|Elevation||3,478 m (11,411 ft) |
|Location||Marie Byrd Land, Antarctica|
|Parent range||Flood Range|
|Mountain type||Shield volcano|
|Last eruption||8350 BCE ± 1000 years|
Mount Berlin is the sixth highest volcano in Antarctica, located 16 km west of Mount Moulton in Marie Byrd Land near the eastern coast of the Ross Sea. It is composed of two coalesced shield volcanoes: Merrem Peak (3,000 m) and Berlin Crater (3,478 m). The volcanic structure is considered active, as steaming fumaroles have been observed near the rim of the northern and western calderas, producing fumarolic ice towers.
Geomorphology and geography
Mount Berlin is 3,478 metres (11,411 ft) high:1564 and lies in Marie Byrd Land. It is the highest volcano in the Flood Range and the most impressive as well.:229 Mount Moulton lies 30 kilometres (19 mi) farther east,:1566 it is a 40 kilometres (25 mi) long volcanic mountain range with ages of 5.3 million years ago.:797 Mount Berlin lies 100 kilometres (62 mi) away from the coast.:57 The volcano protrudes from the West Antarctic Ice Cap and is itself covered with ice in its summit area.:796
Mount Berlin is a large stratovolcano. It has a summit crater 2 kilometres (1.2 mi) wide, with pyroclastic materials exposed in its rims.:1567 A subsidiary crater is known as Merrem Crater,:1569 which is 2.5 by 1 kilometre (1.55 mi × 0.62 mi) wide:1570 and lies 3.5 kilometres (2.2 mi) west of the main summit.:797 These two volcanoes coalesce together to form the Berlin volcano.:229 Mafic volcanic rocks on the north flank may indicate that monogenetic cinder cones formed. An ignimbrite has been identified on the southeastern flank, a type of volcanic activity which is uncommon for Marie Byrd Land volcanoes.:1566 Older volcanics are exposed at Brandenburger Bluff, dates range around 2,738,000 ± 63,000 years ago.:1569 Brandenburger Bluff lies northwest of the main summit.:797 Unlike the rest of Mount Berlin, which is formed by flow rocks, Brandenburger Bluff is formed by layered hyaloclastite tuffs.:229 One interpretation is that Mount Berlin is formed by two trachytic volcanoes on top of a hydroclastic base.:230 Incipient glacial cirques have been identified.:57
Phonolithic and phonotephritic rocks are found at Brandenburger Bluff.:1570 Over time, the contents of iron in the rocks erupted by Mount Berlin increased and that of silica and potassium. This might indicate that eruptions of Mount Berlin were fed by a large magma chamber,:809 but the more likely explanation is that different eruptions tapped different "batches" of magma which were progressively less evolved.:810
Tephrochronology has been used to reconstruct the history of volcanic activity in Antarctica. Tephra from Mount Berlin has been identified in ice cores of the West Antarctic Ice Sheet, in the Mount Moulton ice cap and Vostok ice core. Other rocks on Berlin have been dated directly.:1568–1569 The oldest exposed ice in West Antarctica has been determined through tephrochronology data stemming from Mount Berlin tephra as being older than 492,000 years.:1579
Volcanic activity commenced in the Pliocene.:151 The oldest volcanic activity occurred 2.74 ± 0.06 million years ago at Brandenburger Bluff and involved subglacial and subaerial phreatomagmatic activity.:1570 Benmoreitic volcanism was active also at Wedemeyer Rocks south of the Berlin main edifice 2.58 ± 0.2 million years ago. Later, trachytic volcanism occurred at Mefford Knoll west of the main edifice 630,000 ± 30,000 and southwest at Kraut Rocks 620,000 ± 50,000 years ago.:226 Volcanic activity then shifted to Merrem Peak, starting 571,000 ± 8,900 years ago. Activity on Merrem Peak was accompanied by flank eruptions forming ignimbrites.:1570 Activity finally shifted to Mount Berlin proper, raising the summit of the volcano.:1571–1572 Mount Berlin had a phase of increased volcanic activity between 24,000 and 28,000 years ago, according to tephra data. Some eruptions at Berlin were large scale Plinian eruptions, forming eruption columns exceeding heights of 28 kilometres (17 mi):1577 and depositing volcanic ash over large areas.
Individual volcanic eruptions at Berlin occurred 135,600 ± 900 years ago, 118,100 ± 1,300 years ago, 92,100 ± 900 years ago, which was the origin of the so-called marine "Tephra A", 14,500 ± 3,800 and 10,300 ± 5,300 years ago.:799 Two pyroclastic deposits in the Berlin crater wall are dated 25,500 ± 2,000 and 18,200 ± 5,800 years ago.:1572 Over time, volcanic activity migrated south-southwestward.:1569 Berlin further had volcanic activity in the Holocene, including a lava flow beneath an ice tower that is dated 10,300 ± 2,700 years ago. A tephra dated 7,756 BC is similar to a lava flow from Mount Berlin in terms of composition and may originate from an eruption there. Another similar tephra is dated 9,346 BCE.
LeMasurier in 1990 identified the volcano as "potentially active". Fumarolic activity has formed ice towers that emit steam,:1565 making it the only volcano in Marie Byrd Land with ongoing geothermal activity.:1569 One ice cave associated with an ice tower had rock temperatures measured at 12 °C (54 °F).:1572 These fumarolic phenomena all occur along the northern and western rims of the Berlin Crater.:229 Volcano-tectonic earthquakes have been identified at Mount Berlin. They occur at depths of 15–20 kilometres (9.3–12.4 mi).
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