Scientists have used Raijin to solve a long-standing mystery surrounding Australia's only active volcanic area.

The 500 kilometre long region stretches from Melbourne to the South Australian town of Mount Gambier, which surrounds a dormant volcano that last erupted only 5,000 years ago.

"Volcanoes in this region of Australia are generated by a very different process to most of Earth's volcanoes, which occur on the edges of tectonic plates, such as the Pacific Rim of Fire," says lead researcher Dr Rhodri Davies from ANU.

"We have determined that this Australian volcanism arises from a unique interaction between variations in the continent's thickness, and its movement at seven centimetres a year northwards towards New Guinea and Indonesia.

The volcanic area is comparatively shallow (less than 200 kilometres deep) in an area where a 2.5 billion-year-old part of the continent meets a thinner, younger section, formed in the past 500 million years or so.

These variations in thickness drive currents within the underlying mantle, which draw heat up to the surface.

"This boundary runs the length of eastern Australia, but our computer model demonstrates, for the first time, how Australia's northward drift results in an isolated hotspot in this region," Dr Davies said.

The researchers used state-of-the-art techniques and more than one million CPU hours to model these currents on Raijin.

"We run high resolution 3D models that cover, spatially, the whole of southeast Australia and use more than 1000 cores per run. There are not many computers in the world that are large enough for us to run these sorts of simulations at that scale," Dr Davies said.

"Without Raijin I couldn't have done any of the simulations. All of my research goes through the NCI."

Dr Davies will now apply his research technique to other volcanic mysteries around the globe.

"There are around 50 other similarly isolated volcanic regions around the world, several of which we may now be able to explain," he said.

It is difficult to predict where or when future eruptions might occur, Dr Davies said.

"There hasn't been an eruption in 5,000 years, so there is no need to panic. However, the region is still active and we can't rule out any eruptions in the future."

The research is published in the Journal Geology.