Mount Takahe

Template:Short description Template:Infobox mountain

Mount Takahe is a Template:Convert snow-covered shield volcano in Marie Byrd Land, Antarctica, Template:Convert from the Amundsen Sea. It is a Template:Circa Template:Convert mountain with parasitic vents and a caldera up to Template:Convert wide. Most of the volcano is formed by trachytic lava flows, but hyaloclastite is also found. Snow, ice, and glaciers cover most of Mount Takahe. With a volume of Template:Convert, it is a massive volcano; the parts of the edifice that are buried underneath the West Antarctic Ice Sheet are probably even larger. It is part of the West Antarctic Rift System along with 18 other known volcanoes.

The volcano was active in the Quaternary period.Template:Efn Radiometric dating has yielded ages of up to 300,000Template:Nbspyears for its rocks, and it reached its present height about 200,000Template:Nbspyears ago. Several tephra layers encountered in ice cores at Mount Waesche and Byrd Station have been attributed to Mount Takahe, although some of them were later linked to eruptions of Mount Berlin instead. The tephra layers were formed by explosive or phreatomagmatic eruptions. Major eruptions took place around 17,700Template:Nbspyears ago—possibly forming an ozone hole over Antarctica—and in the early Holocene.Template:Efn Mount Takahe's last eruption occurred about 7,600 years ago, and there is no present-day activity.

Geography and geomorphologyEdit

The mountain's name refers to the takahē, a flightless nearly extinct bird from New Zealand; members of the 1957–1958 Marie Byrd Land Traverse party nicknamed an aircraft that had resupplied them "takahe".Template:Sfn It was first visited in 1957–1958 and again in 1968,Template:Sfn 1984–1985 and 1998–1999.Template:Sfn

Mount Takahe is at the Bakutis Coast,Template:Sfn eastern Marie Byrd Land, Antarctica. Bear Peninsula<ref name="Herzfeld2004" /> and the Amundsen Sea coast are Template:Convert north of Mount Takahe.Template:Sfn It is an isolated mountain,Template:Sfn and the closest other volcanoes are Mount Murphy Template:Convert Template:Sfn and Toney Mountain Template:Convert away.Template:Sfn No major air routes or supply roads to Antarctic stations pass close to the mountain,Template:Sfn and some parts of the cone are accessible only by helicopter.Template:Sfn

The volcanic mountain rises Template:Convert above the ice levelTemplate:Sfn with maximum elevation Template:Convert.Template:Sfn Template:Sfn<ref name="GVP" />Template:Efn It is an undissected nearly perfect cone,Template:Sfn a Template:Convert shield volcano Template:Sfn with an exposed volume of about Template:Convert.Template:Sfn The subglacial part, which might bottom out at Template:Convert below sea level,Template:Sfn could have an even larger volumeTemplate:Sfn and is elongated in an east–west direction.Template:Sfn On its summit lies a flat, snow-filled Template:Convert caldera Template:Sfn with a Template:Convert and Template:Convert volcanic neck.Template:Sfn A lava dome may crop out inside the caldera. Radial fissure vents are found around the volcano, and vents also occur around the caldera rim.Template:Sfn There are at least threeTemplate:Sfn parasitic vents with basaltic composition on its lower flanks,Template:Sfn with three cinder cones found on the western and southern slopes.Template:Sfn One of these cinder cones has been described as a subdued Template:Convert vent.Template:Sfn The Jaron Cliffs are found on the southern slope.Template:Sfn

File:Mount Takahe (8141434004).jpg

Cliffs on the lower part of the volcano

The volcano is largely uneroded, mostly hiding the internal structure which would clarify its history.Template:Sfn Template:SfnOnly twelve outcrops,Template:Efn with a total area of less than Template:Convert, emerge from the ice.Template:Sfn Based on these outcrops, lava flows with a thickness of Template:Convert Template:Sfn appear to be widespread on Mount Takahe, while pyroclastic rocks such as deposits of Strombolian eruptions, lapilli tuffs Template:Sfn and lahar deposits are less common.Template:Sfn Occurrences of pyroclastic rocks at the summit have been correlated with tephra deposits elsewhere in Antarctica.Template:Sfn Additionally, obsidian-bearingTemplate:Sfn and recently erupted lava bomb-and-block units crop out in the caldera rim,Template:Sfn at Bucher Rim.Template:Sfn Tuyas have been reported.<ref name="Smellie2021" />

