The Subduction Dichotomy of Strong Plates and Weak Slabs
Robert I. Petersen1, Dave R. Stegman1, and Paul J. Tackley21Institute of Geophysics and Planetary Physics University of California, San Diego 9500 Gilman Drive, La Jolla CA 92093-0225, USA 2Institute für Geophysik ETH Zürich Sonneggstrasse 5, 8092 Zürich, Switzerland
Received: 25 Mar 2016 – Accepted for review: 29 Mar 2016 – Discussion started: 05 Apr 2016
Abstract. A key element of plate tectonics on Earth is that the lithosphere is subducting into the mantle. Subduction results from forces that bend and pull the lithosphere into the interior of the Earth. Once subducted, lithospheric slabs are further modified by dynamic forces in the mantle and their sinking is inhibited by the increase in viscosity of the lower mantle. These forces are resisted by the material strength of the lithosphere. Using geodynamic models we investigate several subduction models wherein we control material strength by setting a maximum viscosity for the surface plates and the subducted slabs independently. We find that the models which produce results most analogous to observations of subduction on Earth are characterized by a dichotomy of lithosphere strengths. These models have strong lithospheric plates at the surface which promotes Earth-like single-sided subduction. At the same time these models have weakened lithospheric subducted slabs which pile, bend or lie flat at the top of the lower mantle reproducing the spectrum of slab morphologies observed on Earth.
Petersen, R. I., Stegman, D. R., and Tackley, P. J.: The Subduction Dichotomy of Strong Plates and Weak Slabs, Solid Earth Discuss., doi:10.5194/se-2016-56, in review, 2016.