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This view of the Grand Canyon of the Yellowstone is from below Lower Falls, looking downstream. The splendid yellow-brown walls of the canyon consist predominantly of rhyolite tuff and lava (Sulfur Creek and Canyon flow, respectively), which erupted nearly 500,000 years ago. Both units have been intensely altered by hydrothermal fluids. (USGS photograph by Steven R. Brantley.) This report is also available on CD-ROM from: U.S. Geological Survey Information Services, Box 25286 |
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Suggested citation and version history
U.S. Department of the Interior
KEN SALAZAR, Secretary
U.S. Geological Survey
Marcia K. McNutt, Director