| Mount Takahe | |
|---|---|
 Aerial view looking east. The prominent ridge at the center-left with the shadow behind is Gill Bluff. | |
| Highest point | |
| Elevation | 3,460 m (11,350 ft)[1] |
| Prominence | [2][3] |
| Listing | Volcanoes in Antarctica |
| Coordinates | 76°17′S112°05′W / 76.28°S 112.08°W /-76.28; -112.08 (Mount Takahe)[1] |
| Geography | |
  Mount Takahe Location in SW Antarctica | |
| Continent | Antarctica |
| Region | Marie Byrd Land, |
| Geology | |
| Mountain type | Shield volcano |
| Volcanic field | Marie Byrd Land Volcanic Province |
| Last eruption | 5550 BC (?)[1] |
Mount Takahe is a 3,460-metre-high (11,350 ft) snow-coveredshield volcano inMarie Byrd Land,Antarctica, 200 kilometres (120 mi) from theAmundsen Sea. It is ac. 30-kilometre-wide (19 mi) mountain withparasitic vents and acaldera up to 8 kilometres (5 mi) wide. Most of the volcano is formed bytrachyticlava flows, buthyaloclastite is also found. Snow, ice, andglaciers cover most of Mount Takahe. With a volume of 780 km3 (200 cu mi), it is a massive volcano; the parts of the edifice that are buried underneath theWest Antarctic Ice Sheet are probably even larger. It is part of theWest Antarctic Rift System along with 18 other known volcanoes.
The volcano was active in theQuaternary period.[a]Radiometric dating has yielded ages of up to 300,000 years for its rocks, and it reached its present height about 200,000 years ago. Severaltephra layers encountered inice cores atMount Waesche andByrd Station have been attributed to Mount Takahe, although some of them were later linked to eruptions ofMount Berlin instead. The tephra layers were formed byexplosive orphreatomagmatic eruptions. Major eruptions took place around 17,700 years ago—possibly forming anozone hole over Antarctica—and in the earlyHolocene.[b] Mount Takahe's last eruption occurred about 7,600 years ago, and there is no present-day activity.
The mountain's name refers to thetakahē, a flightless nearly extinct bird fromNew Zealand; members of the 1957–1958 Marie Byrd Land Traverse party nicknamed an aircraft that had resupplied them "takahe".[5] It was first visited in 1957–1958 and again in 1968,[6] 1984–1985 and 1998–1999.[7]
Mount Takahe is at theBakutis Coast,[8] easternMarie Byrd Land,Antarctica.Bear Peninsula[9] and theAmundsen Sea coast are 200 kilometres (120 mi) north of Mount Takahe.[10] It is an isolated mountain,[8] and the closest other volcanoes areMount Murphy 100 kilometres (62 mi)[11] andToney Mountain 140 kilometres (87 mi) away.[12] No majorair routes or supply roads toAntarctic stations pass close to the mountain,[13] and some parts of the cone are accessible only by helicopter.[14]
The volcanic mountain rises 2,100 metres (6,900 ft) above the ice level[15] with maximum elevation 3,460 metres (11,350 ft).[16][17][1][c] It is an undissected nearly perfect cone,[8] a 30-kilometre-wide (19 mi)shield volcano[16] with an exposed volume of about 780 cubic kilometres (190 cu mi).[21] The subglacial part, which might bottom out at 1,340–2,030 metres (4,400–6,660 ft) below sea level,[22] could have an even larger volume[21] and is elongated in an east–west direction.[23] On its summit lies a flat, snow-filled 8-kilometre-wide (5 mi)caldera[8] with a 10-metre-wide (33 ft) and 15-metre-high (50 ft)volcanic neck.[24] Alava dome maycrop out inside the caldera. Radialfissure vents are found around the volcano, and vents also occur around the caldera rim.[25] There are at least three[26]parasitic vents withbasaltic composition on its lower flanks,[27] with threecinder cones found on the western and southern slopes.[25] One of these cinder cones has been described as a subdued 100-metre-wide (330 ft) vent.[24] TheJaron Cliffs are found on the southern slope.[25]
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The volcano is largely uneroded, mostly hiding the internal structure which would clarify its history.[28][29]Only twelveoutcrops,[d] with a total area of less than 0.5 square kilometres (0.19 sq mi), emerge from the ice.[31] Based on these outcrops,lava flows with a thickness of 2–10 metres (6 ft 7 in – 32 ft 10 in)[14] appear to be widespread on Mount Takahe, whilepyroclastic rocks such as deposits ofStrombolian eruptions,lapillituffs[32] andlahar deposits are less common.[25] Occurrences of pyroclastic rocks at the summit have been correlated withtephra deposits elsewhere in Antarctica.[33] Additionally,obsidian-bearing[34] and recently eruptedlava bomb-and-block units crop out in the caldera rim,[35] atBucher Rim.[36]Tuyas have been reported.[37]
