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55-419: The Mount Poster Formation was the first described in 1985, found on the locality of the same name, with exposures across northwestern areas of the southern Black Coast, Orville Coast, and eastern Ellsworth Land. It was found to be made of pyroclastic rocks along lava flows, all from intracaldera origin, interbedded with few sedimentary rocks. Originally, dating analyses indicated ages 189 ± 3 Ma-188 ± 3 Ma for

110-433: A crater , the feature is actually a type of sinkhole , as it is formed through subsidence and collapse rather than an explosion or impact. Compared to the thousands of volcanic eruptions that occur over the course of a century, the formation of a caldera is a rare event, occurring only a few times within a given window of 100 years. Only eight caldera-forming collapses are known to have occurred between 1911 and 2018, with

165-485: A volcanic eruption . An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the structural integrity of such a chamber, greatly diminishing its capacity to support its own roof, and any substrate or rock resting above. The ground surface then collapses into the emptied or partially emptied magma chamber, leaving a large depression at the surface (from one to dozens of kilometers in diameter). Although sometimes described as

220-461: A caldera collapse at Kīlauea , Hawaii in 2018. Volcanoes that have formed a caldera are sometimes described as "caldera volcanoes". The term caldera comes from Spanish caldera , and Latin caldaria , meaning "cooking pot". In some texts the English term cauldron is also used, though in more recent work the term cauldron refers to a caldera that has been deeply eroded to expose

275-409: A caldera, possibly an ash-flow caldera. 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. Mars has the tallest volcano in

330-806: A contributor to the expedition. 75°08′S 69°10′W  /  75.133°S 69.167°W  / -75.133; -69.167 . A mountain, 1,705 metres (5,594 ft) high, standing 7 nautical miles (13 km; 8.1 mi) northeast of Mount Edward in the Sweeney Mountains. Discovered and photographed by the RARE, 1947–48. Mapped by USGS from surveys and United States Navy air photos, 1961-67. Named by US-ACAN for W.H. Jenkins, hospital corpsman at South Pole Station, winter party 1963. 75°07′S 68°45′W  /  75.117°S 68.750°W  / -75.117; -68.750 . Peak standing 6 nautical miles (11 km; 6.9 mi) east of Mount Jenkins in

385-400: 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. 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

440-589: A group of mountains of moderate height and about 40 nautical miles (74 km; 46 mi) extent, located 30 nautical miles (56 km; 35 mi) north of the Hauberg Mountains in eastern Ellsworth Land , Antarctica. Download coordinates as: The Sweeney Mountains are in the southeast of Ellsworth Land . They are east of the Merrick Mountains , northeast of the Behrendt Mountains , north of

495-444: A lacustrine body with associated subaerial fluvial units. Fossil plant remains indicate a terrestrial environment, with conifers dominating and suggesting a preference for volcanic-rich soil. Lacustrine layers with volcanic influence are recovered in the connected Cañadón Asfalto Formation . The fossil palaeoassemblage is dominated by plants, suggesting a fully terrestrial or lacustrine setting, without any marine evidence. The material

550-467: A magma chamber whose magma is rich in silica . Silica-rich magma has a high viscosity , and therefore does not flow easily like basalt . The magma typically also contains a large amount of dissolved gases, up to 7 wt% for the most silica-rich magmas. When the magma approaches the surface of the Earth, the drop in confining pressure causes the trapped gases to rapidly bubble out of the magma, fragmenting

605-671: A maximum of ~300 m black finely laminated mudstone and sandstone. Analyses of intracaldera ignimbrites in the Mount Poster Formation yielded an age of 183.4 ± 1.4 Ma, around the same time as volcanic activity in other regions like Karoo-Ferrar . Zircon analysis were conducted on eight samples of silicic ignimbrite spanning from the Sweeney Mountains to Lyon Nunataks, with ages ranging from 185.2 ± 1.5 Ma to 177.5 ± 2.2 Ma, while detrital zircons from sedimentary rocks at Potter Peak West indicate again 183 ± 4 Ma. These findings indicate that volcanic activity began either slightly before or at

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660-735: A native continental arc, yet more recent studies suggest it is a collection of terranes merged onto the Gondwana margin. In the Antarctic Peninsula and eastern Ellsworth Land, volcanic and plutonic rocks formed during the subduction of oceanic lithosphere, marking different periods of volcanic activity. These rocks, part of the Antarctic Peninsula Volcanic Group , range from Early Jurassic to Tertiary age and exhibit various facies and ages, though their relationships are not fully understood. The Mesozoic volcanic-sedimentary layers in

