Caldera

A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber/reservoir in a volcanic eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is lost. The ground surface then collapses downward into the emptied or partially emptied magma chamber, leaving a massive depression at the surface (from one to dozens of kilometers in diameter). Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Only seven caldera-forming collapses are known to have occurred since 1900, most recently at Bárðarbunga volcano, Iceland in 2014.[1]

Mount Mazama eruption timeline
Mount Mazama's eruption timeline, an example of caldera formation

Etymology

The term caldera comes from Spanish caldera, and Latin caldaria, meaning "cooking pot". In some texts the English term cauldron is also used. The term caldera was introduced into the geological vocabulary by the German geologist Leopold von Buch when he published his memoirs of his 1815 visit to the Canary Islands,[note 1] where he first saw the Las Cañadas caldera on Tenerife, with Montaña Teide dominating the landscape, and then the Caldera de Taburiente on La Palma.

Caldera formation

Origin of volcanic caldera via analogue model
Animation of analogue experiment showing origin of volcanic caldera in box filled with flour.
Toba zoom
Landsat image of Lake Toba, on the island of Sumatra, Indonesia (100 km/62 mi long and 30 km/19 mi wide, one of the world's largest calderas). A resurgent dome formed the island of Samosir.

A collapse is triggered by the emptying of the magma chamber beneath the volcano, sometimes as the result of a large explosive volcanic eruption (see Tambora in 1815), but also during effusive eruptions on the flanks of a volcano (see Piton de la Fournaise in 2007)[2] or in a connected fissure system (see Bárðarbunga in 2014–2015). If enough magma is ejected, the emptied chamber is unable to support the weight of the volcanic edifice above it. A roughly circular fracture, the "ring fault", develops around the edge of the chamber. Ring fractures serve as feeders for fault intrusions which are also known as ring dikes. Secondary volcanic vents may form above the ring fracture. As the magma chamber empties, the center 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 square kilometers.

Mineralization in calderas

Caldera formation
Caldera formation under water.

Some calderas are known to host rich ore deposits. Metal-rich fluids can circulate through the caldera, forming hydrothermal ore deposits of metals such as lead, silver, gold, mercury, lithium and uranium.[3] One of the world's best-preserved mineralized calderas is the Sturgeon Lake Caldera in northwestern Ontario, Canada, which formed during the Neoarchean era[4] about 2,700 million years ago.[5]

Types of caldera

Explosive caldera eruptions

If the magma is rich in silica, the caldera is often filled in with ignimbrite, tuff, rhyolite, and other igneous rocks. Silica-rich magma has a high viscosity, and therefore does not flow easily like basalt. As a result, gases tend to become trapped at high pressure within the magma. When the magma approaches the surface of the Earth, the rapid off-loading of overlying material causes the trapped gases to decompress rapidly, thus triggering explosive destruction of the magma and spreading volcanic ash over wide areas. Further lava flows may be erupted.

If volcanic activity continues, the center of the caldera may be uplifted in the form of a resurgent dome such as is seen at Cerro Galán, Lake Toba, Yellowstone, etc., by subsequent intrusion of magma. A silicic or rhyolitic caldera may erupt hundreds or even thousands of cubic kilometers 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 some 650,000 years ago, it released about 1,000 km3 of material (as measured in dense rock equivalent (DRE)), 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 km3 (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 74,000 years ago, this Indonesian volcano released about 2,800 cubic kilometres (670 cu mi) dense-rock equivalent of ejecta. This was the largest known eruption during the ongoing Quaternary period (the last 2.6 million years) and the largest known explosive eruption during the last 25 million years. In the late 1990s, anthropologist Stanley Ambrose[6] 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. More recently, Lynn Jorde and Henry Harpending proposed that the human species was reduced to approximately 5,000-10,000 people.[7] There is no direct evidence, however, that either theory is correct, and there is no evidence for any other animal decline or extinction, even in environmentally sensitive species.[8] There is evidence that human habitation continued in India after the eruption.[9]