GlaciationEdit

Mount Takahe is almost entirely covered by ice of the West Antarctic Ice Sheet,Template:Sfn which rises about Template:Convert above sea level.Template:Sfn A tributary of the Thwaites Glacier passes close by.Template:Sfn There are two small glaciers on the volcano itself, on the southwestern and northern flanks.Template:Sfn They are eroding eruption products from the summit area,Template:Sfn and moraines have been mapped both on the western flank and in the summit caldera.Template:Sfn Glacial erosion is slight, with only a few corries cut into the lower slopes.<ref name="AndrewsLeMasurier1973" /> The ice cover on the mountain includes both snow-covered and ice-covered areas,Template:Sfn with sastrugi and other wind-roughened surfaces.Template:Sfn The cold dry polar environment retards weathering.Template:Sfn Air temperatures are usually below freezing.Template:Sfn

Some rock units at the foot of the volcano were emplaced underneath ice or waterTemplate:Sfn and feature hyaloclastite and pillow lavas. These units rise to about Template:Convert above the present-day ice level.Template:Sfn Some of these units, such as Gill Bluff, Möll Spur and Stauffer Bluff, are "hydrovolcanic deltas" comparable to lava deltas Template:Sfn Template:Sfn which formed when lava flows or parasitic vents entered the ice, generating meltwater lakes around them.Template:Sfn They crop out at the base of the volcano and are well preserved.Template:Sfn 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.Template:Sfn The deltas may have formed during ice highstands 66,000 and 22,000–15,000Template:Nbspyears ago.Template:Sfn

GeologyEdit

The West Antarctic Rift System is a basin and range province similar to the Great Basin in North America;Template:Sfn it cuts across AntarcticaTemplate:Sfn from the Ross Sea to the Bellingshausen Sea.Template:Sfn The Rift became active during the Mesozoic.Template:Efn Owing to thick ice cover it is not clear whether it is currently active,Template:Sfn and there is no seismic activity. Most of the Rift lies below sea level.Template:Sfn To the south it is flanked by the Transantarctic Mountains and to the north by the volcanic province of Marie Byrd Land. Volcanic activity in Marie Byrd Land commenced about 34Template:Nbspmillion years ago, but high activity began 14Template:Nbspmillion years ago.Template:Sfn A major uplifted dome, Template:Convert in width, is centred on the Amundsen Sea coast and is associated with the Rift.Template:Sfn

File:MountTakaheMap.jpg

Topographic map of Mount Takahe

About 18 central volcanoes were active in Marie Byrd Land from the Miocene Template:Efn to the Holocene.Template:Sfn Among the volcanic areas in Marie Byrd Land are the Flood Range with Mount Berlin, the Ames Range, the Executive Committee Range with Mount Sidley and Mount Waesche, the Crary Mountains, Toney Mountain, Mount Takahe and Mount Murphy.Template:Sfn These volcanoes mainly occur in groups or chains,Template:Sfn but there also are isolated edifices.Template:Sfn Mount Takahe is located in the eastern Marie Byrd Land volcanic provinceTemplate:Sfn and with an estimated volume of Template:Convert Template:Efn Template:Sfn could be the largest of the Marie Byrd Land volcanoes, comparable to Mount Kilimanjaro in Africa.Template:Sfn

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.Template:Sfn The volcanoes are all surmounted by rocks composed of trachyte, phonolite, pantellerite, or comendite.Template:Sfn Their activity has been attributed either to the reactivation of crustal structures or to the presence of a mantle plume.Template:Sfn The volcanoes rise from a Paleozoic basement.Template:Sfn

Mount Takahe may feature a large magma chamber<ref name="Splettstoesser1990" /> and a heat flow anomaly has been found.Template:Sfn A magnetic anomaly has also been linked to the mountain.<ref name="Behrendt1963" />

CompositionEdit

Trachyte is the most common rock on Mount Takahe, phonolite being less common. Basanite, hawaiite, and mugearite are uncommon,Template:Sfn but the occurrence of benmoreite Template:Sfn and pantellerite has been reported,Template:Sfn and some rocks have been classified as andesites.Template:Sfn Hawaiite occurs exclusively in the older outcrops, basanite only in parasitic ventsTemplate:Sfn and mugearite only on the lower sector of the volcano.Template:Sfn Despite this, most of the volcano is believed to consist of mafic rocks with only about 10–15% of felsic rocks,Template:Sfn 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.Template:Sfn Ice-lava interactions produced hyaloclastite, palagonite and sideromelane.Template:Sfn No major changes in magma chemistry occurred during the last 40,000Template:Nbspyears Template:Sfn but some variation has been recorded.Template:Sfn

