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Norris Basin – A Variety of Hydrothermal Features

Hidden : 08/20/2007
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Geocache Description:

The Norris Geyser Basin has an example of four hydrothermal features: fumaroles, mud pots, springs, and geysers. Each of these is the result of specific combinations of ground water, heat, and fissures.

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 :

  1. The text "GC15A16 Norris Basin – A Variety of Hydrothermal Features" on the first line
  2. The number of people in your group.
  3. the relative topographic elevation of each of the four types of features.
  4. is there a relationship between the feature’s elevation and the amount of ground water needed to form these features
  5. 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

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