Caldera 7592 223524225 2008-07-04T13:07:30Z Pululahuawiki 6678455 /* Notable calderas */ {{otheruses}} [[Image:Santorini Landsat.jpg|thumb|300px|right|Satellite image of [[Santorini]]. The Minoan caldera is at the lower part of the image and formed in the [[Minoan eruption]] approx. 3615 [[Before Present|BP]]. The whole caldera is formed of three overlapping calderas. Clockwise from centre: Nea Kameni; Palea Kameni; Aspronisi; Therasia; Thera]] A '''caldera''' is a [[volcano|volcanic]] feature formed by the collapse of land following a volcanic eruption. They are sometimes confused with [[volcanic crater]]s. The word comes from [[Spanish language|Spanish]], meaning "cauldron". As a matter of fact, in some texts the English term '''cauldron''' is also used. In 1815, the German geologist [[Leopold von Buch]] visited the Las Cañadas Caldera [[Teide]], [[Tenerife]] and the [[Caldera de Taburiente]], [[La Palma]], both in the [[Canary Islands]]. When he published his memoirs he introduced the term "caldera" into the geological vocabulary. ==Caldera formation== A collapse is triggered by the emptying of the [[magma chamber]] beneath the volcano, usually as the result of a large [[volcano|volcanic eruption]]. If enough magma is erupted, the emptied chamber will not be able to support the weight of the ''volcanic edifice'' above it. A roughly circular fracture - the "Ring Fault" develops around the edge of the chamber. These ''ring fractures'' serve as feeders for fault intrusions which are also known as ring dykes. Secondary volcanic vents may form above the ring fracture. As the magma chamber empties, the centre of the volcano within the ring fracture begins to collapse. The collapse may occur as the result of a single cataclysmic eruption, or it may occur in stages as the result of a series of eruptions. The total area that collapses may be hundreds or thousands of km<sup>2</sup>. [[Image:Toba zoom.jpg|thumb|300px|right|[[Landsat]] image of [[Lake Toba]]. A [[resurgent dome]] formed the island of [[Samosir]].]] ===Explosive calderas=== If the [[magma]] is rich in [[silica]], the caldera is often filled in with [[ignimbrite]], [[tuff]], [[rhyolite]], and other [[igneous rock]]s. Silica-rich magma does not flow like [[basalt]] due to having a high [[viscosity]]. As a result, gases tend to become trapped at high pressure within the magma. When the magma approaches the surface of the Earth, the gases decompress rapidly, causing explosive destruction of the magma and spreading [[volcanic ash]] over wide areas. Further [[lava]] flows may be erupted. If volcanic activity continues the centre of the caldera may be uplifted in the form of a ''[[resurgent dome]]'' such as is seen seen at [[Galán|Cerro Galán]], [[Toba]], [[Yellowstone]] etc; by subsequent intrusion of magma. A ''silicic'' or ''rhyolitic caldera'' may erupt hundreds or even thousands of [[cubic kilometer]]s of material in a single event. Even small caldera-forming eruptions, such as [[Krakatoa]] in 1883 or [[Mount Pinatubo]] in 1991, may result in significant local destruction and a noticeable drop in temperature around the world. Large calderas may have even greater effects. When [[Yellowstone