Mount Takahe is almost entirely covered by ice of theWest Antarctic Ice Sheet,[31] which rises about 1,300 metres (4,300 ft) above sea level.[11] A tributary of theThwaites Glacier passes close by.[38] There are two smallglaciers on the volcano itself, on the southwestern and northern flanks.[11] They are eroding eruption products from the summit area,[35] andmoraines have been mapped both on the western flank and in the summit caldera.[29] Glacial erosion is slight, with only a fewcorries cut into the lower slopes.[39] The ice cover on the mountain includes both snow-covered and ice-covered areas,[40] withsastrugi and other wind-roughened surfaces.[41] The cold dry polar environment retardsweathering.[14] Air temperatures are usually below freezing.[41]
Some rock units at the foot of the volcano were emplaced underneath ice or water[31] and featurehyaloclastite andpillow lavas. These units rise to about 350–400 metres (1,150–1,310 ft) above the present-day ice level.[15] Some of these units, such as Gill Bluff,Möll Spur andStauffer Bluff, are "hydrovolcanic deltas" comparable tolava deltas[42][11] which formed when lava flows orparasitic vents entered the ice, generating meltwater lakes around them.[43] They crop out at the base of the volcano and are well preserved.[44] Ice elevation was not stable during the emplacement of these deltas, and meltwater drained away, leading to the formation of diverse structures within the hyaloclastite deltas.[45] The deltas may have formed during ice highstands 66,000 and 22,000–15,000 years ago.[46]
The West Antarctic Rift System is abasin and range province similar to theGreat Basin inNorth America;[47] it cuts across Antarctica[48] from theRoss Sea to theBellingshausen Sea.[49] The Rift became active during theMesozoic.[e] Owing to thick ice cover it is not clear whether it is currently active,[48] and there is noseismic activity. Most of the Rift lies below sea level.[50] To the south it is flanked by theTransantarctic Mountains and to the north by the volcanic province ofMarie Byrd Land. Volcanic activity in Marie Byrd Land commenced about 34 million years ago, but high activity began 14 million years ago.[51] A major uplifted dome, 1,200 by 500 kilometres (750 mi × 310 mi) in width, is centred on the Amundsen Sea coast and is associated with the Rift.[52]
About 18central volcanoes were active in Marie Byrd Land from theMiocene[f] to theHolocene.[15] Among the volcanic areas in Marie Byrd Land are theFlood Range withMount Berlin, theAmes Range, theExecutive Committee Range withMount Sidley andMount Waesche, theCrary Mountains,Toney Mountain, Mount Takahe andMount Murphy.[53] These volcanoes mainly occur in groups or chains,[51] but there also are isolated edifices.[47] Mount Takahe is located in the eastern Marie Byrd Land volcanic province[7] and with an estimated volume of 5,520 cubic kilometres (1,320 cu mi)[g][55] could be the largest of the Marie Byrd Land volcanoes, comparable toMount Kilimanjaro in Africa.[56]
Most of these volcanoes are large, capped off by a summit caldera and appear to have begun as fast-growing shield volcanoes. Later, calderas formed. Eventually, late in the history of the volcanoes parasitic vents were active.[15] The volcanoes are all surmounted by rocks composed oftrachyte,phonolite,pantellerite, orcomendite.[57] Their activity has been attributed either to the reactivation ofcrustal structures or to the presence of amantle plume.[48] The volcanoes rise from aPaleozoicbasement.[51]
Mount Takahe may feature a largemagma chamber[58] and aheat flow anomaly has been found.[59] Amagnetic anomaly has also been linked to the mountain.[60]
