Mount Takahe

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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 eighteen other known volcanoes.

The volcano was active in the QuaternaryTemplate:Efn. Radiometric dating has yielded ages of 300,000Template:Nbspyears and less for its rocks; the fast-growing volcano reached its present height about 200,000 years 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 HoloceneTemplate:Efn. Mount Takahe's last eruption occurred about 7,600 years ago; there is no present-day activity.

## Geography and geomorphology

Mount Takahe is at the Bakutis Coast,Template:Sfn eastern Marie Byrd Land, Antarctica. Bear Peninsula and the Amundsen Sea coast are Template:Convert north of Mount Takahe.Template:Sfn It is an isolated mountain,Template:Sfn and the closest volcanoes are Mount Murphy Template:ConvertTemplate:Sfn and Toney Mountain Template:Convert away.Template:Sfn

No major air routes or supply roads to Antarctic stations pass close to the volcano,Template:Sfn and some parts of the edifice are accessible only by helicopter.Template:Sfn The name of the volcano 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 Mount Takahe was first visited in 1957–1958 and again in 1968.Template:Sfn

The volcano rises Template:Convert above the ice levelTemplate:Sfn to a maximum elevation of Template:Convert.Template:SfnTemplate:SfnTemplate:Efn It is an undissected nearly perfect cone,Template:Sfn a Template:Convert shield volcanoTemplate: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 calderaTemplate: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
Only twelve outcropsTemplate:Efn, with a total area of less than Template:Convert, emerge from the ice that covers Mount Takahe.Template:Sfn The interior structure of the volcano is unknown.Template:Sfn Based on these outcrops, lava flows with a thickness of Template:ConvertTemplate:Sfn appear to be widespread on Mount Takahe, while pyroclastic rocks such as deposits of Strombolian eruptions, lapilli tuffsTemplate: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 Additional, obsidian-bearingTemplate:Sfn and recently erupted lava bomb-and-block units crop out in the caldera rim,Template:Sfn at Bucher Rim.Template:Sfn

### Glaciation

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 to Mount Takahe.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 not pronounced, only a few corries cut into the lower slopes. 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 polar environment is cold and dry, which slows weathering processes.Template:Sfn Air temperatures recorded at Mount Takahe 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:SfnTemplate: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

## Geology

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 MesozoicTemplate: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
About 18 central volcanoes were active in Marie Byrd Land from the MioceneTemplate: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 could be the largest of these 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 and a heat flow anomaly underneath the ice has been found at the volcano.Template:Sfn A magnetic anomaly has also been linked to Mount Takahe.

### Composition

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 benmoreiteTemplate: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:NbspyearsTemplate: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 history

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 old 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:NbspyearsTemplate:Sfn or even less than 200,000Template:Nbspyears, which would imply a fast growth of the edifice.Template:Sfn 192,000±6,300Template:Nbspyears-old rocks 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, 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 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.

### Tephra in ice cores

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 60,000–57,000Template: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:SfnTemplate:Sfn

Tephra layers from Mount Takahe have also been found at Dome C, Dome F, Mount Waesche,Template:Sfn Siple DomeTemplate:SfnTemplate:Efn and elsewhere in Antarctica.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.

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 DivideTemplate:Sfn and at Taylor Glacier in the McMurdo Dry Valleys, where they constrain estimates of the rate of deglaciation. 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.

### Holocene and recent activity

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 the Takahe edificeTemplate:Sfn and to two 6217 and 6231 BC tephra layers at Siple Dome.Template:Sfn Tephra from a 8,200Template:Nbspbefore present eruption has been recorded at Siple Dome and Mount Waesche. 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. Another eruption reported by the Global Volcanism Program may have occurred in 7050 BC. At Siple Dome, a further eruption between 10,700 and 5,600Template:Nbspyears ago is recorded 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.

The Global Volcanism Program reports 5550 BC as the date of the most recent eruption, and the volcano is currently considered dormant. There is no evidence of fumarolic activity or warm ground,Template:SfnTemplate:Sfn unlike at Mount Berlin, which is the other young volcano of Marie Byrd Land.Template:Sfn Mount Takahe has been prospected for the possibility of obtaining geothermal energy.

## See also

* List of Ultras of Antarctica
* List of volcanoes in Antarctica

## References

1. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Herzfeld2004`
2. ↑ 2.0 2.1 2.2 Cite error: Invalid `<ref>` tag; no text was provided for refs named `GVP`
3. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `AndrewsLeMasurier1973`
4. ↑ 4.0 4.1 Cite error: Invalid `<ref>` tag; no text was provided for refs named `Splettstoesser1990`
5. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Behrendt1963`
6. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Anderson2002`
7. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Smellie1999`
8. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `KohnoFujii1999`
9. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Giordano2012`
10. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Baggenstos2018`
11. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Chowdhry Beeman2019`
12. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Iverson2015`
13. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `CorrVaughan2008`
14. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `GVPE`
15. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Taylor2004`
16. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Zielinski2006`
17. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `PMehra2016`

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