Images

Photograph looking south across the rugged andesitic northern end of the compositionally zoned Callahan Flow toward the main vent at Cinder Butte (partly covered by snow.) USGS photograph by Tanya Blacic

Eruptions of the Yellowstone volcanic system have included the two largest volcanic eruptions in North America in the past few million years; the third largest was at Long Valley in California and produced the Bishop ash bed. The biggest of the Yellowstone eruptions occurred 2.1 million years ago, depositing the Huckleberry Ridge ash bed.

USGS scientists measuring temperature in a deep borehole in Long Valley Caldera with the Sierra Nevada mountains in the background.

USGS scientist Wes Hildreth at a 2004 Meritorious Service Award Ceremony. Photo courtesy of Mike Diggles.

Gas bubbles through a sample bottle containing alkaline solution, allowing for separation of different gas phases.

South Fork scoria cone (center) is seen from the NW with Ramshaw Meadow (upper left) behind it. Templeton Mountain is the rounded peak beyond South Fork cone, and Olancha Peak on the crest of the Sierra Nevada is on the center horizon.

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.

Apollo 16 astronauts John Young (right) and Charlie Duke (left) ride in Earth-adapted Lunar Roving Vehicle "Grover" in the Coso Volcanic Field near Ridgecrest California, November 1971. Photo by NASA.

University of Texas professor William R. Muelhberger (left foreground) with Apollo 16 commander John W. Young (right foreground), astronaut Charles Duke (center), geologist David Wones (second left), and astronaut Anthony England on an Apollo 16 geology field trip to Mono Craters in June 1971. Photo by NASA.

View of Donald A. Beattie (manager of NASA's lunar surface experiments) during a geological field trip to the Medicine Lake Volcano, California in September 1965. Beattie was joined by astronauts William Anders (Apollo 8), Alan Bean (Apollo 12), and Rusty Schweikert (Apollo 9). Photo by NASA.

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.