Nature
Long Valley Caldera in eastern California, beside Mammoth Mountain, is one of Earth’s largest calderas, formed about 760,000 years ago when a colossal eruption emptied a magma chamber and collapsed the ground. The blast sent pyroclastic flows across the region, spread ash across much of the western United States, and left the Bishop Tuff that still shapes the surrounding landscape. The caldera remains geologically active, with a resurgent dome, Hot Creek, hot springs, fumaroles, and nearby younger volcanic features including Mammoth Mountain and the Mono–Inyo Craters. Modern earthquake swarms, uplift, and changing springs and gas emissions have kept it under close United States Geological Survey monitoring since 1982.
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