Trachyte is the most common rock on Mount Takahe, phonolite being less common.Basanite,hawaiite, andmugearite are uncommon,[29] but the occurrence ofbenmoreite[17] and pantellerite has been reported,[22] and some rocks have been classified asandesites.[61] Hawaiite occurs exclusively in the older outcrops, basanite only in parasitic vents[25] and mugearite only on the lower sector of the volcano.[62] Despite this, most of the volcano is believed to consist ofmafic rocks with only about 10–15% offelsic rocks,[63] as the upper visible portion of the volcano could be resting on a much larger buried base. The parasitic vents probably make up less than 1% of the edifice.[10] Ice-lava interactions produced hyaloclastite,palagonite andsideromelane.[11] No major changes in magma chemistry occurred during the last 40,000 years[64] but some variation has been recorded.[65]
All these rocks appear to have a common origin and define an alkaline[29]–peralkaline suite.[66]Phenocrysts include mainlyplagioclase, with less commonolivine andtitanomagnetite;[67]apatite has been reported as well.[61] The magmas appear to have formed throughfractional crystallization at varying pressures,[68] and ultimately came from thelithosphere at 80–90-kilometre (50–56 mi) depth,[69] that was affected bysubduction processes[70] over 85 million years ago.[6]
The volcano was active in the lateQuaternary.[5]Radiometric results reported in 1988 include ages of less than 360,000 years for rocks in the caldera rim and of less than 240,000 years for volcanic rocks on the flanks.[71] In his 1990 bookVolcanoes of the Antarctic Plate and Southern Oceans LeMasurier gave 310,000±90,000 years ago as the oldest date for samples tested, citing unpublishedK-Ar dates,[5] but in a 2016 review of dates for Mount Takahe LeMasurier reported that none were older than 192,000 years.[72] A 2013 paper also by LeMasurier reported maximum ages of 192,000 years for caldera rim rocks and of 66,000 years for lower flank rocks.[22] The entire volcano may have formed in less than 400,000 years[73] or even less than 200,000 years, which would imply rapid growth of the edifice.[22] Rocks aged 192,000±6,300 years old are found at the summit caldera, implying that the volcano had reached its present-day height by then.[74]
Early research indicated that most of Mount Takahe formed underneath the ice, but more detailed field studies concluded that most of the volcano developed above the ice surface.[31] The ice surface has fluctuated over the life of Mount Takahe with an increased thickness duringmarine isotope stages 4 and 2,[75] explaining why units originally emplaced under ice or water now lie above the ice surface[35] and alternate with lava flow deposits.[8] These elevated deposits were emplaced about 29,000–12,000 years ago[76] while the lava delta-like deposits are between about 70,000 and 15,000 years old.[77] After it grew out of the ice, Mount Takahe increased in size through the emission of lava flows with occasional pyroclastic eruptions.[78] Outcrops in the summit region indicate that most eruptions were magmatic, but somehydromagmatic activity occurred.[35] Cinder cones andtuff cones formed during the late stage of activity.[1]
Tephra layers inice cores drilled atByrd Station have been attributed to Mount Takahe.[79] The volcano reaches an altitude high enough that tephras erupted from it can readily penetrate thetropopause and spread over Antarctica through thestratosphere.[80] The occurrence of several volcanic eruptions in the region about 30,000 years ago has been suggested to have causeda cooling of the climate of Antarctica,[81] but it is also possible that the growth of the ice sheets at that time squeezed magma chambers at Mount Takahe and thus induced an increase of the eruptive activity.[82]
Assuming that most tephra layers at Byrd come from Mount Takahe, it has been inferred that the volcano was very active between 60,000 and 7,500 years ago, with nine eruptive periods and two pulses between 60,000 and 57,000 and 40,000–14,000 years ago. In the latter part of the latter period hydrovolcanic eruptions became dominant at Mount Takahe, with a maximum around the time when theWisconsin glaciation ended.[78] It is possible that between 18,000 and 15,000 years ago, either acrater lake formed in the caldera or the vents were buried by snow and ice. The caldera itself might have formed between 20,000 and 15,000 years ago, probably not through a largeexplosive eruption.[64]
