| Mount Petras | |
|---|---|
 Map of Mount Petras | |
| Highest point | |
| Elevation | 2,865 m (9,400 ft)  |
| Coordinates | 75°51′S128°38′W / 75.850°S 128.633°W [1] |
| Naming | |
| Etymology | Named for Theodore Argyres Petras |
| Geography | |
  Mount Petras | |
Mount Petras is a mountain in Antarctica. It consists of volcanic rocks, most of Cretaceous age but there is also an Eocene-Oligocene volcanic system that may have been emplaced inside of thin ice. It is part of the Marie Byrd Land Volcanic Province and is its oldest volcano.
Mount Petras lies in the coastal region of Marie Byrd Land, Antarctica, [1] and is located within the McCuddin Mountains together with Mount Flint [2] which lies northwest of Mount Petras. [3] The complex Mount Petras-Mount Flint-Reynolds Ridge is also known as Petras Range. [4] It lies 200–250 kilometres (120–160 mi) inland from the Amundsen Sea coast. [5]
It is an angular mountain [5] consisting of rocky spurs in an area of 5 by 8 kilometres (3.1 mi × 5.0 mi), [6] which form two ridges form a semicircular ice-filled bowl. [7] Two other summits are 2,325 metres (7,628 ft) high Putzke Peak northeast of Mount Petras, 2,716 metres (8,911 ft) high Schwob Peak south and 2,440 metres (8,010 ft) high Peter Nunatak southeast. Other outcrops occur farther southwest at Navarrette Peak, southeast at Wallace Rock [8] and northeast at Erven Nunataks. [9] The existence of an explosion crater on its northern side was inferred by González-Ferran in 1972. [10]
Both basement and volcanic rocks emerge from the West Antarctic Ice Sheet as a nunatak. The volcanic and basement rocks are separated by an unconformity at 2,700 metres (8,900 ft) elevation. [1] The highest summit of Mount Petras lies on the western ridge [7] at 2,867 metres (9,406 ft) elevation above sea level of which about 900 metres (3,000 ft) are above the West Antarctic Ice Sheet. [11] Most of the volcanic rocks are hawaiite with some mugearite, [12] while the basement is rhyodacitic [11] and mostly consists of a Cretaceous volcanic complex that makes up the bulk of Mount Petras. [5] The basement also includes schists, [13] paragneisses [14] and gneisses. [15] The mugearite occurs in the form of a lava flow, while the hawaiites form volcaniclastic deposits as tuff breccias [16] and lapilli tuffs. [17] Moraine debris and talus cover exposed rocks. [7]
Mount Petras is part of the volcanic province of Marie Byrd Land, which may be a product of a mantle plume. Other volcanoes in this province of West Antarctic volcanoes are the Ames Range, Crary Mountains, Executive Committee Range, Flood Range, Hobbs Coast nunataks, Kohler Range, Mount Murphy, Mount Siple, Mount Takahe and Mount Waesche. Some of these volcanoes are still active today. [11] Marie Byrd Land itself is a crustal dome, with its "summit" in the area of Mount Petras; the dome was probably formed by the impingement of the mantle plume under the crust [18] and volcanism may have spread outwards away from Mount Petras. [3]
Argon-argon dating has yielded ages of 36 and 29-27 million years for the volcanic rocks, making them the oldest in Marie Byrd Land. [19] The volcano probably formed at the surface, perhaps in contact with an early Oligocene ice sheet [1] or more likely mountain glaciers, [20] as the rocks display evidence that the volcanic eruptions took place in shallow water, most likely meltwater. [21] The basement rocks have yielded Cretaceous ages [11] and contain zircons of Devonian-Carboniferous age, [14] with some rocks reaching ages of 1364 million years. [22]
The volcanic history of Mount Petras is important for reconstructing the volcanic and glacial history of Marie Byrd Land. [1] During the late Cretaceous and Eocene-late Cenozoic, continental rifting occurred in the Ross Sea and West Antarctic Ice Sheet area. Beginning with the Oligocene, an ice sheet began to develop in Antarctica and acquired present-day dimensions during the Miocene or Pliocene. [11]
Mount Petras was discovered during the 1939-1941 United States Antarctic Service Expedition and named after the pilot of the expedition. [5] It was visited in 1959, 1967–1968, 1977-1978 and 1993-1994 by field expeditions. [23] During the 20th century, Mount Petras was viewed as a volcano that had formed deep under ice on a Cenozoic marine erosion surface covering West Antarctica, which had then been deformed by tectonic uplift. [1]
Marie Byrd Land (MBL) is an unclaimed region of Antarctica. With an area of 1,610,000 km2 (620,000 sq mi), 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 century.
