Mount Diablo is not a volcano, but has volcanic "domes." Geologist Jean Hetherington helps us see those mushroom-shaped hills as clues to our landscape's dynamic history. 

From a tour of Perkins Canyon presented by Save Mount Diablo. Featuring Seth Adams, Jean Hetherington, and Ken Lavin. Music by Phil Heywood. Photographs by Scott Hein and others. Production by Joan Hamilton.