It cannot be entirely ruled out that Byrd Station tephras originate at other volcanoes of Marie Byrd Land[83] such as Mount Berlin. In particular, tephra layers between 30,000 and 20,000 years ago have been attributed to the latter volcano.[84][85]
Tephra layers from Mount Takahe have also been found atDome C,[86]Dome F,[87] Mount Takahe itself,[88] Mount Waesche,[89]Siple Dome[90][h] and elsewhere in Antarctica.[89] Apart from ice cores, tephras attributed to Mount Takahe have been found insediment cores taken from the sea.[91] Volcanic eruptions at Mount Takahe lack thepyroclastic flow deposits observed in other large explosive eruptions.[14] The thickness of the Byrd ice core tephras attributed to Mount Takahe suggested that the eruptions were not large,[83] but later research has indicated that largePlinian eruptions also occurred.[92]
A series of eruptions about 200 years long took place at Mount Takahe 17,700 years ago.[93] These eruptions have been recorded from ice cores at theWAIS Divide[93] and atTaylor Glacier in theMcMurdo Dry Valleys, where they constrain estimates of the rate ofdeglaciation.[94] These eruptions released a large quantity ofhalogens into the stratosphere,[93] which together with the cold and dry climate conditions of thelast glacial maximum would presumably have led to massiveozone destruction and the formation of anozone hole.[95]Bromine andsulfur isotope data indicate that the amount ofUV radiation in the atmosphere did increase at that time in Antarctica.[95] As is the case with the present-day ozone hole, the ozone hole created by the Takahe eruptions might have altered the Antarctic climate and sped up deglaciation, which was accelerating at that time,[96] but later research has determined that the warming was most likely not volcanically forced.[97]
Activity waned after this point, two hydromagmatic eruptions being recorded 13,000 and 9,000 years ago and a magmatic eruption 7,500 years ago.[64] This last eruption is also known from the Byrd ice core[98] and may correspond to an eruption 8,200±5,400 years ago[85] recorded at Mount Waesche[99] and the Takahe edifice[74] and to two 6217 and 6231BC tephra layers at Siple Dome.[100] Tephra from a 8,200 before present eruption has been recorded at Siple Dome and Mount Waesche.[101] A 7,900 before present eruption at Mount Takahe is one of the strongest eruptions at Siple Dome and Byrd Station of the last 10,000 years.[102] Another eruption reported by theGlobal Volcanism Program may have occurred in 7050 BC.[103] At Siple Dome, a further eruption between 10,700 and 5,600 years ago is recorded[104] and one tephra layer around 1783 BC (accompanied by increasedsulfate concentrations in ice) might also come from Mount Takahe.[105] Glass shards atLaw Dome emplaced in 1552 and 1623AD may come from this volcano as well.[106]
The Global Volcanism Program reports 5550 BC as the date of the last known eruption,[1] and the volcano is currently considereddormant.[107] There is no evidence offumarolic activity or warm ground,[108][5] unlike at Mount Berlin, which is the other young volcano of Marie Byrd Land.[109]Seismic activity recorded at 9–19 kilometres (5.6–11.8 mi) depth around the volcano may be linked to its activity.[110] Mount Takahe has been prospected for the possibility of obtaininggeothermal energy.[58]
Named features of the mountain, clockwise from the north, include Clausen Glacier, Knezevich Rock, Stauffer Bluff, Oeschger Bluff, Bucher Rim, Jaron Cliffs, Möll Spur, Steuri Glacier, Cadenazzi Rock, Roper Point and Gill Bluff.[111]
| Feature | Coordinates | Description |
|---|---|---|
| Clausen Glacier | 76°10′S112°03′W / 76.167°S 112.050°W /-76.167; -112.050 (Clausen Glacier) | A narrow glacier draining northward from the summit of Mount Takahe. The terminus of the glacier is just west of Knezevich Rock. It was mapped by theUnited States Geological Survey (USGS) from surveys and United States Navy aerial photographs, 1959–66. It was named by the United StatesAdvisory Committee on Antarctic Names (US-ACAN) for Henrik B. Clausen (University of Bern, Switzerland),United States Antarctic Research Program (USARP) glaciologist atByrd Station, 1969–70.[112] |
