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93-564: Mount Melbourne is a 2,733-metre-high (8,967 ft) ice-covered stratovolcano in Victoria Land , Antarctica , between Wood Bay and Terra Nova Bay . It is an elongated mountain with a summit caldera filled with ice with numerous parasitic vents ; a volcanic field surrounds the edifice. Mount Melbourne has a volume of about 180 cubic kilometres (43 cu mi) and consists of tephra deposits and lava flows ; tephra deposits are also found encased within ice and have been used to date

186-458: A composite volcano , is a conical volcano built up by many alternating layers ( strata ) of hardened lava and tephra . Unlike shield volcanoes , stratovolcanoes are characterized by a steep profile with a summit crater and explosive eruptions. Some have collapsed summit craters called calderas . The lava flowing from stratovolcanoes typically cools and solidifies before spreading far, due to high viscosity . The magma forming this lava

279-467: A magma chamber ; basaltic rocks are less common. Geothermal heat flow on Mount Melbourne has created a unique ecosystem formed by mosses and liverworts that grow between fumaroles, ice towers , and ice hummocks . This type of vegetation is found at other volcanoes of Antarctica and develops when volcanic heat generates meltwater from snow and ice, thus allowing plants to grow in the cold Antarctic environment. These mosses are particularly common in

372-545: A protected area known as Cryptogam Ridge within and south of the summit caldera. Mount Melbourne lies in North Victoria Land , facing Wood Bay of the Ross Sea . To the southeast lies Cape Washington and due south lies Terra Nova Bay ; Campbell Glacier runs west from the volcano and Tinker Glacier lies north of the volcanic field . The seasonal Italian Mario Zucchelli Station lies 40 kilometres (25 mi) from

465-575: A volcanology research program on Mount Melbourne in the late 1980s, establishing a volcanological observatory in 1988. In 1990 they installed seismic stations around Mount Melbourne and between 1999 and 2001 a network of geodetic measurement stations around Terra Nova Bay, including several aimed at monitoring the Mount Melbourne volcano. Beginning in 2012 Korean scientists at the Jang Bogo Station added another seismic station network to monitor

558-747: A 4-inch thick ash layer can weigh 120-200 pounds and can get twice as heavy when wet. Wet ash also poses a risk to electronics due to its conductive nature. Dense clouds of hot volcanic ash can be expelled due to the collapse of an eruptive column , or laterally due to the partial collapse of a volcanic edifice or lava dome during explosive eruptions . These clouds are known as pyroclastic surges and in addition to ash , they contain hot lava , pumice , rock , and volcanic gas . Pyroclastic surges flow at speeds over 50 mph and are at temperatures between 200 °C – 700 °C. These surges can cause major damage to property and people in their path. Lava flows from stratovolcanoes are generally not

651-474: A fast moving mudflow . Lahars are typically about 60% sediment and 40% water. Depending on the abundance of volcanic debris the lahar can be fluid or thick like concrete. Lahars have the strength and speed to flatten structures and cause great bodily harm, gaining speeds up to dozens of kilometers per hour. In the 1985 eruption of Nevado del Ruiz in Colombia , Pyroclastic surges melted snow and ice atop

744-666: A few hectares. Typically, the soil consists of a thin sand layer with organic matter covering scoria gravel . In some places, the ground is too hot to be touched. Mount Melbourne is one of several volcanoes in Antarctica that feature such geothermal soils. Fumarolic landforms include ice towers, fumaroles, ice "roofs", caves in snow and firn, bare ground, ice hummocks surrounding fumarolic vents, puddles formed by condensed water vapour and steaming ground: The caves and ice towers release water-vapour -rich warm air. Fumarole temperatures can reach 60 °C (140 °F), contrasting with

837-515: A final intermediate composition . When the magma nears the top surface, it pools in a magma chamber within the crust below the stratovolcano. The processes that trigger the final eruption remain a question for further research. Possible mechanisms include: These internal triggers may be modified by external triggers such as sector collapse , earthquakes , or interactions with groundwater . Some of these triggers operate only under limited conditions. For example, sector collapse (where part of

930-475: A mildly alkaline suite rich in potassium , unlike the rocks elsewhere in the volcanic field. The rest of the volcanic field also features alkali basalts , basanite and mugearite . Phenocrysts include aegirine , amphibole , anorthoclase , augite , clinopyroxene , fayalite , hedenbergite , ilmenite , kaersutite , magnetite , olivine , plagioclase and sanidine . Gneiss , granulite , harzburgite , lherzolite and tholeiite xenoliths are found in

1023-668: A nearly perfect cone-like profile that has drawn comparisons to Mount Etna in Italy and Mount Ruapehu in New Zealand. Lava domes and short lava flows form the summit while volcanic mounds, cones, domes and scoria cones dot its flanks; 6.4 kilometres (4 mi) from the summit is a large parasitic vent on the north-northeastern slope, which generated several lava flows. Part of the edifice rises from below sea level. Pyroclastic flow deposits – a rarity for Antarctic volcanoes – have been reported. The total volume of

