The Long Valley Caldera

The Long Valley Caldera was born more than 760,000 years ago. A cataclysmic explosion of such magnitude, ash was found as far away as Nebraska! Bordered by Mammoth Mountain, the Mono Basin, the Glass Mountains and Crowley Dam, a mountaintop of nearly 12,500 feet was literally blown off.

Remnants of the explosion are visible today on the Sherwin grade in the pinkish-white ash deposits known as "Bishop Tuff". Highway 395 has been chiseled through much of this ancient formation.

The caldera and its perimeters may be best viewed from the McGee Creek road, above Crowley Lake, as it ascends toward the McGee Creek Pack Station.