All these rocks appear to have a common origin and define an alkalineTemplate:Sfn–peralkaline suite.Template:Sfn Phenocrysts include mainly plagioclase, with less common olivine and titanomagnetite;Template:Sfn apatite has been reported as well.Template:Sfn The magmas appear to have formed through fractional crystallization at varying pressures,Template:Sfn and ultimately came from the lithosphere at Template:Convert depth,Template:Sfn that was affected by subduction processesTemplate:Sfn over 85Template:Nbspmillion years ago.Template:Sfn

Eruption historyEdit

The volcano was active in the late Quaternary.Template:Sfn Radiometric results reported in 1988 include ages of less than 360,000Template:Nbspyears for rocks in the caldera rim and of less than 240,000Template:Nbspyears for volcanic rocks on the flanks.Template:Sfn In his 1990 book Volcanoes of the Antarctic Plate and Southern Oceans LeMasurier gave 310,000±90,000Template:Nbspyears ago as the oldest date for samples tested, citing unpublished K-Ar dates,Template:Sfn but in a 2016 review of dates for Mount Takahe LeMasurier reported that none were older than 192,000Template:Nbspyears.Template:Sfn A 2013 paper also by LeMasurier reported maximum ages of 192,000Template:Nbspyears for caldera rim rocks and of 66,000Template:Nbspyears for lower flank rocks.Template:Sfn The entire volcano may have formed in less than 400,000Template:Nbspyears Template:Sfn or even less than 200,000Template:Nbspyears, which would imply rapid growth of the edifice.Template:Sfn Rocks aged 192,000±6,300Template:Nbspyears old are found at the summit caldera, implying that the volcano had reached its present-day height by then.Template:Sfn

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.Template:Sfn The ice surface has fluctuated over the life of Mount Takahe with an increased thickness during marine isotope stages 4 and 2,Template:Sfn explaining why units originally emplaced under ice or water now lie above the ice surfaceTemplate:Sfn and alternate with lava flow deposits.Template:Sfn These elevated deposits were emplaced about 29,000–12,000Template:Nbspyears ago<ref name="Anderson2002" /> while the lava delta-like deposits are between about 70,000Template:Nbspand 15,000Template:Nbspyears old.Template:Sfn After it grew out of the ice, Mount Takahe increased in size through the emission of lava flows with occasional pyroclastic eruptions.Template:Sfn Outcrops in the summit region indicate that most eruptions were magmatic, but some hydromagmatic activity occurred.Template:Sfn Cinder cones and tuff cones formed during the late stage of activity.<ref name="GVP" />

Tephra in ice coresEdit

Tephra layers in ice cores drilled at Byrd Station have been attributed to Mount Takahe.Template:Sfn The volcano reaches an altitude high enough that tephras erupted from it can readily penetrate the tropopause and spread over Antarctica through the stratosphere.Template:Sfn The occurrence of several volcanic eruptions in the region about 30,000Template:Nbspyears ago has been suggested to have caused a cooling of the climate of Antarctica,Template:Sfn 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.Template:Sfn

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 57,000Template:Nbspand 40,000–14,000Template:Nbspyears ago. In the latter part of the latter period hydrovolcanic eruptions became dominant at Mount Takahe, with a maximum around the time when the Wisconsin glaciation ended.Template:Sfn It is possible that between 18,000 and 15,000Template:Nbspyears ago, either a crater lake formed in the caldera or the vents were buried by snow and ice. The caldera itself might have formed between 20,000 and 15,000Template:Nbspyears ago, probably not through a large explosive eruption.Template:Sfn

It cannot be entirely ruled out that Byrd Station tephras originate at other volcanoes of Marie Byrd LandTemplate:Sfn such as Mount Berlin. In particular, tephra layers between 30,000Template:Nbspand 20,000Template:Nbspyears ago have been attributed to the latter volcano.Template:Sfn Template:Sfn

Tephra layers from Mount Takahe have also been found at Dome C,<ref name="Smellie1999" /> Dome F,<ref name="KohnoFujii1999" /> Mount Takahe itself,Template:Sfn Mount Waesche,Template:Sfn Siple Dome Template:Sfn Template:Efn and elsewhere in Antarctica.Template:Sfn Apart from ice cores, tephras attributed to Mount Takahe have been found in sediment cores taken from the sea.Template:Sfn Volcanic eruptions at Mount Takahe lack the pyroclastic flow deposits observed in other large explosive eruptions.Template:Sfn The thickness of the Byrd ice core tephras attributed to Mount Takahe suggested that the eruptions were not large,Template:Sfn but later research has indicated that large Plinian eruptions also occurred.<ref name="Giordano2012" />

