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Mammoth Mountain is a 3,369-m (11,053 ft) high lava-dome complex on the southwest topographic rim of Long Valley Caldera. It is considered to represent a magmatic system distinct from Long Valley Caldera and the Mono-Inyo Craters.


Summary

Eruptions at Mammoth Mountain occurred from 100,000 ot 50,000 years ago. Mammoth Mountain is surrounded by at least 35 mafic vents that are part of the same magmatic system and include Red Cones, two closely spaced basaltic cinder cones located southwest of Mammoth Mountain and southeast of Devils Postpile National Monument. The cones, whose name derives from colorful mantling scoria deposits, are unglaciated and were radiocarbon dated at about 8,000 years ago. Phreatic eruptions, distinct from those at South Inyo Craters, took place about 700 years ago from vents on the north side of Mammoth Mountain. Recent volcanic unrest, including seismicity, gas emission, and tree kill, is thought to be related to a dike intrusion beneath Mammoth Mountain in 1989. Both Long Valley Caldera and Mammoth Mountain have experienced episodes of heightened unrest over the last few decades (earthquakes, ground uplift, and/or volcanic gas emissions). As a result, the USGS manages a dense array of field sensors providing the real-time data needed to track unrest and assess hazards.

News

Date published: May 13, 2020

Unpacking CalVO's new seismic monitoring boxes

If you've noticed any changes to the earthquake counts released in CalVO's weekly updates, don't worry - some behind-the-scenes improvements to our monitoring system have been implemented which allow us to focus on unrest specifically related to our volcanoes and volcanic regions.

Date published: September 13, 2016

What's Under Long Valley? Water, Heat, and Molten Rock!

A picture is worth a thousand words—USGS Post Doctoral Fellow Jared Peacock's new 3D geophysical model for the Long Valley Caldera and Mammoth Mountain reveals a subsurface marked by active hydrothermal reservoirs (hot water and fluids), bodies of...

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