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1116-463: A north–south direction, with palagonitized outcrops that expose dikes . Perfectly preserved scoria cones occur at Pinckard Table north of the volcanic field, while Harrow Peak is a heavily eroded lava plug . The total volume of volcanic rocks is about 250 cubic kilometres (60 cu mi) and their emplacement apparently altered the path of the Campbell Glacier. Mount Melbourne is part of

1209-425: A pyroclastic flow traveled for several hundreds of meters above the sea. A pyroclastic flow can interact with a body of water to form a large amount of mud, which can then continue to flow downhill as a lahar . This is one of several mechanisms that can create a lahar. In 1963, NASA astronomer Winifred Cameron proposed that the lunar equivalent of terrestrial pyroclastic flows may have formed sinuous rilles on

1302-438: A research team at Kiel University , Germany, of pyroclastic flows moving over the water. When the reconstructed pyroclastic flow (stream of mostly hot ash with varying densities) hit the water, two things happened: the heavier material fell into the water, precipitating out from the pyroclastic flow and into the liquid; the temperature of the ash caused the water to evaporate, propelling the pyroclastic flow (now only consisting of

1395-739: A result of intraplate volcanism on oceanic islands far from plate boundaries. Examples are Teide in the Canary Islands , and Pico do Fogo in Cape Verde . Stratovolcanoes in the East African Rift include Ol Doinyo Lengai in Tanzania, and Longonot in Kenya. Subduction zone volcanoes form when hydrous minerals are pulled down into the mantle on the slab. These hydrous minerals, such as chlorite and serpentine , release their water into

1488-476: A result of certain explosive eruptions ; they normally touch the ground and hurtle downhill or spread laterally under gravity. Their speed depends upon the density of the current, the volcanic output rate, and the gradient of the slope. The word pyroclast is derived from the Greek πῦρ ( pýr ), meaning "fire", and κλαστός ( klastós ), meaning "broken in pieces". A name for pyroclastic flows that glow red in

1581-461: A significant threat to humans or animals because the highly viscous lava moves slowly enough for everyone to evacuate. Most deaths attributed to lava are due to related causes such as explosions and asphyxiation from toxic gas . Lava flows can bury homes and farms in thick volcanic rock which greatly reduces property value. However, not all stratovolcanoes erupt viscous and sticky lava . Nyiragongo , near Lake Kivu in central Africa ,

1674-527: Is a passive release of gas during periods of dormancy. As per the above examples, while eruptions like Mount Unzen have caused deaths and local damage, the impact of the June 1991 eruption of Mount Pinatubo was seen globally. The eruptive columns reached heights of 40 km and dumped 17 megatons of SO 2 into the lower stratosphere . The aerosols that formed from the sulfur dioxide (SO 2 ), carbon dioxide (CO 2 ), and other gases dispersed around

1767-432: Is a trachytic ignimbrite that crops out at Edmonson Point. It consists of three units of ash-supported, lapilli- and pumice -rich deposits with intercalated breccia lenses that reach a thickness of 30 metres (98 ft). They are two ignimbrite units separated by a base surge deposit. Faulting has offset the sequences, which are intruded by dikes. The Edmonson Point ignimbrite was produced by large Plinian eruptions and

1860-791: Is about 115,000 years old. The eruption deposited tephra into the Ross Sea, and correlative tephra layers were found in the Talos Dome ice core. After this ignimbrite, a series of dikes gave rise to the Adelie Penguin Rookery lava field. This lava field, which probably formed subglacially, is made up by numerous blocky lava flows with glassy margins that reach a thickness of 300 metres (1,000 ft) and are formed by hawaiite and benmoreite . They were fed through numerous dikes, which also gave rise to small scoria cones and spatter cones , and were emplaced non-contemporaneously. A tuff cone rises from

1953-724: Is at the intersection of three geological structures: the Rennick Graben of Cretaceous age, the Victoria Land Basin and the Polar   3 magnetic anomaly. The Terror Rift in the Victoria Land Basin runs between Mount Melbourne and Mount Erebus and appears to be related to their existence. Mount Melbourne appears to lie in a graben; the marginal faults on the eastern flank of Mount Melbourne are still active with earthquakes. North–south-trending faulting may also be responsible for

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2046-468: Is considered improbable given the long duration of fumarolic activity; a lava-heated system would have cooled down by now. There are no detailed meteorological records of the summit region. Winds blow mostly from the west and more rarely from the northwest. Catabatic winds blow from the Priestly and Reeves valleys. Precipitation is scarce. During winter, polar night lasts about three months. Temperatures in

2139-429: Is considered to be quiescent and a low-hazard volcano. Ongoing deformation and seismic activity occurs at Mount Melbourne, and the latter may be caused either by the movement of fluids underground or by fracturing processes. Icequakes caused by glacier movement also occur. Geothermal activity was steady between 1963 and 1983, while ground deformation commenced in 1997. This deformation was probably caused by changes in

2232-438: Is covered by volcanic ejecta including lapilli and lava bombs , probably the products of the most recent eruption, which overlie a 15-metre-thick (49 ft) layer of pumice lapilli. Three small, nested craters formed by phreatomagmatic eruptions occur on the southern rim of the summit caldera. Pyroclastic fall deposits crop out in the northern rim of the caldera and there are more alternating lava-tephra sequences elsewhere in

