View source for Geyser


{{otheruses}}

[[Image:GeysirEruptionNear.jpg|250px|thumb|right|[[Strokkur]] geyser, [[Iceland]]]]

A '''geyser''' is a [[hot spring]] characterized by intermittent discharge of water ejected turbulently and accomplished by a vapor phase. The name ''geyser'' comes from ''[[Geysir]]'', the name of an erupting spring at [[Haukadalur]], [[Iceland]]; that name, in turn, comes from the [[Iceland]]ic verb ''gjósa'', “to gush”.

The formation of geysers requires a favourable [[hydrogeology]] which exists in only a few places on Earth, and so they are fairly rare phenomena. There must be a volcanic heat source. Generally all geyser field sites are located near active volcanic areas. The surface water works its way down to an average depth of around {{dist m ft|2134}} where it meets up with the hot rocks. About 1,000 exist worldwide, with about half of these in [[Yellowstone National Park]], [[United States|U.S.]] A geyser's eruptive activity may change or cease due to ongoing mineral deposition within the geyser plumbing, exchange of functions with nearby hot springs, earthquake influences, and human intervention.<ref>Bryan, T.S. 1995</ref>

Erupting fountains of liquefied [[nitrogen]] have been observed on [[Neptune (planet)|Neptune]]'s moon [[Triton (moon)|Triton]], as have [[Martian spiders|possible signs]] of carbon dioxide eruptions from [[Mars]]' south polar ice cap. These phenomena are also often referred to as ''geysers''. Instead of being driven by geothermal energy, they seem to rely on solar heating aided by a kind of solid-state [[greenhouse effect]]. On Triton, the [[nitrogen]] may erupt to heights of {{convert|8|km|mi|0}}.

== Formation and working ==
Geysers are temporary geological features. The life span of a geyser is, at the most, only a few thousand years. Geysers are generally associated with volcanic areas.<ref name="wyo">[http://www.wyojones.com/how__geysers_form.htm How geysers form] Gregory L. Jones; wyojones.com Retrieved on [[2008-04-05]]</ref> Geysers are caused when underground chambers of water are heated to the boiling point by the volcanic rock. When heat causes the water to boil, pressure forces a superheated column of steam and water to the surface. Their formation specifically requires the combination of 3 geologic conditions that are usually found in volcanic terrain.<ref name="wyo"/>
* '''Intense heat'''- The heat needed for geyser formation comes from [[magma]] when it is near the surface of the earth.The fact that they need heat much higher than normally found near the earth's surface is the reason they are associated with volcanoes or volcanic areas.  Geysers, though rare, are found in the same geologic settings where volcanic heat sources are available.
* '''[[Water]]'''- The water a geyser ejects comes from snow and rain. When precipitation reaches the ground, most of it drains into rivers and streams. A small portion, perhaps 5% gets, soaked into the ground. Moving gradually through tiny cracks it finds its way into the underground tunnels that make up the plumbing of a geyser, then is shot to the surface during an eruption. Travel from the surface down through the rock and out through a geyser eruption can take up-to a time period of 500 years.<ref name="leekry">Lee Krystek [http://www.unmuseum.org/geysers.htm Weird Geology: Geysers] unmuseum.org Retrieved on [[2008-03-28]]</ref>
* '''A plumbing system'''- In order for the heated water to form a geyser a plumbing system is required. This includes a reservoir to hold the water while it is being heated. Geysers are generally aligned along faults, the cracks in the earth formed by earthquakes.<ref name="wyo"/> The plumbing system is made up of a system of [[fracture]]s, [[fissure]]s, porous spaces and sometimes cavities. Constrictions in the system are essential to the building up of pressure before an eruption.
Ultimately, the temperatures near the bottom of the geyser rise to a point where boiling begins; steam bubbles rise to the top of the column. As they burst through the geyser's vent, some water overflows or splashes out, reducing the weight of the column and thus the pressure on the water underneath. With this release of pressure, the superheated water flashes into [[steam]], boiling violently throughout the column. The resulting froth of expanding steam and hot water then sprays out of the geyser hole.<ref name="wyo"/>

