What is a geyser? This page contains definitions for some using thermal features names. Some of these definitions can be confusing since they have been used differently by different people over time. Nature contributes to this confusion. A spring long considered a hot spring have been known to have eruptions and therefore can be classified as a geyser. As you read and apply these definitions remember that nature is hard to "pigeon-hole" with confining definitions. That is one of the wonders of nature.
Pink Geyser, Lower Geyser Basin , Yellowstone National Park, Photo copyright Gregory L. Jones
GEYSER: A hot springs that periodically erupts hot water and steam into the air before it stops to recharge. Steam is a key component as if provides the energy for a true geyser.
CONE GEYSER-- A geyser that erupts from a mound of geyserite (cone).
example- Castle Geyser, Upper geyser Basin, Yellowstone National Park. Photo copyright Gregory L. Jones, all rights reserved.
FOUNTAIN GEYSER- A geyser that erupts from a pool with a splashing action.
example: Fountain Geyser, Lower Geyser Basin, Yellowstone National Park. Photo copyright Gregory L. Jones, all rights reserved.
PERPETUAL SPOUTER- A hot springs that shoots water into the air continuously without stopping to recharge. An erupting hot spring is not a geyser unless it is periodic. Periodic spouter's eruptions do not reach great heights.
example: Steady Geyser, Lower Geyser Basin, Yellowstone National Park. Photo copyright Gregory L. Jones, all rights reserved.
HOT SPRINGS-- A pool or discharge of hot water that does not throw water into the air. ( It should be noted that a few pools in Yellowstone long thought to be only hot springs, have surprised observers by erupting. Some of these surprises have followed earthquakes.) Escaping gases can cause the hot spring to spout or "boil" even when water temperatures are below the boiling point.
FUMAROLES-- a vent which emits a mixture of steam and other volcanic gases. Gases that mix with the steam can include Hydrogen Sulfide, Carbon Dioxide, chlorine gases, sulfur dioxide and minor amounts of carbon monoxide, fluorine and boron compounds, ammonia, and several other compounds that are found in some volcanic gases. Fumaroles are sometimes classified by the types of gases that are in the mixture. (see solfatara below). In Yellowstone and in some other area fumaroles may be found in areas where water supply is limited and the water is converted to steam before it reaches the surface.
example: Large Fumarole on Crater Wall Location Central Crater, White Island, New Zealand . Photo copyright Christian Treber, used by permission. Visit Christian's site.
SOLFATARA-- A type of fumarole which emits sulfurous gases.
MUD POT-- A mud thermal feature where there is not sufficient water to carry away mud and clay size particles so that they accumulate in the vent or crater of the thermal feature. Gases moving up through the thick heavy mud causes it to bubble like a pot of cooking wheat cereal (mush).
MUD VOLCANO--A volcano shaped features that extrudes or ejects a mixture of water, gases, mud and clay. The escaping gases can cause upward splattering of mud which builds cones of ejected mud and clay around the vents.
example: mud cone found in the Sulfur Cauldron area, near the Mud Volcano area, Yellowstone National Park. Photo copyright Gregory L. Jones, all rights reserved.
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