Disputas: Marcus Beuchert

Prøveforelesning

Bedømmelseskomité

Professor Paul J. Tackley, The Institute of Geophysics, ETH Zürich
Professor Nick Kusznir, Department of Earth and Ocean Sciences, University of Liverpool
Dr. Dani W. Schmid, Physics of Geological processes, University of Oslo

Leder av disputas:  Nils Roar Sælthun

Veileder:  Yuri Podladchikov, Nina Simon og Lars Rüpke

Sammendrag

The plate tectonics theory of the 1960s revolutionized our understanding of how our planet works. We know now that the Earth consists of several large rigid tectonic plates that move relative to each other on top of a hot, flowing interior. The goal of computational geodynamics, to which this work is a contribution, is to quantify and understand Earth interior processes by means of numerical modelling. Our work investigated mostly the very old interior of some plates, e.g. Africa or North America, which dates back almost to the very beginning of our planet. Those old portions of the tectonic plates are called cratons and they are thicker and colder than most other, younger portions of the plates. The possibility that cratons have been stable throughout Earth history has recently been questioned by some numerical models. At Phyics of Geological Processes (PGP), a centre of excellence at the University of Oslo, we developed new numerical models which show that the stability of cratons can be explained from classical physical flow laws derived from laboratory experiments. In our approach, we took into account the fact that the rigid plates behave like a solid and compared our approach to classical fluid-based approaches. Our results show that cratons can be stable both with and without taking into account the solid nature of plates. Yet, we found that the stress distributions inside the plates are substantially different for fluid-based and solid-based approaches. This has important implications for more complex future numerical models which take into account the stress-dependence of deformation. Since scientist have not yet succeeded in developing a numerical model that satisfactorily reproduces plate tectonics, using more realistic flow laws like in our study might be an important step towards reaching this goal.

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