2325-681: Is more fresh water available there. The steam freezes in the cold air, forming the ice hummocks that act as a shelter and maintain stable humidity and temperature. The geothermal heating and the availability of freshwater sets these volcanic biological communities apart from other Antarctic vegetation communities that are heated by the sun. Some bacterial species are nitrogen fixing . Genetic analysis has found that some mosses at Mount Melbourne are mutating, yielding genetic variation. The hot, wet soils at Mount Melbourne host thermophilic organisms, making Mount Melbourne an island of thermophilic life on an ice-cold continent. Cold-tolerant microbes coexist with

2418-414: Is not effective enough at most sites. It is possible that underground liquid water reservoirs form in some areas, however. The steam is produced by the melting and evaporation of snow and ice, and is then channelled through rocks to the vents. Atmospheric air likely circulates underground and is heated, eventually exiting in ice towers. An early theory that the ice towers formed on top of a cooling lava flow

2511-476: Is often felsic , having high to intermediate levels of silica (as in rhyolite , dacite , or andesite ), with lesser amounts of less viscous mafic magma . Extensive felsic lava flows are uncommon, but can travel as far as 8 km (5 mi). The term composite volcano is used because the strata are usually mixed and uneven instead of neat layers. They are among the most common types of volcanoes; more than 700 stratovolcanoes have erupted lava during

2604-548: Is sometimes abbreviated to PDC (pyroclastic density current). Several mechanisms can produce a pyroclastic flow: Flow volumes range from a few hundred cubic meters to more than 1,000 cubic kilometres (240 cu mi). Larger flows can travel for hundreds of kilometres, although none on that scale has occurred for several hundred thousand years. Most pyroclastic flows are around one to ten cubic kilometres ( 1 ⁄ 4 – 2 + 1 ⁄ 2  cu mi) and travel for several kilometres. Flows usually consist of two parts:

2697-451: Is the most famous example of a hazardous stratovolcano eruption. It completely smothered the nearby ancient cities of Pompeii and Herculaneum with thick deposits of pyroclastic surges and pumice ranging from 6–7 meters deep. Pompeii had 10,000-20,000 inhabitants at the time of eruption. Mount Vesuvius is recognized as one of the most dangerous of the world's volcanoes, due to its capacity for powerful explosive eruptions coupled with

2790-450: Is typically between 700 and 1,200 °C (1,300-2,200 °F). Volcanic bombs are masses of unconsolidated rock and lava that are ejected during an eruption. Volcanic bombs are classified as larger than 64mm (2.5 inches). Anything below 64mm is classified as a volcanic block . When erupted Bombs are still molten and partially cool and solidify on their descent. They can form ribbon or oval shapes that can also flatten on impact with

2883-908: Is unusual in Antarctica but other occurs elsewhere, including on Bouvet , Deception Island , Mount Erebus and the South Sandwich Islands . The geothermal area at the summit of Mount Melbourne makes up Antarctic Specially Protected Area   118, which contains two specially restricted areas around Cryptogam Ridge and some markers used in studies of volcano deformation. Some algae from Mount Melbourne were accidentally transferred to Deception Island or Mount Erebus. Edmonson Point and Cape Washington have Adelie penguin and emperor penguin rookeries and south polar skuas and Weddel seals are also found. More than twenty-four lichen plus six moss species (including Bryum argenteum moss) have been found at Edmonson Point, as well as microbial mats formed by cyanobacteria. Nematodes and collembola complete

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2976-403: Is very dangerous because its magma has an unusually low silica content , making it much less viscous than other stratovolcanoes. Low viscosity lava can generate massive lava fountains , while lava of thicker viscosity can solidify within the vent, creating a volcanic plug . Volcanic plugs can trap gas and create pressure in the magma chamber, resulting in violent eruptions. Lava

3069-524: The 1883 eruption of Krakatoa , supported by experimental evidence, shows that pyroclastic flows can cross significant bodies of water. However, that might be a pyroclastic surge , not flow, because the density of a gravity current means it cannot move across the surface of water. One flow reached the Sumatran coast as far as 48 kilometres (26 nautical miles) away. A 2006 BBC documentary film, Ten Things You Didn't Know About Volcanoes , demonstrated tests by

3162-557: The Allan Hills , in Dome ;C and in the Siple Dome ice cores may come from Mount Melbourne. Some marine tephra layers originally attributed to Mount Melbourne may instead come from Mount Rittmann, and many tephra layers in the area have compositions that do not match these from Mount Melbourne. There are additional tephra layers attributed to the volcano: The Edmonson Point ignimbrite

3255-800: The Holocene Epoch (the last 11,700 years), and many older, now extinct, stratovolcanoes erupted lava as far back as Archean times. Stratovolcanoes are typically found in subduction zones but they also occur in other geological settings. Two examples of stratovolcanoes famous for catastrophic eruptions are Krakatoa in Indonesia (which erupted in 1883 claiming 36,000 lives) and Mount Vesuvius in Italy (which erupted in 79 A.D killing an estimated 2,000 people). In modern times, Mount St. Helens (1980) in Washington State , US, and Mount Pinatubo (1991) in