Caldera]] last erupted ~640 ka, it released ~1,000 km<sup>3</sup> of dense rock equivalent (DRE) material, covering a substantial part of [[North America]] in up to two metres of debris. By comparison, when [[Mount St. Helens]] erupted in 1980, it released ~1.2 km<sup>3</sup> (DRE) of ejecta. The ecological effects of the eruption of a large caldera can be seen in the record of the [[Lake Toba]] eruption in [[Indonesia]]. ===Toba=== About 75,000 years ago, this Indonesian volcano released ~2.8 x 10<sup>3</sup> km<sup>3</sup> DRE of ejecta, the largest known eruption within the [[Quaternary]] Period (last 1.8 million years). In the late 1990s, [[anthropologist]] Stanley Ambrose<ref>http://www.anthro.uiuc.edu/faculty/ambrose/</ref> proposed that a [[volcanic winter]] induced by this eruption reduced the [[human]] population to about 2,000 - 20,000 individuals, resulting in a [[population bottleneck]] (''see'' [[Toba catastrophe theory]]). More recently several geneticists, including Lynn Jorde and [[Henry Harpending]] have proposed that the human race was reduced to approximately 5,000 to 10,000 people.<ref>http://www.bbc.co.uk/science/horizon/1999/supervolcanoes_script.shtml</ref> Whichever figure is right, the fact remains that the human race seemingly came close to extinction about 75,000 years ago. Eruptions forming even larger calderas are known, especially [[La Garita Caldera]] in the [[San Juan Mountains]] of [[Colorado]], where the ~5.0 x 10<sup>3</sup> km<sup>3</sup> Fish Canyon Tuff was blasted out in a major single eruption ~27.8 million years ago. At some points in [[geological time]], rhyolitic calderas have appeared in distinct clusters. The remnants of such clusters may be found in places such as the [[San Juan Mountains]] of [[Colorado]] (erupted during the [[Tertiary Period]]) or the [[Saint Francois Mountain Range]] of [[Missouri]] (erupted during the [[Proterozoic]]). [[Image:La Cumbre - ISS.JPG|thumb|300px|right|Satellite photograph of [[Fernandina Island]]'s summit caldera]] ===Non-explosive calderas=== Some volcanoes, such as [[Kīlauea]] on the island of [[Hawaii (island)|Hawaii]], form calderas in a different fashion. In the case of Kilauea, the magma feeding the volcano is [[basalt]] which is silica poor. As a result, the magma is much less [[viscous]] than the magma of a rhyolitic volcano, and the magma chamber is drained by large lava flows rather than by explosive events. The resulting calderas are also known as subsidence calderas, and can form more gradually than explosive calderas. For instance, the caldera atop [[Fernandina Island]] underwent a collapse in 1968, when parts of the caldera floor dropped 350 meters.<ref>http://www.volcano.si.edu/world/volcano.cfm?vnum=1503-01=&VErupt=Y&VSources=Y&VRep=Y&VWeekly=Y&volpage=photos&photo=062078</ref> [[Kilauea]] Caldera has an inner crater known as Halema‘uma‘u, which has often been filled by a lava lake. At the summit of largest volcano on Earth, [[Mauna Loa]] is a subsidence caldera called Moku‘āweoweo Caldera. It is very frequent for a caldera to become empied by drainage of melted lava troughout a breach on the caldera's rim. The [[Caldera de Taburiente]] and the Caldereta, both in the island of [[La Palma]] ([[Canary Islands]]) are '''calderas''' emptied by a river of lava some 500.000 years ago. ==Mineralization== Some calderas are known to support rich [[mineralogy]]. One of the world's best preserved mineralized calderas is the [[Neoarchean]] [[Sturgeon Lake Caldera]] in [[northeastern Ontario]], [[Canada]].