Toney Mountain is an elongated snow-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 ...

, long and rising to at Richmond Peak, located southwest of

Kohler Range Kohler Range ) is a mountain range in the Marie Byrd Land of Antarctica. The range is about 64 km (40 mi) long and stands between the base of Martin Peninsula and Smith Glacier. The range is composed of two ice-covered plateaus which are oriented ...

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 ...

. Toney Mountain is an elongated volcanic

massif In geology, a massif ( or ) is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole. The term also refers to a ...

that rises from a

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

lava plateau A volcanic plateau is a plateau produced by volcanism, volcanic activity. There are two main types: lava plateaus and pyroclastic plateaus. Lava plateau Lava plateaus are formed by highly fluid basaltic lava during numerous successive erup ...

. A wide summit

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 ...

tops the volcano, and is elongated in east-west direction; this orientation is shared with calderas on other volcanoes in Marie Byrd Land and reflects regional tectonic stress. The slopes of the volcano feature

parasitic vents 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 ...

and glacial

corries The Corries were a Scottish folk group that emerged from the Scottish folk revival of the early 1960s. The group was a trio from their formation until 1966 when founder Bill Smith left the band but Roy Williamson and Ronnie Browne continued ...

, and are much steeper north of the volcano than south of it. Most of the mountain is covered by ice and its eastern sector may be a

crater Crater may refer to: Landforms *Impact crater, a depression caused by two celestial bodies impacting each other, such as a meteorite hitting a planet *Explosion crater, a hole formed in the ground produced by an explosion near or below the surfac ...

. That the mountain is mostly ice covered makes it difficult to determine its composition, the origin of the elongated shape of the volcano and the volcanological relation between the

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...

cinder cone A cinder cone (or scoria cone) is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions o ...

s and the main volcanic pile. Its volume may be about . The plateau and parasitic cones are formed by

hawaiite Hawaiite is an olivine basalt with a composition between alkali basalt and mugearite. It was first used as a name for some lavas found on the island of Hawaii. It occurs during the later stages of volcanic activity on oceanic islands such as Haw ...

and the few outcrops on the main volcano by

benmoreite Benmoreite is a silica-undersaturated volcanic rock of intermediate composition. It is a sodium-rich variety of trachyandesite and belongs to the alkalic suite of igneous rocks. Nepheline benmoreite An origin by fractionation from basanite th ...

and

comendite Comendite is a hard, peralkaline igneous rock, a type of light blue grey rhyolite. Phenocrysts are sodic sanidine with minor albite and bipyramidal quartz. Iddings, Joseph Paxson, 1913, ''Igneous rocks: composition, texture and classification'', v ...

. They contain

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 ...

s of

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more prope ...

pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...

and titanaugite in the former and of

clinopyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...

feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...

and

. An age of 9.1 million years ago has been obtained on a basaltic lava flow beneath the volcano, and it has been inferred that the basal plateau formed between 10.1 and 9.1 million years ago. The massif is younger, with ages ranging from 1 million years in its lower parts to 500,000 years ago.

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

eruptions may have also occurred at Toney Mountain as indicated by 30 kyr ash layers in ice cores from

Byrd Station The Byrd Station is a former research station established by the United States during the International Geophysical Year by U.S. Navy Seabees during Operation Deep Freeze II in West Antarctica. History A joint Army, Navy, Air Force, and Marin ...

, although

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 are also candidates. During that time period, a number of volcanic eruptions occurred in Antarctica as recorded by ash layers in ice; this coincides with the coldest period of the

Wisconsin glaciation The Wisconsin Glacial Episode, also called the Wisconsin glaciation, was the most recent glacial period of the North American ice sheet complex. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cor ...

and it is possible that the effects of ash clouds from the Antarctic eruptions caused this period of cold global temperatures. On the other hand, it is also possible that growing ice sheets during this period compressed

magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it upw ...

s and thus triggered explosive eruptions. Toney Mountain lies in

, a tectonically and volcanically active region of Antarctica. There, a layer of basaltic rocks up to thick underlie a series of

felsic In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted with mafic rocks, whi ...

volcanic edifices. These basaltic rocks in turn are emplaced above a

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

basement A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. It generally is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, ...

with

granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...

intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

s of

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

, which crops out in some mountain ranges. Beneath Toney Mountain, the basaltic floor rises from an elevation of beneath sea level, and the volcano is situated on the floor of a

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...

. The region is further characterized by a large dome-like uplift, part of the

West Antarctic Rift System The West Antarctic Rift System is a series of rift valleys between East and West Antarctica. It encompasses the Ross Embayment, the Ross Sea, the area under the Ross Ice Shelf and a part of Marie Byrd Land in West Antarctica, reaching to the b ...

, and it may reflect the presence of a stationary hotspot. Toney Mountain was probably among those viewed from a distance by Admiral

Byrd Byrd commonly refers to: * William Byrd (c. 1540 – 1623), an English composer of the Renaissance * Richard E. Byrd (1888–1957), an American naval officer and explorer Byrd or Byrds may also refer to: Other people * Byrd (surname), includin ...

and others of the USAS in plane flights from the ship ''Bear'' in February 1940. It was mapped in December 1957 by the oversnow traverse party from Byrd Station to the

Sentinel Range The Sentinel Range is a major mountain range situated northward of Minnesota Glacier and forming the northern half of the Ellsworth Mountains in Antarctica. The range trends NNW-SSE for about and is 24 to 48 km (15 to 30 mi) wide. Man ...

, 1957–58, led by C.R. Bentley who proposed the name. Named after George R. Toney, scientific leader at Byrd Station in 1957, a participant in several Antarctic and Arctic operations, serving in both field and administrative capacities.

References

* {{cite book , editor1-last = LeMasurier , editor1-first = W. E. , editor2-last = Thomson , editor2-first = J. W. , title = Volcanoes of the Antarctic Plate and Southern Oceans , publisher =

American Geophysical Union The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of Earth, atmospheric, ocean, hydrologic, space, and planetary scientists and enthusiasts that according to their website includes 130,000 people (not members). AGU's act ...

, year = 1990 , isbn = 978-0-87590-172-5 , page = 512 pp

External links

"Mount Toney, Antarctica" on Peakbagger
Polygenetic shield volcanoes Calderas of Antarctica Volcanoes of Marie Byrd Land Pleistocene shield volcanoes

See also

References

External links