3348-662: The McMurdo Volcanic Group , which includes the active volcano Mount Erebus . This volcanic group is one of the largest alkaline volcanic provinces in the world, comparable with that of the East African Rift , and is subdivided into the Melbourne, the Hallett and the Erebus volcanic provinces. The volcanic group consists of large shield volcanoes mainly near the coast, stratovolcanoes and monogenetic volcanoes which formed parallel to

3441-573: The Philippines have erupted catastrophically, but with fewer deaths. Stratovolcanoes are common at subduction zones , forming chains and clusters along plate tectonic boundaries where an oceanic crust plate is drawn under a continental crust plate (continental arc volcanism, e.g. Cascade Range , Andes , Campania ) or another oceanic crust plate ( island arc volcanism, e.g. Japan , Philippines , Aleutian Islands ). Stratovolcanoes also occur in some other geological settings, for example as

3534-639: The basal flow hugs the ground and contains larger, coarse boulders and rock fragments, while an extremely hot ash plume lofts above it because of the turbulence between the flow and the overlying air, admixing and heating cold atmospheric air causing expansion and convection. Flows can deposit less than 1 meter to 200 meters in depth of loose rock fragment. The kinetic energy of the moving cloud will flatten trees and buildings in its path. The hot gases and high speed make them particularly lethal, as they will incinerate living organisms instantaneously or turn them into carbonized fossils: Testimonial evidence from

3627-891: The magma is too viscous to allow easy escape of volcanic gases . As a consequence, the tremendous internal pressures of the trapped volcanic gases remain and intermingle in the pasty magma . Following the breaching of the vent and the opening of the crater, the magma degasses explosively. The magma and gases blast out with high speed and full force. Since 1600 CE , nearly 300,000 people have been killed by volcanic eruptions . Most deaths were caused by pyroclastic flows and lahars , deadly hazards that often accompany explosive eruptions of subduction-zone stratovolcanoes. Pyroclastic flows are swift, avalanche-like, ground-sweeping, incandescent mixtures of hot volcanic debris, fine ash , fragmented lava , and superheated gases that can travel at speeds over 150 km/h (90 mph). Around 30,000 people were killed by pyroclastic flows during

3720-443: The mantle which decreases its melting point by 60 to 100 °C. The release of water from hydrated minerals is termed " dewatering ", and occurs at specific pressures and temperatures for each mineral, as the plate descends to greater depths. This allows the mantle to partially melt and generate magma . This is called flux melting . The magma then rises through the crust , incorporating silica-rich crustal rock, leading to

3813-473: The westerlies , which may explain why the vegetation is species-poor. Pohlia nutans may have arrived only recently on Mount Melbourne, or this volcano is not as favourable for its growth as Mount Rittmann, where this moss is more common. Its colonies are less vigorous on Mount Melbourne than Campylopus pyriformis . Condensing fumarole gases and meltwater from snow form the water supply of this vegetation. Mosses are concentrated around fumarolic vents as there

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3906-607: The 1902 eruption of Mount Pelée on the island of Martinique in the Caribbean . During March and April 1982, El Chichón in the State of Chiapas in southeastern Mexico , erupted 3 times, causing the worst volcanic disaster in that country's history and killied more than 2,000 people in pyroclastic flows . Two Decade Volcanoes that erupted in 1991 provide examples of stratovolcano hazards. On 15 June, Mount Pinatubo erupted and caused an ash cloud to shoot 40 km (25 mi) into

3999-449: The 1960s, by German ones in the 1970s and 1980s and by Italian-based parties in the 1980s and 1990s. The volcano and its summit can be accessed from the stations by helicopter. Mount Melbourne is an elongated stratovolcano formed by lava flows and tephra fall deposits, with gentle slopes. The volcano is uneroded and forms a cone with a base area of 25 by 55 kilometres (16 mi × 34 mi). Viewed from afar, Mount Melbourne has

4092-481: The 1982 eruption of Galunggung in Java , British Airways Flight 9 flew into the ash cloud, causing it to sustain temporary engine failure and structural damage. Although no crashes have happened due to ash, more than 60, mostly commercial aircraft , have been damaged. Some of these incidents resulted in emergency landings. Ashfalls are a threat to health when inhaled and are also a threat to property. A square yard of

4185-585: The 5,321 m (17,457 ft) high Andean volcano. The ensuing lahar killed 25,000 people and flooded the city of Armero and nearby settlements. As a volcano forms, several different gases mix with magma in the volcanic chamber. During an eruption the gases are then released into the atmosphere which can lead to toxic human exposure. The most abundant of these gases is H 2 O ( water ) followed by CO 2 ( carbon dioxide ), SO 2 ( sulfur dioxide ), H 2 S ( hydrogen sulfide ), and HF ( hydrogen fluoride ). If at concentrations of more than 3% in

4278-424: The Mount Melbourne volcanic field but diverse mantle domains and assimilation and fractional crystallization processes appear to have played a role. The magmatic system that feeds Mount Melbourne appears to have a composition distinct from the one associated with the Mount Melbourne volcanic field. Hydrothermal alteration has affected parts of the summit area, leaving yellow and white deposits that contrast with

