Indo-Australian Plate

The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters. It was formed by the fusion of Indian and Australian plates approximately 43 million years ago.[1]

Plates tect2 bis en
In orange and red is the Indo-Australian plate, shown as divided between the Indian Plate and the Australian Plate

Plate movements

The eastern part (Australia) is moving northward at the rate of 5.6 cm (2.2 in) per year while the western part (India) is moving only at the rate of 3.7 cm (1.5 in) per year due to the impediment of the Himalayas. This differential movement has resulted in the compression of the former plate near its centre at Sumatra and the division into the Indian and Australian Plates.[2][3]

A third plate, known as the Capricorn Plate, may also be separating off the western side of the Indian plate as part of the continued breakup of the Indo-Australian Plate.[4]

Separation

Recent studies, and evidence from seismic events such as the 2012 Indian Ocean earthquakes, suggest that the Indo-Australian Plate may have broken up into two or three separate plates due primarily to stresses induced by the collision of the Indo-Australian Plate with Eurasia along what later became the Himalayas,[5][6] and that the Indian Plate and Australian Plate have been separate since at least 3 million years ago.[7]

References

  1. ^ "The Indo-Australian Plate". austhrutime.com.
  2. ^ "Earth cracking up under Indian Ocean". New Scientist. 26 September 2012. Retrieved 14 March 2018.
  3. ^ Delescluse, Matthias; Chamot-Rooke, Nicolas; Cattin, Rodolphe; Fleitout, Luce; Trubienko, Olga; Vigny, Christophe (26 September 2012). "April 2012 intra-oceanic seismicity off Sumatra boosted by the Banda-Aceh megathrust". Nature. 490 (7419): 240. doi:10.1038/nature11520 – via www.nature.com.
  4. ^ Siegel, Lee (26 September 2012). "Sumatra quake was part of crustal plate breakup: Study shows huge jolt measured 8.7, ripped at least 4 faults". Phys.Org. Retrieved 6 October 2012.
  5. ^ "Press Release: An Earth Plate Is Breaking in Two". www.columbia.edu.
  6. ^ R. R. Hillis, R. D. Müller. Evolution and Dynamics of the Australian Plate
  7. ^ Stein, Seth; Sella, Giovanni; Okai, Emile A. (2002). "The January 26, 2001 Bhuj Earthquake and the Diffuse Western Boundary of the Indian Plate" (PDF). Plate Boundary Zones. Geodynamics Series. American Geophysical Union. pp. 243–254. doi:10.1029/GD030p0243. ISBN 9781118670446. Retrieved 26 December 2015.
2018 West Java earthquake

On 23 January 2018, at 13:34:50 Western Indonesian Time (06:34:54 UTC), an earthquake struck the Indonesian island of Java near the regency of Lebak. The earthquake, measured 5.9 on the Mww, occurred approximately 40 kilometres south of the village of Binuangeun at a depth of 43.9 kilometres. The earthquake was categorized as a strong and shallow earthquake.Strong shaking were widely reported across Banten, Lampung, West Java, Central Java and Jakarta. The tremor in Jakarta was much harder than in other recent quakes. By the virtue of its distance from the Indo-Australian plate, the capital normally does not experience strong tremors. Two people were indirectly killed by the earthquake.

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 Ocean

Australian 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 began rifting 85 million years ago and completely separated roughly 45 million years ago. The Australian plate later fused with the adjacent Indian Plate beneath the Indian Ocean to form a single Indo-Australian Plate. However, recent studies suggest that the two plates have once again split apart and have been separate plates for at least 3 million years and likely longer. The Australian Plate includes the continent of Australia, including Tasmania, as well portions of New Guinea, New Zealand, and the Indian Ocean basin.

Banda Sea Triple Junction

The Banda Sea Triple Junction is a geologic triple junction where three tectonic plates meet: the Indo-Australian Plate, the Pacific Plate and the Eurasian Plate. It is located on the seafloor of the Banda Sea off the west coast of the island of New Guinea. The plate boundaries which meet at this triple junction are all subduction zones (trenches).

Capricorn Plate

The Capricorn Plate is a proposed minor tectonic plate lying beneath the Indian Ocean basin in the southern and eastern hemispheres. The original theory of plate tectonics as accepted by the scientific community in the 1960s assumed fully rigid plates and relatively narrow, distinct plate boundaries. However, research in the late 20th and early 21st centuries suggests that certain plate junctions are diffuse across several dozen or even hundred kilometres. The Capricorn Plate is a relatively rigid piece of oceanic crust along the far western edge of the former Indo-Australian Plate. The Capricorn Plate was once joined with the Indian Plate and the Australian Plate to form the Indo-Australian Plate, but recent studies suggest that the Capricorn Plate began separating from the Indian and Australian Plates between 18 million years ago and 8 million years ago along a wide, diffuse boundary.

Carlsberg Ridge

The Carlsberg Ridge is the northern section of the Central Indian Ridge, a divergent tectonic plate boundary between the African Plate and the Indo-Australian Plate, traversing the western regions of the Indian Ocean.

