Mammoth Mountain Is Itself a Volcano
Near Mammoth Lakes, California
The mountain that people ski down every winter is not an ordinary peak. Mammoth Mountain is a young volcano, or more precisely a cluster of at least twenty five overlapping lava domes, built up from thick, pasty lava that oozed out and piled high rather than flowing far. It sits on the southwestern rim of the Long Valley Caldera and forms the southern end of the Mono and Inyo Craters, a chain of volcanic vents stretching about twenty five miles north toward Mono Lake.
Mammoth Mountain's own eruptions ended roughly fifty thousand years ago, but the broader chain to the north has erupted far more recently, some vents only about six hundred years ago, which makes this one of the youngest volcanic areas in the lower states. The mountain has not gone quiet inside. High on its slopes, vents called fumaroles still hiss out warm volcanic steam and gas, and the ground in places is chemically altered by rising heat.
After earthquake swarms rattled the region in the early nineteen eighties, the United States Geological Survey began watching this mountain closely, because the same forces that built it are still stirring beneath the snow.
