Images

Bubbling Spring, a feature of Hot Creek in the Long Valley Caldera, California, occasionally "boils" due to high water temperature.

Cinder Cone erupted in the year 1666 in the Lassen Volcanic Region of northern California.

Medicine Lake lies within the shallow basin of Medicine Lake caldera. Glass Mountain flow, draped over the east side of the volcano, is the youngest lava flow at the volcano. The northeasternmost dacite tongue extends nearly to the bottom of the photo (distal lobes are outlined to enhance visibility).

Glass Mountain obsidian flow at Medicine Lake volcano, California. Glass Mountain is a spectacular, nearly treeless, steep-sided rhyolite and dacite obsidian flow that erupted just outside the eastern caldera rim and flowed down the steep eastern flank of Medicine Lake volcano.

Hydrothermal system and water flow in the subsurface beneath Long Valley Caldera, California. Cartoon Illustration from USGS FS 2007-3045.

Aerial photo of Mount Shasta's southwestern flank in a low-snow period. The Hotlum cone is on the right, while the Shastina dome is to the left.

Hot springs and their associated rising steam may be found in Hot Spring Cove on the southeastern point of Paoha Island in the Mono Lake Volcanic Field. USGS photo by Deborah Bergfeld.

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.

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).

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.

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.