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Obsidian Cliff exposes the interior of a thick rhyolite lava flow that erupted about 180,000 years ago. The vertical columns are cooling fractures that formed as the thick lava flow cooled and crystallized in a previously eroded valley bottom. The flow consists of obsidian, a dark rhyolitic volcanic glass. Photograph by S.R. Brantley on 23 May 2001. |
| Close view of rocks from Obsidian Cliff showing cavities lined with microcrystals, formed by gases as the glass cooled from high temperatures. Photograph by S.R. Brantley on 23 May 2001. | |
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This photo shows columnar basalt at Sheepeater Cliff. The long vertical columns of the cliff are bounded by cooling fractures that formed as the thick lava flow cooled forming a regular set of joints perpendicular to the cooling surfaces at the top, bottom, and sides of the flow. This flow of Swan Lake Flat Basalt erupted sometime between 320,000 and 640,000 years ago. Photograph by S.R. Brantley on 20 May 2001. |
| Columns of the Sheepeater Cliff, bounded by contractional cooling fractures typically are regular polygons, which here are seen to be hexagonal in cross section. Photograph by S.R. Brantley on 20 May 2001. | |
| The two dark lava flows seen here in the Narrows of the Grand Canyon of the Yellowstone River erupted about 1.3 million years ago at about the time of the second caldera-forming rhyolitic ash-flow eruption, west of Yellowstone National Park. Thick layers of stream-deposited gravels lie beneath and between the two lava flows visible in this photo. The cliffs eroded into pinnacles below the lower basalt are older volcanic rocks of the Absorka volcanic field. Photograph by S.R. Brantley on 21 May 2001. | |
| View across The Narrows of the Grand Canyon of the Yellowstone. The lowest part of the cliff is composed of river-deposited gravel. Above that is a single columnar-jointed basalt flow overlain by glacial till. Photograph by S.R. Brantley on 21 May 2001. | |
| Columnar jointing is seen in The Narrows of the Grand Canyon of the Yellowstone. These columns formed as a result of a basaltic lava flow contracting while cooling. The basalt flow lies on fluvial gravels and later was erosionally truncated at the top of the columns, now overlain by glacial deposits. Photograph by David E. Wieprecht on September 1996. | |
| Outcrop of the Junction Butte basalt alongside the road at Overhanging Cliff. The zone of prominent columnar jointing at the base of this thick lava flow formed by contraction cooling; it overlies stream-deposited sediments and is overlain by a zone of irregularly intersecting joints. Photograph by S.R. Brantley on 21 May 2001. | |
| Silver Gate above Mammoth Hot Springs, showing jumbled blocks of old travertine deposited by now-extinct hot springs. These blocks are parts of a large landslide that has brought them down from the cliffs of Terrace Mountain above. Photograph by David E. Wieprecht in September 1998. | |
| Mesa Falls ash-flow tuff and underlying fallout ash exposed in a quarry near Ashton, Idaho. This area was near the depositional margin of the ash flows and consequently the ash-flow tuff is nonwelded and contained abundant large pumice blocks. The tuff was deposited during a large eruption that produced the Henrys Fork caldera southwest of Yellowstone National Park 1.2 million years ago. Photograph by Dan Dzurisin. | |
| Close view of Mesa Falls ash-flow tuff and underlying fallout ash exposed in a quarry near Ashton, Idaho. Photograph by Robert L. Christiansen in July 1983. | |
| Polygonal joints intersect on a steep dip slope erosionally stripped to near the base of an upper platy-jointed zone of member C, Huckleberry Ridge Tuff. Photograph by Robert L. Christiansen on 23 July 1970. | |
| At Golden Gate, only a few kilometers from Mammoth Hot Springs, this is one of the most accessible and widely seen exposures of the Huckleberry Ridge Tuff, which erupted during the first volcanic cycle of the Yellowstone Plateau volcanic field about 2.1 million years ago. This exposure of the Huckleberry Ridge Tuff is located about 20 km north from the rim of the caldera that formed as a consequence of its eruption. The Huckleberry Ridge Tuff is also found on top of Mount Everts, the broad peak 6 km in the distance. Based on the distribution of the tuff, scientists infer that a broad river valley probably existed between here and Mount Everts. The tuff filled or partly buried that valley. Photograph by S.R. Brantley on 20 May 2001. | |
| 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 Tuff and Canyon flow, respectively), which erupted nearly 500,000 years ago. Both units have been intensely altered by hydrothermal fluids. Photograph by S.R. Brantley on 20 May 2001. | |
