Mammoth Hot Springs is located more than 20 miles north of the Yellowstone Caldera. Even this far from the caldera, the same magma that powers the hydrothermal features inside the caldera heats the ground water at mammoth. As with the other hydrothermal features at the park, these hot springs are the result of a unique combination of bedrock, ground water, heat, and subsurface cracks.
In the Paleozoic (sometime between 245 to 570 million years ago) a shallow sea covered the area. Beneath this sea, a layer of limestone formed. Much later when during the formation of the various calderas in Yellowstone (see Yellowstone Caldera at Madison Junction ) rhyolitic magma erupted through the layers of limestone either blowing it out or melting it. However, this far north of the caldera the limestone bedrock remained.
Rain water and snow melt combine with carbon dioxide in the air to form a weak acid called carbonic acid. These waters then infiltrate into the ground and come in contact with still cooling or still molten magma between 3 and 8 miles of the surface (very shallow for magma). This hot, slightly acidic ground water dissolves the limestone bedrock quite easily and much more easily than the rhyolite bedrock found in the caldera. Then cracks in the bedrock allow the hot water to flow back up to the surface where the water cools and evaporates forcing the dissolved limestone to precipitate (turn back into a solid) forming the travertine terraces. There is even evidence that the bacteria and algae in the pools increase the rate of precipitation of travertine.
This far from the caldera the ground water is not heated as much. The maximum temperature found while drilling was only 167 deg. F, not hot enough to boil, even at this altitude, but still hot enough to be dangerous. So what bubbles you do see in the pools are not from boiling, but carbon dioxide coming out of solution just like a carbonated drink that is opened.
Send me a note with :
- The text "GC14ZQZ Mammoth Hot Springs" on the first line
- The number of people in your group.
- The travertine along the trail at the coordinates. Take a very close look. I am looking for the very small features.
- Why it is important to stay on the trails based on your observations in #1.
- The difference in color between Liberty Cap (N44 58.360 W110 42.255) and Minerva Terrace (N44 58.247 W110 42.295) and what would account for that difference.
The above information was compiled from the following sources:
- NPS informational Pannel
- Mammoth Hot Springs Trail Guide Including Lower Terraces and Upper Terrace Dirve, Yellowstone National Park, Yellowstone Association, April 2007
- Yellowstone Digital Slide File, National Park Service; http://www.nps.gov/archive/yell/slidefile/graphics/diagrams/Page.htm
- Fritz, William J., Roadside Geology of the Yellowstone Country, Mountain Press Publishing Company, May 1989.
Placement approved by the
Yellowstone National Park