The author meets Leon Silver, a Cal Tech geologist. Summarize their conversation.

Leon Silver, a Cal Tech geologist, talks with the author about earthquakes, rocks, and debris. Leon says that earth faults in Southern California lead to earthquakes that break and batter rocks. When he flew over the San Gabriel Mountains after a 6.2-magnitude earthquake, Leon noticed unstable mountain debris high above homes. The geologist is able to see how everything works together to create earth movement and dangerous debris conditions.