Mount Moulton is a complex of ice-covered

shield volcano A shield volcano is a type of volcano named for its low profile, resembling a warrior's shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more v ...

es, standing east of

Mount Berlin Mount Berlin is a high glacier-covered volcano in Marie Byrd Land, Antarctica, from the Amundsen Sea. It is a mountain with parasitic vents that consists of two coalesced volcanoes; Berlin proper with the wide Berlin Crater and Merrem P ...

in the

Flood Range The Flood Range () is an Antarctic range of large snow-covered mountains extending in an E-W direction for about 96 km (60 mi) and forming a right angle with the southern end of the Ames Range in Marie Byrd Land. Discovered by the Byrd ...

Marie Byrd Land Marie Byrd Land (MBL) is an unclaimed region of Antarctica. With an area of , it is the largest unclaimed territory on Earth. It was named after the wife of American naval officer Richard E. Byrd, who explored the region in the early 20th centur ...

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...

. It is named for Richard S. Moulton, chief dog driver at West Base. The volcano is of Pliocene age and is presently inactive. The Prahl Crags are located on the southern slopes of Mount Moulton and are part of a

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

. There, an exposed area of blue ice can be found; this ice contains

tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they rem ...

layers from mainly neighbouring Mount Berlin volcano and some of the ice is almost half a million years old.

Geology and geomorphology

Mount Moulton lies in

Western Antarctica West Antarctica, or Lesser Antarctica, one of the two major regions of Antarctica, is the part of that continent that lies within the Western Hemisphere, and includes the Antarctic Peninsula. It is separated from East Antarctica by the Transa ...

and in the region of the

West Antarctic Ice Sheet The Western Antarctic Ice Sheet (WAIS) is the segment of the Antarctic ice sheet, continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere. The WAI ...

. It is part of a system of volcanoes including

Mount Takahe Mount Takahe is a snow-covered shield volcano in Marie Byrd Land, Antarctica, from the Amundsen Sea. It is a mountain with parasitic vents and a caldera up to wide. Most of the volcano is formed by trachytic lava flows, but hyaloclastite ...

and Mount Waesche as well as of recently active subglacial volcanism. The volcano is named for Richard S. Moulton, chief dog driver of the

United States Antarctic Service Expedition The United States Antarctic Service Expedition (1939–1941), often referred to as Byrd’s Third Antarctic Expedition, was an expedition jointly sponsored by the United States Navy, State Department, Department of the Interior and The Treasu ...

; the western end of the

where Mount Moulton lies was visited by this expedition in December 1940. Other field expeditions took place in 1967-1968, 1977-1978, 1993-1994 and 1999-2000. MountMoultonMap

The volcano appears to be of

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Gawne Nunatak, which is a

parasitic cone A parasitic cone (also adventive cone or satellite cone) is the cone-shaped accumulation of volcanic material not part of the central vent of a volcano. It forms from eruptions from fractures on the flank of the volcano. These fractures occur ...

. There is no evidence of eruptive or thermal activity unlike at its neighbour Mount Berlin.

Earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

s have been recorded at Mount Moulton and are either of volcano-tectonic origin or due to the movement of

ice Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...

along the flanks of the volcano. The mountain is high, rising about above the ice surface on its northern flank, and located within the

; Mount Berlin lies across the wide, high-elevation Wells Saddle to the west and

Kohler Dome Kohler Dome () is a rounded, snow-covered elevation at that rises slightly above the general level of the extreme eastern part of the Mount Moulton massif, in Marie Byrd Land, Antarctica. It was mapped by the United States Geological Survey from g ...

is east of Moulton. Even farther east lie

Mount Bursey Mount Bursey is a broad, ice-covered mountain, high, which forms the eastern end of the Flood Range in Marie Byrd Land, Antarctica. It was discovered by members of the United States Antarctic Service (USAS) on aerial flights in 1940, and named ...

Mount Andrus Mount Andrus is a shield volcano 3.2 km (2 mi) SE of Mount Boennighausen in the SE extremity of Ames Range, in Marie Byrd Land, Antarctica. Mapped by USGS from surveys and U.S. Navy air photos, 1964–68. Named by US-ACAN for Lt. Carl ...

Mount Kosciuszko Mount Kosciuszko ( ; Ngarigo: , ), previously spelled Mount Kosciusko, is mainland Australia's tallest mountain, at 2,228 metres (7,310 ft) above sea level. It is located on the Main Range of the Snowy Mountains in Kosciuszko National ...

and

Mount Kauffman Mount Kauffman is a prominent mountain, high, that surmounts the northwest end of the Ames Range in Marie Byrd Land, Antarctica. It was mapped by the United States Geological Survey from surveys and U.S. Navy air photos, 1959–65, and named by ...

