Round Mountain, seen here from the west, rises above the floor of High Valley. Round Mountain is the northernmost of a N-S-trending chain of basaltic-andesite cinder cones at the eastern end of the Clear Lake volcanic field. A lava flow from Round Mountain underlies part of the High Valley. Many of the basaltic-andesite and andesitic lava flows of the Clear Lake field are contaminated with crustal materials. They often contain xenocrysts of quartz up to several cm in size that are known locally as "Lake County Diamonds."

Photo by Paul Kimberly, 1997 (Smithsonian Institution).

This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.

Clear Lake Volcanic Field