Huckleberry and Lava Creek Tuffs on Mount Everts, YNP.

This cliff marks the location where scientists in the 1960s first recognized that more than one enormous caldera-forming eruption had occurred at Yellowstone. This view of Mount Everts is looking north from the Grand Loop Road across Lava Creek Canyon about 3 km downstream from Undine Falls. A key to understanding the welded tuff deposits here was recognizing two small stream valleys that had cut through the Huckleberry Ridge Tuff on both sides of the cliff.

The main cliff near the top of Mount Everts in the top center is the Huckleberry Ridge Tuff; part of the cliff consists of a slump block that has dropped several meters from the main cliff (click on image for larger-sized image). Where the cliff ends at the trees on the right, however, scientists recognized the profile of a buried stream valley that had been eroded through the Huckleberry Ridge Tuff. This valley had been filled by another welded tuff deposit that clearly was erupted well after the Huckleberry Ridge Tuff. This younger tuff was named after Lava Creek, and scientists quickly found many other exposures of this unit elsewhere inside and outside the park. On the left side of the cliff, another paleovalley was also filled by the Lava Creek Tuff.

This location is about 20 km from the rims of the two calderas that formed when the Huckleberry Ridge and Lava Creek Tuffs erupted. Here, the Huckleberry Ridge Tuff still is quite thick and densely welded, attesting to its high temperature of eruption and emplacement. The area of initial distribution of the tuff continues many tens of kilometers down valley beyond here. Both welded tuffs actually lies within a broad paleovalley, of which the Lava Creek Tuff-filled paleovalleys were smaller tributaries. The tuffs lie on easily eroded marine shales that are more than 65 million years old.