Unexpected Insights into the Composition of the Earth from Magnetotellurics

Many of our most long-standing ideas about the composition and structure of the Earth are from seismic data. These ideas are therefore underpinned by the parameters that control seismic velocity, like temperature and major element chemistry. More recently, high-quality magnetotelluric (MT) models of the electrical conductivity structure of the Earth have begun to emerge. In many cases these models have shown unexpected features such as extensive high conductivity zones in the mantle of old, tectonically stable plates where seismic velocities are fast. Since electrical conductivity is controlled by different parameters than seismic velocity, these models can help us make significant advances in understanding Earth evolution. In this talk I will discuss recent progress in making quantitative interpretations of MT models in terms of mantle temperature and composition and the important questions about Earth dynamics that these interpretations raise. By combining seismic and MT interpretations we can produce even more accurate models for mantle structure and evolution. I will discuss the application of these results to problems including constraining mantle viscosity for glacial isostatic adjustment modelling and measuring the composition of other planetary bodies.

Host: Doug Wiens

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