Gravity, Deformation and the Earth's Crust, as Studied by Centrifuged Models [Book Review]

Abstract

This is a delightful and timely little book that cannot help stimulating a wide range of earth scientists. The author, who is a leader in the field of model simulation of tectonic phenomena, uses a large-capacity centrifuge to duplicate in a scale model the effects of gravity in the earth. By "spinning up" appropriately scaled models which consist initially of flat-lying but unstably stratified layers, he is able to study the evolution of salt domes, batholiths, the rise of magma, and the sinking of heavy masses. In the process, he generates many secondary effects such as buckling, rifting, overthrusting, rim synclines, doming, transform faulting, and many more that are remarkably similar to geologic phenomena. The blow recently dealt to vertical tectonics by ocean floor spreading could tend to make one forget the important role of gravity and buoyancy in worldwide tectonics. Ramberg stresses the importance of heterogeneous convection, where melting or other phase changes, rather than thermal expansion, provide the buoyancy necessary to initiate the motion. The reviewer agrees with Ramberg that the density reduction caused by partial melting in the low-velocity zone of the upper mantle has profound tectonic implications.

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