Images

This lava flow of basaltic andesite composition erupted in the High Valley area. The blocky appearance of this flow top is termed 'A'ā (pronounced "ah-ah"), which is a Hawaiian term for lava flows that have a rough rubbly surface composed of broken lava blocks called clinkers. USGS photo by Dawnika Blatter

Kyle R. Anderson is a Volcano Geophysicist who works at the USGS California Volcano Observatory.

This outcropping of rocks along Morgan Valley Road is comprised of dacite, the most common composition in the Clear Lake Volcanic Field. Dacite contains more silica than basalt but less than rhyolite, so it’s commonly referred to as an “intermediate” composition.

Phil Dawson, a Volcano Seismologist with the California Volcano Observatory, stands next to a volcanic rock on the flank of Mount Shasta, California.

Joshua Crozier is a Mendenhall Postdoctoral Fellow working at the USGS California Volcano Observatory

Devils Kitchen in the Lassen Volcanic Region (within the bounds of the Lassen Volcanic National Park) is the second largest of Lassen's hydrothermal areas, after Bumpass Hell. Located in the Warner Valley in the southeast corner of the Park, Devils Kitchen contains boiling springs, mudpots, hot streams, and steam vents. USGS photo courtesy of Deb Bergfeld

Eruption episode 1 contains the oldest rocks in the Clear Lake Volcanic Field. The rock on the ridge in the background., located off Butts Canyon Road, is a lava flow that erupted around 2 million years ago.

Morro Rock is the westernmost peak in a chain of hills known locally as the “Morros” or the “Nine Sisters.”. It is a volcanic neck or plug composed of dacite which crystallized in the vent of a volcano and was later exposed by erosion. USGS photo by J. Ball

A southwesterly view of Mount Konocti, which is one of the largest volcanic features in the Clear Lake Volcanic Field. Buckingham Peninsula can also be seen stretching from the base of Mount Konocti into the foreground toward the eastern shore of the lake.  USGS photo by J.Ball

Ash-flow tuff (ignimbrite) on the fire road leading to the summit of Mount St. Helena, mapped as part of the intracaldera Sonoma volcanics. 

The Moraga Volcanics, one of several volcanic formations found in the Berkeley Hills Volcanic Field, frame a view of Mount Diablo to the east. The basaltic lava flows and their associated lapilli tuffs can be found in the Sibley Volcanic Regional Preserve. USGS photo by J. Ball

Geologists often break off the weathered surfaces of rocks in the field to get at the fresh, clean cores. This makes it easier to see the original mineralogy of the rock in question without oxidation, alteration, or other environmental impacts. USGS photo by D. Blatter

Geologists often break off the weathered surfaces of rocks in the field to get at the fresh, clean cores. This makes it easier to see the original mineralogy of the rock in question without oxidation, alteration, or other environmental impacts. USGS photo by D. Blatter.

These freshly excavated boulders along Spruce Grove Road are basalt, which is an iron and magnesium-rich rock that’s fairly uncommon in the Clear Lake Volcanic Field.

Eruption episode 3 is the most voluminous in the history of the Clear Lake Volcanic Field. Episode 3 rocks are of intermediate composition, primarily dacite, and make up many of the topographic high points in the field, including Mt. Konocti, where this photo is taken.

Andy Calvert and Tony Pivarunas drill into the face of a lava flow on Ash Creek Butte, a Pleistocene shield volcano northeast of Mount Shasta. USGS photo by Dawnika Blatter

USGS-Cascades Volcano Observatory geophysicist Rebecca Kramer works on station PR05, which is part of the Mount Rainier lahar detection network (Mount Rainier is pictured in the distance). The purpose of the site visit was to upgrade the power system and deploy infrasound equipment. 

Cinder cones (or scoria cones) are relatively small, steep-sided volcanoes that are constructed around a single vent when lava is ejected into the air, breaks into smaller pieces, and builds up around the sides of the vent. This photo is looking across the quarry which exposes the interior of a cinder cone east of Clearlake Oaks in the Clear Lake Volcanic Field.

Located at the midpoint of Clear Lake in Lake County, California, Buckingham Peninsula shows evidence of young explosive volcanism in the Clear Lake Volcanic Field. Little Borax Lake, enclosed within the Buckingham golf course, is a water-filled maar crater, as is Horseshoe Bay to its northeast. USGS photo by J. Ball.

Rhyolite lavas in the Yellowstone Caldera younger than 631,000 years

Thurston Lake and Mount Konocti, Clear Lake Volcanic Field, California.