The Scotia Plate (Spanish: Placa Scotia) is a tectonic plate on the edge of the South Atlantic and Southern Ocean. Thought to have formed during the early Eocene with the opening of the Drake Passage that separates South America from Antarctica, it is a minor plate whose movement is largely controlled by the two major plates that surround it: the South American Plate and Antarctic Plate.
Roughly rhomboid, extending between South Sandwich Plate is moving east at 5.5 cm (2.2 in)/year in an absolute reference frame. It takes its name from the steam yacht Scotia of the Scottish National Antarctic Expedition (1902–04), the expedition that made the first bathymetric study of the region.and , the plate is 800 km (500 mi) wide and 3,000 km (1,900 mi) long. It is moving WSW at 2.2 cm (0.87 in)/year and the
The Scotia Plate is made of oceanic crust and continental fragments now distributed around the Scotia Sea. Before the formation of the plate began (40Ma), these fragments formed a continuous landmass from Patagonia to the Antarctic Peninsula along an active subduction margin. At present the plate is almost completely submerged, with only the small exceptions of the South Georgia Islands on its northeastern edge and the southern tip of South America.
|Approximate area||1,651,000 km2 (637,000 sq mi)|
|Features||Scotia Sea, South Georgia, Drake Passage|
|1Relative to the African Plate|
Together with the Sandwich Plate, the Scotia Plate joins the southernmost Andes to the Antarctic Peninsula, just like the Caribbean Plate joins the northernmost Andes to North America, and these two plates are comparable in several ways. Both have volcanic arcs at their eastern ends, the South Sandwich Islands on the Sandwich Plate and the Lesser Antilles on the Caribbean Plate, and both plates also had a major impact on global climate when they closed the two major gateways between the Pacific and Atlantic Oceans during the Mesozoic and Cenozoic.
The northern edge of the Scotia Plate is bounded by the South American Plate, forming the North Scotia Ridge. The North Scotia ridge is a left-lateral, or sinistral, transform boundary with a transform rate of roughly 7.1 mm/yr. The Magallanes–Fagnano Fault is passing through Tierra del Fuego.
The northern ridge stretches from Isla de los Estados off Tierra del Fuego in the west to the microcontinent South Georgia in the east, with a series of shallow banks in between: Burdwood, Davis, Barker, and Shag Rocks. North of the ridge is the 3 km (1.9 mi) deep Falkland Trough.
Experts in plate tectonics have been unable to determine whether the South Georgian Islands are part of the Scotia Plate or have been recently accreted to the South American Plate. Surface expressions of the plate boundary are found north of the islands suggesting a long-term presence of the transform fault there. Yet seismic studies have identified strain and thrusting south of the islands indicating the possible shift of the transform fault to an area south of the island. It has also been suggested that the plate bearing the islands may have broken off from the Scotia Plate, forming a new independent South Georgia microplate, yet there is little evidence to make this conclusion.
The South Georgia microcontinent was originally connected to the Roca Verdes back-arc basin (southern-most Tierra del Fuego) until the Eocene. Before that, this basin went through a series of geological transformations during the Cretaceous, through which South Georgia was first buried, then made a topographic feature again by the Late Cretaceous. At about 45 Ma, South Georgia, still part of the South American Plate, got buried again and something, possibly rotation of the Fuegian Andes, completed the break-up and allowed South Georgia a second exhumation. During the Oligocene (34–23 Ma) South Georgia was reburied again as seafloor spreading took place in the West Scotia Sea. 10 Ma, finally, the South Georgia microcontinent was uplifted as a result of the collision with the Northeast Georgia Rise.
The southern edge of the plate is bordered by the Antarctic Plate, forming the South Scotia Ridge, a left-lateral transform boundary sliding at a rate of roughly 7.4–9.5 mm/yr that occupies the southern half of the Antarctic-Scotia plate boundary. The relative motion between the Scotia Plate and the Antarctic Plate on the western boundary is 7.5–8.7 mm/yr. Though the South Scotia Ridge is overall a transform fault, small sections of the ridge are spreading to make up for the somewhat jagged shape of the boundary.
At the eastern tip of the Antarctic Peninsula, the beginning of South Scotia Ridge, a small and heavily dissected bank degenerates into several outcrops dominated by Paleozoic and Cretaceous rocks. A small basin, Powel Basin, separates this cluster from the South Orkney microcontinent composed of Triassic and younger rocks.
The eastern continuation of the ridge, the Scotia Arc east of the South Sandwich Plate, are the South Sandwich island arc and trench. This volcanic active island arc has submerged ancestors in Jane and Discovery banks in the southern ridge.
