Maar eruption deposit, Clear Lake Volcanic Field, California

The layered deposits shown in this picture were created by a maar eruption, when magma and volcanic gasses interact with groundwater to create an explosive eruption. Maar eruptions like these commonly generate craters, some of which can be seen along the western shore of Clear Lake. Soda Bay, near where this photo was taken, is a maar crater. The layered nature of this deposit is a result of the particles from many discrete eruptions falling on top of one another over a short period of time. USGS photo by Dawnika Blatter