July 2016

New paper: Subduction controls the distribution and fragmentation of Earth’s tectonic plates by Mallard et al. in Nature



The theory of plate tectonics describes how the surface of Earth is split into an organized jigsaw of seven large plates1 of similar sizes and a population of smaller plates whose areas follow a fractal distribution. The reconstruction of global tectonics during the past 200 million years suggests that this layout is probably a long-term feature of Earth, but the forces governing it are unknown. Previous studies3, 5, 6, primarily based on the statistical properties of plate distributions, were unable to resolve how the size of the plates is determined by the properties of the lithosphere and the underlying mantle convection.

Here we demonstrate that the plate layout of Earth is produced by a dynamic feedback between mantle convection and the strength of the lithosphere. Using three-dimensional spherical models of mantle convection that self-consistently produce the plate size–frequency distribution observed for Earth, we show that subduction geometry drives the tectonic fragmentation that generates plates. The spacing between the slabs controls the layout of large plates, and the stresses caused by the bending of trenches break plates into smaller fragments. Our results explain why the fast evolution in small back-arc plates7, 8 reflects the marked changes in plate motions during times of major reorganizations. Our study opens the way to using convection simulations with plate-like behaviour to unravel how global tectonics and mantle convection are dynamically connected.

Download the preprint here: http://geologie.ens-lyon.fr/augur/wp-content/uploads/2016/08/Mallard2016_augury.pdf

Screenshot 2016-08-22 12.52.07 http://www.nature.com/nature/journal/v535/n7610/full/nature17992.html

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AUGURY @EGU 2016 in Vienna



From left to right: M. Arnould, M. Bocher, D. Bower, S. Brändli, P. Tackley, M. Gérault, N. Coltice, N. Flament and C. Jain.

EGU 2016 took place in Vienna between the 17th and the 23rd of April. We presented our work in progress through 4 posters from the team in Lyon. Nicolas Flament (Sydney) presented his work, as well as the team of Zurich. The meeting was a chance for Maelis Arnould, who started her PhD in September, to sit with her two advisors from across oceans (N. Flament and N. Coltice).

The group of Lyon presented a poster and a presentation at the session organised by Claudia Alves de Jesus Rydin (ERC): “Promoting and supporting equality of opportunities in geosciences”. As a feminine group, we were happy to share our experience on how we try to promote women in sciences, focusing on local actions and emphasizing democracy through a flat organisation. It was the occasion to speak with people on this subject that matters a lot for us.

N. Coltice gave a talk about getting funded through ERC, pointing that it is a difficult but important task to find ways to take into account the decline of funding for the operation of everyday collectivity.

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