Images

Southern tip of the Lemhi Range on the northeastern margin of the eastern Snake River Plain showing the caldera wall of the 6.27 million year old Blue Creek caldera, in the Heise volcanic field.  Also shown are other units from the Heise volcanic field including the Kilgore Tuff and the Blacktail Creek Tuff.  In the foreground is the much thicker sequence

An eruption of Daisy Geyser in the Upper Geyser Basin of Yellowstone National Park. The geyser erupts boiling water at about 93 °C (200 °F). Photo by Shaul Hurwitz on April 12, 2007.

Hydrothermal deposits on Mars. (A) This image was acquired by the Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment camera on November 22, 2006.  It shows a bright plateau of layered rocks about 90 meters (98 yards) across called, “Home Plate.”  NASA image: PSP_001513_1655_red; Image Credit: NASA/JPL-Caltech/Univ. of Arizona.

National Agriculture Imagery Program natural-color image from September 9, 2006, showing newly mapped thermal areas (outlined in yellow) on the north side of the Mallard Lake resurgent dome.

Guardian Geyser and Norris Geyser Basin, Yellowstone National Park.

Aerial view of Excelsior Geyser (in the foreground) and Grand Prismatic Spring in Yellowstone’s Midway Geyser Basin. The colors around the thermal features are locations of different thermophile communities. These thermophiles fix carbon, both from the atmosphere and from the hot water. Credit Jim Peaco; June 22, 2006; Catalog #20386d; Original #IT8M4075

Old Faithful Geyser in eruption. Under Yellowstone Research Permit YELL-SCI-8030, 13 mineralized wood specimens were collected from the geyser mound. The dates of the mineralized wood samples imply that such eruptions did not take place for over a century between the mid-13^th to mid-14^th centuries.

Rangers attempting to clean trash out of Morning Glory Pool in September 1975. National Park Service photograph Dan Ing.

Aerial (balloon) view of Norris Geyser Basin, Yellowstone National Park, looking northwest from the south.  USGS Photo by Brita Graham Wall, 2005.

Grand Prismatic Spring, Midway Geyser Basin, Yellowstone National Park.  Grand Prismatic is the largest hot spring in Yellowstone and the third largest in the world. Photograph by Robert Fournier.

Eruptions of the Yellowstone volcanic system have included the two largest volcanic eruptions in North America in the past few million years; the third largest was at Long Valley in California and produced the Bishop ash bed. The biggest of the Yellowstone eruptions occurred 2.1 million years ago, depositing the Huckleberry Ridge ash bed.

A comparison of black cinders from Cinder Pool, in Norris Geyser Basin (left), with yellow cinders from an unnamed pool in the West Nymph Creek thermal area (right).  The Cinder Pool cinders are black due to finely dispersed pyrite, whereas the yellow color of cinders from the West Nymph Creek pool is due to the lack of pyrite.

Heise cliffs, the type location for the 4.45–7.0 million year old Heise Group from the Heise volcanic field, which preceded the Yellowstone Plateau volcanic field.  Most of the cliffs exposed here are rhyolitic, densely welded, rhyolitic pyroclastic density flow deposits.  USGS Photo by L. A. Morgan (May 2005).

Map showing earthquake focal mechanisms in the Yellowstone region.

Densely welded rhyolites from the central Snake River Plain.  USGS Photo by L. A. Morgan (May 2004).

Exposure of rhyolite volcanic rocks in the central Snake River Plain showing a thick sequence of 10-12 million-year-old, densely welded, pyroclastic density flow units (darker units from middle of photo to top of hill) overlying a thick sequence of white, friable, ash fall deposits.  USGS Photo by L. A. Morgan (May 2004).

Angel Terrace, Mammoth Hot Springs, Yellowstone National Park. Travertine deposits are abundant in the area. Photo by JoAnn Holloway, 2003.

Image of the western face of Mount Moran. Note the dark stripe that marks a mafic intrusion (the “diabase dike”) and the vestiges of the Cambrian-aged Flathead Sandstone Formation (about 50 vertical feet in thickness) at the summit.

Moraines and glacial erratics (boulders) near Junction Butte in northeast Yellowstone National Park. Cosmogenic age dating of these erratics was used to determine when glaciers retreated from the Yellowstone Plateau.

Simplified geologic map detailing locations of volcanics at Sepulcher Mountain and igneous intrusion at Electric Peak and surrounding area. This map is Fig. 2.

Slow cooling of a basaltic lava flow that was erupted about 500,000 years ago resulted in the formation of hexagonal columns at Sheepeater Cliff, in Yellowstone National Park.