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Mount Everts exposures of two separate ash-flow tuffs

Detailed Description

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. In this view, Mount Everts is seen to the north of the Grand Loop Road, across the canyon of Lava Creek. On these cliffs of welded tuff, scientists in the 1960s first recognized that more than one great caldera-forming eruption had occurred in the Yellowstone region. A key to understanding the significance of these welded tuffs was the recognition that several small stream valleys had been cut through the Huckleberry Ridge Tuff after it was emplaced here within a broad stream-cut valley but before emplacement of the Lava Creek Tuff.

The cliffs on both sides of the view expose Huckleberry Ridge Tuff (click on image for larger-sized image). Locally at the base of the cliff a white layer of fallout ash that mantled the ground before the main sustained eruptions generated the Huckleberry Ridge ash flows that came to rest here as welded tuff. The cliff, where it appears to sag in the middle of the view, preserves the profile of a buried stream valley that had been eroded through the Huckleberry Ridge Tuff and later filled by the younger welded tuff, named for nearby Lava Creek. This and several other similar small paleovalleys were tributary to an ancestral valley of Lava Creek that had been eroded down through the Huckleberry Ridge Tuff but not as deeply as the present canyon of Lava Creek.

Many other exposures of both of these units have since been recognized elsewhere, both inside and outside Yellowstone National Park. This location is about 20 km from the respective margins of the two calderas that formed when the Huckleberry Ridge and Lava Creek Tuffs erupted. Outcrops of the Huckleberry Ridge Tuff continue many tens of kilometers down-valley beyond here. Despite its considerable distance from its source caldera, the tuff here is quite thick and is densely welded, attesting to its high temperature of eruption and emplacement.


Public Domain.