== Eruptions ==
Geyser activity, like all [[hot spring]] activity, is caused by surface water gradually seeping down through the ground until it meets rock heated by [[magma]]. The [[geothermal (geology)|geothermal]]ly heated water then rises back toward the surface by [[convection]] through porous and fractured rocks. Geysers differ from non-eruptive hot springs in their subterranean structure; many consist of a small vent at the surface connected to one or more narrow tubes that lead to underground reservoirs of water.<ref name="leekry"/>
<div class="thumb tright">
<div style="width: 600px;" class="thumbinner">
{| style="background: none;" cellspacing="2" cellpadding="0"
| class="thumbimag'n" | [[Image:geyser exploding 1 large.jpg|150px|]]
| class="thumbimage" | [[Image:geyser exploding 2 large.jpg|150px|]]
| class="thumbimage" | [[Image:geyser exploding 3 large.jpg|150px|]]
| class="thumbimage" | [[Image:geyser exploding 4 large.jpg|150px|]]
|- style="vertical-align: top;"
|<div class="thumbcaption">1. Steam rises from heated water</div>
|<div class="thumbcaption">2. Pulses of water swell upward</div>
|<div class="thumbcaption">3. Surface is broken</div>
|<div class="thumbcaption">4. Ejected water spouts upward and falls back</div>
|}
</div>
</div>

As the geyser fills, the water at the top of the column cools off, but because of the narrowness of the channel, convective cooling of the water in the reservoir is impossible. The cooler water above presses down on the hotter water beneath, not unlike the lid of a [[pressure cooker]], allowing the water in the reservoir to become [[superheating|superheated]], i.e. to remain [[liquid]] at temperatures well above the [[boiling point]].<ref name="leekry"/>

The rocks in the nearby region produce a material called geyserite. Geyserite is mostly [[silicon dioxide]] (SiO<sub>2</sub>), is dissolved from the rocks and gets deposited on the walls of the geyser's plumbing system and on the surface. The deposits make the channels carrying the water up to the surface pressure-tight. This allows the pressure to be carried all the way to the top and not be leaked out into the loose gravel or soil that are normally under the geyser fields.<ref name="leekry"/>

Eventually the water remaining in the geyser cools back to below the boiling point and the eruption ends; heated groundwater begins seeping back into the reservoir, and the whole cycle begins again. The duration of eruptions and time between successive eruptions vary greatly from geyser to geyser; [[Strokkur]] in Iceland erupts for a few seconds every few minutes, while [[Grand Geyser]] in the [[United States|U.S.]] erupts for up to 10&nbsp;minutes every 8–12&nbsp;hours.<ref name="leekry"/>
{{clear}}

== General categorization ==
There are two types of geysers: ''fountain geysers'' which erupt from pools of water, typically in a series of intense, even violent, bursts; and ''cone geysers'' which erupt from cones or mounds of siliceous sinter (also known as [[geyserite]]), usually in steady jets that last anywhere from a few seconds to several minutes. [[Old Faithful Geyser|Old Faithful]], perhaps the best-known geyser at Yellowstone National Park, is an example of a cone geyser. [[Grand Geyser]], the tallest predictable geyser on earth, also at Yellowstone National Park, is an example of a fountain geyser.<ref>[http://www.geocities.com/dmonteit/ov_quick_guide.htm Yellowstone thermal features] Yahoo! Inc. Retrieved on [[2008-04-02]]</ref>
<div class="thumb tleft">
<div style="width: 400px;" class="thumbinner">
{| style="background: none;" cellspacing="2" cellpadding="0"
| class="thumbimag'n" | [[Image:Fountain geyser.jpg|200px|]]
| class="thumbimage" | [[Image:Old Faithful Geyser Yellowstone National Park.jpg|176px|]]
|- style="vertical-align: top;"
|<div class="thumbcaption">1. Fountain geyser (erupting from the pool)</div>
|<div class="thumbcaption">2. Old Faithful geyser (cone geyser having mound of siliceous sinter) in [[Yellowstone National Park]] erupts approximately every 91 minutes</div>
|}
</div>
</div>
The intense transient forces inside erupting geysers are the main reason for their rarity. There are many volcanic areas in the world that have [[hot spring]]s, [[mud pot]]s and [[fumarole]]s, but very few with geysers. This is because in most places, even where other necessary conditions for geyser activity exist, the rock structure is loose, and eruptions will erode the channels and rapidly destroy any nascent geysers.<ref name="hsp">[http://www.scienceclarified.com/landforms/Faults-to-Mountains/Geyser-and-Hot-Spring.html Plumbing system] Advameg Inc. Retrieved on [[2008-04-02]]</ref>

