The subfield of geology called geodynamics most commonly refers to the motions associated with convection in the mantle.   These are slow by human standards and lead to phenomena such as plate motions, seafloor spreading, mountain building, and volcanos.  But the Earth’s interior actually undergoes motion on a whole range of timescales.  The shortest of these occurs within seismic waves – in which the vibrations triggered by earthquakes cause tiny elastic movements of the material as they pass through.  And the longest of these are the large-scale viscous motions of the convecting mantle driven by the temperature difference between the bottom and the top of the mantle.  But there are a whole range of intermediate timescale motions lasting, hours, days, years, and millennia.  
Harriet Lau is an Assistant Professor in Department of Earth and Planetary Sciences at the University of California at Berkeley.  In this episode the describes the motions of the solid Earth that take place over these intermediate timescales and explains what they can reveal about the Earth’s interior.
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