The
Mono–Inyo Craters is a volcanic chain of craters, domes and lava flows in
Eastern California that stretches 25 miles (40 km) from the northwest shore of
Mono Lake to the south of
Mammoth Mountain. The
Mono Lake Volcanic Field forms the northernmost part of the chain and consists of two volcanic islands in the lake and one
cinder cone volcano on its northwest shore. Most of the
Mono Craters, which make up the bulk of the northern part of the Mono–Inyo chain, are
phreatic (steam explosion) volcanoes that have since been either plugged or over-topped by
rhyolite domes and lava flows. The
Inyo Craters form much of the southern part of the chain and consist of phreatic explosion pits, and rhyolitic lava flows and domes. The southernmost part of the chain consists of
fumaroles and explosion pits on Mammoth Mountain and a set of cinder cones south of the mountain; the latter are called the
Red Cones.
Multiple eruptions from 40,000 to 600 years ago created the Mono Craters, and eruptions 5,000 to 500 years ago formed the Inyo Craters. Lava flows 5,000 years ago built the Red Cones, and explosion pits on Mammoth Mountain were excavated in the last 1,000 years. These eruptions most likely originated from small magma bodies rather than from a single, large magma chamber like the one that produced the massive Long Valley Caldera eruption 760,000 years ago. During the past 3,000 years, eruptions have occurred every 250 to 700 years.
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