Craig Pass Closed for the Season; Mammoth to Norris Closed Sept. 14-30
The road linking West Thumb and Old Faithful is closed for the season—traffic should detour through West Thumb, Lake, and Canyon. The road from Mammoth to Norris is closed for two weeks—traffic should detour over Dunraven Pass. More »
Mammoth Area Geologic Highlights
Mammoth Hot Springs
Mammoth Hot Springs are a surficial expression of the deep volcanic forces at work in Yellowstone. Although these springs lie outside the caldera boundary, scientists surmise that the heat from the hot springs comes from the same magmatic system that fuels other Yellowstone thermal areas. A large fault system runs between Norris Geyser Basin and Mammoth, which may allow thermal water to flow between the two. Also, multiple basalt eruptions have occurred in this area. Thus, basalt may be a heat source for the Mammoth area.
The Mammoth area exhibits much evidence of glacial activity from the Pinedale Glaciation. The summit of Terrace Mountain is covered with glacial till, thereby dating the travertine formation there to earlier than the end of the Pinedale Glaciation. Several thermal kames, including Capitol Hill and Dude Hill, are major features of the Mammoth Village area. Ice-marginal stream beds are in evidence in the small, narrow valleys where Floating Island Lake and Phantom Lake are found. In Gardner Canyon, one can see the old, sorted gravel bed of the Gardner River covered by unsorted glacial till.
Be sure to review our Mammoth Hot Springs Online Tour.
For other geological information, please see Natural Highlights of the Mammoth Area.
Did You Know?
Prior to the establishment of the National Park Service, the U.S. Army protected Yellowstone between 1886 and 1918. Fort Yellowstone was established at Mammoth Hot Springs for that purpose.