Most geysers form in places where there is volcanic [[rhyolite]] rock which dissolves in hot water and forms [[mineral]] deposits called siliceous sinter, or [[geyserite]], along the inside of the plumbing systems. Over time these deposits cement the rock together tightly, strengthening the channel walls and enabling the geyser to persist; as mentioned in the previous section.<ref name="hsp" />

Geysers are fragile phenomena and if conditions change, they can ‘die’. Many geysers have been destroyed by people throwing litter and debris into them; others have ceased to erupt due to dewatering by [[geothermal power]] plants. The [[Geysir|Great Geysir of Iceland]] has had periods of activity and dormancy. During its long dormant periods, eruptions were sometimes humanly-induced—often on special occasions—by the addition of [[surfactant]]s to the water. Inducing eruptions at Geysir is no longer done, as the forced eruptions were damaging the geyser's special plumbing system. Following an [[earthquake]] in [[Iceland]] in 2000 the geyser became somewhat more active again. Initially the geyser erupted about eight times a day. As of July 2003, Geysir erupts several times a week.<ref name="hsp" />

== Biology of geysers ==
{{see|Thermophile|Hyperthermophile}}

[[Image:Grand prismatic spring.jpg|right|thumb|300px|Hyperthermophiles produce some of the bright colors of [[Grand Prismatic Spring]], Yellowstone National Park]]

The specific colours of geysers derive from the fact that despite the apparently harsh conditions, life is often found in them (and also in other hot [[habitat (ecology)|habitats]]) in the form of [[thermophiles|thermophilic]] [[prokaryote]]s. No known [[eukaryote]] can survive over {{convert|60|°C|°F|0|lk=on}}.<ref name="bot">Lethe E. Morrison, Fred W. Tanner; Studies on Thermophilic Bacteria 
Botanical Gazette, Vol. 77, No. 2 (Apr., 1924), pp. 171-185</ref>

In the 1960s, when the research of ''biology of geysers'' first appeared, scientists were generally convinced that no life can survive above around {{convert|73|°C|°F|0|lk=off}}—the upper limit for the survival of [[cyanobacteria]], as the structure of key cellular [[protein]]s and [[DNA|deoxyribonucleic acid]] (DNA) would be destroyed. The optimal temperature for thermophilic bacteria was placed even lower, around {{convert|55|°C|°F|0|lk=off}}.<ref name="bot" />

