Shetland Plate | |
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![]() Shetland Plate shaded in red. | |
Type | Minor |
Coordinates | 62°10′S61°00′W / 62.167°S 61.000°W |
Movement1 | Northwest |
Speed1 | 1 to 2 cm (0.39 to 0.79 in)/yr |
Features | South Shetland Islands, Southern Ocean |
1Relative to the African Plate |
The Shetland Plate, or South Shetland Plate, is a tectonic microplate located off the tip of the Antarctic Peninsula that contains the South Shetland Islands. [1] The plate is bordered on three sides by the Antarctic Plate, while 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 a rift zone, with the Antarctic Plate creating the Bransfield Basin. [2] 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. [1]
The Shetland Plate started forming 3 to 4 million years ago. [2] Prior to formation, the Shetland Plate was part of the Antarctic Plate adjacent to the Antarctic Peninsula. During this period, the Phoenix Plate to the northwest, was subducting under the Antarctic Peninsula and the South Shetland Islands, which created the South Shetland Trench. [3] Approximately 3 million years ago spreading stopped at the Antarctic-Phoenix spreading center in Drake Passage. The Phoenix Plate is now considered part of the larger Antarctic Plate due to a lack of relative movement between the two since spreading ceased. [3] However, subduction in the South Shetland Trench did not cease. Slab rollback of the former Phoenix Plate underneath the South Shetland Islands caused rifting to develop in the Antarctic Peninsula creating the Shetland Plate and the Bransfield Basin. Rifting centers in the Bransfield Basin continue to separate the Shetland Plate from the Antarctic Peninsula. [4]
The South Shetland Trench forms the northwest border of the Shetland Plate. The trench is formed by the subduction of the Antarctic Plate in the north under the Shetland Plate in the south. [2] Subduction along this trench has slowed significantly over time, from 4 to 6 centimetres (1.6 to 2.4 in) per year over the last 30 million years to 1 to 2 centimetres (0.39 to 0.79 in) per year in the last 6 million years. [3] [5] Current subduction is caused by the movement of the Shetland Plate northward, as well as, slab rollback of the former Phoenix Plate.
The Bransfield Basin forms the southeast border of the Shetland Plate. The basin separates the Shetland Plate on the north and the Antarctic Plate to the south. The basin is a back-arc rift basin. [2] The basin ranges from 1,300 metres (4,300 ft) to more than 2,700 metres (8,900 ft) deep. [6]
The Shackleton Fracture Zone is the northeast border of the Shetland Plate. [5] The fracture zone is a series of parallel transform faults separating the Scotia Plate from the Shetland Plate. This border with the Scotia Plate is the only Shetland Plate boundary that is not with the Antarctic Plate. [2]
The Hero Fracture Zone is the southwest boundary of the Shetland Plate. This feature separates the Shetland Plate from the Antarctic Plate. These parallel faults connect the Bransfield Basin in the south to the South Shetland Trench in the north. [5]
Absolute K-Ar ages indicate volcanism has been active from the Cenozoic to the present. Current volcanism can be seen at Deception Island and Penguin Island. Plutons of calc-alkaline compositions, formed from a type of magma created above subduction zones, date from the Cenozoic to the Miocene and is coincident with the active subduction of the Phoenix plate under Antarctica. More recent Pliocene dated volcanism in the Bransfield basin has transitional chemistry between subduction zone calc-alkaline and mid ocean ridge tholeiitic magmas. The transitional chemistry can be explained by back-arc rifting in the Bransfield Basin. [7] [8]
Since the early 1980s, earthquakes have been recorded in the Shetland Plate. The amount of data has been limited by remoteness, severe weather, and a lack of permanent seismic stations in the area. [8] [9] Intermediate depth earthquakes (35–55 km) under the South Shetland Islands indicate that subduction is still occurring at the Shetland Trench. [8]
The Ring of Fire is a tectonic belt of volcanoes and earthquakes.
The Antarctic Plate is a tectonic plate containing the continent of Antarctica, the Kerguelen Plateau, and some remote islands in the Southern Ocean and other surrounding oceans. After breakup from Gondwana, 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 Australian Plate is a major tectonic plate in the eastern and, largely, southern hemispheres. Originally a part of the ancient continent of Gondwana, Australia remained connected to India and Antarctica until approximately 100 million years ago when India broke away and began moving north. Australia and Antarctica had begun rifting by 96 million years ago and completely separated a while after this, some believing as recently as 45 million years ago, but most accepting presently that this had occurred by 60 million years ago.
The Scotia Plate is a minor tectonic plate on the edge of the South Atlantic and Southern oceans. Thought to have formed during the early Eocene with the opening of the Drake Passage that separates Antarctica and South America, it is a minor plate whose movement is largely controlled by the two major plates that surround it: the Antarctic Plate and the South American Plate. The Scotia Plate 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.
The Phoenix Plate was a tectonic plate that existed during the early Paleozoic through late Cenozoic time. It formed a triple junction with the Izanagi and Farallon plates in the Panthalassa Ocean as early as 410 million years ago, during which time the Phoenix Plate was subducting under eastern Gondwana.
The Seal Nunataks are a group of 16 islands called nunataks emerging from the Larsen Ice Shelf east of Graham Land, Antarctic Peninsula. The Seal Nunataks have been described as separate volcanic vents of ages ranging from Miocene to Pleistocene. There are unconfirmed reports of Holocene volcanic activity.
