Like its close neighbour, New Guinea, Australia was once part of the southern supercontinent of Gondwanaland. Geologically, they are on the same tectonic plate. When world sea levels were low, the two shared shorelines (which now lie 100 to 140 metres below sea level). They combined with lands now under water, sometimes known as Greater Australia. The two huge countries became separated when the area now known as the Torres Strait flooded after the end of the last glacial period. Big as Australia is, it was much bigger in the past. The end of the last ice age saw sea levels rise, and the old connections were broken.