "mobile belts," which are virtually continuous and form a definite and characteristic pattern. In the first part of this paper, the pattern of these mobile belts is briefly described and analyzed, special weight being given to Haug's hypothetical reconstruction. The essential continuity of these belts points to the conclusions (1) that they are the result of stress conditions in the earth's spheroid as a whole and not of local stresses independent from point to point; and (2) that their pattern, therefore, offers a clue to the mechanics which dominate the major diastrophism of the earth. In the second part the results of experiments (largely by the author) are presented which show that the pattern of the earth's mobile belts is unlike that displayed (a) by wrinkles formed on a thin shell adhering to a contracting core; (b) by fractures produced by compression on a thin shell adhering to a contracting core; that it bears a distinct likeness, on the other hand, to the pattern of fractures produced by tension on a thin shell adhering to an expanding core.