Frequently Asked Questions: Mammoth Hot Springs

Are the springs drying up?
No, the overall activity and volume of water discharge remain relatively constant; most of the water flows underground.

Why are the dry springs so white?
Limestone, a naturally white rock, underlies this area. Hot water dissolves the mineral calcium carbonate from the limestone, which is deposited at the surface to form travertine. Colors in the hot springs come from thermophiles.

Where does the water come from?
In the surrounding mountains, rain and snow soak through the ground. The water is heated below the surface. As it rises, it dissolves the limestone rock that lies beneath the Mammoth area. Sometimes the water is concentrated in a few springs while at other times it may spread across many outlets. In every case, water follows the path of least resistance, which could be above ground or underground. Scientists estimate that, at any given time, about 10% of the water in the Mammoth Hot Springs system is on the surface; the other 90% is underground.

Does the heat for the hot springs come from the Yellowstone Caldera?
Mammoth Hot Springs lies to the north of the caldera. Scientists continue to study where the heat for the hot springs comes from. One possibility is the volcano’s magma chamber, similar to the heat source for other thermal areas closer to the 640,000-year-old caldera. There may also be basaltic magma bodies, related to the Yellowstone volcano, deep underground between Norris and Mammoth, which could be a contributing heat source.

Can we soak in the hot springs?
No, the travertine features are very fragile. You may soak in bodies of water fed by runoff from hydro­thermal features, such as Boiling River north of Mammoth. It is open in daylight hours and closed during times of high water.

How was Bunsen Peak formed?
At 8,564 feet, Bunsen Peak (south of Mammoth) is an intrusion of igneous material (magma) formed approximately 50 million years ago. Bunsen Peak and the “Bunsen burner” were named for physicist Robert Wilhelm Bunsen. He was involved in pioneering geyser research in Iceland. His theory on geyser activity was published in the 1800s, and is still considered accurate.

What were these old buildings?
Many of the older buildings grouped together in Mammoth belong to Fort Yellowstone, built by the US Army from 1891 to 1913, when it managed the park. A self-guided trail goes through this National Historic Landmark District.

What is the 45th parallel?
On the road between the North Entrance and Mammoth, a sign marks the 45th parallel of latitude, which is halfway between the Equator and the North Pole. The majority of the Montana–Wyoming state line does not follow the parallel through the park.

What forms the canyon north of Mammoth?
The canyon is the face of Mount Everts, 7,841 feet high. It consists of layered sandstones and shales—sedimentary deposits from a shallow inland sea 70–140 million years ago. Its steep cliffs—eroded by glaciers, floods, and landslides—provide habitat for bighorn sheep. It was named for explorer Truman Everts, a member of the 1870 Washburn Expedition who became lost. He was found east of the mountain, near Blacktail Plateau.

What animals can I see in this area?
Elk live here all year, and are wild and unpredictable. Each year visitors are chased, trapped, and sometimes injured by elk. Look for Uinta ground squirrels in front of the visitor center and among the hotel cabins during summer. You might see bighorn sheep in the canyon north of Mammoth. South of Bunsen Peak is Swan Lake Flat, where visitors often see elk, bison, and sometimes grizzlies and wolves. It is also an excellent place for watching cranes, ducks, and other birds.

Historic Areas & Structures


Last updated: March 22, 2018

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