The James Ross Island Volcanic Group is a

stratigraphic unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize it ...

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...

age distributed on

James Ross Island James Ross Island is a large island off the southeast side and near the northeastern extremity of the Antarctic Peninsula, from which it is separated by Prince Gustav Channel. Rising to , it is irregularly shaped and extends in a north–south ...

and

Vega Island Vega Island is a small island to the northwest of James Ross Island, on the Antarctic Peninsula. It is separated from James Ross Island by Herbert Sound. The island was named by Otto Nordenskjold, leader of the Swedish Antarctic Expedition (190 ...

of the

James Ross Island group The James Ross Island group is a group of islands located close to the northeastern tip of the Antarctic Peninsula. The largest islands in the group are James Ross Island, Snow Hill Island, Vega Island, and Seymour Island. The islands lie to ...

, the

Tabarin Tabarin was the street name assumed by the most famous of the Parisian street charlatans, Anthoine Girard (c. 1584 – August 16, 1633), who amused his audiences in the Place Dauphine by farcical dialogue with his brother Philippe (as Mondo ...

and

Trinity The Christian doctrine of the Trinity (, from 'threefold') is the central dogma concerning the nature of God in most Christian churches, which defines one God existing in three coequal, coeternal, consubstantial divine persons: God the F ...

peninsulas of

Graham Land Graham Land is the portion of the Antarctic Peninsula that lies north of a line joining Cape Jeremy and Cape Agassiz. This description of Graham Land is consistent with the 1964 agreement between the British Antarctic Place-names Committee and ...

and surrounding islands in the Prince Gustav and

Antarctic The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...

sounds. The

volcanic group A volcanic group is a stratigraphic group consisting of volcanic strata. They can be in the form of volcanic fields, volcanic complexes and cone A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequ ...

consists predominantly of

alkali basalt Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields. Alkali basalt ...

s with minor

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 ...

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 ...

s and

mugearite Mugearite () is a type of oligoclase-bearing basalt, comprising olivine, apatite, and opaque oxides. The main feldspar in mugearite is oligoclase. Mugearite is a sodium-rich member of the alkaline magma series. In the TAS classification of volc ...

s. They are interpreted to have been deposited by volcanic eruptions in an

extensional In any of several fields of study that treat the use of signs — for example, in linguistics, logic, mathematics, semantics, semiotics, and philosophy of language — an extensional context (or transparent context) is a syntactic environment in w ...

back-arc A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most of ...

setting after

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

had ceased along the western margin of the

Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctic ...

K–Ar dating Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Potassium ...

of these rocks suggest that they were erupted from about 7 million years ago up until about a few hundred thousand years ago. However,

volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic r ...

s as young as only a few thousand years old may exist on James Ross Island. Rocks of the James Ross Island Volcanic Group comprise Surtseyan

tuff cone Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...

s and Strombolian

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, as well as

lava delta Lava deltas, similar to river deltas, form wherever sufficient sub-aerial flows of lava enter standing bodies of water. The lava cools and breaks up as it encounters the water, with the resulting fragments filling in the adjacent seabed topography ...

s and overlying subaerial lava flows. The dominating feature of the James Ross Island Volcanic Group is

Mount Haddington Mount Haddington is a massive high shield volcano comprising much of James Ross Island in Graham Land, Antarctica. It is wide and has had numerous subglacial eruptions throughout its history, forming many tuyas. Some of its single eruptions w ...

, a massive

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 ...

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

-to-

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

Subdivisions

The James Ross Island Volcanic Group includes the following

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

s: *Cape Lachman Formation *Cape Well-met Formation *Dobson Dome Formation *Donnachie Cliffs Formation *Ekelof Point Formation *Forster Cliffs Formation *Hamilton Formation *Jefford Point Formation *Johnson Mesa Formation *Jonkers Mesa Formation *Keltie Head Formation *Kipling Mesa Formation *Lachman Crags Formation *Lookalike Peaks Formation *Palisade Nunatak Formation *Patalamon Mesa Formation *Sandwich Bluff Formation *Smellie Peak Formation *Stickle Ridge Formation *Sungold Hill Formation *Taylor Bluff Formation *Terrapin Hill Formation *Tumbledown Formation *Vertigo Cliffs Formation

Features

The James Ross Island Volcanic Group includes the following volcanic features: * Abel Nunatak *

Andersson Island Andersson Island is a long and wide volcanic island of the James Ross Island Volcanic Group, located at the eastern end of the Tabarin Peninsula, Antarctica. The island was originally named Uruguay Island by the Swedish Antarctic Expedition, 1 ...

Brown Bluff Brown Bluff is a basalt tuya on the Tabarin Peninsula of northern Antarctica. It formed in the last 1 million years as a result of subglacial eruptions within an englacial lake. The volcano's original diameter is thought to have been about ...

Buttress Hill Buttress Hill () is a flat-topped hill, high, with steep rock cliffs on the west side, standing east of the most northern of the Seven Buttresses on Tabarin Peninsula in the northeastern extremity of the Antarctic Peninsula. It is an inferred vo ...

