Here Caroline Beghein Ph.D. gives a very nice general introduction to plate tectonics.
From Plate Tectonics to Deep Earth Dynamics
Published on Sep 2, 2016
A Seismological Journey Inside the Earth.
2016 IRIS/SSA Distinguished Lecturer
Caroline Beghein Ph.D., U.C. Los Angeles
August 29, 2016 at the OMSI Science Pub, Venetian Theater.
The motion of the tectonic plates that divide the Earth's surface explains many geological features and events - from mountain building, to deep oceanic trenches, to earthquakes, tsunami generation, and the presence of volcanoes. These motions at the surface are driven by processes deeper inside the Earth, in particular by the overturn of the mantle through convection: hot, lighter rocks rise to the surface and cold, denser material sinks.
This process causes solid rocks in the mantle to flow and deform over geological time scales. To understand what happens at the surface, we need to study the deep Earth interior. We cannot, however, directly sample rocks from the mantle. Instead, scientists use recordings of the waves generated by earthquakes to map the physical properties of mantle rocks.
From Plate Tectonics to Deep Earth Dynamics: A Seismological Journey Inside the Earth