However, the observations proved that it is actually possible for life to exist at high temperatures and that some bacteria prefer even temperatures higher than boiling point of [[water (molecule)|water]]. Dozens of such bacteria are known nowadays.<ref>Michael T. Madigan and Barry L. Marrs; [http://atropos.as.arizona.edu/aiz/teaching/a204/extremophile.pdf Extremophiles] atropos.as.arizona.edu Retrieved on [[2008-04-01]]</ref>
[[Thermophile]]s prefer temperatures from {{convert|50|°C|°F|0|lk=off}} to {{convert|70|°C|°F|0|lk=off}} whilst [[hyperthermophile]]s grow better at temperatures as high as {{convert|80|°C|°F|0|lk=off}} to {{convert|110|°C|°F|0|lk=off}}. As they have heat-stable enzymes that retain their activity even at high temperatures, they have been used as a source of thermostable [[tool]]s, that are important in [[medicine]] and [[biotechnology]],<ref>Vielle, C.; Zeikus, G.J.  ''Hyperthermophilic Enzymes: Sources, Uses, and Molecular Mechanisms for Thermostability.''  Microbiology and Molecular Biology Reviews.  2001, '''65(1)''', 1-34.</ref> for example in manufacturing [[antibiotic]]s, [[plastic]]s, [[detergent]]s (by the use of heat-stable enzymes [[lipase]]s, [[pullulanase]]s and [[protease]]s), and fermentation products (for example [[ethanol]] is produced). The fact that such bacteria exist also stretches our imagination about life on other [[celestial body|celestial bodies]], both inside and outside of [[solar system]]. Among these, the first discovered and the most important for biotechnology is ''[[Thermus aquaticus]]''.<ref>[http://www.udel.edu/chem/bahnson/chem645/websites/Heaton/ Industrial Uses of Thermophilic Cellulase] [[University of Delaware]], Retrieved on [[2008-03-29]]</ref>

== Major geyser fields and their distribution ==
[[Image:World geyser distribution.gif|300px|thumb|right|Distribution of major geysers in the world.]]
Geysers are quite rare, requiring a combination of [[water]], [[heat]], and fortuitous [[plumbing]]. The combination exists in few places on Earth.<ref>Glennon, J.A. and Pfaff R.M. 2003; Bryan 1995</ref><ref name="uweb">Glennon, J Allan[http://www.uweb.ucsb.edu/~glennon/geysers/world.htm "World Geyser Fields"] Retrieved on [[2008-04-04]]</ref>

=== Yellowstone National Park ===
{{main|Yellowstone National Park}}
Yellowstone is the largest geyser locale, containing thousands of hot springs, and approximately 300 to 500 geysers. It is home to half of the world's total number of geysers in its nine geyser basins. It is located in [[Wyoming]], [[United States]].<ref>[http://www.nps.gov/yell/naturescience/geysers.htm "Yellowstone geysers"] nps.gov Retrieved on [[2008-03-20]]</ref> Yellowstone includes the tallest active geyser ([[Steamboat Geyser]] in [[Norris Geyser Basin]]), as well as the renowned [[Old Faithful Geyser]], [[Beehive Geyser]], Giantess Geyser, Lion Geyser, Plume Geyser, Aurum Geyser, [[Castle Geyser]], Sawmill Geyser, [[Grand Geyser]], Oblong Geyser, [[Giant Geyser]], [[Daisy Geyser]], Grotto Geyser, Fan & Mortar Geysers, & [[Riverside Geyser]], all in the [[Upper Geyser Basin]] which alone contains nearly 180 geysers.<ref name="uweb"/>

