The Clear Lake volcanic field erupted in association with and within the San Andreas Fault Zone. Although the San Andreas fault is the hallmark fault associated with the transform tectonic boundary between the Pacific and North American plates, the “boundary” between plates is more accurately described by a zone of faulting than by a single fault.
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Faults bounding the Clear Lake Volcanic Field
The Clear Lake volcanic field erupted in association with and within the San Andreas Fault Zone. Although the San Andreas fault is the hallmark fault associated with the transform tectonic boundary between the Pacific and North American plates, the “boundary” between plates is more accurately described by a zone of faulting than by a single fault.
Faults bounding the Geysers Geothermal Complex
Just as the Bartlett Springs and Maacama faults are the major bounding faults of the Clear Lake volcanic field, the Collayami (purple) and Maacama (green) faults bound the Geysers Geothermal Field.
Just as the Bartlett Springs and Maacama faults are the major bounding faults of the Clear Lake volcanic field, the Collayami (purple) and Maacama (green) faults bound the Geysers Geothermal Field.
Mount Konocti, Clear Lake Volcanic Field, and CalVO geologist Seth Burgess
CalVO geologist Seth Burgess looking across Clear Lake at Mount Konocti, a prominent volcanic dome complex within the Clear Lake volcanic field. Photo courtesy of Alexander Rubin.
CalVO geologist Seth Burgess looking across Clear Lake at Mount Konocti, a prominent volcanic dome complex within the Clear Lake volcanic field. Photo courtesy of Alexander Rubin.
Andesite on Highway 175, Clear Lake Volcanic Field, California
This outcrop is along Highway 175, near Hobergs, and is comprised of andesite. Andesite contains more silica than basalt, but less than dacite.
This outcrop is along Highway 175, near Hobergs, and is comprised of andesite. Andesite contains more silica than basalt, but less than dacite.
Kelsey Creek rhyodacite lava, Clear Lake Volcanic Field, California
Rhyodacite has more silica than dacite and less than rhyolite. This flow-banded rhyodacite is gorgeous in outcrop and is around a half million years old.
Rhyodacite has more silica than dacite and less than rhyolite. This flow-banded rhyodacite is gorgeous in outcrop and is around a half million years old.
Eruption Episode 4 rocks, Clear Lake Volcanic Field, California
The cinder cone in the distance is Round Mountain, which is being actively quarried for road rock. Eruption episode 4 is the most recent in the Clear Lake Volcanic Field, and is characterized primarily by lava flows, cinder cones (like the one pictured), and maar deposits.
The cinder cone in the distance is Round Mountain, which is being actively quarried for road rock. Eruption episode 4 is the most recent in the Clear Lake Volcanic Field, and is characterized primarily by lava flows, cinder cones (like the one pictured), and maar deposits.