The ridge of which the Carlsberg Ridge is a part extends northward from a triple point junction near the island of Rodrigues (the Rodrigues Triple Point) to a junction with the Owen Fracture Zone. The ridge started its northwards propagation in the late Maastrichtian and reached the incipient Arabian Sea in the Eocene. Then it continued to accrete basalt but did not propagate for nearly 30 Ma. Then, in the early Miocene it started to propagate westwards towards the Afar hot spot, opening the Gulf of Aden.The Carlsberg Ridge is seismically active, with a major earthquake being recorded by the U.S. Geological Survey at 7.6 on the moment magnitude scale on July 15, 2003.The submarine ridge was discovered by the Danish research vessel Dana during the Carlsberg Foundation's Oceaonographic Expedition around the world (1928–1930), better known as the 2nd Dana Expedition, and named after the Carlsberg Foundation, which funded the entire expedition and subsequent analysis and publication of results.

Chaman Fault

The Chaman Fault is a major, active geological fault in Pakistan and Afghanistan that runs for over 850 km. Tectonically, it is actually a system of related geologic faults that separates the Eurasian Plate from the Indo-Australian Plate. It is a terrestrial, primarily transform, left-lateral strike-slip fault. The slippage rate along the Chaman fault system as the Indo-Australian Plate moves northward (relative to the Eurasian Plate) has been estimated at 10 mm/yr or more. In addition to its primary transform aspect, the Chaman fault system has a compressional component as the Indian Plate is colliding with the Eurasian Plate. This type of plate boundary is sometimes called a transpressional boundary.From the south, the Chaman fault starts at the triple junction where the Arabian Plate, the Eurasian Plate and the Indo-Australian Plate meet, which is just off the Makran Coast of Pakistan. The fault tracks northeast across Balochistan and then north-northeast into Afghanistan, runs just to the west of Kabul, and then northeastward across the right-lateral-slip Herat fault, up to where it merges with the Pamir fault system north of the 38° parallel. The Ghazaband and Ornach-Nal faults are often included as part of the Chaman fault system. South of the triple junction, where the fault zone lies undersea and extends southwest to approximately 10°N 57°E, it is known as the Owen Fracture Zone.

While there is general agreement that the fault is slipping at a rate of at least 10 mm/yr, there is a report of volcanic rocks in Pakistan dated to 2 m.y. BP which have been offset such as to indicate a slip rate of 25–35 mm/yr. Offsets have been described throughout the fault in Pakistan that are young enough that “only the alluvium of the bottom of active dry washes is not displaced.”The parallel mountain ranges of eastern Balochistan, (east to west) the Kirthar Mountains, the Khude Mountains, the Zarro Mountains, the Pab Mountains and the Mor Mountains, are a result of the compressional plate boundary and are aligned parallel to the Chaman fault movement. The fault itself is west of these ranges.

Clarence Fault

The Clarence Fault is an active dextral (right lateral) strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate, from the transform Alpine Fault to the Hikurangi Trench subduction zone.

Eurasian Plate

The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia. It also includes oceanic crust extending westward to the Mid-Atlantic Ridge and northward to the Gakkel Ridge.

The eastern side is a boundary with the North American Plate to the north and a boundary with the Philippine Sea Plate to the south and possibly with the Okhotsk Plate and the Amurian Plate. The southerly side is a boundary with the African Plate to the west, the Arabian Plate in the middle and the Indo-Australian Plate to the east. The westerly side is a divergent boundary with the North American Plate forming the northernmost part of the Mid-Atlantic Ridge, which is straddled by Iceland. All of the volcanic eruptions in Iceland, such as the 1973 eruption of Eldfell, the 1783 eruption of Laki, and the 2010 eruption of Eyjafjallajökull, are caused by the North American and the Eurasian Plates moving apart, which is a result of divergent plate boundary forces.

The geodynamics of central Asia is dominated by the interaction between the Eurasian and Indian Plates. In this area, many subplates or crust blocks have been recognized, which form the Central Asian and the East Asian transit zones.

Hikurangi Trench

The Hikurangi Trench, also called the Hikurangi Trough, is an oceanic trench in the bed of the Pacific Ocean off the east coast of the North Island of New Zealand, lying between the southern end of the Cook Strait and the Chatham Rise. It is the southward continuation of the much deeper Kermadec Trench. It lies in the Hikurangi Margin subduction zone, which is the southern extension of the Kermadec-Tonga subduction zone. The Hikurangi Margin is the subduction zone where the thick oceanic Hikurangi Plateau is subducting beneath continental crust of the Indo-Australian Plate. By contrast, the Kermadec and Tonga trenches represent the parts of the subduction zone where oceanic crust of the Pacific Plate is subducting beneath oceanic crust of the Indo-Australian Plate.

Although shallower than the trenches north of it, the Hikurangi Trench reaches depths of 3,000 metres as close as 80 kilometres from shore. Its maximum depth is about 3,750 metres (12,300 ft).At the southern end of the trench, off the coast of the Marlborough region, the seabed rises sharply, and because of the prevailing winds and tides in this area, many deep water species are found close to the shore. This food source attracts the whales for which the town of Kaikoura is famous.