The western edge of the plate is bounded by the Antarctic Plate, forming the Shackleton Fracture Zone and the southern Chile Trench. The Southern Chile Trench is a southern extension of the subduction of the Antarctic and Nazca plates below South America. Heading south along the ridge, the subduction rate decreases until its remaining oblique motion evolves into the Shackleton Fracture Zone transform boundary. The south-western edge of the plate is bounded by the Shetland microplate separating the Shackleton Fracture Zone and the South Scotia Ridge.
North of South Shetland Islands and along the southern half of the Shackleton Fracture Zone is the remnant of the Phoenix Plate (also known as Drake or Aluk Plate). Around 47 Ma the subduction of the Phoenix Plate started as the propagation of the Pacific-Antarctic Ridge continued. The last collision between Phoenix ridge segments and the subduction zone was 6.5 Ma and at 3.3 Ma movements had stopped and the remnants of the Phoenix Plate was incorporated into the Antarctic Plate. The southern part of the Shackleton Fracture Zone is the former eastern edge of the Phoenix Plate.
The eastern edge of the Scotia Plate is a spreading ridge bounded by the South Sandwich microplate, forming the East Scotia Ridge. The East Scotia Ridge is a back-arc spreading ridge that formed due to subduction of the South American Plate below the South Sandwich Plate along the South Sandwich Island arc. Exact spreading rates are still being disputed in the literature, but it has been agreed that rates range between 60–90 mm/yr.
The banks of northern Central Scotia Sea are superposed on oceanic basement and the spreading centre of the West Scotia Sea. Analyses of samples of volcaniclastic rocks from these sites indicate they are constructs of a continental arc and in some cases oceanic arc similar to those being formed in the currently active South Sandwich Arc. The oldest volcanic arc activity in the central and eastern regions of the Scotia Sea are 28.5 Ma. The South Sandwich forarc originated in the Central Scotia Sea at that time but has since been translated eastward by the back-arc spreading centre of the East Scotia Ridge.
The timing of the formation of the Scotia Plate and opening of the Drake Passage have long been the subject of much debate due to the important implications for changes in ocean currents and shifts in paleoclimate. The thermal isolation of Antarctica, engendering the formation of the Antarctic ice sheet, has largely been attributed to the opening of the Drake Passage.
The Scotia Plate originated about Mesozoic at the Panthalassic margins of the Gondwana supercontinent between two Precambrian cratons, the Kalahari and East Antarctic Cratons, now located in Africa and Antarctica. Its development was also influenced by the Río de la Plata Craton in South America. The initial cause for its formation was the break-up of Gondwana in what became the south-west Indian Ocean.(Ma), during the late
The earliest marine fossils found on the Maurice Ewing Bank, on the eastern end of the Falkland Plateau, are associated with the Indian and Tethys Oceans and probably slightly more than 150 Ma. The Weddell Sea opened and spread along the southern margin of the Falkland Plateau and into the Rocas Verdes back-arc basin which extends from South Georgia and along the Patagonian Andes. Fragments of the inverted oceanic basement of this basin are preserved as ophiolitic complexes in this area, including the Larsen Harbour complex on South Georgia. This makes it possible to restore the original position of the South Georgia microcontinent south of the Burdwood Bank on the western North Scotia Ridge south of the Falkland Islands.
The Rocas Verdes basin was filled with turbidites derived from the volcanic arc on its Pacific margin and partly from its continental margin. The Weddell Sea continued to expand which led to the extension between the Patagonian Andes and the Antarctic Peninsula. In the Mid-Cretaceous (100 Ma) the spreading rate in South Atlantic increased significantly and the Mid-Atlantic Ridge grew from 1200 km to 7000 km. This led to compressional deformations along the western margin of the South American Plate and the obduction of the Rocas Verdes basement onto this margin. Structures associated with this obduction are found from Tierra del Fuego to South Georgia. The acceleration of the westward motion of South America and the inversion of the Rocas Verde Basin finally lead to the initiation of the Scotia Arc. This inversion had a strike-slip component which can be seen in the Cooper Bay dislocation on South Georgia. This geological regime lead to the uplift and elongation of the Andes and the embryonic North Scotia Ridge, which resulted in the initial eastward relocation of the South Georgia microcontinent and formation of the Central Scotia Sea.
