Images

A sulfur flow over acid-sulfate ground at Brimstone Basin near the eastern shore of Yellowstone Lake. The flows formed when native sulfur deposits were ignited during a forest fire. Photo by Shaul Hurwitz, September 2008.

Roadcut in light pink ash-flow deposits of the Lava Creek Tuff on Grand Loop Road near Tuff Cliff.  The color and closely spaced jointing are characteristic of the Lava Creek Tuff map unit.  The steep faces and dense nature of the roadcut exposures indicate that a moderate degree of welding occurred and has not been subsequently modified by hydrothermal al

Lower Falls and Grand Canyon of the Yellowstone River.  The river here is eroding young, post-caldera rhyolite that was softened by hydrothermal alteration.  The V shape of the canyon indicates that the river is actively eroding in response to regional uplift.  Photo by Richard Tollo, George Washington University, August 12, 2008.

GPS station P714, located in Panther Meadow south of Mammoth Hot Springs in Yellowstone National Park. Photo by EarthScope Consortium, June 2008.

Left hand plot shows a focal mechanism from an earthquake where the fault is horizontal (red line), and the motion is right-lateral strike skip.  The initial direction of wave motion (either back toward the source or away from the source is shown by the arrows.  Right hand plot shows the associated beachball diagram, with compressional (“C”) and tensional

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.

Monitoring station VALT was installed on the crater floor of Mount St. Helens in 2006. It was called VALT because a vault-like structure about the size of a large doghouse was built into the rocky deposits to protect the state-of-the-art (at that time) broadband seismometer from environmental variables such as temperature and humidity.

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.

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.

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.

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).

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.

(Top) 1996–2000 interferogram draped over a 30-m DEM and showing uplift centered a few kilometers (miles) west of South Sister volcano. (Bottom) Geochemical data on top of the 1996–2000 interferogram. The columns show chloride (Cl) and sulfate (SO4) concentrations at sampled springs.