Images

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

CalVO's Stuart Wilkinson skis out to a remote seismic instrument in the Long Valley volcanic region to perform routine maintenance.

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

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

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.

View from entrance of Valentine Cave toward interior shows the raised lines of high-lava marks on wall on wall of central pillar. USGS photo by J. Donnelly-Nolan.

Wes spent much of his 48 years with the USGS working in the Long Valley Caldera. USGS photo by Emily Montgomery-Brown.

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

USGS scientists Deb Bergfeld and Laura Clor collect samples of the gas from the old Gas Hill wellhead in Kelseyville, CA. USGS photo by Jen Lewicki.

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.

A typical California serpentinite shining in the sun. The greenish hues come from the minerals lizardite, antigorite, and chrysotile. USGS photo by J. Ball.

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.

Catastrophic landslide near Oso, Washington, March 22, 2014.

Wes Hildreth is an expert when it comes to studying the Long Valley Caldera. Here, he is standing on Tertiary basalt lava flows on the north rim of the caldera, view to the southeast with Lake Crowley visible in the center of the caldera, and McGee Mountain above the lake on the skyline.

Map showing one-year probability of accumulation of 1 centimeter (0.4 inch) or more of tephra from eruptions of volcanoes in the Cascade Range.

CalVO geologist Mae Marcaida examines thin layers of volcanic ash sandwiched between thick beds of sediment deposited by ancestral Mono Lake in eastern California. Each ash layer is evidence of a past explosive eruption of the Mono Craters, which began erupting about 65,000 years ago just south of present-day Mono Lake.

Wes Hildreth was a lifelong runner, an activity that aided him in his field work.

Geologists examine tephra deposits to better understand the early eruptive behavior of the Medicine Lake Volcano, evidence of which can be found as far away as central Oregon.