=== Dolina Geiserov ===
{{main|Dolina Geiserov}}
Dolina Geiserov is one of the geysers in the [[Valley of Geysers]] in the [[Kamchatka Peninsula]] of [[Russia]]. The area was discovered and explored by T.I. Ustinova in 1941. Approximately 200 geysers exist in the area along with many hot-water springs and perpetual spouters. The area was formed due to vigorous [[volcano|volcanic]] activity. The peculiar way of eruptions are an important feature of these geysers. Most of the geysers erupt at angles, and only very few have the geyser cones that exist at many other of the world's geyser fields.<ref name="uweb"/> On [[June 3]] [[2007]] a massive [[mudflow]] influenced two thirds of the valley.<ref name="NG">{{cite news | first=Aalok | last=Mehta | title=Photo in the News: Russia's Valley of the Geysers Lost in Landslide | url=http://news.nationalgeographic.com/news/2007/06/070605-geyser-valley.html | publisher=[[National Geographic]] | date=2008-04-16 | accessdate=2007-06-07 }}</ref> It was then reported that a thermal lake was forming above the valley.<ref>{{cite news |first=Luke |last=Harding |authorlink= |coauthors= |title=Mudslide fully changes terrain in Kamchatka’s Valley of Geysers |url=http://www.guardian.co.uk/russia/article/0,,2095579,00.html |work= |publisher=[[Guardian Unlimited]] |date=2007-06-05 |accessdate=2008-04-16 }}</ref> Few days later, waters were observed to have receded somewhat, exposing some of the submerged features. Velikan Geyser, one of the field's largest, was not buried in the slide and has recently been observed to be active.<ref>{{cite news|first=Igor |last=Shpilenok|title=June 2007 Special release - The Natural Disaster at the Valley of the Geysers |url=http://www.shpilenok.com/new/index.htm|date-2007-06-09|accessdate=2008-04-16}}</ref>

=== El Tatio ===
[[Image:ElTatioMovie.ogg|thumb|right|A geyser bubbling at El Tatio geyser field]]
{{main|El Tatio}}
The name "El Tatio" roughly translates as "the grandfather".  El Tatio is located in the high valleys on the Andes surrounded by many active Volcanoes in [[Chile]], [[South America]] at around 4,200 meters above mean sea level.  The valley is home to approximately 80 geysers at present.  It became the largest geyser field in the [[Southern Hemisphere]] after the destruction of many of the [[New Zealand]] geysers, and is the third largest geyser field in the world.  The salient feature of these geysers is that the height of their eruptions is very low, tallest being only six meters high. The average geyser eruption height at El Tatio is about {{dist m ft|0.75}}<ref name="uweb"/><ref>Glennon, J.A. and Pfaff. R.M., 2003)</ref>

=== Taupo Volcanic Zone ===
{{main|Taupo Volcanic Zone}}
The Taupo Volcanic Zone is located on the [[North Island]] in [[New Zealand]]. It is {{convert|350|km|mi|0}} long by {{convert|50|km|mi|0}} wide and lies over a [[subduction]] zone in the earth's crust. [[Mount Ruapehu]] marks its southwestern end, while the submarine Whakatane volcano (85 kilometres beyond [[White Island]]) is considered its northeastern limit.<ref>Gamble, J. A., I. C. Wright and J. A. Baker (1993). "[http://www.rsnz.org/publish/nzjgg/1993/40.php Seafloor geology and petrology in the oceanic to continental transition zone of the Kermadec-Havre-Taupo Volcanic Zone arc system, New Zealand]" ''New Zealand Journal of Geology and Geophysics'', 36, 417-435.</ref> Many geysers in this zone were destroyed due to [[Geothermal]] developments and a hydroelectric reservoir, but several dozen geysers still exist. In the beginning of the twentieth century, the largest geyser ever known, the [[Waimangu Geyser]] existed in this zone. It began erupting in 1900 and erupted periodically for four years until a [[landslide]] changed the local [[water table]]. Eruptions of Waimangu would typically reach {{dist m ft|160}} and some superbursts are known to have reached {{dist m ft|500}}.<ref name="uweb"/> Recent scientific work indicates that the earth's crust below the zone may be as little as {{convert|5|km|mi|0}} thick.  Beneath this lies a film of [[magma]] {{convert|50|km|mi|0}} wide and {{convert|160|km|mi|0}} long.<ref>[http://www.stuff.co.nz/4202557a11.html Central North Island sitting on magma film] Paul Easton, The Dominion Post, 15 September 2007. Retrieved [[2008-04-16]]</ref>

