East Tasman Plateau
Coordinates: 43°58′S 150°29′E / 43.96°S 150.48°E The East Tasman Plateau is a submerged microcontinent south east of Tasmania. Its area is 50,000 square kilometres (19,000 sq mi), and it is mostly from 2,500 to 3,000 metres (8,200 to 9,800 ft) deep. It is a circular piece of continental rocks surrounded by oceanic crust. Volcanism occurred there 36 million years ago. The East Tasman Plateau is separated from the island of Tasmania by 100 kilometres (62 mi) of deeper water, and the East Tasman Saddle is a higher ridge connecting the plateau to the Freycinet Peninsula region of the Tasmanian East Coast. This ridge runs north west from the plateau. South-west of the plateau is the L'Atalante Depression.
Prior to tectonic rifting, the East Tasman Plateau microcontinent was attached to the southeast of Tasmania and the north east of the South Tasman Rise. To the northeast, east and south east of the plateau was the Lord Howe Rise. In the Cretaceous period, the continental breakup of Gondwana started near Tasmania. About 83 million years ago a rift entered the east coast of Tasmania from the south and split off the Lord Howe Rise from the South Tasman Rise to the west.Sea floor spreading continued to move this continental sliver away to the east from Tasmania and Australia, and the rift jumped into the Lord Howe Rise and separated off the East Tasman Plateau. The detachment of the East Tasman Plateau from the Lord Howe Rise has left a large gulf on the west side of the Lord Howe Rise around 38°S 162°E where it used to be.
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