Eruptions forming even larger calderas are known, especially La Garita Caldera in the San Juan Mountains of Colorado, where the 5,000 cubic kilometres (1,200 cu mi) Fish Canyon Tuff was blasted out in eruptions about 27.8 million years ago.[10][11]

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 (formed during the Oligocene, Miocene, and Pliocene epochs) or the Saint Francois Mountain Range of Missouri (erupted during the Proterozoic eon).[12]

La Cumbre - ISS
Satellite photograph of the summit caldera on Fernandina Island in the Galápagos archipelago.
Nemrut Caldera aerial
Oblique aerial photo of Nemrut Caldera, Van Lake, Eastern Turkey

Non-explosive calderas

Iss038e012569, Caldera Sollipulli
Sollipulli Caldera, located in central Chile near the border with Argentina, filled with ice. The volcano is in the southern Andes Mountains within Chile's Parque Nacional Villarica.[13]

Some volcanoes, such as the large shield volcanoes Kīlauea and Mauna Loa on the island of Hawaii, form calderas in a different fashion. The magma feeding these volcanoes 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 collapsed in 1968 when parts of the caldera floor dropped 350 metres (1,150 ft).[14]

Extraterrestrial calderas

Since the early 1960s, it has been known that volcanism has occurred on other planets and moons in the Solar System. Through the use of manned and unmanned spacecraft, volcanism has been discovered on Venus, Mars, the Moon, and Io, a satellite of Jupiter. None of these worlds have plate tectonics, which contributes approximately 60% of the Earth's volcanic activity (the other 40% is attributed to hotspot volcanism).[15] Caldera structure is similar on all of these planetary bodies, though the size varies considerably. The average caldera diameter on Venus is 68 km (42 mi). The average caldera diameter on Io is close to 40 km (25 mi), and the mode is 6 km (3.7 mi); Tvashtar Paterae is likely the largest caldera with a diameter of 290 km (180 mi). The average caldera diameter on Mars is 48 km (30 mi), smaller than Venus. Calderas on Earth are the smallest of all planetary bodies and vary from 1.6–80 km (1–50 mi) as a maximum.[16]

The Moon

The Moon has an outer shell of low-density crystalline rock that is a few hundred kilometers thick, which formed due to a rapid creation. The craters of the Moon have been well preserved through time and were once thought to have been the result of extreme volcanic activity, but actually were formed by meteorites, nearly all of which took place in the first few hundred million years after the Moon formed. Around 500 million years afterward, the Moon's mantle was able to be extensively melted due to the decay of radioactive elements. Massive basaltic eruptions took place generally at the base of large impact craters. Also, eruptions may have taken place due to a magma reservoir at the base of the crust. This forms a dome, possibly the same morphology of a shield volcano where calderas universally are known to form.[15] Although caldera-like structures are rare on the Moon, they are not completely absent. The Compton-Belkovich Volcanic Complex on the far side of the Moon is thought to be a caldera, possibly an ash-flow caldera.[17]

Mars

The volcanic activity of Mars is concentrated in two major provinces: Tharsis and Elysium. Each province contains a series of giant shield volcanoes that are similar to what we see on Earth and likely are the result of mantle hot spots. The surfaces are dominated by lava flows, and all have one or more collapse calderas.[15] Mars has the largest volcano in the Solar System, Olympus Mons, which is more than three times the height of Mount Everest, with a diameter of 520 km (323 miles). The summit of the mountain has six nested calderas.[18]

Venus

Because there is no plate tectonics on Venus, heat is mainly lost by conduction through the lithosphere. This causes enormous lava flows, accounting for 80% of Venus' surface area. Many of the mountains are large shield volcanoes that range in size from 150–400 km (95–250 mi) in diameter and 2–4 km (1.2–2.5 mi) high. More than 80 of these large shield volcanoes have summit calderas averaging 60 km (37 mi) across.[15]