=== Iceland ===
{{main|Iceland}}
[[Image:white dome geyser eruption.jpg|235px|thumb|right|Eruption of White Dome Geyser in Yellowstone]]
Iceland is an island country off the western coast of Europe in the [[Atlantic Ocean]]. Geysers and hot springs are distributed all over the island. The geyser, or the local name ''geysir'' are located in [[Haukadalur]]. Geysers are known to have existed in at least a dozen other areas on the island. The "Great Geysir", which first erupted in the 14th century, gave rise to the word "geyser". It used to erupt every 60 minutes until the early 1900s when it became dormant. Earthquakes in June 2000 subsequently reawakened the giant and it now erupts approximately every 8 to 10 hours and may reach up to {{dist m ft|61}}.<ref name="uweb"/><ref>Gardner Servian, Solveig[http://website.lineone.net/~polar.publishing/geysersoficeland.htm "Geysers of Iceland"] Retrieved on [[2008-04-16]]</ref>

=== Extinct/Dormant geyser fields ===

There used to be two large geysers fields in [[Nevada]]—[[Beowawe, Nevada|Beowawe]] and [[Steamboat Springs, Nevada|Steamboat Springs]]—but they were destroyed by the installation of nearby geothermal power plants. At the plants, geothermal drilling reduced the available heat and lowered the local [[water table]] to the point that geyser activity could no longer be sustained.<ref name="uweb"/>

Many of New Zealand’s geysers have been destroyed by humans in the last century. Several New Zealand geysers have also become dormant or extinct by natural means. The main remaining field is [[Whakarewarewa]] at [[Rotorua]].<ref>[http://www.whakarewarewa.com/ "Whakarewarewa, The Thermal Village"] Retrieved [[2008-04-04]]</ref> Two thirds of the geysers at [[Orakei Korako]] were flooded by the Ohakuri hydroelectric dam in 1961. The [[Wairakei]] field was lost to a geothermal power plant in 1958. The Taupo Spa field was lost when the [[Waikato River]] level was deliberately altered in the 1950s. The [[Rotomahana]] field was destroyed by the [[Mount Tarawera]] eruption in 1886.

== Misnamed geysers ==

[[Image:Wallenborn-brubbel.ogg| thumb| thumbtime=76 |150px| Cold-water geyser [[:de:Wallender Born|Brubbel]] (Germany)]]

There are various other types of geysers which are different in nature compared to the normal steam-driven geysers. These geysers not only differ in their style of eruption but also in the cause that makes them erupt. Such geysers are not true geysers but are yet referred as one as they all emit water under pressure.

;Artificial geysers
In a number of places where there is geothermal activity, wells have been drilled and fitted with impermeable casements that allow them to erupt like geysers. Even though the vents of such geysers are artificial, it is tapped into a natural hydrothermal system. Though these are so-called ''artificial geysers'', technically known as ''erupting geothermal wells'', are not true geysers. Little Old Faithful Geyser, in [[Calistoga, California]], is probably an example of it. The geyser erupts from the casing of the a well drilled in the late 1800s. According to Dr. John Rinehart in his book ''A Guide to Geyser Gazing'' (1976 p.49), a man had drilled into the geyser in search for water. He had actually "simply opened up a dead geyser".<ref>Jones, Wyoming [http://www.wyojones.com/of_califonia.htm "Old Faithful Geyser of California"] ''WyoJones' Geyser Pages'' Retrieved on [[2008-03-31]]</ref>