The Royal Society Range is a mountain range in Victoria Land, Antarctica. With its summit at 4,025 metres (13,205 ft), the massive Mount Lister forms the highest point in this range. Mount Lister is located along the western shore of McMurdo Sound between the Koettlitz, Skelton and Ferrar glaciers. Other notable local terrain features include Allison Glacier, which descends from the west slopes of the Royal Society Range into Skelton Glacier.
Mount Hampton is a shield volcano with a circular ice-filled caldera. It is a twin volcano with Whitney Peak to the northwest and has erupted phonolite rocks. It is the northernmost of the volcanoes which comprise the Executive Committee Range in Marie Byrd Land, Antarctica and was active during the Miocene.
Mount Melbourne is a 2,733-metre-high (8,967 ft) ice-covered stratovolcano in Victoria Land, Antarctica, between Wood Bay and Terra Nova Bay. It is an elongated mountain with a summit caldera filled with ice with numerous parasitic vents; a volcanic field surrounds the edifice. Mount Melbourne has a volume of about 180 cubic kilometres (43 cu mi) and consists of tephra deposits and lava flows; tephra deposits are also found encased within ice and have been used to date the last eruption of Mount Melbourne to 1892 ± 30 years. The volcano is fumarolically active.
Mount Morning is a shield volcano at the foot of the Transantarctic Mountains in Victoria Land, Antarctica. It lies 100 kilometres (62 mi) from Ross Island. Mount Morning rises to an elevation of 2,723 metres (8,934 ft) and is almost entirely mantled with snow and ice. A 4.1 by 4.9 kilometres wide summit caldera lies at the top of the volcano and several ice-free ridges such as Hurricane Ridge and Riviera Ridge emanate from the summit. A number of parasitic vents mainly in the form of cinder cones dot the mountain.
Mount Moulton is a 40-kilometre-long (25 mi) complex of ice-covered shield volcanoes, standing 25 kilometres (16 mi) east of Mount Berlin in the Flood Range, Marie Byrd Land, Antarctica. It is named for Richard S. Moulton, chief dog driver at West Base. The volcano is of Pliocene age and is presently inactive.
Mount Sidley is the highest dormant volcano in Antarctica, a member of the Volcanic Seven Summits, with a summit elevation of 4,181–4,285 metres (13,717–14,058 ft). It is a massive, mainly snow-covered shield volcano which is the highest of the five volcanic mountains that comprise the Executive Committee Range of Marie Byrd Land. The feature is marked by a 5 km wide caldera on the southern side and stands NE of Mount Waesche in the southern part of the range.
Mount Takahe is a 3,460-metre-high (11,350 ft) snow-covered shield volcano in Marie Byrd Land, Antarctica, 200 kilometres (120 mi) from the Amundsen Sea. It is a c. 30-kilometre-wide (19 mi) mountain with parasitic vents and a caldera up to 8 kilometres (5 mi) 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 780 km3 (200 cu mi), 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.
Toney Mountain is an elongated snow-covered shield volcano, 60 km (37 mi) long and rising to 3,595 m (11,795 ft) at Richmond Peak, located 56 km (35 mi) southwest of Kohler Range in Marie Byrd Land, Antarctica.
Mount Waesche is a mountain of volcanic origin at the southern end of the Executive Committee Range in Marie Byrd Land, Antarctica. It is 3,292 metres (10,801 ft) high, and stands 20 kilometres (12 mi) southwest of Mount Sidley, the highest volcano in Antarctica. The mountain lies southwest of the Chang Peak caldera and is largely covered with snow and glaciers, but there are rock exposures on the southern and southwestern slopes.
The Pleiades are a volcanic group in northern Victoria Land of Antarctica. It consists of youthful cones and domes with Mount Atlas/Mount Pleiones, a small stratovolcano formed by three overlapping cones, being the dominant volcano and rising 500 m (1,600 ft) above the Evans Névé plateau. Two other named cones are Alcyone Cone and Taygete Cone, the latter of which has been radiometrically dated to have erupted during the Holocene. A number of tephra layers across Antarctica have been attributed to eruptions of this volcanic group, including several that may have occurred within the last few hundred years.
