Images

Groundhog scoria cone, the youngest of the Golden Trout Creek volcanic field, and the source of a lava flow that traveled 6 km to the west down Golden Trout Creek. The cone erupted through light-colored Mesozoic granitic rocks of the Sierra Nevada batholith visible in the distance. Photo by Rick Howard, 2002 (courtesy of Del Hubbs, U.S. Forest Service).

Map of volcanic ashfall. Areas of the United States that once were covered by volcanic ash from Yellowstone's giant eruptions 2 million and 630,000 years ago, compared with ashfall from the 760,000-year-old Long Valley caldera eruptions at Mammoth Lakes, California, and the 1980 eruption of Mount St. Helens, Washington.

This animation of the tectonic evolution of western North America shows the birth and lengthening of the San Andreas fault as the triple junction moves north over the past 40 million years. Over time, the Farallon plate is consumed by subduction beneath North America and the divergent boundary (a.k.a.

An aerial view looking south of the Long Valley volcanic region in the area of Mono Lake, showing a line of rhyolite lava domes and explosion craters. An inset map shows the locations of silcic magmatic centers in the Long Valley area.

A tumulus in the Coso Volcanic Field, California. This lava was probably more viscous than the lava found in the Hawaii tumuli.

Mt. Konocti erupted during the most recent stage of volcanism (01. Ma to 10,000 years ago), and a future eruption from the same site would be devastating to the nearby inhabitants.

Mount Konocti, the most distinct volcanic feature of the Clear Lake Volcanics as viewed to the west from Cinder Cone.

Lassen Peak's Devastated Area photographed from the air in 1994.

Mount Konocti, a mostly dacitic composite cone, on the western shore of Clear Lake, California. Thurston Lake is in the foreground.

The original Lassen Volcano Observatory building, provided by the US Forest Service, about 1926. The observatory consisted of a small office over a 10x10 ft concrete cellar which housed two custom-built seismographs. A small cottage nearby housed Ruy H. Finch, the head of and sole scientist at the Observatory for much of its existence. (Photo by R.H.

The founder of the Lassen Volcano Observatory (1926-1935) and second Director of the Hawaiian Volcano Observatory (1940-1951), Ruy Herbert Finch conducted research in both Hawaii and throughout the Western United States.

Coso Hot Springs in Coso volanic fields, Feb 4, 1920.

Lassen Peak photographed from the Devastated Area about 4 hours before the explosive eruption of May 22, 1915.

Benjamin F. Loomis Historical Photograph Collection: Lost Creek drainage area covered in mud, rocks, and debris from a mudflow off Lassen Peak. Photo courtesy of NPS.

Steam issuing from summit of Lassen Peak from head of Lost Creek following mudflow. "Hot Rock"(large boulder) in foreground. Photographs taken a few hours prior to second major eruption and hot blast.

Benjamin F. Loomis Historical Photograph Collection: Lassen Peak showing new lava flow on summit and large mudflows on slopes. Photo courtesy of NPS.

A second view of Lassen Peak and the Deveastated Area following an explosive eruption and mudflowk. The crater of the volcano is visible, revealing that a lava dome which had previously been growing there was destroyed by the explosion. Subsequently, a lava flow began refilling the crater, and was mistakenly thought to have created the mudflow. 

Lassen Peak photographed from the Devastated Area prior to the 1914-1915 eruption that changed the landscape.

Horse-drawn carriage on road in Sisson, California, El Monte Hotel in foreground, Mount Shasta in the background. Image courtesy of the Library of Congress.

Photograph of the town of Sisson (later (1922) the town of Mt. Shasta) in the distance at the foot of Mount Shasta in winter. Snow covered fir trees in the foreground. Photo courtesy of University of Southern California Libraries and California Historical Society. Digitally reproduced by the USC Digital Library.

In a February 5, 2019 visit, USGS Director Jim Reilly was given a tour of CalVO facilities, including the Operations Room. Here Emily Montgomery-Brown explains the networks that monitor California's threatening volcanoes.