;Cold-water geysers
Cold-water geysers' eruption is similar to their hot water counterparts, except that [[Carbon Dioxide|CO<sub>2</sub>]] bubbles drive the eruption instead of steam. In cold-water geysers, CO<sub>2</sub>-laden water lies in a confined aquifer, in which water and CO<sub>2</sub> are trapped by less permeable overlying strata. This water and CO<sub>2</sub> can escape this strata only weak regions like faults, joints, or drilled wells. A drilled borehole provides an escape for the pressurized water and CO<sub>2</sub> to reach the surface. The magnitude and frequency of such eruptions depend on various factors such as plumbing depth, CO<sub>2</sub> concentrations, aquifer yield etc. The column of water exerts enough pressure on the gaseous CO<sub>2</sub> so that it remains in the water in small bubbles. When the pressure decreases due to formation of a fissure, the CO<sub>2</sub> bubbles expand. This expansion dispaces the water and causes the eruption.The appearance of cold-water geysers may be quite similar to their steam-driven counterparts; however, often CO<sub>2</sub>-laden water is more white and frothy.<ref>Glennon, J. Alan[http://www.uweb.ucsb.edu/~glennon/crystalgeyser/ "Carbon-Dioxide-Driven, Cold-Water Geysers"] Retrieved on [[2008-04-01]]</ref> The best known of these is probably [[Crystal Geyser]], near [[Green River, Utah]]..<ref>[[Glennon, J.A.]] 2005; [[Glennon, J.A.]] and Pfaff, R.M. 2005</ref> There are also two cold-water geysers in Germany: [[:de:Wall ender Born|Brubbel]] and [[:de:Geysir Andernach|Geysir Andernach]].

A '''perpetual spouter''' is a natural hot spring that spouts water constantly without stopping for recharge. Some of these are incorrectly called geysers, but because they are not periodic in nature they are not considered true geysers.<ref>WyoJones[http://www.wyojones.com/geyserdef.htm "Thermal Feature Definitions"] ''WyoJones'' Retrieved on [[2008-04-03]]</ref>

== Commercial uses of geysers ==
[[Image:Strokkur, Iceland.jpg|thumb|150px|Geyser in Iceland; as a tourist spot.]]
Geysers are used for various activities such as [[electricity]] generation, heating and [[tourism]]. Many geothermal reserves are found all around the world. Geysers in Iceland are one of the most commercially viable geyser location in the world. Since 1920's hot water directed from the geysers have been used to heat greenhouses and used to grow food that could not have been cultivated in Iceland's inhospitable climate.<ref>[http://www.american.edu/TED/geyser.htm Geysers and Energy] american.edu Retrieved on [[2008-04-12]]</ref> Steam and hot water from the geysers has also been used for heating homes since 1943 in Iceland. In 1979
the U.S. Department of Energy (DOE)  actively promoted development of geothermal energy in the '''Geysers-Calistoga Known Geothermal Resource Area''' ([http://www.osti.gov/bridge/servlets/purl/6817678-VCD58M/6817678.PDF KGRA]) through a variety of research programs and the Geothermal Loan Guarantee Program and was thus obligated by law to assess its potential environmental impacts.<ref>Kerry O’Banion  and Charles Hall [http://www.osti.gov/bridge/servlets/purl/6817678-VCD58M/6817678.PDF Geothermal energy and the land resource: conflicts and constraints in The Geysers- Calistoga KGRA] osti.gov Retrieved on [[2008-04-12]]</ref>

== Nitrogen geysers on Triton ==
{{main|Cryovolcano}}
One of the great surprises of the [[Voyager 2]] flyby of [[Neptune (planet)|Neptune]] in 1989 was the discovery of geysers on its moon, [[Triton (moon)|Triton]]. Astronomers noticed dark plumes rising to some 8&nbsp;km above the surface,and depositing material up to 150&nbsp;km downstream.,<ref>{{cite web
 | date = [[June 1]], [[2005]]
 | title = Triton (Voyager)
 | publisher = NASA (Voyager The Interstellar Mission)
 | url = http://voyager.jpl.nasa.gov/science/neptune_triton.html
 | accessdate = 2008-04-03
}}</ref>
[[Image:Geyser on Triton.gif|thumb|left|Dark streaks deposited by geysers on Triton]]
All the geysers observed were located between 50° and 57°S, the part of Triton's surface close to the [[subsolar point]]. This indicates that solar heating, although very weak at Triton's great distance from the Sun, probably plays a crucial role. It is thought that the surface of Triton probably consists of a semi-[[Transparency (optics)|transparent]] layer of frozen [[nitrogen]] white in colour, which creates a kind of [[greenhouse effect]], heating the frozen material beneath it until it breaks the surface in an eruption. A temperature increase of just 4&nbsp;[[kelvin|K]] above the ambient surface temperature of 37&nbsp;K could drive eruptions to the heights observed. But more likely these eruptions are caused by [[tidal force]]s.<ref name="harv">Kirk, R.L., Branch of Astrogeology[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?db_key=AST&bibcode=1990LPI....21..633K&letter=.&classic=YES&defaultprint=YES&whole_paper=YES&page=633&epage=633&send=Send+PDF&filetype=.pdf "Thermal Models of Insolation-driven Nitrogen Geysers on Triton"] ''[[Harvard University|Harvard]]'' Retrieved [[2008-04-08]]</ref>

