Postcard of Mammoth Hot Springs photographed by Frank J. Haynes, no date. Mammoth Hot Springs is a large complex of hot springs on a hill of travertine in Yellowstone NP adjacent to Fort Yellowstone and the Mammoth Hot Springs Historic District. It was created over thousands of years as hot water from the spring cooled and deposited calcium carbonate (over two tons flow into Mammoth each day in a solution). Although these springs lie outside the caldera boundary, their energy has been attributed to the same magmatic system that fuels other Yellowstone geothermal areas. Yellowstone National Park is a national park located primarily in the state of Wyoming, although it also extends into Montana and Idaho. It was established by Congress and signed into law by President Ulysses S. Grant on March 1, 1872.
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Album / Science Source / NPS Photo/Frank J. Haynes