Io

Io, unusually, is heated by solid flexing due to the tidal influence of Jupiter and Io's orbital resonance with neighboring large moons Europa and Ganymede, which keeps its orbit slightly eccentric. Unlike any of the planets mentioned, Io is continuously volcanically active. For example, the NASA Voyager 1 and Voyager 2 spacecraft detected nine erupting volcanoes while passing Io in 1979. Io has many calderas with diameters tens of kilometers across.[15]

List of volcanic calderas

Crater lake oregon
Crater Lake, Oregon, formed around 5,680 BC
Aniakchak-caldera alaska
Aniakchak-caldera, Alaska
Teopan
Coatepeque Caldera, El Salvador crater lake
Pinatubo92pinatubo caldera crater lake
Mount Pinatubo, Philippines
Yankicha
Caldera of the island Yankicha/Ushishir, Kuril Islands
Laacher See - Luftaufnahme
Aerial view of the Laacher See, Germany.
Lake taupo landsat
Satellite photo of Lake Taupo

Erosion calderas

See also

  • Complex volcano – A landform of more than one related volcanic centre
  • Somma volcano – A volcanic caldera that has been partially filled by a new central cone
  • Supervolcano – Volcano that has erupted 1000 cubic km in a single eruption
  • Volcanic Explosivity Index – qualitative scale indicating the explosive intensity of volcanic eruptions

Notes

  1. ^ Leopold von Buch's book Physical Description of the Canary Isles was published in 1825

References

  1. ^ Gudmundsson, M.T.; et al. (2016). "Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow" (PDF). Science. 353 (6296): aaf8988–1 – aaf8988–8. doi:10.1126/science.aaf8988.
  2. ^ "Piton de la Fournaise". Smithsonian Institution. 2019.
  3. ^ John, David A. (1 February 2008). "Supervolcanoes and Metallic Ore Deposits". Elements. 4 (1): 22. doi:10.2113/GSELEMENTS.4.1.22. ISSN 1811-5209.
  4. ^ "UMD: Precambrian Research Center". University of Minnesota, Duluth. Archived from the original on 4 March 2016. Retrieved 20 March 2014.
  5. ^ Ron Morton. "Caldera Volcanoes". University of Minnesota, Duluth. Retrieved 3 July 2015.
  6. ^ "Stanley Ambrose page". University of Illinois at Urbana-Champaign. Retrieved 20 March 2014.
  7. ^ Supervolcanoes, BBC2, 3 February 2000
  8. ^ Gathorne-Hardy, F. J.; Harcourt-Smith, W. E. H. (2003). "The super-eruption of Toba, did it cause a human bottleneck?". Journal of Human Evolution. 45 (3): 227–30. doi:10.1016/S0047-2484(03)00105-2. PMID 14580592.
  9. ^ Petraglia, M.; Korisettar, R.; Boivin, N.; Clarkson, C.; Ditchfield, P.; Jones, S.; Koshy, J.; Lahr, M. M.; Oppenheimer, C.; Pyle, D.; Roberts, R.; Schwenninger, J. L.; Arnold, L.; White, K. (2007). "Middle Paleolithic Assemblages from the Indian Subcontinent Before and After the Toba Super-Eruption". Science. 317 (5834): 114–16. Bibcode:2007Sci...317..114P. doi:10.1126/science.1141564. PMID 17615356.
  10. ^ "What's the Biggest Volcanic Eruption Ever?". livescience.com. 10 November 2010. Retrieved 1 February 2014.
  11. ^ Best, MG (2013). "The 36–18 Ma Indian Peak–Caliente ignimbrite field and calderas, southeastern Great Basin, USA: Multicyclic super-eruptions". Geosphere. 9 (4): 864–950. Bibcode:2013Geosp...9..864B. doi:10.1130/GES00902.1.
  12. ^ Kisvarsanyi, Eva (1981). "Geology of the Precambrian St. Francois terrane, southeastern Missouri". Report of Investigations (Missouri Geological Survey) No. 64.
  13. ^ "EO". Earthobservatory.nasa.gov. 23 December 2013. Retrieved 20 March 2014.
  14. ^ "Fernandina: Photo". Global Volcanism Program. Smithsonian Institution.
  15. ^ a b c d e Parfitt, L.; Wilson, L. (19 February 2008). "Volcanism on Other Planets". Fundamentals of Physical Volcanology. Malden, MA: Blackwell Publishing. pp. 190–212. ISBN 978-0-632-05443-5. OCLC 173243845.
  16. ^ Gudmundsson, A. (2008) Magma chamber geometry, fluid transport, local stresses and rock behaviour during collapse caldera formation in Gottsmann, J. and Marti, J. (editors) (2008) Caldera Volcanism: Analysis, Modelling and Response, Amsterdam, Elsevier. p. 319, citing Lipman, P. (2000).
  17. ^ Chauhan, M.; Bhattacharya, S.; Saran, S.; Chauhan, P.; Dagar, A. (2015). "Compton–Belkovich Volcanic Complex (CBVC): An ash flow caldera on the Moon". Icarus. 253: 115–29. Bibcode:2015Icar..253..115C. doi:10.1016/j.icarus.2015.02.024.
  18. ^ Philip's World Reference Atlas including Stars and Planets ISBN 0-7537-0310-6 Publishing House Octopus publishing Group Ltd p. 9
  • Clough, C. T.; Maufe, H. B.; Bailey, E. B. (1909). "The Cauldron-Subsidence of Glen Coe, and the Associated Igneous Phenomena". Quarterly Journal of the Geological Society. 65 (1–4): 611–78. doi:10.1144/GSL.JGS.1909.065.01-04.35.
  • Gudmundsson, A (2008). Magma-Chamber Geometry, Fluid Transport, Local Stresses, and Rock Behavior During Collapse Caldera Formation. In Gottsmann J. & Marti, J (Ed. 10) Caldera Volcanism: Analysis, Modeling, and Response (314–46) Elsener, Amsterdam, The Netherlands
  • Kokelaar, B. P; and Moore, I. D; 2006. Glencoe caldera volcano, Scotland. ISBN 9780852725252. 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.

