Many processes in geology affect the temperature of rocks.  Erosion is one example — as a surface is eroded, the rocks below get closer to the surface, cooling as they go.  So if we know the temperature history of a rock, we can infer its erosion history.  Becky Flowers has a thermochronology lab in which she determines the cooling history of rocks as recorded in specific crystals they contain, such as zircon and apatite.  She explains how this works, and how she has used her results to unravel histories such as that of the Grand Canyon, the South African plateau, and even of that of the lunar surface. Becky Flowers is a Professor of Geological Sciences at the University of Colorado, Boulder. She has a thermochronology lab in which she measures the amounts of the different radioactive decay products within crystals to figure out the cooling history of rocks. Knowing how rocks cooled gives us new insights on geological histories and processes of many parts of the Earth, and even of the Moon. For podcast illustrations, and to learn more about Geology Bites, go to geologybites.com.