4371-538: The Shield Nunatak stage that is 400,000 to 100,000 years old, and the recent Mount Melbourne stage. Volcanic activity migrated north from Cape Washington towards the Transantarctic Mountains and eventually became centralized at Mount Melbourne. During the last hundred thousand years Mount Melbourne has produced about 0.0015 cubic kilometres per year (0.00036 cu mi/a) of magma. The earliest records of

4464-515: The Terror Rift. These anomalies above 100 kilometres (62 mi) depth are focused under Mount Melbourne and the neighbouring Priestley Fault. A low gravity anomaly over Mount Melbourne may reflect either the presence of low-density volcanic rocks or of a magma chamber under the volcano. Trachyandesite and trachyte are the most common rocks on Mount Melbourne, with basalt being less common and mostly occurring around its base. The rocks define

4557-590: The Transantarctic Mountains. Volcanic activity of the McMurdo Volcanic Group is tied to continental rifting and commenced during the Oligocene . It is unclear whether this is caused by a local hotspot beneath the area or mantle convection in the area of the West Antarctic Rift . The latter is one of the largest continental rifts on Earth but little known and possibly inactive today. The Ross Sea and

4650-423: The Victoria Land Basin developed along this rift and were deeply buried, while the Transantarctic Mountains were rapidly uplifted during the last fifty million years and are on the "shoulder" of the rift. The line separating the two is a major crustal suture , with large differences in elevation and crustal thickness across the suture. Many of the volcanoes appear to have formed under the influence of fault zones in

4743-816: The air, when breathed in CO 2 can cause dizziness and difficulty breathing. At more than 15% concentration CO 2 causes death. CO 2 can settle into depressions in the land, leading to deadly, odorless pockets of gas. SO 2 classified as a respiratory, skin, and eye irritant if come into contact with. It is known for its pungent egg smell and role in ozone depletion and has the potential to cause acid rain downwind of an eruption. H 2 S has an even stronger odor than SO 2 as well as being even more toxic. Exposure for less than an hour at concentrations of over 500 ppm causes death. HF and similar species can coat ash particles and once deposited can poison soil and water. Gases are also emitted during volcanic degassing, which

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4836-741: The air. It produced large pyroclastic surges and lahar floods that caused a lot of damage to the surrounding area. Pinatubo , located in Central Luzon just 90 km (56 mi) west-northwest of Manila , had been dormant for six centuries before the 1991 eruption. This eruption was one of the 2nd largest in the 20th century. It produced a large volcanic ash cloud that affected global temperatures, lowering them in areas as much as .5 °C. The volcanic ash cloud consisted of 22 million tons of SO 2 which combined with water droplets to create sulfuric acid . In 1991 Japan's Unzen Volcano also erupted, after 200 years of inactivity. It's located on

4929-591: The area, and increased activity in the last thirty million years has been correlated to the reactivation of faults. Mount Melbourne is part of a volcano alignment that includes The Pleiades , Mount Overlord , Mount Rittmann  – all large stratovolcanoes – which with the Malta Plateau form the Melbourne province of the McMurdo Volcanic Group. In addition, this province consists of numerous smaller volcanic centres, volcanic intrusions and sequences of volcanic rocks, and it has been active for

5022-401: The biota of Edmonson Point. The vegetation on Mount Melbourne grows mainly on terrain heated to temperatures of over 10 to 20 °C (50 to 68 °F), and there are gradations in vegetation type from colder to warmer temperatures. There are differences between the vegetation and bacterial communities at Cryptogam Ridge and those on the northwest slope of Mount Melbourne; distinct soils may be

5115-403: The black volcanic rocks. Hydrothermal sinter deposits have formed in geothermal areas from past liquid water flow. Clay containing allophane , amorphous silica and feldspar are found in the summit area. Mount Melbourne was active beginning 3.0–2.7   million years ago. Activity has been subdivided into an older Pliocene Cape Washington stage, an early Pleistocene Random Hills stage,

5208-418: The bulk of the volcano and appears to be younger than the summit. Radiometric dating has shown that the appearance of a landform at Mount Melbourne is not indicative of its age; some well preserved vents are older than heavily eroded ones. On the other hand, a lack of proper margins of error and lack of details on which samples were dated has been problematic for radiometric dating efforts. Tephra found at

5301-406: The caldera. Glaciers emanating from snowfields on the volcano have deposited moraines ; these and tills from both Pleistocene and Holocene glaciations crop out at Edmonson Point. Tephra layers crop out in ice cliffs and seracs and testify to recent eruptions, including the one that deposited the ejecta and lapilli pumice units on the summit. Tephra bands are also found in other glaciers of

5394-450: The cold air. Fumaroles release gases containing excesses of volcanic carbon dioxide and methane . Hydrogen sulfide gas has been detected too, but only at low concentrations which do not prevent the development of vegetation. Yellow deposits have been identified as sulfur . The geothermal manifestations appear to be powered mainly by steam , as there is no evidence of geothermal landforms related to liquid water flow and heat conduction

