Mammoth Lakes Ranger District is located in the northern half of Inyo National Forest, and is centered around the town of Mammoth Lakes, CA. While known for winter sports, it is also a mecca for mountain biking and fishing enthusiasts when the snow melts. Hiking and equestrian trails go into wilderness areas of Sierra Nevada.
During a gigantic eruption about 760,000 years ago, an area bordered by what is now Mammoth Mountain, the Glass Mountains and Crowley Lake (approximately 12 miles wide by 18 miles long), collapsed to form the Long Valley Caldera. The eruption produced the Bishop Tuff, a pinkish-red rock that can be seen along US 395 on the Sherwin Grade. Three hundred and fifty square miles were buried beneath 500 feet of Bishop Tuff. Ash from the eruption has been found as far east as Nebraska. Later, other volcanoes erupted along the rim of this gigantic Caldera, one of which was Mammoth Mountain, which grew on the rim of the Caldera over 50,000 years ago.
Volcanic eruptions have continued within the Caldera and north along the Inyo-Mono volcanic chain. Eruptions at Obsidian Dome, South Deadman Dome and Panum Crater all occurred as recently as 500 to 800 years ago. The bottom of the Mono Lake was pushed up above the lake surface by an injection of magma to form Paoha (the white) Island approximately 300 years ago.
Spectacular views from Minaret Vista survey this canyon full of recreational opportunities. Camp, fish, hike and explore Devils Postpile National Monument, Reds Meadow Resort and Agnew Meadows. Devils Postpile National Monument website has additional shuttlebus information.
Mono Lake Ranger District is the northernmost district of Inyo National Forest. The western portion of the district is adjacent to Yosemite National Park, and includes one of the most spectacular and accessible areas of the Sierra Nevada. To the east is Mono Lake, and the world's largest stand of majestic Jeffrey Pines.