In this small area is a variety of hydrothermal features.
The heat for all of these features comes from the same heat
source that powers all the hydrothermal features in the park,
a chamber of magma that is between 3 and 8 miles below the
surface. For magma, this is very close to the surface. However
the combination of available ground water and the
configuration of the underground fissures are different for
each.
Ground water is readily available near springs and geysers.
Springs form where the underground fissures have unimpeded path to
the surface so the hot water flows out relatively constantly (see
Mammoth Basin for more details). Geysers form where there are
constrictions in the fissures that sometimes trap escaping gasses
(see
Upper Geyser Basin for details).
Near mud pots and fumaroles, there is less groundwater. At mud
pots, ground water becomes acidic and breaks down the bedrock to
clay. Since there is not much water, the clay and acids are not
washed away. Fumaroles are mostly steam because what little ground
water flows into the fissures boils away. (see
Mud Pots for details)
Surrounding these features is siliceous sinter. Silica dissolved
out of the rhyolite bedrock is redeposited at the surface as the
water temperature and ambient pressure drop. This sometimes form
thin sheets that appear to be solid ground. It is believed that
siliceous sinter only forms above ground.
Logging requirements:
Send me a note with :
- The text "GC15A16 Norris Basin – A Variety of Hydrothermal
Features" on the first line
- The number of people in your group.
- the relative topographic elevation of each of the four types of
features.
- is there a relationship between the feature’s elevation and the
amount of ground water needed to form these features
- Find an example of each of the 4 types of features
- Hot Spring
- Geyser
- Mud pot
- Fumarole
The above information was compiled from the
following sources:
- Fritz, William J., Roadside Geology of the
Yellowstone Country, Mountain Press Publishing Company, May
1989.
- West Thumb Geyser Basin Trail Guide including
Fishing Cone and Thumb Paint Pots, Yellowstone National Park,
Yellowstone Association, April 2007
- The Geologic Story of Yellowstone National
Park, William R. Keefer Illustrated by John R. Stacy, GEOLOGICAL
SURVEY BULLETIN 1347 1975.
Placement approved by the
Yellowstone National Park