5487-674: The dark is nuée ardente (French, "burning cloud"); this was notably used to describe the disastrous 1902 eruption of Mount Pelée on Martinique , a French island in the Caribbean. Pyroclastic flows that contain a much higher proportion of gas to rock are known as "fully dilute pyroclastic density currents" or pyroclastic surges . The lower density sometimes allows them to flow over higher topographic features or water such as ridges, hills, rivers, and seas. They may also contain steam, water, and rock at less than 250 °C (480 °F); these are called "cold" compared with other flows, although

5580-406: The edifice is about 180 cubic kilometres (43 cu mi). A 1-kilometre-wide (0.62 mi) crater or caldera sits at the top of the volcano. The highest point of the volcano lies east-northeast of the caldera and reaches 2,733 metres (8,967 ft) elevation. The caldera has an incomplete rim and is filled with snow, leaving a 500-metre-wide (1,600 ft) depression. The rim of the caldera

5673-492: The ejecta layer on the summit. One large eruption took place 13,500 ± 4,300 years ago. Three cryptotephra layers in Edisto Inlet (close to Cape Hallett ) have been attributed to eruptions that took place between 1,677 and 1,615 years before present; a tephra layer from Roosevelt Island dates to the same time. These eruptions probably took place on parasitic vents of Mount Melbourne. Two more parasitic eruptions took place in

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5766-512: The emission of tephra recorded in the Talos Dome ice core. The eruptions of the last 120,000 years probably caused the anomalous thinning of the Campbell Glacier during that time, which is unlike the behaviour of other Antarctic glaciers. Rocks at the summit have ages of between 260,000 and 10,000 years. Individual eruptions have been dated to 10,000 ± 20,000, 80,000 ± 15,000, 260,000 ± 60,000 and 15,000 ± 35,000 years ago. Highly imprecise ages of late Pleistocene to Holocene age have been obtained from

5859-540: The flank of a volcano collapses in a massive landslide) can only trigger the eruption of a very shallow magma chamber . Magma differentiation and thermal expansion also are ineffective as triggers for eruptions from deep magma chambers . In recorded history , explosive eruptions at subduction zone ( convergent-boundary ) volcanoes have posed the greatest hazard to civilizations. Subduction-zone stratovolcanoes, such as Mount St. Helens , Mount Etna and Mount Pinatubo , typically erupt with explosive force because

5952-474: The form of scoria cones and tuff rings with hyaloclastite deposits, lava flows and pillow lavas . Some of these volcanoes formed under ice. The volcanic field forms a peninsula which is separated by steep faults from the Transantarctic Mountains to the north. Among these volcanoes is Shield Nunatak southwest from Mount Melbourne, a subglacial volcano , now exposed, that may have formed during

6045-611: The geothermal system. Future moderate to large explosive eruptions such as Plinian eruptions are possible. The prevailing winds would transport volcanic ash eastward across the Ross Sea, and the ash might affect research stations close to Mount Melbourne such as Mario Zucchelli, Gondwana and Jang Bogo. The hazards of Antarctic volcano eruptions are poorly known. Mount Melbourne is remote, and thus renewed eruptions would likely not impact any human habitations but regional environmental or even global climate impacts, as well as disruptions of air travel, are possible. Italian scientists began

6138-478: The ground. Volcanic Bombs are associated with Strombolian and Vulcanian eruptions and basaltic lava . Ejection velocities ranging from 200 to 400 m/s have been recorded causing volcanic bombs to be destructive. Lahars (from a Javanese term for volcanic mudflows) are a mixture of volcanic debris and water. Lahars can result from heavy rainfall during or before the eruption or interaction with ice and snow. Meltwater mixes with volcanic debris causing

6231-458: The high population density of the surrounding Metropolitan Naples area (totaling about 3.6 million inhabitants). In addition to potentially affecting the climate, volcanic ash clouds from explosive eruptions pose a serious hazard to aviation . Volcanic ash clouds consist of ash which is made of silt or sand sized pieces of rock, mineral, volcanic glass . Ash grains are jagged, abrasive, and don't dissolve in water. For example, during

6324-423: The history of the volcano. During the last hundred thousand years the magma chamber became established; this allowed both the differentiation of trachytes and the occurrence of large eruptions. A gap in the rock spectrum ("Daly gap") with a scarcity of benmoreite and mugearite has been noted at Mount Melbourne and other volcanoes in the region. There is no agreement on which processes contributed to petrogenesis in

6417-500: The island of Kyushu about 40 km (25 mi) east of Nagasaki . Beginning in June, a newly formed lava dome repeatedly collapsed. This generated a pyroclastic flow that flowed down the mountain's slopes at speeds as high as 200 km/h (120 mph). The 1991 eruption of Mount Unzen was one of the worst volcanic disasters in Japan's history, once killing more than 15,000 people in 1792. The eruption of Mount Vesuvius in 79 AD

6510-455: The last 21,000 to 17,000 years. The Cape Washington ridge consists mostly of lava, including pillow lava, overlaid by scoria cones, and is the remnant of a shield volcano. Edmonson Point is another volcanic complex in the volcanic field that formed partly while interacting with glaciers and partly through phreatomagmatic activity. Other volcanoes in the field are Baker Rocks , Oscar Point and Random Hills . These volcanoes are aligned mainly in