Between the Late Cretaceous and the Early Oligocene (90–30 Ma) little changed in the region, except for the subduction of the Phoenix Plate along the Shackleton Fracture Zone. The Late Paleocene and Early Eocene (60–50 Ma) saw the formation of South Scotia Sea and South Scotia Ridge — the first sign of separation of the southern Andes and the Antarctic Peninsula — which resulted in seafloor spreading in the West Scotia Sea and hence the initial opening of a deep Drake Passage. The ongoing lengthening of the North Scotia Ridge beyond the Burdwood Bank caused South Georgia to move further east. The banks of the North Scotia Ridge contain volcanic rocks similar to those found in Tierra del Fuego, including on Isla de los Estados on the easternmost tip.
During the early Eocene (50 Ma), the Drake Passage between the southern tip of South America at Cape Horn and the South Shetland Islands of Antarctica was a small opening with limited circulation. A change in relative motion between the South American Plate and the Antarctic Plate would have severe effects, causing seafloor spreading and the formation of the Scotia Plate. Marine geophysical data indicates that motion between the South American Plate and the Antarctic Plate shifted from N-S to WNW-ESE accompanied by an eightfold increase in the separation rate. This shift in spreading initiated crustal thinning and by 30–34 Ma, the West Scotia Ridge formed.
One of the most prominent features in the Scotia Plate itself is the median valley known as the West Scotia Ridge. It was produced by two plates that are no longer independently active: the Magallanes and Central Scotia Plates. The ridge consists of seven segments separated by right-lateral transform offsets of various lengths. The western region of the Scotia Plate can be dated to 26–5.5 Ma. A complex pattern of spreading prior to 26 Ma is probably present in the oldest parts of this spreading regime; i.e. west of Terror Rise (north of Elephant Island) and on the shelf slope of Tierra del Fuego. Until 17 Ma the Central Scotia Plate moved quickly eastwards, fuelled by the eastern trench migration, but both plates have moved very slowly since.
The Andes or Andean Mountains (Spanish: Cordillera de los Andes) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The Andes also have the 2nd most elevated highest peak of any mountain range, only behind the Himalayas. The range is 7,000 km (4,300 mi) long, 200 to 700 km (120 to 430 mi) wide (widest between 18° south and 20° south latitude), and has an average height of about 4,000 m (13,000 ft). The Andes extend from north to south through seven South American countries: Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile and Argentina.
Along their length, the Andes are split into several ranges, separated by intermediate depressions. The Andes are the location of several high plateaus – some of which host major cities such as Quito, Bogotá, Cali, Arequipa, Medellín, Bucaramanga, Sucre, Mérida and La Paz. The Altiplano plateau is the world's second-highest after the Tibetan plateau. These ranges are in turn grouped into three major divisions based on climate: the Tropical Andes, the Dry Andes, and the Wet Andes.
The Andes Mountains are the highest mountain range outside Asia. The highest mountain outside Asia, Argentina's Mount Aconcagua, rises to an elevation of about 6,961 m (22,838 ft) above sea level. The peak of Chimborazo in the Ecuadorian Andes is farther from the Earth's center than any other location on the Earth's surface, due to the equatorial bulge resulting from the Earth's rotation. The world's highest volcanoes are in the Andes, including Ojos del Salado on the Chile-Argentina border, which rises to 6,893 m (22,615 ft).
The Andes are also part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that form the western "backbone" of North America, Central America, South America and Antarctica.Antarctic Plate
The Antarctic Plate is a tectonic plate containing the continent of Antarctica, the Kerguelen Plateau and extending outward under the surrounding oceans. After breakup from Gondwana (the southern part of the supercontinent Pangea), the Antarctic plate began moving the continent of Antarctica south to its present isolated location causing the continent to develop a much colder climate. The Antarctic Plate is bounded almost entirely by extensional mid-ocean ridge systems. The adjoining plates are the Nazca Plate, the South American Plate, the African Plate, the Somali Plate, the Indo-Australian Plate, the Pacific Plate, and, across a transform boundary, the Scotia Plate.
The Antarctic Plate has an area of about 60,900,000 km2 (23,500,000 sq mi). It is the Earth's fifth-largest plate.