* Cain Nunatak * Carlson Island * Cockburn Island *

Corry Island Corry Island is an island long and high, lying off the south coast of the Trinity Peninsula between Vega Island and Eagle Island. This is believed to be the feature sighted by a British expedition under James Clark Ross, 1839–43, and named ...

Devil Island Devil Island is a 128 ha, ice-free island about 2 km long, in the James Ross Island group near the north-eastern tip of the Antarctic Peninsula. It lies in a small cove 1 km north of Vega Island, east of the Trinity Peninsula. ...

Dobson Dome Dobson Dome () is a prominent snow-covered, dome-shaped mountain high between Rohss Bay and Croft Bay, in the northern portion of James Ross Island. It was surveyed by the Falkland Islands Dependencies Survey of 1958–61, and it was named by the ...

Donnachie Cliff Donnachie Cliff () is a cliff on Ulu Peninsula, James Ross Island, rising to about northeast of Back Mesa. Following geological work by the British Antarctic Survey, 1985–86, it was named by the UK Antarctic Place-Names Committee after Thomas D ...

* Eagle Island ** Scree Peak * Egg Island * False Island Point *

Flett Buttress Flett Buttress () is a rock crag rising to northwest of Mount Haddington on James Ross Island. It provides the highest exposure of volcanic rock on the island. It was named by the UK Antarctic Place-Names Committee in 1987 after William R. Flett, ...

Förster Cliffs James Ross Island is a large island off the southeast side and near the northeastern extremity of the Antarctic Peninsula, from which it is separated by Prince Gustav Channel. Rising to , it is irregularly shaped and extends in a north–south ...

* Gamma Hill * Cape Gordon *Mount Haddington * Jonassen Island *

Keltie Head Keltie Head () is a rounded headland with vertical cliffs which rise to a small ice dome high, forming the northwestern end of Vega Island, south of Trinity Peninsula, Antarctica. It was discovered by the Swedish Antarctic Expedition under Otto N ...

* Lachman Crags * Léal Bluff *

Lockyer Island Lockyer Island is an island 2.5 mi long, lying off the south shore of James Ross Island in the SW entrance to Admiralty Sound in Antarctica. Named Cape Lockyer by Capt. James Clark Ross, Jan. 7, 1843, at the request of Capt. Francis R.M. ...

Lomas Ridge James Ross Island is a large island off the southeast side and near the northeastern extremity of the Antarctic Peninsula, from which it is separated by Prince Gustav Channel. Rising to , it is irregularly shaped and extends in a north–south ...

* Mahogany Bluff *

Cone Nunatak Cone Nunatak () is a nunatak, high, which appears conical on its north side but has brown rock cliffs on its south face, lying south-southeast of Buttress Hill on the Tabarin Peninsula, at the northeast extremity of the Antarctic Peninsula. I ...

* Organpipe Nunatak *

Palisade Nunatak Ulu Peninsula () is that portion of James Ross Island northwest of the narrow neck of land between Rohss Bay and Croft Bay, extending from Cape Obelisk to Cape Lachman. Named descriptively by the United Kingdom Antarctic Place-Names Committee (UK-AP ...

Paulet Island Paulet Island is a circular island about in diameter, lying south-east of Dundee Island, off the north-eastern end of the Antarctic Peninsula. Because of its large penguin colony, it is a popular destination for sightseeing tours. Descripti ...

* Persson Island * Cape Purvis *

Red Island Red Island may refer to: * Red Island, Newfoundland and Labrador * Red Island, Queensland * Red Island (Antarctica) * Red Island (Grenadines), in St Vincent and the Grenadines * Red Island Holiday Camp, in Ireland *Rhode Island, meaning red island * ...

* Rosamel Island *

Sandwich Bluff Sandwich Bluff () is a flat-topped mountain, 610 m, broken sharply at its west side by a steep dark bluff standing slightly west of center on Vega Island in the James Ross Island group. Discovered by the Swedish Antarctic Expedition The Swedish ...

* Seacatch Nunataks *

Sentinel Buttress Sentinel Buttress () is a prominent crag containing a volcanic breccia sequence, rising to 535 m east of Palisade Nunatak at the head of Rohss Bay, James Ross Island. So named by the United Kingdom Antarctic Place-Names Committee The UK Antarctic ...

Stark Point Stark Point () is a rocky point on the east side of Croft Bay, northern James Ross Island. It is formed by almost vertical cliffs which rise from the sea to 285 meters. Surveyed by Falkland Islands Dependencies Survey (FIDS) in August 1953. The desc ...

* Stickle Ridge * Sungold Hill * Tail Island * Terrapin Hill * Tongue Rocks * Virgin Hill * Vortex Island

References

{{reflist Volcanoes of Graham Land Miocene volcanoes Pliocene volcanoes Pleistocene volcanoes Volcanic groups Geologic formations of Antarctica

Subdivisions

Features

See also

References