Plate motion and mantle plumes in thermal and themochemical convection
Final Report Abstract
Thermal plumes and thermochemical piles have been considered to explain the complex structure of the core-mantle boundary. Both affect the dynamics of the Earth’s mantle and its temporal evolution. As the tectonic plates are an essential part of the mantle convection, the plate motion is also affected by the thermal and chemical structures in the mantle. Applying a numerical thermochemical model of mantle convection with a complex rheology, we investigated the plumes and piles in combination with plate-like surface motion. Our models have shown that the presence of a dense CMB layer generally reduces the mobility of the surface plates and delays the onset of plate motion, but during plate evolution a variety of plume classes occur leaving a complex structure at the CMB. We find large elevated areas with sharp edges and a flat or slightly dented top for piles with plumes atop. Plume clusters also cause large elevated areas with sharp edges but the top is mainly flat with only a few smaller peaks. Typically these structures are also less wide than the pile-plume complexes. Smaller elevations close to the large structures are explained by either line-plumes or wind-driven thermals. The latter appear when heat is trapped beneath subducted slabs spreading over the CMB.
Publications
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2020. A numerical study of of thermal and chemical structures at the core-mantle boundary. Earth Planet. Sci. Lett. 116498
Stein, C., Mertens, M., Hansen, U.