| Knezevich Rock | 76°10′S112°00′W / 76.167°S 112.000°W /-76.167; -112.000 (Knezevich Rock). | A rock outcrop on the lower part of the north slope of Mount Takahe. It lies at the east side of the mouth of Clausen Glacier. It was mapped by the USGS from surveys and United States Navy aerial photography, 1959–66. It was named by the US-ACAN for Nick Knezevich Jr., United States Navy, electronics technician at South Pole Station, 1974.[113] |
| Stauffer Bluff | 76°10′S111°46′W / 76.167°S 111.767°W /-76.167; -111.767 (Stauffer Bluff). | A rocky bluff at the northeast extremity of Mount Takahe. It was mapped by the USGS from surveys and United States Navy tricamera aerial photographs, 1959–66. It was named by the US-ACAN for Bernhard Stauffer (University of Bern, Switzerland), USARP glaciologist at Byrd Station, 1968–69 and 1969–70.[114] |
| Oeschger Bluff | 76°24′S111°48′W / 76.400°S 111.800°W /-76.400; -111.800 (Oeschger Bluff). | A flat-topped snow and rock bluff that projects from the southeast part of Mount Takahe. It was mapped by the USGS from surveys and United States Navy tricamera aerial photography, 1959–66. It was named by the US-ACAN for Hans Oeschger (University of Bern, Switzerland), USARP glaciologist at Byrd Station, 1968–69 and 1969–70.[115] |
| Bucher Rim | 76°19′S112°00′W / 76.317°S 112.000°W /-76.317; -112.000 (Bucher Rim) | A rocky eminence on the south portion of the rim of the extinct volcano Mount Takahe. It was mapped by the USGS from surveys and United States Navy tricamera aerial photographs, 1959–66. It was named by the US-ACAN for Peter Bucher (University of Bern, Switzerland), USARP glaciologist at Byrd Station, 1969–70.[116] |
| Jaron Cliffs | 76°23′S112°10′W / 76.383°S 112.167°W /-76.383; -112.167 (Jaron Cliffs). | A line of steep, snow-covered cliffs on the south side of Mount Takahe. It was mapped by the USGS from ground surveys and United States Navy air photographs, 1959–66. It was named by the US-ACAN for Helmut P. Jaron, aurora researcher at Byrd Station in 1963.[117] |
| Möll Spur | 76°23′S112°09′W / 76.383°S 112.150°W /-76.383; -112.150 (Möll Spur). | A jagged rock spur which juts southward from Jaron Cliffs on the southern slope of Mount Takahe. It was mapped by the USGS from surveys and United States Navy tricamera aerial photographs, 1959–66. It was named by the US-ACAN for Markus Moll (University of Bern, Switzerland), USARP glaciologist at Byrd Station, 1969–70.[118] |
| Steuri Glacier | 76°23′S112°24′W / 76.383°S 112.400°W /-76.383; -112.400 (Steuri Glacier). | A glacier descending the southern slopes of Mount Takahe. The feature is 3.5 nautical miles (6.5 km; 4.0 mi) west of Moll Spur. It was mapped by the USGS from surveys and United States Navy aerial photography, 1959–66. It was named by the US-ACAN for Heinrich Steuri (University of Bern, Switzerland), USARP glaciologist at Byrd Station, 1968–69.[119] |
| Cadenazzi Rock | 76°18′S112°39′W / 76.300°S 112.650°W /-76.300; -112.650 (Cadenazzi Rock). | A rock outcrop 1.5 nautical miles (2.8 km; 1.7 mi) east of Roper Point on the west slope of Mount Takahe. It was mapped by the USGS from surveys and United States Navy tricamera aerial photographs, 1959–66. It was named by the US-ACAN for Lieutenant Michael P. Cadenazzi, United States Navy, LH-34 helicopter commander. He flew close support missions for USARP scientists during the 1969–70 and 1970–71 seasons.[120] |
| Roper Point | 76°19′S112°54′W / 76.317°S 112.900°W /-76.317; -112.900 (Roper Point). | A largely ice-covered point, but with some rock exposures, at the west extremity of Mount Takahe. It was mapped by the USGS from ground surveys and United States Navy air photographs, 1959–66. It was named by the US-ACAN for Nathaniel A. Roper, aurora researcher at Byrd Station in 1963.[121] |
| Gill Bluff | 76°14′S112°33′W / 76.233°S 112.550°W /-76.233; -112.550 (Gill Bluff). | A rock bluff on the northwest side of Mount Takahe. It was mapped by the USGS from ground surveys and United States Navy air photographs, 1959–66. It was named by the US-ACAN for Allan Gill, aurora researcher at Byrd Station in 1963.[122] |
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