715-583: A noticeable drop in temperature around the world. Large calderas may have even greater effects. The ecological effects of the eruption of a large caldera can be seen in the record of the Lake Toba eruption in Indonesia . 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 Eocene Rum Complex of Scotland,

770-552: A peninsular landmass connected with mainland South America. While there is a fit of the main surrounding continents and landmasses, the position of the inlet fragments along the Transantarctic margin of East Antarctica is complex. Local sediments where sourced mostly from the Mount Poster Caldera, followed by recycled-orogen materials. Local vulcanism was likely dominated by large-volume ( Ultra-Plinian ) eruptions, providing

825-489: A potential rhyolitic volcanic source to nearby Transantarctic Area (ex. Mawson Formation ). The Mount Poser layers suggests they were likely deposited within a Volcanic crater , indicated by similar composition, strong bonding, extensive layering, and the presence of faults and dykes around the edges that mark the boundaries of such crater, resembling units recovered in western United States and Alaska , where volcanic activity created similar landscapes. The differences seen on

880-539: Is dominated by wood trunks and root horizons. The leaf-based macroflora is conifer-dominated and corresponds to genera recovered in the Argentinian Cañadón Asfalto Formation , where cuticular analisis of the same taxa suggests common environmental stress. This fits also with the local foliar remains, that are consistent with growth between eruptive phases. Equisetites Stems Lowland and Riverside Warm to temperate, relatively wet Plants of

935-711: 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 keep 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. Sweeney Mountains The Sweeney Mountains ( 75°06′S 069°15′W  /  75.100°S 69.250°W  / -75.100; -69.250  ( Sweeney Mountains ) ) are

990-709: Is known to have continued in the Middle-Late Jurassic, as evidenced in the Latady Group deposition. The Ellsworth Land Volcanic Group belongs to the Patagonia - Antarctic Peninsula sequence, along the Mapple & Brennecke Formations and the N and Ellsworth-Whitmore terrane isolated granitoids. This units form part of the wider first-stage event (V1) of the Chon Aike Province, proving connection with both areas in

1045-529: Is relatively young (1.25 million years old) and unusually well preserved, and it remains one of the best studied examples of a resurgent caldera. The ash flow tuffs of the Valles caldera, such as the Bandelier Tuff , were among the first to be thoroughly characterized. About 74,000 years ago, this Indonesian volcano released about 2,800 cubic kilometres (670 cu mi) dense-rock equivalent of ejecta. This

1100-583: Is the Sturgeon Lake Caldera in northwestern Ontario , Canada, which formed during the Neoarchean era about 2.7 billion years ago. In the San Juan volcanic field , ore veins were emplaced in fractures associated with several calderas, with the greatest mineralization taking place near the youngest and most silicic intrusions associated with each caldera. Explosive caldera eruptions are produced by

1155-576: The Hauberg Mountains , northwest of the Wilkins Mountains and west of the Scaife Mountains . The region to the north, extending to the English Coast , is largely featureless. Features and nearby features, from west to east, include Morgan Nunataks, Mount Smart, Mount Ballard, Mount Edward, Mount Jenkins, Potter Peak, Anderson Nunataks and Hagerty Peak. The Sweeney Mountains were discovered by

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1210-499: The Ronne Antarctic Research Expedition (RARE), 1947–48, under Finn Ronne , who named these mountains after Mrs. Edward C. Sweeney, a contributor to the expedition. 75°22′S 70°35′W  /  75.367°S 70.583°W  / -75.367; -70.583 . A small group of nunataks located at the southwest extremity of the Sweeney Mountains. First observed from the air by the RARE, 1947–48. Mapped by

1265-500: 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. The caldera produced by such eruptions is typically filled in with tuff, rhyolite , and other igneous rocks . The caldera is surrounded by an outflow sheet of ash flow tuff (also called an ash flow sheet ). If magma continues to be injected into

1320-649: The Sweeney Mountains , where is present in most peaks, where is characterized by silicic ignimbrite , featuring diverse weathering patterns and lithology dominated by feldspar -rich ignimbrite. Additionally, it contains lithic-rich sections with quartzite fragments and traces of red mudstone , along with late-stage epidote and quartz veining. Well-consolidated units exhibit distinguishable fiamme, while less consolidated ignimbrites contain flattened pumices, occasionally found alongside deformed ignimbrites. The sedimentary facies are more typically tens of metres thick, with