The South Sandwich Plate or the Sandwich Plate is a small tectonic plate (microplate) 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 microplate.
The Scotia Arc is the island arc system forming the north, east and south border of the Scotia Sea. The northern border, the North Scotia Ridge, comprises Isla de los Estados at the tip of Tierra del Fuego, the Burdwood, Davis, and Aurora Banks; the Shag, South Georgia Island and Clerke Rocks. The eastern border comprises the volcanic South Sandwich Islands flanked by the South Sandwich Trench. The southern border, the South Scotia Ridge, comprises Herdman, Discovery, Bruce, Pirie, and Jane Banks; the South Orkney Islands and Elephant Island. The Bransfield Strait, finally, separates the arc from the South Shetland Islands and James Ross Island flanking the tip of the Antarctic Peninsula.
The Macquarie Triple Junction is a geologically active tectonic boundary located at 61°30′S161°0′E at which the historic Indo-Australian Plate, Pacific Plate, and Antarctic Plate collide and interact. The term Triple Junction is given to particular tectonic boundaries at which three separate tectonic plates meet at a specific, singular location. The Macquarie Triple Junction is located on the seafloor of the southern region of the Pacific Ocean, just south of New Zealand. This tectonic boundary was named in respect to the nearby Macquarie Island, which is located southeast of New Zealand.
The New Hebrides Plate, sometimes called the Neo-Hebridean Plate, is a minor tectonic plate located in the Pacific Ocean. While most of it is submerged as the sea bottom of the North Fiji Basin, the island country of Vanuatu, with multiple arc volcanoes, is on the western edge of the plate. It is bounded on the south-west by the Australian Plate, which is subducting below it at the New Hebrides Trench. The Vanuatu subduction zone is seismically active, producing many earthquakes of magnitude 7 or higher. To its north is the Pacific Plate, north-east the Balmoral Reef Plate and to its east the Conway Reef Plate.
The Mariana Plate is a micro tectonic plate located west of the Mariana Trench which forms the basement of the Mariana Islands which form part of the Izu–Bonin–Mariana Arc. It is separated from the Philippine Sea Plate to the west by a divergent boundary with numerous transform fault offsets. The boundary between the Mariana and the Pacific Plate to the east is a subduction zone with the Pacific Plate subducting beneath the Mariana. This eastern subduction is divided into the Mariana Trench, which forms the southeastern boundary, and the Izu–Ogasawara Trench the northeastern boundary. The subduction plate motion is responsible for the shape of the Mariana plate and back arc.
This is a list of articles related to plate tectonics and tectonic plates.
The geology of Russia, the world's largest country, which extends over much of northern Eurasia, consists of several stable cratons and sedimentary platforms bounded by orogenic (mountain) belts.
Melville Peak is a prominent peak surmounting Cape Melville, the eastern cape of King George Island, in the South Shetland Islands off Antarctica. It represents an eroded stratovolcano of unknown age and contains a volcanic crater at its summit. A volcanic ash layer similar in composition to Melville Peak has been identified 30 km (19 mi) away from the volcano and may indicate Melville Peak has been volcanically active in the last few thousand years.
The Antarctic Peninsula, roughly 1,000 kilometres (650 mi) south of South America, is the northernmost portion of the continent of Antarctica. Like the associated Andes, the Antarctic Peninsula is an excellent example of ocean-continent collision resulting in subduction. The peninsula has experienced continuous subduction for over 200 million years, but changes in continental configurations during the amalgamation and breakup of continents have changed the orientation of the peninsula itself, as well as the underlying volcanic rocks associated with the subduction zone.
The Pacific Ocean evolved in the Mesozoic from the Panthalassic Ocean, which had formed when Rodinia rifted apart around 750 Ma. The first ocean floor which is part of the current Pacific Plate began 160 Ma to the west of the central Pacific and subsequently developed into the largest oceanic plate on Earth.
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 from Smith Island 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 long by 70 kilometres wide with a depth of 1.3 kilometres, the Central basin is 230 kilometres long by 60 kilometres wide with a depth of 1.9 kilometres, and the Eastern basin is 150 kilometres long by 40 kilometres wide with a depth of over 2.7 kilometres. 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 deep.
The Chile Ridge, also known as the Chile Rise, is a submarine oceanic ridge formed by the divergent plate boundary between the Nazca Plate and the Antarctic Plate. It extends from the triple junction of the Nazca, Pacific, and Antarctic plates to the Southern coast of Chile. The Chile Ridge is easy to recognize on the map, as the ridge is divided into several segmented fracture zones which are perpendicular to the ridge segments, showing an orthogonal shape toward the spreading direction. The total length of the ridge segments is about 550–600 km.
The Hunter Fracture Zone is a sinistral (left-lateral) transform faulting fracture zone, that to its south is part of a triple junction with the New Hebrides Trench, and the North Fiji Basin Central Spreading Ridge. The Hunter Fracture Zone, with the Hunter Ridge, an area with recent volcanic activity to its north, is the southern boundary of the North Fiji Basin. This boundary area in the south-western part of the Hunter Fracture Zone is associated with hot subduction, and a unique range of volcanic geochemistry.