External links

Caldera OpenLinux

Caldera OpenLinux (COL) is a defunct Linux distribution that was originally introduced by Caldera in 1997 based on the German LST Power Linux distribution, and then taken over and further developed by Caldera Systems (now SCO Group) since 1998. A successor to the Caldera Network Desktop put together by Caldera since 1995, OpenLinux was an early "business-oriented distribution" and foreshadowed the direction of developments that came to most other distributions and the Linux community generally.

Ceraunius Tholus

Ceraunius Tholus is a volcano on Mars located in the Tharsis quadrangle at 24.25° north latitude and 262.75° east longitude, part of the Uranius group of volcanoes. It is 130 kilometres (81 mi) across, approximately 8,500 metres (27,887 ft) high and is named after a classical albedo feature name.

It is generally believed to be a basaltic shield with the lower part buried beneath plain forming lavas. Earlier interpretations suggested that it is a stratovolcano. The slopes on Ceraunius Tholus are quite steep with an average slope of 8° with many radial erosion channels and pitted valleys extending from just below the rim of the caldera toward the base of the volcano. The current view is that the valleys were eroded by water. Interesting features on Ceraunius Tholus are three large canyons at the northwest flank of Ceraunius Tholus which are up to 2.5 km wide and 300 m deep. The biggest of these three also appears to be the youngest and protrude from the lowest point of the volcanic caldera and ends at the interesting crater Rahe (an oblique impact crater with measures of 35 × 18 km), just north from the volcano where it formed a depositional fan. Its origin is still debatable and there are four main models proposed: fluvial action, volcanic flows, valley being a lava channel or some combination of previously mentioned models.Ceraunius appears small compared to other larger volcanoes, but it is almost as tall as Earth's Mount Everest.The caldera of Ceranius Tholus is also dotted with many collapse pits, which are distinct from impact craters as they have no rim and vary in abundance across the caldera.

