You can access one or more small images like the one presented here by clicking the specific "feature" in the Long Valley area that are listed below.

Then, by clicking on the small image that you want to look at in more detail, you will get a mid-sized image and additional information about the image. By clicking on the mid-size image, you will get a large image (800 x 500 pixels). Click on the image at left to try it out.

Map of the Long Valley area

Volcanism in the Long Valley area

The rugged landscape of the Long Valley area owes much of its beauty and appeal to the striking geologic features created by growth of the imposing peaks of the high Sierra Nevada, glaciation, and volcanic eruptions. Residents and visitors alike are confronted with these features whether skiing down the steep slopes of Mammoth Mountain, digging through lava, glacial deposits, or pumice in order to construct foundations for buildings and roads, or exploring the area's hot springs, craters, and craggy peaks.

Long Valley Caldera was created about 760,000 years ago by an enormous explosive eruption. Scientists estimate that about 600 km³ (140 mi³) of magma was erupted, mainly as hot pyroclastic flows; this eruption ejected at least 50 times more magma than the 1991 eruption of Mount Pinatubo in the Philippines. The ejection of so much molten rock partially evacuated the magma reservoir, which caused the ground to collapse into the reservoir. The result was an enormous depression between 17 and 32 km in diameter!

This massive eruption was followed by hundreds of smaller eruptions over the next few hundred thousand years. These eruptions of lava flows, domes, and pyroclastic flows were concentrated in the central and western parts of the caldera. At the same time, the central section of the caldera was bowed upward in response to new magma rising into the shallow reservoir. The upward rise of the caldera floor created the "resurgent dome", a broad, dome-shaped highland of post-caldera lava domes about 9 km in diameter that stands about 500 m above the surrounding low-lands that form the caldera "moat."

Mammoth Mountain was built by the eruption of at least 12 different steep domes and thick lava flows. These eruptions occurred between about 200,000 and 50,000 years ago. Volcanic activity then moved northward to the Mono Lake area about 35,000 years ago to build the Mono Craters, a collection of more than 30 overlapping lava flows, domes, cones, and craters. The most recent eruptions in the area occurred from the Mono Craters and Inyo Craters about 600 years ago, and from Negit Island in Mono Lake about 250 years ago.

Long Valley Caldera

• Caldera rim
• Resurgent dome
• Bishop Tuff
• Post-caldera volcanic flows and deposits

Mammoth Mountain

• Views from atop summit
• Various views of Mammoth Mountain
• Trees killed by carbon dioxide gas

Mono Craters

• Aerial views of Mono Craters
• Mono Lake
• Paoha and Negit islands, Mono Lake

Inyo Craters

• Wilson Butte
• Obsidian flow
• Glass Creek flow
• South Deadman flow
• Inyo Craters