Australia is located in the center of the Indo-Australian plate. Since the Late Precambrian, the western three-quarters of the continent has been fixed. However, the eastern quarter showed more activity. During the [I009 / Paleozoic Era], it was the location of the Tasman [G 16 / Geosyncline] where sediments were deposited until about 200 million years ago when they were welded into northeastern Australia by igneous intrusions and tectonic movements.
Soon after, the supercontinent of [N005 / Pangea broke into two] lesser continents - Laurasia and Gondwanaland - which split further into the continents that exist today. The northward migration of the southern continents eventually closed off the Tethys Sea, first in the west with the rapid 'drift' of India that opened up the Indian Ocean and last in the east when Australia reached its present position.
Australia broke away from Antarctica some 53 million years ago, moving northward at about 3/4 inch per year. This forced the evolving scleractinian corals into the [G 31 / tropical] areas of what is now the western Pacific Ocean. With 500 species known in this region today, it has the greatest diversity of coral in the world.