Ceraunius Tholus is probably late Hesperian in age.

Complex volcano

A complex volcano, also called a compound volcano, is mixed landform consisting of related volcanic centers and their associated lava flows and pyroclastic rock. They may form due to changes in eruptive habit or in the location of the principal vent area on a particular volcano. Stratovolcanoes can also form a large caldera that gets filled in by a lava dome, or else multiple small cinder cones, lava domes and craters may develop on the caldera's rim.Although a comparatively unusual type of volcano, they are widespread in the world and in geologic history. Metamorphosed ash flow tuffs are widespread in the Precambrian rocks of northern New Mexico, which indicates that caldera complexes have been important for much of Earth's history. Yellowstone National Park is on three partly covered caldera complexes. The Long Valley Caldera in eastern California is also a complex volcano; the San Juan Mountains in southwestern Colorado are formed on a group of Neogene-age caldera complexes, and most of the Mesozoic and Cenozoic rocks of Nevada, Idaho, and eastern California are also caldera complexes and their erupted ash flow tuffs. The Bennett Lake Caldera in British Columbia and the Yukon Territory is another example of a Cenozoic (Eocene) caldera complex.

Crater lake

A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite, or in the crater left by an artificial explosion caused by humans. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not made. Crater lakes covering active (fumarolic) volcanic vents are sometimes known as volcanic lakes, and the water within them is often acidic, saturated with volcanic gases, and cloudy with a strong greenish color. For example, the crater lake of Kawah Ijen in Indonesia has a pH of under 0.5. Lakes located in dormant or extinct volcanoes tend to have fresh water, and the water clarity in such lakes can be exceptional due to the lack of inflowing streams and sediment.

DR-DOS

DR-DOS (DR DOS, without hyphen up to and including version 6.0) is an operating system of the DOS family, written for IBM PC-compatible personal computers. It was originally developed by Gary A. Kildall's Digital Research and derived from Concurrent PC DOS 6.0, which was an advanced successor of CP/M-86. As ownership changed, various later versions were produced with names including Novell DOS and Caldera OpenDOS.

DR-WebSpyder

DR-WebSpyder was a DOS web browser, mail client and operating system environment developed by Caldera UK in 1997. It was based on the DR-DOS operating system and networking components from Novell as well as the Arachne web browser by Michal Polák of xChaos software. The system was designed to run on low-end desktop systems, but being able to boot and execute from disk as well as from ROM or network, it was also tailored for x86-based thin clients and embedded systems with or without disk drives. Using the web browser as its principal user interface, it could be also used for kiosk systems and set-top boxes. Named Embrowser, it has been ported to Linux in 1999 and was called Embedix Browser since 2000.

La Garita Caldera

La Garita Caldera is a large supervolcanic caldera in the San Juan volcanic field in the San Juan Mountains near the town of Creede in southwestern Colorado, United States. It is west of La Garita, Colorado. The eruption that created the La Garita Caldera is among the largest known volcanic eruptions in Earth's history, as well as being one of the most powerful known supervolcanic events.

La Pacana

La Pacana is a Miocene age caldera in northern Chile's Antofagasta Region. Part of the Central Volcanic Zone of the Andes, it is part of the Altiplano-Puna volcanic complex, a major caldera and silicic ignimbrite volcanic field. This volcanic field is located in remote regions at the Zapaleri tripoint between Chile, Bolivia and Argentina.

La Pacana along with other regional volcanoes was formed by the subduction of the Nazca Plate beneath the South American Plate in the Peru-Chile Trench. La Pacana is situated in a basement formed by various Paleozoic formations and Tertiary ignimbrites and volcanoes. Several major faults cross the region at La Pacana and have influenced its volcanic activity.