6603-513: The last eruption of Mount Melbourne to 1892 ± 30 years . The volcano is fumarolically active. The volcano is part of the McMurdo Volcanic Group , and together with The Pleiades , Mount Overlord , Mount Rittmann and the Malta Plateau forms a subprovince, the Melbourne volcanic province. The volcanism is related both to the West Antarctic Rift and to local tectonic structures such as faults and grabens . Mount Melbourne has mainly erupted trachyandesite and trachyte , which formed within

6696-552: The lava field and is formed by monogenetic volcano ejecta, including lava bombs encasing granite fragments and bombs large enough to leave craters in the ash they fell in. Ropy basalt lava flows with an uncertain source vent, and a undissected scoria cone rise above the lava field and complete the Edmonson Point system. The Adelie Penguin Rookery lava field was erupted about 90,000 years ago, and its emplacement may have been accompanied by

6789-485: The lighter material) along on a bed of steam at an even faster pace than before. During some phases of the Soufriere Hills volcano on Montserrat, pyroclastic flows were filmed about 1 km ( 1 ⁄ 2  nmi) offshore. These show the water boiling as the flow passes over it. The flows eventually built a delta, which covered about 1 km (250 acres). Another example was observed in 2019 at Stromboli when

6882-504: The only occurrences of Campylopus pyriformis on warm ground in Antarctica. Mount Melbourne along with Mount Erebus, Mount Rittmann and Deception Island is one of four volcanoes in Antarctica known for having geothermal habitats, although other poorly studied volcanoes such as Mount Berlin , Mount Hampton and Mount Kauffman may also have them. In South America, high-elevation geothermal environments similar to Mount Melbourne are found at Socompa . Vegetation on geothermally heated terrain

6975-462: The past twenty-five million years. Volcanic edifices buried under sediment are also part of the Melbourne province, including a cone southeast of Cape Washington, which has a size comparable to that of Mount Melbourne. Mount Melbourne and its volcanic field are over a basement of Precambrian to Ordovician age, which consists of volcanic and metamorphic rocks of the Wilson Terrane . The volcano

7068-694: The post-LGM period. During the late Holocene after 5,000 years before present , glaciers advanced again as part of the Neoglacial . One minor advance occurred in the last c.  650 years. Algae , lichens , liverworts and mosses grow on geothermally heated terrain on the upper parts of Mount Melbourne. Algae form crusts on the heated ground. Mosses form cushions and often occur around steam vents and under ice hummocks . The moss species Campylopus pyriformis does not grow leaves on Mount Melbourne. Pohlia nutans forms small shoots. The two moss species form separate stands which occur at different sites of

7161-405: The reason for such differences. These communities must have reached Mount Melbourne from far away. Transport was probably by wind as there is no flowing water in the region. Mount Melbourne was recently active, has a polar night lasting thirteen weeks, has soils containing toxic elements such as mercury , is distant from ecosystems that could be the source of colonization events, and lies away from

7254-482: The region. They form when snow accumulates on top of tephra that fell onto ice and in the case of Mount Melbourne they indicate eruptions during the last few thousand years. Volcanic sediments from Mount Melbourne are also found in Terra Nova Bay. The Campbell Glacier carries glacial erratics derived from Mount Melbourne. Mount Melbourne is surrounded by a volcanic field consisting of 60 exposed volcanoes, which have

7347-490: The same timeframe. Tephrochronology has yielded an age of 1892 ± 30   CE for the last eruption. This eruption deposited a major tephra layer around the volcano, which crops out mainly on its eastern side and in the Aviator and Tinker Glaciers. The three small craters on the rim of the Mount Melbourne summit crater formed at the end of this eruption. No eruptions have been observed during historical time, and Mount Melbourne

7440-460: The size of Mount Pinatubo affected the weather for a few years; with warmer winters and cooler summers observed. A similar phenomenon occurred in the April 1815, the eruption of Mount Tambora on Sumbawa island in Indonesia . The Mount Tambora eruption is recognized as the most powerful eruption in recorded history. Its eruption cloud lowered global temperatures as much as 0.4 to 0.7 °C. In

7533-515: The summit region have been variously reported to either not exceed −30 °C (−22 °F) or to range between −6 and −20 °C (21 and −4 °F). Seasonal temperature variation is high and reaches 30 °C (54 °F). During the Last Glacial Maximum (LGM), a marine ice sheet occupied Terra Nova Bay. The "Terra Nova Drift " was deposited between 25,000 and 7,000 years ago and is overlaid by later moraines from retreating ice during

7626-450: The summit region. Small creeks flow down the eastern flank of Mount Melbourne; they are fed by meltwater during summer and quickly disappear when the snow is gone. The mountain is covered with permanent ice, which extends to the coast and leaves only a few exposures of the underlying rock; rocky outcrops are most exposed on the eastern flank. The caldera hosts a névé that generates a westward-flowing glacier . An icefall lies northwest of

