The country is situated on the Pacific Ring of Fire, at the point of collision of several tectonic plates. Geologically, the island of New Guinea is a northern extension of the Indo-Australian tectonic plate, forming part of a single land mass which is Australia-New Guinea (also called ''Sahul'' or ''Meganesia''). It is connected to the Australian segment by a shallow continental shelf across the Torres Strait, which in former ages lay exposed as a land bridge, particularly during ice ages when sea levels were lower than at present. As the Indo-Australian Plate (which includes landmasses of India, Australia, and the Indian Ocean floor in between) drifts north, it collides with the Eurasian Plate. The collision of the two plates pushed up the Himalayas, the Indonesian islands, and New Guinea's Central Range. The Central Range is much younger and higher than the mountains of Australia, so high that it is home to rare equatorial glaciers.