With an age of 71,000 years, SP Mountain is the youngest volcanic feature in the northern part of the San Francisco volcanic field. This basaltic andesite cone has a sharp rimmed profile, radial symmetry, and steep flanks, all characteristic of a young volcanic feature. The cone is made of bombs and lapilli. The base of the cone is 3,900 feet (1,200 m) across and 820 feet (250 m) tall. Photo by Steve Mattox, 1989.
A blocky lava flow was erupted early in the history of this vent. The flow is 50 feet (15 m) thick near the cone. Near the terminus of the flow, about 4 miles (7 km) away, the flow is 180 feet (55 m) thick. Photo by Steve Mattox, 1989.
View north from Crater 160 to SP Mountain. SP Mountain it the dark cone left of center. Photo by Steve Mattox, 1989.
Aerial view looking north to SP Mountain. An older graben cuts across the top-left corner of the photo. Note two fingers of the SP lava flows that spilled into the graben. Photograph by Wendell Duffield, U.S. Geological Survey.