Yellowstone caldera viewed from Mount Washburn

Yellowstone caldera viewed from Mount Washburn.  The caldera is the low-lying area extending from the foothills of Mount Washburn in the foreground to the rugged mountains on the horizon.  The incised valley of the Yellowstone River stretches from left to right in the middle distance.  Steep valley walls are illuminated by sunlight in the center.  Mount Washburn is a remnant andesitic volcano of the Eocene Absaroka Range.  The hike along the access road to the summit (where this photograph was taken) presents many opportunities to observe lavas and volcanogenic sedimentary deposits. This geologically rich hike is an excellent field trip in itself.  Photo by Richard Tollo, George Washington University, August 8, 2009.