Vitrophyre breccia in the Tolay Volcanic Field

This exposure of volcanic breccia is a volcanic rock comprised of broken pieces of vitrophyre, a welded volcanic glass. The breccia is found in the Tolay Volcanics, a sequence of rhyolite, andesite, and basalt at least 1220 m thick. The 9 Ma Tolay Volcanics are equivalent to the Berkeley Hills Volcanics. Photo courtesy of Ross Wagner.