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.[2] 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.[3] The Australian Plate includes the continent of Australia, including Tasmania, as well portions of New Guinea, New Zealand, and the Indian Ocean basin.

Australian Plate
The Australian Plate
TypeMajor
Approximate area47,000,000 km2 (18,000,000 sq mi)[1]
Movement1northeast
Speed162–70 mm/year
FeaturesAustralia, New Guinea, New Zealand, Indian Ocean
1Relative to the African Plate

Geography

The northeasterly side is a complex but generally convergent boundary with the Pacific Plate. The Pacific Plate is subducting under the Australian Plate, which forms the Tonga and Kermadec Trenches, and the parallel Tonga and Kermadec island arcs. It has also uplifted the eastern parts of New Zealand's North Island.

The continent of Zealandia, which separated from Australia 85 million years ago and stretches from New Caledonia in the north to New Zealand's subantarctic islands in the south, is now being torn apart along the transform boundary marked by the Alpine Fault.

South of New Zealand the boundary becomes a transitional transform-convergent boundary, the Macquarie Fault Zone, where the Australian Plate is beginning to subduct under the Pacific Plate along the Puysegur Trench. Extending southwest of this trench is the Macquarie Ridge.

The southerly side is a divergent boundary with the Antarctic Plate called the Southeast Indian Ridge (SEIR).

The subducting boundary through Indonesia is not parallel to the biogeographical Wallace line that separates the indigenous fauna of Asia from that of Australasia. The eastern islands of Indonesia lie mainly on the Eurasian Plate, but have Australasian-related fauna and flora. Southeasterly lies the Sunda Shelf.

Origins

Depositional age of the Mount Barren Group on the southern margin of the Yilgarn Craton and zircon provenance analysis support the hypothesis that collisions between the PilbaraYilgarn and YilgarnGawler Cratons assembled a proto-Australian continent approximately 1,696 million years ago (Dawson et al. 2002).[4]

See also

References

  1. ^ "Sizes of Tectonic or Lithospheric Plates". Geology.about.com. 2014-03-05. Retrieved 2015-12-25.
  2. ^ "New Look at Gondwana's Breakup". Livescience.com. 2013-07-05. Retrieved 2015-12-25.
  3. ^ Stein, Seth; Sella, Giovanni F.; 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 2015-12-25.
  4. ^ Dawson, Galvin C.; Krapež, Bryan; Fletcher, Ian R.; McNaughton, Neal J.; Rasmussen, Birger (2002). "Did late Palaeoproterozoic assembly of proto-Australia involve collision between the Pilbara, Yilgarn and Gawler Cratons? Geochronological evidence from the Mount Barren Group in the Albany–Fraser Orogen of Western Australia". Precambrian Research. 118 (3–4): 195–220. doi:10.1016/S0301-9268(02)00110-9. ISSN 0301-9268.
Balmoral Reef Plate

The Balmoral Reef Plate is a small tectonic plate (microplate) located in the south Pacific north of Fiji. Clockwise from the north, it borders the Pacific Plate, Australian Plate, Conway Reef Plate, and the New Hebrides Plate. The northern and western borders are a divergent boundary while the rest of the borders are transform and convergent boundaries. The Balmoral Reef Plate's ocean crust is less than 12 million years old and is spreading between the New Hebrides and Tonga subduction.

Bird's Head Plate

The Bird's Head Plate is a minor tectonic plate incorporating the Bird's Head Peninsula, at the western end of the island of New Guinea. Hillis and Müller consider it to be moving in unison with the Pacific Plate. Bird considers it to be unconnected to the Pacific Plate.The plate is separating from the Australian Plate and the small Maoke Plate along a divergent boundary to the southeast. Convergent boundaries exist along the north, between the Bird's Head and the Caroline Plate, the Philippine Sea Plate and the Halmahera Plate to the northwest. A transform boundary exists between the Bird's Head and the Molucca Sea Collision Zone to the southwest. Another convergent boundary exists between the Bird's Head and the Banda Sea Plate to the south.

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.

Conway Reef Plate

The Conway Reef Plate is a small tectonic plate (microplate) located in the south Pacific west of Fiji. It is bounded on the east and west by convergent boundaries, the western boundary is with the New Hebrides Plate while the eastern is with the Australian Plate. A short transform boundary also exists with the Balmoral Reef Plate.

