Mount Washburn is the north half of one of the ancient Absaroka volcanoes (fig. 26), and many of the rocks and other features related to this volcano, which characterized this great period of volcanism, can be seen along the road between Canyon Village and Tower. In roadcuts just south of Dunraven Pass several thin igneous dikes cut through volcanic breccias. These dikes radiate outward from the nearby central core of the volcano, which lies east of the highway in the vicinity of Washburn Hot Springs. From Dunraven Pass northward for 2-3 miles, the road is lined with lava flows and very coarse breccias that accumulated close to the volcanic neck (fig. 17). Farther north toward Tower Falls, breccias and conglomerates predominate, but the average size of individual rock fragments decreases gradually northward away from the center of eruption. Beds of sandstone then begin to appear in the sequence, having been deposited mainly by streams that drained the north slope of the volcano. [Illustration: IGNEOUS ROCK. Closeup view of intrusive igneous rock (diorite) from the Electric Peak stock in the Gallatin Range; Electric Peak is pictured in figure 37. The rock is composed chiefly of light-colored quartz and feldspar and dark-colored iron and magnesium silicate minerals. (Fig. 20)] At the end of Absaroka volcanism, approximately 40 million years ago (fig. 6), all of Yellowstone lay buried beneath several thousand feet of lavas, breccias, and ash (fig. 18). The landscape must have appeared as a gently rolling plateau, drained by sluggish, meandering streams and dotted here and there by volcanoes still rising above the general level of the ground. This plateau surface, however, probably stood at a maximum of only a few thousand feet above sea level, for animals and plants now found as fossils in the Absaroka volcanic rocks indicate that warm-temperature to even subtropical climates existed during the volcanic period (fig. 19). [Illustration: BUNSEN PEAK, a roughly circular body of intrusive igneous rock, is the eroded remnant of either the “neck” of an Absaroka volcano or a small stock that solidified directly beneath a volcano. The peak rises approximately 1,200 feet above a flat plain (foreground) that is covered by flows of younger basalt. The Yellowstone Tuff, formed by volcanic ash and dust exploded from the central Yellowstone region to the south, underlies the basalt. When erupted, the volcanic debris (as well as the basalt lava) flowed around this high-standing peak. (Fig. 21)] A quiet period