The School of Geography, Earth and Environmental Sciences organises a regular series of research seminars throughout the academic year to which everyone is welcome to attend. Speakers - both external and internal to the University - will talk on topics related to all aspects of Earth Sciences.
Today's speaker is Dr Lars Hansen from the University of Oxford.
The strength of lithosphere is a key factor in many large-scale geodynamic processes. The formation of new tectonic plate boundaries, the relaxation and transfer of stresses after major seismogenic events, and the flexure of plates in response to loading from ice sheets and volcanic islands all depend on the ease with which the lithosphere can be deformed. Although the strength of the lithosphere has been a major research focus for over 40 years, there is still much disagreement in the solid-Earth community.
A wide range of values have been obtained from laboratory experiments on olivine (the most abundant mineral in the lithospheric mantle), and most of these values disagree with geophysical observations. Here Lars presents new results from high-resolution microscopy that shed light on the microphysical mechanisms controlling olivine deformation. These insights help to determine the previous results that are most applicable to Earth's lithosphere.
Lars additionally presents results from new nanoindentation experiments. These experiments reveal phenomena not before documented in geological materials. Importantly, these phenomena provide an explanation for the general disagreement among previous experimental results, leading to a unified model for the strength of the lithosphere.