The Antarctic Plate's movement is estimated to be at least 1 cm (0.4 in) per year towards the Atlantic OceanBransfield Basin
The Bransfield Basin is a back-arc rift basin located off the Northern tip of the Antarctic Peninsula. The basin lies within a Northeast and Southwest trending strait that separates the peninsula from the nearby South Shetland Islands to the Northwest. The basin extends for more than 500 kilometres (310 miles) from Smith Island (South Shetland Islands) to a portion of the Hero Fracture Zone. The basin can be subdivided into three basins: Western, Central, and Eastern. The Western basin is 130 kilometres (81 miles) long by 70 kilometres (43 miles) wide with a depth of 1.3 kilometres (1,400 yards), the Central basin is 230 kilometres (140 miles) long by 60 kilometres (37 miles) wide with a depth of 1.9 kilometres (2,100 yards), and the Eastern basin is 150 kilometres (93 miles) long by 40 kilometres (25 miles) wide with a depth of over 2.7 kilometres (3,000 yards). The three basins are separated by the Deception Island and Bridgeman Island. The moho depth in the region has been seismically interpreted to be roughly 34 kilometres (21 miles) deep.Fueguino
Fueguino is a volcanic field in Chile. The southernmost volcano in the Andes, it lies on Tierra del Fuego's Cook Island and also extends over nearby Londonderry Island. The field is formed by lava domes, pyroclastic cones, and a crater lake.
Volcanic activity at Fueguino is part of the Austral Volcanic Zone, which is formed by the subduction of the Antarctic Plate beneath the South America Plate. The subducting plate has not reached a depth sufficient for proper volcanic arc volcanism, however.
The field bears no trace of glacial erosion on its volcanoes, and reports exist of volcanic activity in 1712, 1820 and 1926.Geology of Chile
The geology of Chile is a characterized by processes linked to subduction such as volcanism, earthquakes and orogeny. The buildings blocks of Chile's geology assembled during the Paleozoic Era. Chile was by then the southwestern margin of the supercontinent Gondwana. In the Jurassic Gondwana begun to split and the ongoing period of crustal deformation and mountain building known as the Andean orogeny begun. In the Late Cenozoic Chile definitely separated from Antarctica, the Andes expienced a great rise accomplained by a cooling climate and the onset of glaciations.
The subduction interactions shaped four main morphostructures of Chile: the Andes; the Intermediate Depression, the Coast Range, and the Peru–Chile Trench off the coast. Since Chile is on an active continental margin, it has many volcanoes. Almost the entire country is subject to earthquakes arising from strains in the Nazca and Antarctic Plates or shallow strike-slip faults. Northern Chilean mineral resources are a major economic resources, and the country is the leading producer of copper, lithium and molybdenum. Most of these mineral deposits were created from magmatic hydrothermal activity. The water required to form those deposits derived from the subducted slab of the oceanic crust beneath the Andes.
The Chilean Easter Island and Juan Fernández Archipelago are volcanic hotspot islands in the eastward-moving Nazca plate. The geology of the Chilean Antarctic Territory has various commonalities with that of mainland Chile.List of tectonic plates
This is a list of tectonic plates on the Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of material: oceanic crust (also called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). The composition of the two types of crust differs markedly, with mafic basaltic rocks dominating oceanic crust, while continental crust consists principally of lower-density felsic granitic rocks.Magallanes-Fagnano Fault
The Magallanes–Fagnano Fault (Spanish: Falla Fagnano–Magallanes) is a continental transform fault. The fault marks a transform boundary between the Scotia Plate and the South American Plate, cutting across continental crust. It runs under the Strait of Magellan's western arm, Almirantazgo Sound and Fagnano Lake.
It has been suggested that the Magallanes-Fagnano Fault is a reactivated suture of pre-Jurassic age separating the basement of two terranes.Malvinas Basin
The Malvinas Basin (Spanish: Cuenca de Malvinas) is a major sedimentary basin in the Argentine Shelf offshore southern Patagonia. The basin borders to the west with the Río Chico-Dungeness High that separates it from the Magallanes Basin. The southern boundary is formed by the Scotia plate boundary. Contrary to the neighbouring North Falkland and Magallanes Basins, the Malvinas Basin is not known to have commercial hydrocarbon reserves.Monte Burney
Monte Burney is a volcano in southern Chile, part of its Austral Volcanic Zone which consists of six volcanoes with activity during the Quaternary. This volcanism is linked to the subduction of the Antarctic Plate beneath the South America Plate and the Scotia Plate.
Monte Burney is formed by a caldera with a glaciated stratovolcano on its rim. This stratovolcano in turn has a smaller caldera. An eruption is reported for 1910, with less certain eruptions in 1970 and 1920.
Tephra analysis has yielded evidence for many eruptions during the Pleistocene and Holocene, including two large explosive eruptions during the early and mid-Holocene. These eruptions deposited significant tephra layers over Patagonia and Tierra del Fuego.Scotia
Scotia is a Latin placename derived from Scoti, a Latin name for the Gaels, first attested in the late 3rd century. ). From the 9th century, its meaning gradually shifted, so that it came to mean only the part of Britain lying north of the Firth of Forth: the Kingdom of Scotland. By the later Middle Ages it had become the fixed Latin term for what in English is called Scotland.
