Close up view of welded Huckleberry Ridge Tuff on Mount Everts, YNP

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.