Indo-Australian plate

The Indo-Australian plate is a tectonic plate that extends from India's border with China and Nepal, encompassing the Indian subcontinent, eastern Indian Ocean, Australia, Melanesia and extending to New Zealand. It is subdivided into two plates that merged 50-55 million years ago, and whose boundaries maintain low tectonic activity: the Australian plate and the Indian plate.

India, Australia, New Guinea, Tasmania, New Zealand, and New Caledonia are all fragments of the ancient supercontinent of Gondwana. As the ocean floor separated, it fragmented these landmasses from one another, and for a time these centers were thought to be dormant and fused into a single plate. However, recent research indicates plate separation, so it will take time for publications to correctly corroborate this fact.

Plate characteristics

The eastern side of the plate is the convergent boundary with the Pacific plate. The Pacific plate sinks beneath the Australian plate and forms the Kermadec trench and the Tonga and Kermadec island arcs. New Zealand is located along the southeastern boundary of the plate, which with New Caledonia forms the southern and northern ends of the former Tasmanian landmass, which separated from Australia 85 million years. The central part of Tasmania sank under the sea.

The southern margin of the plate forms a divergent boundary with the Antarctic plate. The western side is subdivided by the Hindustani Plate which is bounded by the Arabian Plate to the north and the African Plate to the south. The northern margin of the Hindustani plate forms a convergent boundary with the Eurasian plate, which constitutes the active orogenic process of the Himalayas and the Hindukush mountains.

The northeastern side of the Australian plate forms a subduction boundary with the Eurasian plate in the Indian Ocean and between the borders of Bangladesh and Burma, and southwest of the Indonesian islands of Sumatra and Borneo. The subsidence boundary through Indonesia is reflected in the Wallace biogeographic line.

Recent history

There is a consensus that India and Australia have been on a single tectonic plate for at least the last 32 million years. However, taking into account the high level of large earthquakes in the area and the evidence of deformation at the bottom of the central Indian Ocean, it is estimated that the Indo-Australian plate would be dividing and the Ninety East Meridian Ridge would be the border.