In the wake of the 8.0 quake that devastated Peru yesterday, killing more than 350 people, the Chronicle reports that talc found deep in the San Andreas Fault may be the answer to a question that has confounded seismologists: why a 90-mile stretch of the San Andreas Fault has not been more prone to violent earthquakes.

Scientists drilling more than 2 miles deep into the San Andreas Fault have discovered underground patches of talc, nature’s softest known mineral, that could help explain the absence of sharp earthquakes where the fault is “creeping.”…because the talc is so soft – the mineral is used in some baby powders – Moore and Rymer wondered if it could account for the phenomenon of fault creep that has caused the sides of the San Andreas in that region to slide past each other at an inch a year for millions of years rather than triggering abrupt earthquakes.

Read more about earthquakes at the US Geological Survey website.