The rugged desert landscape of Joshua Tree National Park is famous for many features, including impressive outcrops of monzonite, granite, and related granitic rocks – a rock climber’s and nature lovers’ paradise. These rocks, formed miles beneath the surface, now stand out thanks to uplift of the Little San Bernardino Mountains along numerous faults, accompanied by deep erosion which has filled surrounding basins with broad plains of alluvium. The granites reveal clues about the titanic plate interactions that built southern California over hundreds of millions of years, the ascent of countless bodies of magma – some of which doubtlessly fed now long eroded volcanoes – and the origin of gold and other ore deposits.