Yellowstone is located on an active volcano! Three major eruptions have occurred in the last 2.1 million years, most recently 650,000 years ago. Magma only 3-8 miles down provides heat for thermal features at Yellowstone. The Upper Geyser Basin, home to the old faithful, is one of 3 large hot fountain basins along the Firehole River. We were there on a sunny day and we were treated to an eruption from 3 other geysers besides Old Faithful. For miles from the boardwalk, we passed many hot springs, mud pots, and fumaroles.
At the north end of the park, boiling water and steam flow to the surface through limestone, which dissolves to form weak carbonic acid. When hot water reaches the surface, calcium carbonate is deposited to form a travertine terrace from Mammoth Hot Springs. This is the same process that forms a travertine pond in Pamukkale, Turkey.
The visitor center in Canyon Village has the incredible geological appearance of Yellowstone. Yellowstone River Canyon has thunderous waterfalls and multi-colored canyon walls resulting from ongoing geothermal activity.
The crater was left after the last eruption was filled with lava flows. Across the canyon from Tower falls is a remarkable example of the lava flow that cools slowly to form a Basaltic column.
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During the last ice age, 20,000 years ago, ice thickness was more than 4,000 feet. Morain and erratic (rocks carried by glaciers) scattered around the landscape. Glaciers disappeared from Yellowstone thousands of years ago, the result of global warming that began 20,000 years ago. When ice retreated, Homo sapiens entered Yellowstone about 11,000 years ago and there is evidence of their initial existence.
I hope you enjoy a small selection of photos.