Geology
The continent primarily sits on the Indo-Australian Plate. The lands were joined with Antarctica as part of the southern supercontinent Gondwana until the plate began to drift north about 96 million years ago. For most of the time since then, Australia–New Guinea remained a continuous landmass. When the last glacial period ended in about 10,000 BC, rising sea levels formed Bass Strait, separating Tasmania from the mainland. Then between about 8,000 and 6,500 BC, the lowlands in the north were flooded by the sea, separating New Guinea, the Aru Islands, and the Australian mainland.
A northern arc consisting of the New Guinea Highlands, the Raja Ampat Islands, and Halmahera was uplifted by the northward migration of Australia and subduction of the Pacific Plate. The Outer Banda Arc was accreted along the northwestern edge the continent; it includes the islands of Timor, Tanimbar, and Seram.
Read more about this topic: Australia (continent)