In a rebroadcast from September 20, 2009, Keith talks with Anne Sheehan, Professor of Geophysics at the University of Colorado, Boulder. Sheehan talks about using the principles of physics to "see" beneath the crust of the earth. She also explains how earthquakes can teach us about the structure of the earth. Sheehan also explains how the Rocky Mountains were created, and why the plates that created the Nepalese mountains are moving at the speed of a growing fingernail. Aired June 9, 2013.