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Solid Earth An interactive open-access journal of the European Geosciences Union

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Solid Earth, 8, 339-350, 2017
http://www.solid-earth.net/8/339/2017/
doi:10.5194/se-8-339-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
24 Mar 2017
The subduction dichotomy of strong plates and weak slabs
Robert I. Petersen1, Dave R. Stegman1, and Paul J. Tackley2 1Institute of Geophysics and Planetary Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, San Diego, CA 92093-0225, USA
2Institute für Geophysik, ETH Zürich, Sonneggstrasse 5, 8092 Zürich, Switzerland
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 models characterized by a dichotomy of lithosphere strengths produce a spectrum of results that are comparable to interpretations of observations of subduction on Earth. 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 can more easily bend to either lie flat or fold into a slab pile atop the lower mantle, reproducing the spectrum of slab morphologies that have been interpreted from images of seismic tomography.

Citation: Petersen, R. I., Stegman, D. R., and Tackley, P. J.: The subduction dichotomy of strong plates and weak slabs, Solid Earth, 8, 339-350, doi:10.5194/se-8-339-2017, 2017.
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Short summary
In this study we propose a dichotomy in the strength profile of tectonic plates. This apparent dichotomy suggests that plates at the Earth's surface are significantly stronger, by orders of magnitude, than the subducted slabs in the Earth's interior. Strong plates promote single-sided, Earth-like subduction. Once subducted, strong slabs transmit dynamic stresses and disrupt subduction. Slabs which are weakened do not disrupt subduction and furthermore exhibit a variety of observed morphologies.
In this study we propose a dichotomy in the strength profile of tectonic plates. This apparent...
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