Mammoth Mountain, California, USA
U.S. Geological Survey photo by S. R. Brantley, 1978 (fair use policy)
California's Mammoth Mountain sits on the southwest rim of the Long Valley caldera, just east of the Sierra Nevada and south of Lake Tahoe. Mammoth Mountain is a young volcano, and because of numerous small earthquakes beneath the area, it's being closely watched by government geologists. The forest in the front of this picture is growing on the floor of the caldera.
Recently, large numbers of trees have been dying on Mammoth Mountain's flanks. The reason is carbon dioxide gas, rising from an active body of magma below the caldera. This suffocates the trees' roots. To learn more about this phenomenon, see this U.S. Geological Survey fact sheet.
