Australia is the only continent in the world without active volcanoes – but that was not so in the past. There has been regular volcanism throughout Australia's geological history, especially andesitic and rhyolitic volcanism along the eastern margin. The most recent basaltic phase has barely finished. Basalt eruptions started around 70 Ma ago and lasted until the most recent eruptions in South Australia 4600 years ago. There is a close relationship between these basalts and the Great Divide: why?

Rich soils derived from the weathered basalt on elevated country, combined with a cooler and wetter climate form the basis for many of our finest agricultural and horticultural areas.

VOLCANIC PROVINCES

The Australian mainland has no active volcanoes, though there are two active volcanoes in the offshore territory of Heard and McDonald Islands. These two islands are part of the Kerguelen volcanic system and lie about 4000 km southwest of Australia, and some 1500 km north of Antarctica. The volcano, Big Ben, on Heard Island has a high point (Mawson Peak) at 2745m ASL, with a thick mantle of snow and glacial ice, and last erupted in 1992. The McDonald Island volcano is only 230m high, and erupted in 2001 and 2005.

Most of the volcanism in Australia has been of andesites and rhyolites, rocks formed mainly during compressive tectonics when there is considerable melting of continental crust.