The Romans referred to Ireland as "Scotia" around 500 A.D.Scotia (disambiguation)
Scotia is an ancient name for Scotland.Scotia Sea
The Scotia Sea is a sea located at the northern edge of the Southern Ocean at its boundary with the South Atlantic Ocean. It is bounded on the west by the Drake Passage and on the north, east, and south by the Scotia Arc, an undersea ridge and island arc system supporting various islands. The sea sits atop the Scotia Plate. It is named after the expedition ship Scotia.Shackleton Fracture Zone
The Shackleton Fracture Zone (abbreviated as SFZ) is an undersea fracture zone and fault located in the Drake Passage, at the separation between the Scotia Plate from the Antarctic Plate. The Shackleton Fracture Zone runs in a northwest to southeast direction from the South American continental shelf to the South Shetland Islands.Shetland Plate
The Shetland Plate is a tectonic microplate located off the tip of the Antarctic Peninsula and contains the South Shetland Islands. The plate is bordered on three sides by the Antarctic Plate and the fourth side is bordered by the Scotia Plate. The northwestern border is defined by the South Shetland Trench separating the Shetland Plate to the south from the Antarctic Plate to the north. This trench is the remnant of a subduction zone where the defunct Phoenix Plate, now part of the Antarctic Plate, subducted under the Antarctic Peninsula and the Shetland Islands. The southeastern border is rift zone with the Antarctic Plate creating the Bransfield Basin. The southwestern and northeastern boundaries are each part of larger fracture zones. The southwestern border is the Hero Fracture Zone and separates the Antarctic Plate to the southwest from the Shetland Plate to the northeast. The northeastern boundary is the Shackleton Fracture Zone and separates the Shetland Plate to the southwest from the Scotia Plate.South American Plate
The South American Plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African Plate, with which it forms the southern part of the Mid-Atlantic Ridge.
The easterly edge is a divergent boundary with the African Plate; the southerly edge is a complex boundary with the Antarctic Plate, the Scotia Plate, and the Sandwich Plate; the westerly edge is a convergent boundary with the subducting Nazca Plate; and the northerly edge is a boundary with the Caribbean Plate and the oceanic crust of the North American Plate. At the Chile Triple Junction, near the west coast of the Taitao–Tres Montes Peninsula, an oceanic ridge known as the Chile Rise is actively subducting under the South American Plate.
Geological research suggests that the South American Plate is moving westward away from the Mid-Atlantic Ridge: "Parts of the plate boundaries consisting of alternations of relatively short transform fault and spreading ridge segments are represented by a boundary following the general trend." As a result, the eastward-moving and more dense Nazca Plate is subducting under the western edge of the South American Plate, along the continent's Pacific coast, at a rate of 77 mm (3.0 in) per year. The collision of these two plates is responsible for lifting the massive Andes Mountains and for creating the numerous volcanoes which are strewn throughout them.South American–Antarctic Ridge
The South American–Antarctic Ridge (SAAR or AAR) is the tectonic spreading center between the South American Plate and the Antarctic Plate. It runs along the sea-floor from the Bouvet Triple Junction in the South Atlantic Ocean south-westward to a major transform fault boundary east of the South Sandwich Islands. Near the Bouvet Triple Junction the spreading half rate is 9 mm/a (0.35 in/year), which is slow, and the SAAR has the rough topography characteristic of slow-spreading ridges.South Sandwich Plate
The South Sandwich Plate or Sandwich Plate is a minor tectonic plate bounded by the subducting South American Plate to the east, the Antarctic Plate to the south and the Scotia Plate to the west. The plate is separated from the Scotia Plate by the East Scotia Rise, a back arc spreading ridge formed by the subduction zone on its eastern margin.
The South Sandwich Islands are located on this small plate.Territorial claims in Antarctica
There are seven sovereign states who have territorial claims in Antarctica: Argentina, Australia, Chile, France, New Zealand, Norway and the United Kingdom. These countries have tended to place their Antarctic scientific observation and study facilities within their respective claimed territories; however, a number of such facilities are located outside of the area claimed by their respective countries of operation, and countries without claims such as Russia and the United States have constructed research facilities within the areas claimed by other countries.West Scotia Basin
The West Scotia Basin is a submarine basin in the South Atlantic Ocean, near its border with the Southern Ocean. The basin is found southeast of Tierra del Fuego, south of the Falkland Islands, and northeast of the Antarctic Peninsula. It forms the western portion of the Scotia Plate.
Tectonics of South America
|Faults and rift zones|