La Pacana is a supervolcano and is responsible for the eruption of the giant Atana ignimbrite, which reaches a volume of 2,451–3,500 cubic kilometres (588–840 cu mi) and constitutes the fifth-largest explosive eruption known. The Atana ignimbrite was erupted 3.8 ± 0.1 and 4.2 ± 0.1 million years ago, almost simultaneously with the much smaller (volume of 180 cubic kilometres (43 cu mi)) Toconao ignimbrite. The Pujsa ignimbrite was erupted by La Pacana before the Atana/Toconao ignimbrites, and the Filo Delgado and Pampa Chamaca/Talabre ignimbrites afterwards.

Lake Toba

Lake Toba (Indonesian: Danau Toba) is a large natural lake in Sumatra, Indonesia occupying the caldera of a supervolcano. The lake is located in the middle of the northern part of the island of Sumatra, with a surface elevation of about 900 metres (2,953 ft), the lake stretches from 2.88°N 98.52°E / 2.88; 98.52 to 2.35°N 99.1°E / 2.35; 99.1. The lake is about 100 kilometres (62 miles) long, 30 kilometres (19 mi) wide, and up to 505 metres (1,657 ft) deep. It is the largest lake in Indonesia and the largest volcanic lake in the world.Lake Toba Caldera is one of the nineteen Geoparks in Indonesia, which is proposed to be included in the UNESCO Global Geopark.

Lake Toba is the site of a massive supervolcanic eruption estimated at VEI 8 that occurred 69,000 to 77,000 years ago, representing a climate-changing event. Recent advances in dating methods suggest a more accurate identification of 74,000 years ago as the date. It is the largest-known explosive eruption on Earth in the last 25 million years. According to the Toba catastrophe theory, it had global consequences for human populations; it killed most humans living at that time and is believed to have created a population bottleneck in central east Africa and India, which affects the genetic make-up of the human worldwide population to the present.It has been accepted that the eruption of Toba led to a volcanic winter with a worldwide decrease in temperature between 3 to 5 °C (5.4 to 9.0 °F), and up to 15 °C (27 °F) in higher latitudes. Additional studies in Lake Malawi in East Africa show significant amounts of ash being deposited from the Toba eruptions, even at that great distance, but little indication of a significant climatic effect in East Africa.

Long Valley Caldera

Long Valley Caldera is a depression in eastern California that is adjacent to Mammoth Mountain. The valley is one of the Earth's largest calderas, measuring about 20 miles (32 km) long (east-west), 11 miles (18 km) wide (north-south), and up to 3,000 feet (910 m) deep.

Long Valley was formed 760,000 years ago when a supervolcanic eruption released very hot ash that later cooled to form the Bishop tuff that is common to the area. The eruption emptied the magma chamber under the area to the point of collapse. The second phase of the eruption released pyroclastic flows that burned and buried thousands of square miles. Ash from this eruption blanketed much of the western part of what is now the United States.

Microsoft litigation

Microsoft has been involved in numerous high-profile legal matters that involved litigation over the history of the company, including cases against the United States, the European Union, and competitors.

Mount Bromo

For the main article that includes the Sand Sea and the Mount Semeru area, see Bromo Tengger Semeru National Park.Mount Bromo (Indonesian: Gunung Bromo), is an active volcano and part of the Tengger massif, in East Java, Indonesia. At 2,329 meters (7,641 ft) it is not the highest peak of the massif, but is the most well known. The massif area is one of the most visited tourist attractions in East Java, Indonesia. The volcano belongs to the Bromo Tengger Semeru National Park. The name of Bromo derived from Javanese pronunciation of Brahma, the Hindu creator god.

Mount Bromo sits in the middle of a plain called the "Sea of Sand" (Javanese: Segara Wedi or Indonesian: Lautan Pasir), a protected nature reserve since 1919. The typical way to visit Mount Bromo is from the nearby mountain village of Cemoro Lawang. From there it is possible to walk to the volcano in about 45 minutes, but it is also possible to take an organised jeep tour, which includes a stop at the viewpoint on Mount Penanjakan (2,770 m or 9,088 ft) (Indonesian: Gunung Penanjakan). The viewpoint on Mount Penanjakan can also be reached on foot in about two hours.

