Images

Argon geochronology lab in Menlo Park, California.

Microprobe laboratory in Menlo Park, California.

Map showing distribution of Long Valley postcaldera rhyolites. Abbreviations: CD, Casa Diablo geothermal plant; Ski area, Mammoth Mountain Ski Area; LVEW, Long Valley Exploratory Well, 3 km deep, located high on resurgent uplift; s, surficial deposits filling structural lows on resurgent uplift.

Medicine Lake, California simplified hazards map showing potential impact area for ground-based hazards during a volcanic event.

Example Hydrotherm output. Hydrotherm is a three-dimensional simulation of multiphase groundwater flow and heat transport in the temperature range of 0 to 1200 degrees Celsius and the pressure range of 1 to 1000 MPa.

Inverted funnel connected to thermoplastic tubing used to collect gas from a hot spring pool near Lassen Peak, California.

Flow banding of Panum pumice and obsidian of the same composition.

A mud pot releases a burst of gas in the Davis-Schrimpf Seep Field near the Salton Sea. The geothermal area here is related to the same faulting and volcanic system which created the Salton Buttes lava domes. USGS photo by Deb Bergfeld, 2016.

Drew Downs in Iceland with a glacier in hte background.

Main hydrothermal features of the new (2016) 3-D model of the subsurface at Long Valley Caldera. This schematic is based on a survey of the electrical properties of the earth (magnetotellurics) below. Arrows show subsurface water flow, with colors keyed to changing water temperature, from blue (cold) to red (hot). Purple arrows show an extinct hot water pathway.

The photo was taken from a vantage looking up Avalanche Gulch at Red Banks (a line of cliffs along the ridge central to the photograph).

This is a simplified diagram of regional range front faults as they intersect the Long Valley Caldera.

Geologic field-trip guide to Lassen Volcanic National Park and vicinity, California

In this view down from the Point Bonita lighthouse, a sea arch made up of slightly metamorphosed pillow basalts rises from the surf. The green tinge on some of the "pillows" is the result of metamorphism, replacing primary minerals with greener ones such as chlorite and epidote. USGS photo by Jessica L. Ball

Cliffs of Franciscan Complex rocks near the Point Bonita Lighthouse reveal metamorphosed pillow lava at their bases. USGS photo by Jessica L. Ball

C1 and C3 are granitic crystal-melt mush (partially crystallized magma) columns that fed the most recent Mono Craters eruptions. The connection from C1 to South Coulée (SC) is older and colder than the connection from C3 to North Coulée (NC) and Panum Crater (PC), which carries hydrothermal fluid to the surface.

Plot of earthquakes in Mount Shasta region greater than M1.0 from April 3, 2010 to April 3, 2015.

Mount Shasta, California simplified hazards map showing potential impact area for ground-based hazards during a volcanic event.

Lidar images of Shastina cone, west flank of Mount Shasta, California. Details of lava flows and other surficial features are best seen in the image to the right with vegetation removed.

Titanium tubed used to collect gas from a fumarole near Lassen Peak, California.

Volcanic-gas "sniffer" installed at Mammoth Mountain, California measures temperature plus carbon dioxide and other gas concentration from a steaming vent.