, in the

Ames Range The Ames Range is an Antarctic range of snow-covered, flat-topped, steep-sided mountains, extending in a N-S direction for 32 km (20 mi) and forming a right angle with the eastern end of the Flood Range in Marie Byrd Land. They were disc ...

. Mount Moulton is an obstacle to ice flow in the

, which has piled up on the mountain and is about higher on the upstream side. Mount Moulton is formed by a complex of glaciated but largely uneroded

es with two or possibly three ice-filled

s, each of which is about wide. The calderas are apart and located at the Prahl Crags,

Britt Peak Britt Peak () is a small peak, high, just southwest of the summit of Mount Moulton, in the Flood Range of Marie Byrd Land. It was mapped by the United States Geological Survey from surveys and from U.S. Navy air photos, 1959–66, and named by th ...

and potentially

localities. Additionally the Prahl Crags – remnants of the former caldera rim – are found south, Gawne Nunatak west, Edwards Spur northeast and the Moulton Icefalls on the northern side of the mountain. The total volume of the complex is about , comparable to that of

Mount Shasta Mount Shasta ( Shasta: ''Waka-nunee-Tuki-wuki''; Karuk: ''Úytaahkoo'') is a potentially active volcano at the southern end of the Cascade Range in Siskiyou County, California. At an elevation of , it is the second-highest peak in the Cascades ...

in the

Cascade Range The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...

, and is one of the largest volcanoes in the Flood Range and Ames Range. Only the western part of the Mount Moulton emerges from the ice. Volcanic rocks found at Mount Moulton include

pantellerite Pantellerite is a type of volcanic rock, specifically a peralkaline rhyolite. It has a higher iron and lower aluminium composition than comendite. It is named after Pantelleria, a volcanic island in the Strait of Sicily and the type location for ...

phonolite Phonolite is an uncommon extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a variation of the igneous ...

and

trachyte Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and al ...

;

phenocryst 300px, feldspathic phenocrysts. This granite, from the Switzerland">Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter ...

phases found in the pantellerite include

aenigmatite Aenigmatite, also known as ''Cossyrite'' after Cossyra, the ancient name of Pantelleria, is a sodium, iron, titanium inosilicate mineral. The chemical formula is Na2Fe2+5TiSi6O20 and its structure consists of single tetrahedral chains with a repe ...

anorthoclase The mineral anorthoclase ((Na,K)AlSi3O8) is a crystalline solid solution in the alkali feldspar series, in which the sodium-aluminium silicate member exists in larger proportion. It typically consists of between 10 and 36 percent of KAlSi3O8 and ...

fayalite Fayalite (, commonly abbreviated to Fa) is the iron-rich end-member of the olivine solid-solution series. In common with all minerals in the olivine group, fayalite crystallizes in the orthorhombic system (space group ''Pbnm'') with cell para ...

hedenbergite Hedenbergite, Ca Fe Si2 O6, is the iron rich end member of the pyroxene group having a monoclinic crystal system. The mineral is extremely rarely found as a pure substance, and usually has to be synthesized in a lab. It was named in 1819 after M ...

ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...

and

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

Blue ice field

A blue ice field has formed within the caldera of Mount Moulton behind the Prahl Crags, and contains ice almost 500,000 years old. It is the oldest dated ice in

West Antarctica West Antarctica, or Lesser Antarctica, one of the two major regions of Antarctica, is the part of that continent that lies within the Western Hemisphere, and includes the Antarctic Peninsula. It is separated from East Antarctica by the Transant ...

and much older than ice found elsewhere in West Antarctic

ice core An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ic ...

s. Such blue ice fields like those found at Mount Moulton form when glaciers run into an obstacle – in this case the Prahl Crags – and part of the ice starts moving vertically as it undergoes

ablation Ablation ( la, ablatio – removal) is removal or destruction of something from an object by vaporization, chipping, erosion, erosive processes or by other means. Examples of ablative materials are described below, and include spacecraft materi ...

processes like sublimation. In the case of Mount Moulton, this outcrop of ice is about long. The ice has been used to reconstruct past climate states in West Antarctica, including the beginning and end of the last interglacial, and shows evidence that the

collapsed during that interglacial. In addition, recognizable

layers are found in this ice and appear to originate from

explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such ...

s of volcanoes such as Mount Berlin, Mount Takahe and Mount Waesche, although some may come from parasitic vents of Mount Berlin and Mount Moulton. These tephra layers at Mount Moulton crop out in parallel layers and geochemical traits indicate an origin at Mount Berlin although some layers may have been erupted from

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...

volcanoes at Mount Moulton and Mount Berlin. Furthermore, the appearance of the deposits indicates that the eruptions of Mount Berlin were highly explosive. Most likely they eventually fell onto the ice of Mount Moulton, were incorporated in it and then transported downward to the blue ice field.

References

Sources

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Geology and geomorphology

Blue ice field

See also

References

Sources

Further reading