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Mudpots lined up above a volcanic fissure at Hverarönd, Iceland

A mudpot, or mud pool, is a sort of acidic hot spring, or fumarole, with limited water. It usually takes the form of a pool of bubbling mud. The acid and microorganisms decompose surrounding rock into clay and mud.


The mud of a mudpot takes the form of a viscous, often bubbling, slurry. As the boiling mud is often squirted over the brims of the mudpot, a sort of mini-volcano of mud starts to build up, sometimes reaching heights of 1 to 1.5 meters.[1] Although mudpots are often called "mud volcanoes", true mud volcanoes are very different in nature. The mud of a mudpot is generally of white to greyish color, but is sometimes stained with reddish or pink spots from iron compounds. When the slurry is particularly colorful, the feature may be referred to as a paint pot.[2]


Mudpots form in high-temperature geothermal areas where water is in short supply. The little water that is available rises to the surface at a spot where the soil is rich in volcanic ash, clay, and other fine particulates. The thickness of the mud usually changes along with seasonal changes in the water table.[3]

Notable sites[edit]

The geothermal areas of Yellowstone National Park contain several notable examples of both mudpots and paint pots, as do some areas of Azerbaijan, Iceland, New Zealand and Nicaragua.

Several locations in and around the Salton Sea in California are also home to active mudpots,[4] including the moving Niland Geyser.[5][6] In the case of Niland Geyser, its name is somewhat of a misnomer, as the release of carbon dioxide by seismic activity from the nearby San Andreas Fault is responsible for its behaviour, rather than through geothermal activity. The fluid contained within it is near background temperature rather than boiling, measuring around 80 °F (27 °C).[7]

Bumpass Hell in Lassen Volcanic National Park also contains mudpots.

Photo gallery[edit]


  1. ^ Kleinschmidt, Janice (28 February 2006). "Sea of Wonders". Palms Springs Life. Retrieved 21 January 2017.
  2. ^ Chilton (1916). "Death Valley Dodge with O.K. Parker st the Wheel". Motor Agr. Retrieved 21 January 2017.
  3. ^ "Yellowstone National Park: Mudpots". National Park Service. Retrieved 21 January 2017.
  4. ^ Laflin, Patricia B. "The Salton Sea: California;s Overlooked Treasure — Chapter 8 — Mudpots, Geysers and Mullet Island". San Diego State University. Retrieved 21 January 2017.
  5. ^ Francuch, Dean G; Deane, Travis; Zamora, Carol (2019). "The meandering Mundo Mud Pot: Or how Salton Sea tectonics affect international trade". Proceedings of the 70th Highway Geology Symposium: 439-456.
  6. ^ Andrews, Robin George (November 9, 2018). "A bubbling pool of mud is on the move, and no one knows why". National Geographic.
  7. ^ "A San Andreas fault mystery: The 'slow-moving disaster' in an area where the Big One is feared". Los Angeles Times. 2018-11-01. Retrieved 2022-10-14.

External links[edit]