In 2007, Adams' Pack Station hosted a Geology Walk conducted by Dave Douglass, Dean of Sciences at Pasadena City College. He spoke in plain English for us newbies and it was very interesting. I put a microphone on him and this was the result...
Dave's Background:
http://www.gregsuite.com/mountains/Dave_Background.mp3
History of the San Gabriels part 1:
http://www.gregsuite.com/mountains/San_Gab_History_01.mp3
History of the San Gabriels part 2:
http://www.gregsuite.com/mountains/San_Gab_History_02.mp3
History of the San Gabriels part 3:
http://www.gregsuite.com/mountains/San_Gab_History_03.mp3
The Tectonic Plates:
http://www.gregsuite.com/mountains/Tectonic_Plates.mp3
Mapping the San Gabriels:
http://www.gregsuite.com/mountains/Mapping_San_Gabes.mp3
San Gabriel Mountain "Granite":
http://www.gregsuite.com/mountains/San_Gab_Granite.mp3
Gneiss One:
http://www.gregsuite.com/mountains/Gniess_One.mp3
Geology Wrap-Up:
http://www.gregsuite.com/mountains/Geology_WrapUp.mp3