Self-Guided Geologic Tour in Joshua Tree National Monument

Dupras, Don

Joshua Tree National Monument was established in 1936 and contains 870 square miles, most of which is high desert. The Monument encompasses some of the most interesting desert geomorphic features in California. Rugged mountains, prominently exposed granitic monoliths, and exposed fault scarps reveal how geologic processes shaped, and continue to shape, this stark desert landscape. Much of the Monument is above 4,000 feet and steep mountain escarpments border this region to the north and south. The Monument is located about 140 miles east of Los Angeles and is accessible by highway from the north and from the south. The name, Joshua Tree National Monument, is derived from the extensive stands of conspicuous Joshua trees that grow within its boundaries. Joshua trees grow at elevations of 2,000 to 6,000 feet and have keenly pointed bayonet-like leaves that bristle at the end of large club-like branches. Until young Joshua trees attain a height of six feet, their trunks have leaves that reach the ground. As the plant ages and grows in height, these first leaves droop, die, and become closely pressed into a thatch-like mat that covers the trunk and limbs. Some trees have reached heights of 54 feet. The Joshua tree is one of four species of yuccas that are native to California (Vasek and Barbour, 1988). Its unusual and sometimes bizarre shapes have made it a symbol of the California high desert.

Self-Guided Geologic Tour in Joshua Tree National Monument

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