Geothermal Phenomena
4 min read
In areas of high geothermal activity, the following phenomena can be observed:
Hot springs
with temperatures sometimes close to 100 °C. Hot water rises from depth through fractures and permeable rock.
Fumaroles
openings or cracks in the ground that emit steam and volcanic gases. They form where groundwater is heated by hot rocks or magma and mixes with gases rising from depth.
Geysers
hot springs in which groundwater heated by hot rocks erupts periodically at the surface as a mixture of hot water and steam.
Mud pots
shallow acidic pools in which hydrothermal fluids alter rock into clay-rich mud.
Video: 3D model of volcanic activity. Magma formed within the Earth can rise through fractures in the crust and, in some places, reach the surface during a volcanic eruption.
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Probably the most famous geyser in the world is Old Faithful in Yellowstone National Park in the USA.
Castle Geyser in Yellowstone National Park has one of the largest geyserite cones in the world. Its cone and underlying sinter deposits are thousands of years old.
21 pictures
21 pictures
Mysterious Bursting Spring
The Strokkur geyser in the Haukadalur geothermal area in Iceland erupts regularly, every 5—10 minutes.
A geyser is a specific kind of spring that bursts out a mixture of water and steam in regular or irregular intervals, often as high as a few dozen meters. The term is derived from the Icelandic geyser Geysir, whose name comes from the verb geysa, meaning “to gush”, and is now used for similar features worldwide. Geysers occur in only a few geothermal regions of the world, although some of these areas contain large numbers of them. Their heat source is generally associated with volcanic or magmatic activity.
A geyser can form where there is a sufficient supply of groundwater, a strong heat source and an underground plumbing system containing a reservoir and narrow constrictions that allow pressure to build up. Water enters the system through cracks in the Earth’s crust and it accumulates in the underground reservoir. The water in the reservoir is heated by hot rocks associated with underlying magma to temperatures above its normal boiling point. Because the water is under high pressure from the overlying water column, its boiling point is raised and it can remain liquid at temperatures well above 100 °C. As some hot water rises and escapes, the pressure in the reservoir falls. Part of the superheated water then rapidly flashes into steam, which can occupy roughly 1,500 times the volume of the liquid water. The expanding steam forces the overlying water out through the vent. The underground system then refills with groundwater and the cycle begins again.
Geysers require very specific geological and hydrological conditions, which occur mainly in volcanically active regions.
More than half of the world’s geysers are found in Yellowstone National Park (map) in the USA, which contains over 500 geysers. Other major geyser fields occur in Russia, Chile, New Zealand and Iceland. One of the world’s largest geyser fields is the Valley of Geysers on Russia’s Kamchatka Peninsula (map). Other important geyser areas include El Tatio in Chile (map), the Taupō Volcanic Zone in New Zealand (map) and several geothermal regions of Iceland (map).
11 pictures
11 pictures
Steamboat Geyser in Yellowstone National Park, USA, is the world’s tallest active geyser. Its major eruptions can send water more than 90 metres into the air.
Waimangu Geyser in New Zealand, active from 1900 to 1904, occasionally erupted to heights of about 460 metres, making it the tallest geyser ever recorded.
