SP Crater is a Pleistocene-age cinder cone in the north central part of the San Francisco volcanic field. The cone erupted about 50,000 years ago. This lava flow broke out at the north base of the cinder cone and flowed north several kilometers. In spite of being exposed for more than 50,000 years, the lava flow remains in pristine condition. The vent is accessible by unpaved road and is a favorite of people exploring the volcanic field. Image provided courtesy of Google Earth.