1375-574: The United States Geological Survey (USGS) from surveys and United States Navy air photos, 1961-67. Named by the United States Advisory Committee on Antarctic Names (US-ACAN) for William R. Morgan, cook at Eights Station in 1965. 75°16′S 70°14′W  /  75.267°S 70.233°W  / -75.267; -70.233 . A mountain 4 nautical miles (7.4 km; 4.6 mi) southwest of Mount Ballard, in

1430-467: The Early Jurassic as a result of rifting and arc extension during the early stages of the southern Gondwana break-up. The Ellsworth Land Volcanic Group underlies parts of the southern Antarctic Peninsula and eastern Ellsworth Land. At Mount Poster, these volcanic rocks, up to 600 meters thick, and probably exceeds 2 kilometers in total thickness, yet is difficult to know. Ellsworth Land intertongues with

1485-898: The Early Jurassic, with the closest unit in South America being the Tobífera and Lemaire Formations ( Fuegian Andes ), the Quemado Complex ( Austral Patagonia ), the Bahía Laura Volcanic Complex ( Deseado Massif ) and the Marifil , Cañadón Asfalto , Lonco Trapial & Garamilla Formation in Central-Northern Patagonia. Other Units include Bajo Pobre , Cañadón Huemules and Roca Blanca Formations in Argentina. The Antarctic Peninsula has been traditionally interpreted as

1540-417: The Earth's volcanic activity (the other 40% is attributed to hotspot volcanism). 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

1595-529: The Ellsworth land sit atop older metamorphosed sedimentary rocks, like Ordovician to Permian basement on the Trinity Peninsula Group. Plutonic rocks, forming widespread outcrops, dominate the Antarctic Peninsula's igneous landscape, with their full extent and connectivity still not fully understood due to limited exposure and data availability. The Larsen & Latady Basins developed and where filled in

1650-510: The Moon have been well preserved through time and were once thought to have been the result of extreme volcanic activity, but are currently believed to have been 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

1705-647: 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). For their 1968 paper that first introduced the concept of a resurgent caldera to geology, R.L. Smith and R.A. Bailey chose the Valles caldera as their model. Although the Valles caldera is not unusually large, it

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1760-720: 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. 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. Io, unusually,

1815-468: The South Pole Station winter party in 1963. 75°12′S 69°33′W  /  75.200°S 69.550°W  / -75.200; -69.550 . A prominent rock mountain 1,635 metres (5,364 ft) high located centrally along the south margin of the Sweeney Mountains. Discovered by the RARE, 1947 48, under Ronne, who named this summit for Commander Edward C. Sweeney, United States Navy Reserve,

1870-513: The Sweeney Fm and is overlied by the Latady Group, marked by intense folding, thrust faulting, and pluton intrusion during the Late Jurassic to Early Cretaceous period. The Ellsworth Land VG shows considerable alteration and metamorphism, leading to challenges with volcanic sections correlation due to variations in rock types and minor faulting, with an estimated thickness of roughly 1000 meters in

1925-463: The Sweeney Mountains, Ellsworth Land. First observed from aircraft by the RARE, 1947-48. Mapped by USGS from surveys and United States Navy air photos, 1961-67. Named by US-ACAN for Christopher J. Potter, glaciologist at Byrd Station, summer 1965-66. 75°06′S 68°18′W  /  75.100°S 68.300°W  / -75.100; -68.300 . A group of nunataks forming the northeast end of Sweeney Mountains. Discovered and photographed from

1980-461: The air by the RARE, 1947-48. Mapped by USGS from surveys and United States Navy air photos, 1961-67. Named by US-ACAN for Richard E. Anderson, aviation electronics technician on R4D flights in 1961, including a November 4, 1961 reconnaissance flight from Byrd Station to the Eights Coast. 75°17′S 68°11′W  /  75.283°S 68.183°W  / -75.283; -68.183 . Peak in

2035-411: 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. 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

2090-610: The beds under the caldera floor. 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 , where he first saw the Las Cañadas caldera on Tenerife , with Mount Teide dominating the landscape, and then the Caldera de Taburiente on La Palma . A collapse is triggered by

2145-577: The caldera atop Fernandina Island collapsed in 1968 when parts of the caldera floor dropped 350 metres (1,150 ft). 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 crewed and uncrewed 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

2200-664: The collapsed magma chamber, the center of the caldera may be uplifted in the form of a resurgent dome such as is seen at the Valles Caldera , Lake Toba , the San Juan volcanic field, Cerro Galán , Yellowstone , and many other calderas. Because a silicic caldera may erupt hundreds or even thousands of cubic kilometers of material in a single event, it can cause catastrophic environmental effects. Even small caldera-forming eruptions, such as Krakatoa in 1883 or Mount Pinatubo in 1991, may result in significant local destruction and