Geothermal energy may also be important. Unusually for a major satellite, Triton orbits Neptune in a [[Prograde and retrograde motion|retrograde]] orbit—that is, in the opposite direction to Neptune's rotation. This generates tidal forces which are causing Triton's orbit to decay, so that in several billion years time it will reach its [[Roche limit]]<ref>[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1989A%26A...219L..23C&amp;db_key=AST "Roche Limit"]''Harvard'' Retrieved [[2008-04-08]]</ref> with Neptune. The tidal forces may also generate heat inside Triton, in the same way as [[Jupiter (planet)|Jupiter]]'s gravity generates tidal forces on [[Io (moon)|Io]] which drive its extreme volcanic activity.<ref name="harv" />

Each eruption of a Triton geyser may last up to a year, and during this time about {{convert|0.1|km3|l|lk=on}} of material may be deposited downwind. Voyager's images of Triton's southern hemisphere show many streaks of dark material laid down by geyser activity.<ref name="harv" />

== Notes ==
{{reflist|2}}

== References ==
* Bryan, T. Scott (1995). ''The geysers of Yellowstone''. Niwot, Colorado: University Press of Colorado. ISBN 0-87081-365-X
* [[Glennon, J.A.]], Pfaff, R.M. (2003). ''The extraordinary thermal activity of El Tatio Geyser Field, Antofagasta Region, Chile'', Geyser Observation and Study Association (GOSA) Transactions, vol 8. pp. 31-78.
* [[Glennon, J.A.]] (2005). ''[http://www.uweb.ucsb.edu/~glennon/crystalgeyser/index.htm Carbon Dioxide-Driven, Cold Water Geysers]'', University of California, Santa Barbara. Originally posted [[February 12]], [[2004]], last update [[6 May]] [[2005]]. Accessed [[8 June]] [[2007]].
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== External links ==
{{Commons|Geyser}}
{{portalpar|Earth sciences}}
* [http://www.nps.gov/yell/naturescience/geysers.htm ''Geysers and How They Work'' by Yellowstone National Park]
* [http://www.geyserstudy.org/ Geyser Observation and Study Association (GOSA)]
* [http://www.yellowstone.net/geysers/ Geysers of Yellowstone: Online Videos and Descriptions]
* [http://www.uweb.ucsb.edu/~glennon/geysers/ ''About Geysers'' by Alan Glennon]
* [http://www.uweb.ucsb.edu/~glennon/crystalgeyser/ ''Cold Water Geysers'' by Alan Glennon]
* [http://www.unmuseum.org/geysers.htm ''Geysers'', The UnMuseum]
* [http://www.johnstonsarchive.net/geysers/index.html ''Johnston's Archive Geyser Resources'']
* [http://geysircenter.com/english/geology.html ''The Geology of the Icelandic geysers'' by Dr. Helgi Torfason, geologist]
* [http://www.umich.edu/~gs265/geysers.html ''Geysers and the Earth's Plumbing Systems'' by Meg Streepey]

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[[Category:Hydrothermal vents]]
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