Depending on the degree of volcanic activity, the Indonesian Centre for Volcanology and Disaster Hazard Mitigation sometimes issues warnings against visiting Mount Bromo.

Mount Tambora

Mount Tambora, or Tomboro, is an active stratovolcano in the northern part of Sumbawa, one of the Lesser Sunda Islands of Indonesia. It was formed due to the active subduction zones beneath it, and before its 1815 eruption, it was more than 4,300 metres (14,100 feet) high, making it one of the tallest peaks in the Indonesian archipelago.

Tambora's 1815 eruption was the largest in recorded human history. The magma chamber under Tambora had been drained by pre-1815 eruptions and underwent several centuries of dormancy as it refilled. Volcanic activity reached a peak that year, culminating in the eruption. The explosion was heard on Sumatra island, more than 2,000 kilometres (1,200 miles) away. Heavy volcanic ash rains were observed as far away as Borneo, Sulawesi, Java and Maluku islands, and the maximum elevation of Tambora was reduced from about 4,300 metres (14,100 ft) to 2,850 metres (9,350 feet). Although estimates vary, the death toll was at least 71,000 people. The eruption caused global climate anomalies in the following years, while 1816 became known as the "year without a summer" due to the impact on North American and European weather. In the Northern Hemisphere, crops failed and livestock died, resulting in the worst famine of the century.

During a 2004 excavation, archaeologists discovered the remains of a house destroyed and buried by the 1815 eruption. The site has remained intact beneath three metres of pyroclastic deposits and provides insight into the culture that vanished. Today, Mount Tambora is closely monitored for volcanic activity; a powerful eruption would affect millions of Indonesians. The mountain is administered by the Bima Regency in the northeast and by the Dompu Regency in the west and south.

Rafael Caldera

Rafael Antonio Caldera Rodríguez (Spanish pronunciation: [rafaˈel anˈtonjo kalˈdeɾa roˈðɾiɣes] (listen ); 24 January 1916 – 24 December 2009), twice elected President of Venezuela, served for two five-year terms (1969-1974 and 1994-1999), becoming the longest serving democratically elected leader to govern the country in the twentieth century.Widely acknowledged as one of the founders of Venezuela’s democratic system, the main architect of the 1961 Constitution, and a pioneer of the Christian Democratic movement in Latin America, Caldera helped forge an unprecedented period of civilian democratic rule in a country beleaguered by a history of political violence and military caudillos.His leadership established Venezuela’s reputation as one of the more stable democracies in Latin America during the second half of the twentieth century.After graduating with a degree in law and political science from Central University of Venezuela in 1939, Caldera embarked on a 70-year long career that combined political, intellectual and academic activities.

SCO Group

SCO, The SCO Group, The TSG Group, Caldera Systems, and Caldera International are the various names of an American software company that became known for acquiring the Santa Cruz Operation's Server Software and Services divisions, and UnixWare and OpenServer technologies, and then, under CEO Darl McBride, pursuing a series of legal battles known as the SCO-Linux controversies.

The company was part of the Canopy Group, but became independent in March 2005, after the settlement of a lawsuit between the Noorda family and a chairman of the group, Ralph Yarro, also former CEO of the Canopy Group. As part of the settlement, Canopy transferred all of its shares to Yarro.

Later on, Caldera International changed its name to "SCO" and then to "The SCO Group" to reflect that change in focus.

In January 2004, their website, www.sco.com, was attacked by the Mydoom computer virus, which took down the website for 2 weeks using a DDoS attack.In September 2007, SCO filed for Chapter 11 bankruptcy protection. In April 2011, UnXis, Inc. (currently Xinuos) bought The SCO Group, Inc. operating assets and intellectual property rights after having been approved by the bankruptcy court in Delaware. The SCO Group, Inc. then renamed itself TSG Group, Inc. In August 2012, TSG Group, Inc. filed to convert from Chapter 11 bankruptcy protection to Chapter 7 stating "There is no reasonable chance of rehabilitation". On June 14, 2013, Judge David Nuffer ruled on SCO v. IBM motions, granting SCO's motion for reconsideration and reopening the case.

