Indo-Australian Plate
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The Indo-Australian Plate is an overarching name for two tectonic plates that include the continent of Australia and surrounding ocean extending northwest to include the Indian subcontinent and adjacent waters. It is subdivided into two plates along a low active boundary: the Australian Plate and the smaller India Plate. The two plates fused together between 50 to 55 million years age; prior to that time, they moved independently.
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 Pilbara–Yilgarn and Yilgarn–Gawler Cratons assembled a proto-Australian continent approximately 1696±7 Ma (Dawson et al. 2002).[1]
India, Meganesia (Australia, New Guinea, and Tasmania), New Zealand, and New Caledonia are all fragments of the ancient supercontinent of Gondwana. Seafloor spreading separated these land masses from one another, but as the spreading centers became inactive they were thought to have fused into a single plate. Recent research indicates that the plates are separating, however it will take some time to properly publicise this fact. [2], [3]
Recent GPS measurement in Australia confirms the plate's movement as being 35 degrees east of north with a velocity of 67 mm/yr. Note also the same directions and velocities for points at Auckland, Christmas Island and southern India. The slight change in direction at Auckland is presumably due to a slight buckling of the plate there, where it is being compressed by the Pacific Plate.
The easterly side is a convergent boundary with the subducting Pacific Plate. The Pacific Plate subducting under the Australian Plate forms the Kermadec Trench, and the Tonga and Kermadec island arcs. New Zealand lies along the southeastern boundary of the plate. New Zealand and New Caledonia are the southern and northern ends of the former land mass of Tasmantis, which separated from Australia 85 million years ago. The central part of Tasmantis sank below the sea, and now constitutes the Lord Howe Rise.
The southerly side is a divergent boundary with the Antarctic Plate. The westerly side is subdivided with the India Plate that forms a boundary with the Arabian Plate to the north and the African Plate to the south. The northerly side of the Indian Plate is a convergent boundary with the Eurasian Plate forming the Himalaya and Hindu Kush mountains.
The north-east side of the Australian plate forms a subducting boundary with the Eurasian plate on the borders of the Indian Ocean from Bangladesh, to Myanmar (former Burma) to the south-west of Indonesian islands of Sumatra and Borneo. The subducting boundary through Indonesia is reflected in the biogeographical Wallace line that separates the indigenous fauna of Asia from that of Australasia.
[edit] References
- Dawson, Galvin C., Ian R. Fletcher, Bryan Krape, Neal J. McNaughton and Birger Rasmussen. (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, Vol. 118, Issues 3-4, 25 November, pp. 195-220.