The plate boundary continues inland along the Marlborough Fault System, linking through to the Alpine Fault. Here the plates converge much more obliquely, exhibiting transpression instead of subduction.

Indian Plate

The Indian Plate or India Plate is a major tectonic plate straddling the equator in the eastern hemisphere. Originally a part of the ancient continent of Gondwana, India broke away from the other fragments of Gondwana 100 million years ago and began moving north. Once fused with the adjacent Australia to form a single Indo-Australian Plate, recent studies suggest that India and Australia have been separate plates for at least 3 million years and likely longer. The Indian Plate includes most of South Asia—i.e. the Indian subcontinent—and a portion of the basin under the Indian Ocean, including parts of South China and western Indonesia, and extending up to but not including Ladakh, Kohistan and Balochistan.

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.

Louisville Ridge

The Louisville Ridge, also known as the Louisville Seamount Chain, is an underwater chain of over 70 seamounts in the Southwest Pacific Ocean. As one of the longest seamount chains on Earth it stretches some 4,300 km (2,700 mi) from the Pacific-Antarctic Ridge northwest to the Tonga-Kermadec Trench, where it subducts under the Indo-Australian Plate as part of the Pacific Plate. The movement of the Pacific Plate over the Louisville hotspot formed the chain.

Depth-sounding data first revealed the existence of the seamount chain in 1972.

Macquarie Fault Zone

The Macquarie Fault Zone is a major right lateral-moving transform fault along the seafloor of the south Pacific Ocean which runs from New Zealand southwestward to the Macquarie Triple Junction. It is also the tectonic plate boundary between the Indo-Australian Plate to the northwest and the Pacific Plate to the southeast.

The Macquarie Fault Zone includes a component of convergence which increases as it approaches the South Island of New Zealand. Many researchers conclude that the fault zone here is an incipient subduction zone, with oblique motion corresponding to the transition from lateral (strike-slip) motion. In the area known as the Puysegur Trench, the Indo-Australian Plate appears to be starting to sink beneath the Pacific Plate, the reverse of what is occurring off of New Zealand's North Island (see Kermadec-Tonga Subduction Zone).

A major geographic feature which runs along the Macquarie Fault Zone is known as the Macquarie Ridge. This ridge represents both the different relative heights of the abutting plates as well as the component of compression between the plates. The namesake Macquarie Island, named after Lachlan Macquarie lies atop a segment of the Macquarie Ridge.

The Macquarie Fault Zone merges into the Alpine Fault which cuts across the continental crust of New Zealand's South Island.

Macquarie Triple Junction

The Macquarie Triple Junction is a geologically active tectonic boundary located at 61°30′S 161°0′E at which the 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.

Madagascar Plate

The Madagascar Plate or Madagascar block was once attached to the Gondwana supercontinent and later the Indo-Australian Plate.

Rifting in the Somali Basin began at the end of the Carboniferous 300 million years ago, as a part of the Karoo rift system. The initiation of Gondwana breakup, and transform faulting along the Davie Fracture Zone, occurred in the Toarcian (about 182 million years ago) following the eruption of the Bouvet (Karoo) mantle plume. At this time East Gondwana, comprising the Antarctic, Madagascar, Indian, and Australian plates, began to separate from the African Plate. East Gondwana then began to break apart about 115–120 million years ago when India began to move northward. Between 84–95 million years ago rifting separated Seychelles and India from Madagascar.

Since its formation the Madagascar block has moved roughly in conjunction with Africa, and thus there are questions as to whether the Madagascar Plate should be still considered a separate plate.

New Hebrides Plate

The New Hebrides Plate, sometimes called the Neo-Hebridean Plate, is a minor tectonic plate located in the Pacific Ocean near the island nation of Vanuatu. The plate is bounded on the southwest by the Indo-Australian Plate which is subducting below it. The New Hebrides Subduction Zone is extremely active, producing over 20 earthquakes of magnitude 7 or higher in just the past 25 years.

Tonga Plate

The Tonga Plate is a small southwest Pacific tectonic plate or microplate. It is centered at approximately 19° S. latitude and 173° E. longitude. The plate is an elongated plate oriented NNE - SSW and is a northward continuation of the Kermadec linear zone north of New Zealand. The plate is bounded on the east and north by the Pacific Plate, on the northwest by the Niuafo’ou Microplate, on the west and south by the Indo-Australian Plate. The Tonga plate is subducting the Pacific plate along the Tonga Trench. This subduction turns into a transform fault boundary north of Tonga. An active rift or spreading center separates the Tonga from the Australian plate and the Niuafo’ou microplate to the west. The Tonga plate is seismically very active and is rotating clockwise.

These were the plates that moved when the 2009 tsunami hit Samoa.

Wairau Fault

The Wairau Fault is an active dextral (right lateral) strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate, from the transform Alpine Fault to the Hikurangi Trench subduction zone.

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