On a Yosemite cliff, listening
05/05/10 — About every 10 days, falling rock shatters the tranquility of Yosemite National Park. "It's a dynamic place," says park geologist Greg Stock. "Rockfall is the most powerful geologic force acting on the park today. The goal is to eventually predict rockfalls and better constrain the hazard." Enter Valerie Zimmer, a Berkeley geoengineering Ph.D. student who launched her doctoral work studying rockfall in mines using tiny acoustic sensors to document the rock mechanics and geophysical forces underground.