Barronette Peak at the eastern entrance to Yellowstone National Park formed from epiclastic material and air-fall tuff that originated from several andesitic volcanoes in the Absaroka Volcanic Supergroup that were active 20-30 million years prior to Yellowstone eruptions.
Barronette Peak detail.
Bison in Lamar River Valley near the trail that I took to hike to Specimen Ridge.
Petrified tree on Specimen ridge with a view over Lamar River Valley. This and other trees in a forest 50 million years ago were buried rapidly in debris and conglomerate released by the Absaroka Volcanic Supergroup and dead wood components became infused/replaced by silica-rich chemicals.
Wood and bark structurel is maintained in the petrified tree.
Part of a petrified tree partially uncovered in the volcanic conglomerate from the Eocene epoch. The Lamar River is in the glacier-carved valley below.
The eroded edge of Yellowstone River Canyon exposes strata from volcanic activity in the Yellowstone area that occurred in three phases from 48 million to 0.6 million years ago. The strata from top to bottom that capture1.3 million years activity are: glacial till (top); columnar jointed basalt; gravel of volcanic rock; 2nd layer of columnar jointed basalt; gravel; and Eocene conglomerate.
Detail of top columnar jointed basalt. This silica-poor basalt originated from the Yellowstone Plateau volcanic field to the South.
Junction Butte basalt with a lower jointed segment.
Tower Falls is at an area of erosion-resistant volcanic conglomerate.
Lower Falls of the Yellowstone River occurs at a junction between erosion-resistant and erosion-susceptible rhyolite. The three phases of Yellowstone volcanic activity from 48 to 0.6 million years ago were characterized by rhyolitic, basaltic and bimodal lava flows.
The southern rim of Lewis Lake marks the southern rim of the Yellowstone Caldera which was volcanically active 639,000 years ago.
Steam exits fumeroles in the Norris Geyser Basin. Yellowstone's magma chamber is 5 to 7 miles below the surface and heats the rocks that heat the water for the region's hot springs and geysers.