Santorini

Santorini (Greek: Σαντορίνη, pronounced [sandoˈrini]), officially Thira (Greek: Θήρα [ˈθira]) and classic Greek Thera (English pronunciation ), is an island in the southern Aegean Sea, about 200 km (120 mi) southeast of Greece's mainland. It is the largest island of a small, circular archipelago, which bears the same name and is the remnant of a volcanic caldera. It forms the southernmost member of the Cyclades group of islands, with an area of approximately 73 km2 (28 sq mi) and a 2011 census population of 15,550. The municipality of Santorini includes the inhabited islands of Santorini and Therasia, as well as the uninhabited islands of Nea Kameni, Palaia Kameni, Aspronisi and Christiana. The total land area is 90.623 km2 (34.990 sq mi). Santorini is part of the Thira regional unit.The island was the site of one of the largest volcanic eruptions in recorded history: the Minoan eruption (sometimes called the Thera eruption), which occurred about 3,600 years ago at the height of the Minoan civilization. The eruption left a large caldera surrounded by volcanic ash deposits hundreds of metres deep. It may have led indirectly to the collapse of the Minoan civilization on the island of Crete, 110 km (68 mi) to the south, through a gigantic tsunami. Another popular theory holds that the Thera eruption is the source of the legend of Atlantis.It is the most active volcanic centre in the South Aegean Volcanic Arc, though what remains today is chiefly a water-filled caldera. The volcanic arc is approximately 500 km (310 mi) long and 20 to 40 km (12 to 25 mi) wide. The region first became volcanically active around 3–4 million years ago, though volcanism on Thera began around 2 million years ago with the extrusion of dacitic lavas from vents around Akrotiri.

Supervolcano

A supervolcano is a large volcano that has had an eruption with a Volcanic Explosivity Index (VEI) of 8, the largest recorded value on the index. This means the volume of deposits for that eruption is greater than 1,000 cubic kilometers (240 cubic miles).

Supervolcanoes occur when magma in the mantle rises into the crust but is unable to break through it and pressure builds in a large and growing magma pool until the crust is unable to contain the pressure. This can occur at hotspots (for example, Yellowstone Caldera) or at subduction zones (for example, Toba). Large-volume supervolcanic eruptions are also often associated with large igneous provinces, which can cover huge areas with lava and volcanic ash. These can cause long-lasting climate change (such as the triggering of a small ice age) and threaten species with extinction. The Oruanui eruption of New Zealand's Taupo Volcano (about 26,500 years ago) was the world's most recent VEI-8 eruption.

UnixWare

UnixWare is a Unix operating system. It was originally released by Univel, a jointly owned venture of AT&T's Unix System Laboratories (USL) and Novell. It was then taken over by Novell. Via Santa Cruz Operation (SCO) it went on to Caldera Systems, Caldera International, and The SCO Group before it was sold to UnXis (now Xinuos). UnixWare is typically deployed as a server rather than a desktop. Binary distributions of UnixWare are available for x86 architecture computers. UnixWare is primarily marketed as server operating system.

Yellowstone Caldera

The Yellowstone Caldera is a volcanic caldera and supervolcano in Yellowstone National Park in the Western United States, sometimes referred to as the Yellowstone Supervolcano. The caldera and most of the park are located in the northwest corner of Wyoming. The major features of the caldera measure about 34 by 45 miles (55 by 72 km).The caldera formed during the last of three supereruptions over the past 2.1 million years: the Huckleberry Ridge eruption 2.1 million years ago (which created the Island Park Caldera and the Huckleberry Ridge Tuff); the Mesa Falls eruption 1.3 million years ago (which created the Henry's Fork Caldera and the Mesa Falls Tuff); and the Lava Creek eruption approximately 630,000 years ago (which created the Yellowstone Caldera and the Lava Creek Tuff).

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