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.
Logging requirements:
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