| View northward across the Grand Canyon of the Yellowstone from near Point Sublime. Dark cliffs on the right are little-altered rhyolites erupted early in the postcollapse history of the Yellowstone caldera. In contrast, the brightly colored areas to the left reveal the effects of intense hydrothermal alteration of the same rhyolites. The deeper parts of the canyon, including most of the cliffs visible in this view, expose a rhyolite lava flow, the Canyon flow; the cliffs forming a ledge near the top of the cliffs are fused rhyolitic bedded ash-fall tuffs that were so hot as they fell that they welded into dense lava-like rock. The uppermost slopes, largely tree-covered but forming a white rim above the brown and yellow cliffs in the altered part of the canyon, are lacustrine sedimentary rocks, laid down in and near a lake that once filled the caldera before it was drained by downcutting of the Yellowstone River to form the Grand Canyon. Mountains on the skyline beyond the canyon rim are older volcanic rocks of the Absaroka volcanic field that lie outside the Yellowstone caldera. Photograph by Robert L. Christiansen on 24 July 1968. | |
| Mount Everts is located in the northern part of Yellowstone National Park. Huckleberry Ridge Tuff and the Lava Creek Tuff are exposed on Mount Everts. Photograph by S.R. Brantley on 19 May 2001. | |
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Welded Huckleberry Ridge Tuff forms a "rimrock" ledge on Mount Everts just east of Mammoth Hot Springs. This tuff, 2.1 million years old, here lies unconformably on eroded marine sedimentary rocks of Cretaceous age (about 70 million years). At the base of the welded tuff is a white layer of fallout ash of the Huckleberry Ridge Tuff. The Cretaceous sedimentary rocks beneath this ash are reddened, at least in part by heating from the overlying volcanic layers. Photograph by Robert L. Christiansen in July 1983. |
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| Lava Creek here spills over the cliff face of a basalt lava flow that was emplaced about 700,000 years ago. Named after this falls, the Undine Falls Basalt erupted before Yellowstone's third explosive caldera-forming eruption that ejected the Lava Creek Tuff about 640,000 years ago. Scientists first distinguished the Lava Creek Tuff from the 2.1-million-year-old Huckleberry Ridge Tuff in the 1960s on nearby Mount Everts--the first clue that Yellowstone's history included more than one caldera-forming eruption. | |
| Aerial view showing faults associated with the northeastern side of the Yellowstone caldera. The view is looking south. Mirror Lake fills a depression (sag pond) formed by uneven settling of the ground along one of the faults. The low area between the large fault scarp in the sunlight and the next fault scarp to the right is a graben- a depression between two oppositely facing faults. The snow-covered Absaroka Mountains are visible in the far distance; Yellowstone Lake is visible in the upper right of the photo. Access to this remote part of Yellowstone National Park requires special permission. Photograph by Bob Smith, University of Utah in 1992. | |
| Aerial view of several large young rhyolite lava flows erupted within the Yellowstone caldera. This view is toward the NNE from above Bechler Creek; the Gallatin and Absaroka Ranges are visible in the far distance. Photograph by Bob Smith, University of Utah, 1992. | |
| Aerial view toward the south of thick intracaldera rhyolite lava flows of the forested Madison and Pitchstone Plateaus, burying the west rim of the Yellowstone caldera. The plateaus preserve the characteristic form of these thick flows, emplaced as highly viscous lavas with steep scarp-like lobate margins. The Teton Range rises beyond the caldera. on the distant skyline. Photograph by Robert L. Christiansen on 17 July 1977. | |
| View toward the east of outermost fault associated with the northeastern side of the Yellowstone caldera, taken from the top of a fault scarp on the west side of a graben that lies between the faults. The fault scarp in the photo is about 30 m high; note person on horse for scale. Lava Creek Tuff is exposed on the scarp, but glacial deposts mantle the graben surface. Photograph by Bob Smith, University of Utah, 2001. | |
| The cliffs that rim Mount Everts in the northern part of Yellowstone National Park east of Mammoth Hot Springs provide exceptional exposures of both the 2.1-million-year-old Huckleberry Ridge Tuff and the 640,000-year-old Lava Creek Tuff. Photograph by Robert L. Christiansen on 16 October 1967. More info. |
