Dynamic support of the outer rise

Abstract

A model for the origin of the outer rise is proposed which does not require multi‐kilobar deviatoric stresses in the lithosphere. The model includes stresses developed by viscous flow of the lower part of the lithosphere as it is subducted. Besides the outer rise, features similar to an oceanic trench and island arc develop in the model. The elastic upper part of the lithosphere, treated approximately, is subject to extensional stresses on the seaward side of the trench axis. The observed topography of an oceanic trench and outer rise can be produced by a 90 km thick lithosphere subducting at 60 mm/yr if the average viscosity of the lower lithosphere is about 1023 poise. Copyright 1978 by the American Geophysical Union.