Eastern Sierra Photo Gallery [Archive]

MtnEagle

Jun 26, 2004, 04:38 PM

This album is for anything Eastern Sierra, although my entries will focus on the Long Valley Caldera area and it's many features.

Long Valley Caldera is an immense volcano the size of a small valley (10 by 20 miles roughly) that erupted catastrophically somewhere around 720,000-760,000 years ago (current estimates of dating are at 760,000). At that time, the eruption sent 600 cubic kilometers (Compared to Mt. St. Helens at .5 - 2 cubic Kilometers) of ash and other materials as far East as Nebraska and Missouri, as far North as Wyoming and Idaho, and as far South as Arizona and New Mexico. Rocks the size of houses were hurled into Eastern Nevada. This volcano has erupted in smaller events starting from this time over the many thousands of years since.

The volcanic field is as old as 3 million years, and the most recent eruptions have developed along a rift that travels North from within the Caldera to outside the Caldera into Mono Lake. Panum Crater and Obsidian Dome erupted 600 years ago, and Negit Island in Mono Lake is only 250 years old. The local Mono indians have handed down stories from this time.

Mammoth Mountain, and the lesser know Glass Mountain to the East are Composite volcanoes fed by cracks and dikes that are formed at the rim of the ancient Caldera (like the sides of a pie crust). Mammoth mountain drew attention to the previously unknown supervolcano in 1980 just after Mt. St. Helens, when the area was rocked by several magnitude 6 earthquakes which implied that the magma chamber far below was in unrest.

More pictures to come...

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