Bishop Peak, California, USA
(c) 2001 Andrew Alden, licensed to About.com, Inc. (fair use policy)
Bishop Peak is the highest of nine volcanic corescalled the Morros (the noses) or the Nine Sistersthat run from San Luis Obispo to Morro Bay in central California. All of them are volcanic necks dating from the early Miocene 2025 million years ago. All formed as an abrupt change in the local tectonic regime opened this subduction wedge to rhyodacitic volcanism. The sticky, high-silica rhyolite of the Morros, which once were the deep cores of volcanoes, contrasts vividly with the surrounding serpentinite and melange of the Franciscan formation.
The city of San Luis Obispo keeps much of this peak as an open space. The local Sierra Club chapter is working to enhance and preserve this remarkable chain of hills.