<ref>[http://www.d.umn.edu/prc/workshops/S08workshop.html UMD: Precambrian Research Center]</ref> {{Expand-section|date=June 2008}} ==Notable calderas== ''See also [[:Category:Volcanic calderas]] *Africa **[[Ngorongoro Crater]] ([[Tanzania]], Africa) **[[Mount Elgon]] ([[Uganda]]/[[Kenya]]) **[[Chã das Caldeiras]], [[Cape Verde]] **''See ''Europe'' for calderas in the Canary Islands *Asia **[[Aira Caldera]] ([[Kagoshima Prefecture]], [[Japan]]) **[[Mount Aso|Aso]] ([[Kumamoto Prefecture]], [[Japan]]) **[[Mount Halla]] ([[Jeju-do]], [[South Korea]]) **[[Kikai Caldera]] ([[Kagoshima Prefecture]], [[Japan]]) **[[Krakatoa]], [[Indonesia]] **[[Mount Pinatubo]] ([[Luzon]], [[Philippines]]) **[[Taal Volcano]] ([[Luzon]], [[Philippines]]) **[[Lake Toba]] ([[Sumatra]], [[Indonesia]]) ** [[Mount Tambora]] ([[Sumbawa]], [[Indonesia]]) **[[Tao-Rusyr Caldera]] ([[Onekotan]], [[Russia]]) **[[Lake Towada|Towada]] ([[Aomori Prefecture]], [[Japan]]) **[[Lake Tazawa|Tazawa]] ([[Akita Prefecture]], [[Japan]]) **[[Lake Ashi|Ashi]] ([[Kanagawa Prefecture]], [[Japan]]) [[Image:Crater Lake from rim-USGS.jpg|thumb|300px|Crater Lake|[[Crater Lake]], Oregon, formed around 5,680 BC]] [[Image:Mount Pleasant Caldera.jpg|thumb|right|300px|[[Mount Pleasant Caldera]], southwestern [[New Brunswick]], [[Canada]]]] *Americas **USA ***[[Battle Ground Lake State Park]] ([[Washington]], [[United States|US]]) ***[[Mount Aniakchak]] ([[Alaska]], US) ***[[Crater Lake]] on [[Mount Mazama]] ([[Crater Lake National Park]], [[Oregon]], [[United States|US]]) ***[[Mount Katmai]] ([[Alaska]], [[United States|US]]) ***[[La Garita Caldera]] ([[Colorado]], [[United States|US]]) ***[[Long Valley Caldera|Long Valley]] ([[California]], [[United States|US]]) ***[[Island Park Caldera]] ([[Idaho]], [[United States|US]]) ***[[Newberry Volcano]] ([[Oregon]], [[United States|US]]) ***[[Mount Okmok]] ([[Alaska]], [[United States|US]]) ***[[Valles Caldera]] ([[New Mexico]], [[United States|US]]) ***[[Yellowstone Caldera]] ([[Wyoming]], [[United States|US]]) **[[Canada]] ***[[Silverthrone Caldera]] ([[British Columbia]], [[Canada]]) ***[[Mount Edziza]] ([[British Columbia]], [[Canada]]) ***[[Bennett Lake Volcanic Complex]] ([[British Columbia]]/[[Yukon]], [[Canada]]) ***[[The Ash Pit]] ([[British Columbia]], [[Canada]]) ***[[Mount Pleasant Caldera]] ([[New Brunswick]], [[Canada]]) ***[[Sturgeon Lake Caldera]] ([[Ontario]], [[Canada]]) ***[[Mount Skukum Volcanic Complex]] ([[Yukon]], [[Canada]]) ***[[Blake River Megacaldera Complex]] ([[Quebec]]/[[Ontario]], [[Canada]]) ****[[New Senator Caldera]] ([[Quebec]], [[Canada]]) ****[[Misema Caldera]] ([[Ontario]]/[[Quebec]], [[Canada]]) ****[[Noranda Caldera]] ([[Quebec]], [[Canada]]) **[[Ecuador]] ***[[Pululahua Geobotanical Reserve]] **[[El Salvador]] ***[[Lake Ilopango]] ***[[Lake Coatepeque]] **Other ***[[Masaya