Abstract:
This seminar will not so much be a scientific presentation as an introduction to some of the topics and methods that are central to the work of some of the “hard-rock” geologists at Njord.
Firstly, why do we care about earthquakes in the lower crust? The lower crust is the bottom part of the outermost layer of Earth (ca 20-40 km deep). We hardly feel earthquakes happening down there at the Earth’s surface. However, these earthquakes are still interesting to geologists, for two main reasons: 1. Their formation is somewhat enigmatic, because the high confining pressures at depths should prevent earthquakes from happening. 2. Earthquakes modify the properties of rocks, by reducing their grain size, or by allowing fluids to enter the rocks and react with them. As such, they can influence the further development of an area, including the formation of mountains. We try to understand the origins and consequences of such earthquakes by studying natural examples of rocks that were affected by deep earthquakes a long time ago and were brought to the Earth’s surface later on. We observe large-scale structures in the field, take samples, and analyse the microstructures of the samples in the lab. In particular, we use an electron microscopy technique called electron backscatter diffraction (EBSD) to measure the crystallographic orientation of mineral grains in our samples. In the seminar, I will briefly explain how this technique works and how we use EBSD to investigate how minerals and rocks are deformed. I will also present some of the insights into lower crustal earthquakes that we have gotten from our work in Lofoten.
You will find the complete schedule for Njord Seminar Series spring '22 here.
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