Crary Mountains are a group of ice-covered volcanoes in Marie Byrd Land, Antarctica. They consist of two or three shield volcanoes, named Mount Rees, Mount Steere and Mount Frakes, which developed during the course of the Miocene and Pliocene and last erupted about 30,000-40,000 years ago. The first two volcanoes are both heavily incised by cirques, while Mount Frakes is better preserved and has a 4 kilometres (2.5 mi) wide caldera at its summit. Boyd Ridge is another part of the mountain range and lies southeast of Mount Frakes; it might be the emergent part of a platform that underlies the mountain range.
Mount Siple is a potentially active Antarctic shield volcano, rising to 3,110 metres (10,203 ft) and dominating the northwest part of Siple Island, which is separated from the Bakutis Coast, Marie Byrd Land, by the Getz Ice Shelf. Its youthful appearance strongly suggests that it last erupted in the Holocene. It is capped by a 4-by-5-kilometre summit caldera, and tuff cones lie on the lower flanks. Recely Bluff is on the northeast slope of the mountain, about 7 nautical miles (13 km) from the peak. Its volume of 1,800 cubic kilometres (430 cu mi) is comparable to that of Mount Erebus.
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 base of the Antarctic Peninsula. It has an estimated length of 3,000 km (1,900 mi) and a width of approximately 700 km (430 mi). Its evolution is due to lithospheric thinning of an area of Antarctica that resulted in the demarcation of East and West Antarctica. The scale and evolution of the rift system has been compared to that of the Basin and Range Province of the Western United States.
Berry Glacier is an Antarctic glacier, about 25 miles (40 km) long and 5 miles (8 km) wide, draining north between Perry Range and Demas Range into the Getz Ice Shelf on the coast of Marie Byrd Land. This vicinity was first photographed and rudely charted from aircraft of the U.S. Antarctic Service in December 1940, and the glacier was mapped in detail by the U.S. Geological Survey from ground surveys and from U.S. Navy air photos, 1959–66. It was named by the Advisory Committee on Antarctic Names for Commander William H. Berry, U.S. Navy, Air Operations Officer for Task Force 43 during Operation Deep Freeze 1969–72; Operations Officer, 1973.
The Erebus hotspot is a volcanic hotspot responsible for the high volcanic activity on Ross Island in the western Ross Sea of Antarctica. Its current eruptive zone, Mount Erebus, has erupted continuously since its discovery in 1841. Magmas of the Erebus hotspot are similar to those erupted from hotspots at the active East African Rift in eastern Africa. Mount Bird at the northernmost end of Ross Island and Mount Terror at its eastern end are large basaltic shield volcanoes that have been potassium-argon dated 3.8–4.8 and 0.8–1.8 million years old.
Mount Rees is a 2,709 metres (8,888 ft) mountain located 7 nautical miles (13 km) northwest of Mount Steere in the northern end of Crary Mountains, Marie Byrd Land. It was mapped by the U.S. Geological Survey from ground surveys and U.S. Navy air photos, 1959–66, and was named for Manfred H. Rees, aurora scientist at Byrd Station during the 1965–66 season.
The Marie Byrd Land Volcanic Province is a volcanic field in northern Marie Byrd Land of West Antarctica, consisting of over 18 large shield volcanoes, 30 small volcanic centres and possibly many more centres buried under the West Antarctic Ice Sheet. It overlies a 500 km (310 mi) wide and 800 km (500 mi) long dome that has formed as a result of fault blocking within the West Antarctic Rift System.
Mount Berlin is a 3,478-metre (11,411 ft) high glacier-covered volcano in Marie Byrd Land, Antarctica, 100 kilometres (62 mi) from the Amundsen Sea. It is a about 20-kilometre-wide (12 mi) mountain with parasitic vents that consists of two coalesced volcanoes: Berlin proper with the 2-kilometre-wide (1.2 mi) Berlin Crater and Merrem Peak with a 2.5-by-1-kilometre-wide crater, 3.5 kilometres (2.2 mi) away from Berlin. It has a volume of 200 cubic kilometres (48 cu mi) and rises from the West Antarctic Ice Sheet. It is part of the Marie Byrd Land Volcanic Province. Trachyte is the dominant volcanic rock and occurs in the form of lava flows and pyroclastic rocks.
The Hudson Mountains are a mountain range in western Ellsworth Land just east of Pine Island Bay at the Walgreen Coast of the Amundsen Sea. They are of volcanic origin, consisting of low scattered mountains and nunataks that protrude through the West Antarctic Ice Sheet. The Hudson Mountains are bounded on the north by Cosgrove Ice Shelf and on the south by Pine Island Glacier. The mountains were volcanically active during the Miocene and Pliocene, but there is evidence for an eruption about two millennia ago and uncertain indications of activity in the 20th century.