Volcano|Masaya]], [[Nicaragua]] ***[[Lake Atitlan]], [[Guatemala]] ***[[Fernandina Island]], [[Galapagos Islands]], [[Ecuador]] ***[[Galán]], [[Argentina]] *Europe **[[Santorini]] ([[Greece]]) **[[Askja]] ([[Iceland]]) **[[Campi Flegrei]] ([[Italy]]) **[[Lake Bracciano]] ([[Italy]]) **[[Parque Nacional de la Caldera de Taburiente|Caldera de Taburiente]] ([[Spain]]) **[[Las Cañadas]] on [[Teide]] ([[Spain]]) **[[Ardnamurchan]] ([[Scotland]]) **[[Glen Coe]] ([[Scotland]]) [[Image:Lake taupo landsat.jpg|thumb|300px|right|Satellite photo of [[Lake Taupo]]]] *Oceania **[[Lake Taupo]] ([[New Zealand]]) **[[Mount Warning]] ([[Australia]]) **[[Blue Lake, South Australia]] ([[Mt Gambier]]) **[[Kilauea]] ([[Hawaii]], US) **[[Moku‘āweoweo Caldera]] on [[Mauna Loa]] ([[Hawaii]], US) *Antarctica **[[Deception Island]] *Indian Ocean ** [[Cirque de Mafate]], [[Cirque de Salazie]], and [[Cirque de Cilaos]] on [[Réunion]] *Mars **[[Olympus Mons]] Caldera *Venus **[[Maat Mons]] Caldera ==See also== * [[Supervolcano]] * [[Volcanic Explosivity Index]] * [[Somma volcano]] * [[Complex volcano]] ==External links== {{commons|Caldera}} * [http://volcanoes.usgs.gov/Products/Pglossary/caldera.html USGS page on calderas] * [http://volcanodb.com/search.php?type=Caldera List of Caldera Volcanoes] * [http://eis.bris.ac.uk/~gljhg/Workgroup/Workgroup_files/Edited-list-publications_calderas-71206.pdf Collection of references on collapse calderas] (43 pages) * [http://www.bigvolcano.com.au/natural/wollum.htm The Caldera of the Tweed Volcano - Australia] * [http://host.uniroma3.it/progetti/cev/Web%20CEV%20folder/lagarita.html Largest Explosive Eruptions: New results for the 27.8 Ma Fish Canyon Tuff and the La Garita caldera, San Juan volcanic field, Colorado] * [http://www.bbc.co.uk/science/horizon/1999/supervolcanoes_script.shtml] ==Notes== {{reflist}} ==References== * Clough, C. T; Maufe, H. B. & Bailey, E. B; 1909. The cauldron subsidence of Glen Coe, and the Associated Igneous Phenomena. Quart. Journ. Geol. Soc. 65, 611-678. * Kokelaar, B. P; and Moore, I. D; 2006. Glencoe caldera volcano, Scotland. ISBN. 0852725252. Pub. British Geological Survey, Keyworth, Nottinghamshire. There is an associated 1:25000 solid geology map. * Lipman, P; 1999. "Caldera". ''In'' Haraldur Sigurdsson, ed. ''Encyclopedia of Volcanoes''. Academic Press. ISBN 0-12-643140-X * Williams, H; 1941. Calderas and their origin. California University Publ. Geol. Sci. 25, 239-346. [[Category:Depressions]] [[Category:Igneous rocks]] [[Category:Volcanic calderas| ]] [[Category:Volcanology]] [[als:Caldera (Krater)]] [[bg:Калдера]] [[cs:Kaldera]] [[da:Caldera]] [[de:Caldera (Krater)]] [[et:Kaldeera]] [[el:Καλδέρα]] [[es:Caldera volcánica]] [[eo:Kaldero]] [[fr:Caldeira]] [[ko:칼데라]] [[id:Kaldera]] [[is:Sigketill]] [[it:Caldera (geologia)]] [[he:קלדרה]] [[ka:კალდერა]] [[sw:Kaldera]] [[lb:Caldera (Krater)]] [[lt:Kaldera]] [[hu:Kaldera]] [[ms:Kaldera]] [[nl:Caldera]] [[ja:カルデラ]] [[no:Kaldera]] [[nn:Kaldera]] [[pl:Kaldera]] [[pt:Caldeira vulcânica]] [[ro:Caldera]] [[ru:Кальдера]] [[simple:Caldera]] [[sk:Kaldera]] [[sr:Калдера]] [[sh:Kaldera]] [[fi:Kaldera]] [[sv:Caldera]] [[tr:Kaldera]] [[uk:Кальдера]] [[zh:破火山口]]