The way it was

ROCKS retain a “memory” going back millions of years, says Ethan Baxter of
the University of California at Berkeley. Heat and pressure slowly metamorphose
deeply buried rocks, changing their crystalline structure and chemistry. Now
analysis of rocks from the Swiss Alps shows the reaction rates are up to 10 000
times slower than was thought from lab tests (Science, vol 288, p
1411). This will allow us to discover more about conditions millions of years
ago, Baxter says.