7719-449: The summit region. There is evidence of past structural instability (collapse structures) on the eastern and southeastern flanks, and an arcuate (with the shape of an arc) 50-to-100-metre-high (160 to 330 ft) scarp on the eastern flank appears to be an incipient sector collapse . Except for geothermal areas, the ground is bouldery. Some of the coastal areas around the volcano are ice-free and rocky. Frost heave has been observed in

7812-436: The temperature is still lethally high. Cold pyroclastic surges can occur when the eruption is from a vent under a shallow lake or the sea. Fronts of some pyroclastic density currents are fully dilute; for example, during the eruption of Mount Pelée in 1902, a fully dilute current overwhelmed the city of Saint-Pierre and killed nearly 30,000 people. A pyroclastic flow is a type of gravity current ; in scientific literature, it

7905-506: The thermophiles. Other species associated with the vegetation are the protozoan Corythion dubium , which is a testate amoeba common in Antarctica and the only invertebrate found in the geothermal habitats of Mount Melbourne, actinobacteria and various actinomycetes and fungal genera. Several bacterial species were first described from Mount Melbourne's geothermal terrains: Stratovolcano A stratovolcano , also known as

7998-496: The trend in edifice structure, and strike-slip faulting takes place on the eastern flank. Recent offset on faults and Holocene coastal uplift in the area indicates that tectonic activity is ongoing. Tomographic studies have shown an area of low seismic velocity at 80 kilometres (50 mi) depth under the volcano, which may be due to temperatures there being 300 °C (540 °F) hotter than normal. Anomalies underneath Mount Melbourne are connected to similar anomalies under

8091-491: The volcanic field and form the core of many lava bombs. Inclusions in xenoliths indicate that the gaseous components of the Mount Melbourne volcanic field magmas consist mainly of carbon dioxide . The rocks in the volcanic field have porphyritic to vitrophyric textures. The trachytes and mugearites formed through magmatic differentiation in a crustal magma chamber from alkali basalts, defining an alkali basalt-trachyte differentiation series. Basalts were mainly erupted early in

8184-695: The volcano noted its young appearance. Ages obtained on the Mount Melbourne volcanic field include 2.96 ± 0.20   million years, 740,000 ± 100,000 years and 200,000 ± 40,000 years for Baker Rocks, 2.7 ± 0.2   million years and 450,000 ± 50,000 years for Cape Washington, 74,000 ± 110,000 years and 50,000 ± 20,000 years for Edmonson Point, less than 400,000 years for Markham Island , 745,000 ± 66,000 years for Harrows Peak, 1.368 ± 0.090   million years for Pinkard Table , 1.55 ± 0.05   million years, 431,000 ± 82,000 and 110,000 ± 70,000 years for Shield Nunatak, and 2.5 ± 0.1   million years for Willows Nunatak . The northeastern parasitic cone formed after

8277-874: The volcano. In 2016–2019 geochemical, seismological and volcanological research was carried out at Mount Melbourne as part of the ICE-VOLC project. Geothermal activity occurs around the summit crater , on the upper parts of the volcano and on the northwestern slope between 2,400 and 2,500 metres (7,900 and 8,200 ft) elevation. Another geothermal area exists close to Edmonson Point, including fumaroles, thermal anomalies and freshwater ponds. Their temperatures of 15 to 20 °C (59 to 68 °F) are considerably higher than normal atmospheric temperatures in Antarctica. The geothermal areas are visible in infrared light from aircraft. Satellite images have identified areas with temperatures of over 100 to 200 °C (212 to 392 °F). Individual geothermally heated areas cover surfaces of

8370-437: The volcano. Together with occurrences at Mount Erebus, they constitute the highest mosses growing in Antarctica. Small peat deposits have been found. Vegetation is particularly common on a ridge within and south of the main crater, "Cryptogam Ridge". It features a long snow-free area with a gravelly ground, small terraces and stone stripes . Soil temperatures recorded there reach 40 to 50 °C (104 to 122 °F). These are

8463-666: The volcano; the 5th Chinese station in Antarctica (due to be completed in 2022), the Korean Jang Bogo Station , the German Gondwana Station and a neutrino detector are also in the area. Mount Melbourne was discovered and first recognized as a volcano by James Ross in 1841 and named after William Lamb, 2nd Viscount Melbourne , who was then the prime minister of the United Kingdom . The volcano and its surroundings were investigated by New Zealand-based parties in

8556-412: The world. The SO 2 in this cloud combined with water (both of volcanic and atmospheric origin) and formed sulfuric acid , blocking a portion of the sunlight from reaching the troposphere . This caused the global temperature to decrease by about 0.4 °C (0.72 °F) from 1992 to 1993. These aerosols caused the ozone layer to reach the lowest concentrations recorded at that time. An eruption

8649-510: The year following the eruption, most of the Northern Hemisphere experienced cooler temperatures during the summer. In the northern hemisphere , 1816 was known as the " Year Without a Summer ". The eruption caused crop failures, food shortages, and floods that killed over 100,000 people across Europe , Asia , and North America . Pyroclastic flow Pyroclastic flows are the most deadly of all volcanic hazards and are produced as

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