2255-400: 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) 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

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2310-417: The family Cupressaceae Pagiophyllum Lowland and Coastal lake Warm to temperate, can withstand long periods of drought; seasonal climate Plants of the family Araucariaceae or Cheirolepidiaceae Volcanic caldera A caldera ( / k ɔː l ˈ d ɛr ə , k æ l -/ kawl- DERR -ə, kal- ) is a large cauldron -like hollow that forms shortly after the emptying of a magma chamber in

2365-470: The group Equisetales . Usually linked with riversides Cladophlebis Isolated Pinnae Lowland and Riverside Warm to temperate, relatively wet Plants of the family Osmundaceae . [REDACTED] Archangelskya Isolated Pinnae Lowland and Riverside Warm, can withstand long periods of drought; seasonal climate Plants of the group Pteridospermata Taeniopteris Lowland and Riverside Warm to temperate, relatively wet Plants of

2420-414: The group Pentoxylales . Their liana-like anatomy has also led to suggestions of a habit similar to that of brambles Brachyphyllum Branched shoots Upland, Lowland and Riverside ?Warm to temperate, relatively wet Plants of the family Araucariaceae or Cheirolepidiaceae Elatoclaudus Upland and Lowland Warm to temperate, can withstand long periods of drought; seasonal climate Plants of

2475-463: The human species was reduced to approximately 5,000–10,000 people. 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. There is evidence that human habitation continued in India after the eruption. Some volcanoes, such as the large shield volcanoes Kīlauea and Mauna Loa on

2530-429: 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,

2585-479: The layers might indicate different volcanic events from various centers, possibly forming a series of connected or nested craters. The sedimentary layers near the volcanic ones often show signs of heat damage or disturbance by the volcanics: red mudstone next to basaltic flows turns black, and disrupted bedding underlies lava bodies. Sedimentary layers mainly consist of well-sorted sandstone and siltstone with ripple patterns, suggesting deposition in freshwater, likely in

2640-729: The lowermost sections (Lower Pliensbachian ), and 167 ± 3 Ma ( Bathonian ) for different locations within the formation, yet was later constrained to the Toarcian-only, between 183 and 177 Ma. Due to this datations it was allocated in the lowermost section of the Jurassic Latady Basin layers, overlied by what was defined back then as "Latady Formation" (now Latady Group ), now proven to be the Sweeney Formation. The Sweeney Fm rocks outcrop on W Potter Peak, Mount Jenkins, Mount Edward, Mount Ballard and Mount Wasilewski. Local vulcanism

2695-561: The magma to produce a mixture of volcanic ash and other tephra with the very hot gases. The mixture of ash and volcanic gases initially rises into the atmosphere as an eruption column . However, as the volume of erupted material increases, the eruption column is unable to entrain enough air to remain buoyant, and the eruption column collapses into a tephra fountain that falls back to the surface to form pyroclastic flows . Eruptions of this type can spread ash over vast areas, so that ash flow tuffs emplaced by silicic caldera eruptions are

2750-468: The only volcanic product with volumes rivaling those of flood basalts . For example, when Yellowstone Caldera last erupted some 650,000 years ago, it released about 1,000 km of material (as measured in dense rock equivalent (DRE)), covering a substantial part of North America in up to two metres of debris. Eruptions forming even larger calderas are known, such as the La Garita Caldera in

2805-448: 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 of square kilometers. 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. One of the world's best-preserved mineralized calderas

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2860-622: The same time as the initial non-volcanic sedimentation in the Sweeney Formation. More recently, volcanic tuffs at Mount Peterson have been dated at 181.9 + 2.4 Ma and are likely correlated to the other sections. The Toarcian Latady Basin was bracketed between the Ellsworth-Whitmore block, that was located in the Paleopacific along the Marie Byrd Land , Thurston Island, the Antarctic Peninsula and Southern Patagonia, being either islands or

2915-486: The southwest part of the Sweeney Mountains. Mapped by USGS from surveys and United States Navy air photos, 1961-67. Named by US-ACAN for Robert G. Smart, cook at Eights Station in 1965. 75°12′S 70°05′W  /  75.200°S 70.083°W  / -75.200; -70.083 . Mountain in the west part of the Sweeney Mountains. Mapped by USGS from ground surveys and United States Navy air photos, 1961-67. Named by US-ACAN for G.E. Ballard, equipment operator with

2970-402: 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

3025-464: 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 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

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