A number of earthquakes shake the mountain.

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Mammoth Mountain, California
In California there has been a quake swarm at Mammoth mountain that has been going for more than a week. No Eruption yet, but plenty of quakes.

California's Long Valley caldera, near Mammoth Mountain, is the largest supervolcano on the planet, says Alessandro Decet. In the last week it has recorded a few earthquakes, with the most intense a magnitude 3.0. Since everything is still mild in intensity, no alarm or status change was issued. However, the earthquakes are increasingly shallow, signaling that magma may be about to get closer to the surface.

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The Long Valley caldera was formed about 780 million years ago with a huge eruption of hot ash.

Mammoth Mountain is a lava complex on the edge of SW of Long Valley Caldera, California. The last eruption of the lava dome complex itself took place about 57,000 years ago. There are more than 35 volcanic vents fed by the same magma chamber, including Red Cone which two basaltic cinder cones SE of Mammoth Mountain and SE of Devils Postpile National Monument.

The cones, whose names derive from their brightly colored waste repositories, have been radiocarbon dated to about 8900 years ago. Recent turmoil, including seismicity, gas emissions, and killing of trees, is thought to be related to a magmatic intrusion beneath Mammoth Mountain.

Alessandro's webpage.

Interactive map.