Clearlake Oaks cinder cone, Clear Lake Volcanic Field, California

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. This cone is probably about 41,000 years old. USGS photo by Jessica Ball.