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.

Futuna Plate

The Futuna Plate is a very small tectonic plate located near the south Pacific island of Futuna. It is sandwiched between the Pacific Plate to the north and the Australian Plate to the south with the Niuafo'ou Plate to the east.

Geology of New Zealand

The geology of New Zealand is noted for its volcanic activity, earthquakes and geothermal areas because of its position on the boundary of the Australian Plate and Pacific Plates. New Zealand is part of Zealandia, a microcontinent nearly half the size of Australia that broke away from the Gondwanan supercontinent about 83 million years ago. New Zealand's early separation from other landmasses and subsequent evolution have created a unique fossil record and modern ecology.

New Zealand's geology can be simplified into three phases. First the basement rocks of New Zealand formed. These rocks were once part of the super-continent of Gondwana, along with South America, Africa, Madagascar, India, Antarctica and Australia. The rocks that now form the, mostly submerged, continent of Zealandia were then nestled between Eastern Australia and Western Antarctica. Secondly New Zealand drifted away from Gondwana and many sedimentary basins formed, which later became the sedimentary rocks covering the geological basement. The final phase is represented by the uplift of the Southern Alps and the eruptions of the Taupo Volcanic Zone.

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.

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.

Kermadec Plate

The Kermadec Plate is a very long and narrow tectonic plate located west of the Kermadec Trench in the south Pacific Ocean. Also included on this tectonic plate is a small portion of the North Island of New Zealand and the Kermadec Islands. It is separated from the Australian Plate by a long divergent boundary which forms a back-arc basin. This area is highly prone to earthquakes and tsunami.

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.

Maoke Plate

The Maoke Plate is a small tectonic plate located in western New Guinea underlying the Sudirman Range from which the highest mountain on the island- Puncak Jaya rises. To its east is a convergent boundary with the Woodlark Plate. To the south lies a transform boundary with the Australian Plate and the Bird's Head Plate lies to the west.

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.

Niuafo'ou Plate

The Niuafo'ou Plate is a small tectonic plate located west of the islands of Tonga. This plate is sandwiched between the Pacific Plate to the north, the very unstable Tonga Plate to the east and the Australian Plate to the west. It is primarily surrounded by convergent boundaries. This plate is riddled with active faults thus making the area extremely earthquake prone.

Pacific Plate

The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres (40,000,000 sq mi), it is the largest tectonic plate.The Pacific Plate contains an interior hot spot forming the Hawaiian Islands.Hillis and Müller are reported to consider the Bird's Head Plate to be moving in unison with the Pacific Plate. Bird considers them to be unconnected.

Sunda Trench

The Sunda Trench, earlier known as and sometimes still indicated as the Java Trench, is an oceanic trench located in the Indian Ocean near Sumatra, formed where the Australian-Capricorn plates subduct under a part of the Eurasian Plate. It is 3,200 kilometres (2,000 mi) long with a maximum depth of 24,440 feet (7,450 metres). Its maximum depth is the deepest point in the Indian Ocean. The trench stretches from the Lesser Sunda Islands past Java, around the southern coast of Sumatra on to the Andaman Islands, and forms the boundary between Indo-Australian Plate and Eurasian plate (more specifically, Sunda Plate). The trench is considered to be part of the Pacific Ring of Fire as well as one of a ring of oceanic trenches around the northern edges of the Australian Plate.

In 2005, scientists found evidence that the 2004 earthquake activity in the area of the Java Trench could lead to further catastrophic shifting within a relatively short period of time, perhaps less than a decade. This threat has resulted in international agreements to establish a tsunami warning system in place along the Indian Ocean coast.

Timor Plate

The Timor Plate is a microplate in southeast Asia carrying the island of Timor and surrounding islands. The Australian Plate is subducting under the southern edge of the plate, while a small divergent boundary is located on the eastern edge. Another convergent boundary exists with the Banda Sea Plate to the north, and to the west is a transform boundary.

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.

Woodlark Plate

The Woodlark Plate is a small tectonic plate located in the eastern half of the island of New Guinea. The Caroline plate subducts along its northern border while the Maoke Plate converges on the west, the Australian plate converges on the south, and on the east an undefined compressive zone which may be a transform fault marking the boundary with the adjoining Solomon Sea Plate.

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