Abstract:  "The 1 km tall granitic cliffs of Yosemite Valley experience frequent rock falls, primarily as a result of exfoliation.  These events shape the iconic scenery of Yosemite but they also pose substantial hazard and risk for the four million annual visitors to the park.  Recent research utilizing historical data, remote sensing, cliff instrumentation, and cosmogenic exposure dating has greatly expanded our understanding of the processes that promote exfoliation and trigger rock falls.  This work also contributes to ongoing efforts to reduce rock fall-related risk in one of the world's most popular parks."