A series of eruptions about 200 years long took place at Mount Takahe 17,700Template:Nbspyears ago.Template:Sfn These eruptions have been recorded from ice cores at the WAIS Divide Template:Sfn and at Taylor Glacier in the McMurdo Dry Valleys, where they constrain estimates of the rate of deglaciation.<ref name="Baggenstos2018" /> These eruptions released a large quantity of halogens into the stratosphere,Template:Sfn which together with the cold and dry climate conditions of the last glacial maximum would presumably have led to massive ozone destruction and the formation of an ozone hole.Template:Sfn Bromine and sulfur isotope data indicate that the amount of UV radiation in the atmosphere did increase at that time in Antarctica.Template:Sfn 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,Template:Sfn but later research has determined that the warming was most likely not volcanically forced.<ref name="Chowdhry Beeman2019" />

Holocene and recent activityEdit

Activity waned after this point, two hydromagmatic eruptions being recorded 13,000Template:Nbspand 9,000Template:Nbspyears ago and a magmatic eruption 7,500Template:Nbspyears ago.Template:Sfn This last eruption is also known from the Byrd ice coreTemplate:Sfn and may correspond to an eruption 8,200±5,400Template:Nbspyears agoTemplate:Sfn recorded at Mount WaescheTemplate:Sfn and the Takahe edificeTemplate:Sfn and to two 6217 and 6231 BC tephra layers at Siple Dome.Template:Sfn Tephra from a 8,200Template:Nbsp before present eruption has been recorded at Siple Dome and Mount Waesche.<ref name="Iverson2015" /> A 7,900Template:Nbspbefore present eruption at Mount Takahe is one of the strongest eruptions at Siple Dome and Byrd Station of the last 10,000Template:Nbspyears.<ref name="CorrVaughan2008" /> Another eruption reported by the Global Volcanism Program may have occurred in 7050 BC.<ref name="GVPE" /> At Siple Dome, a further eruption between 10,700 and 5,600Template:Nbspyears ago is recorded<ref name="Taylor2004" /> and one tephra layer around 1783 BC (accompanied by increased sulfate concentrations in ice) might also come from Mount Takahe.Template:Sfn Glass shards at Law Dome emplaced in 1552 and 1623 AD may come from this volcano as well.<ref name="Zielinski2006" />

The Global Volcanism Program reports 5550 BC as the date of the last known eruption,<ref name="GVP" /> and the volcano is currently considered dormant.<ref name="PMehra2016" /> There is no evidence of fumarolic activity or warm ground,Template:Sfn Template:Sfn unlike at Mount Berlin, which is the other young volcano of Marie Byrd Land.Template:Sfn Seismic activity recorded at Template:Convert depth around the volcano may be linked to its activity.<ref name="LucasNyblade2021" /> Mount Takahe has been prospected for the possibility of obtaining geothermal energy.<ref name="Splettstoesser1990" />

Template:GeoGroup

Named featuresEdit

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.Template:Sfn

Feature	Coordinates	Description
Template:AnchorClausen Glacier	Template:Coord	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 the United States Geological Survey (USGS) from surveys and United States Navy aerial photographs, 1959–66. It was named by the United States Advisory Committee on Antarctic Names (US-ACAN) for Henrik B. Clausen (University of Bern, Switzerland), United States Antarctic Research Program (USARP) glaciologist at Byrd Station, 1969–70.Template:Sfn
Template:AnchorKnezevich Rock	Template:Coord.	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.Template:Sfn
Template:AnchorStauffer Bluff	Template:Coord.	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.Template:Sfn
Template:AnchorOeschger Bluff	Template:Coord.	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.Template:Sfn
Template:AnchorBucher Rim	Template:Coord	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.Template:Sfn
Template:AnchorJaron Cliffs	Template:Coord.	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.Template:Sfn
Template:AnchorMöll Spur	Template:Coord.	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.Template:Sfn
Template:AnchorSteuri Glacier	Template:Coord.	A glacier descending the southern slopes of Mount Takahe. The feature is Template:Convert 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.Template:Sfn
Template:AnchorCadenazzi Rock	Template:Coord.	A rock outcrop Template:Convert 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.Template:Sfn
Template:AnchorRoper Point	Template:Coord.	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.Template:Sfn
Template:AnchorGill Bluff	Template:Coord.	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.Template:Sfn