Global Volcanism Program | Image GVP-03024
The latest eruption in the Mount Jefferson area occurred from the cinder cone at the lower left on the flank of South Cinder Peak in the center of the photo. The eruption, dated about 1000 years ago, formed the cinder cone and produced a lava flow that split into two lobes. One traveled to the NW, and the other flowed 3.5 km west into Marion Lake.
Photo by Willie Scott, 1973 (U.S. Geological Survey).