Volcanoes in eastern Australia that have not erupted in hundreds of years still pose a threat and emergency services should be better prepared, an expert told a geology conference today.

But another expert thinks Australia should be more worried about fires, storms and earthquakes than volcanoes.

Bernie Joyce, from the University of Melbourne, presented a paper on volcanic hazards today at the 17th Australian Geological Convention of the Geological Society of Australia held in Hobart, Tasmania.

Volcanoes in Victoria, New South Wales and Queensland could erupt at any time, he told ABC Science Online ahead of the conference.

No volcano in Australia has erupted for at least two hundred years, with the most severe eruption at Mt Gambier, near Campbelltown in Victoria, 4500 years ago.

But a sudden eruption could still catch emergency authorities unprepared for the floods, mud flows and ash falls that could follow, said Joyce.

He said the kind of eruption Australia could expect was not on the same scale of the Mt Helen's eruption, which wiped out a large area in the U.S. state of Washington in May 1980. Australia could expect a smaller eruption.

"It hasn't happened in a couple of hundred years so we're not sure what it would look like," said Joyce.

According to Joyce, an eruption could either be an explosion like the one at Mt Gambier, creating a big hole in the ground, or avolcanic eruption common in Queensland and Victoria in the past 50,000 years of a different type.

These eruptions have large lava flows followed by a more gaseous eruption where the lava breaks up into small pieces and builds a cone of cinders and sharp rock material.

There is evidence of these cones and crater lakes around Victoria and southern Queensland, Joyce said.

"In either case you wouldn't get much warning and you would be working out what to do when it came," Joyce said.

Eastern Australia had up to 120 volcanoes less than 50,000 years old, said Joyce, who said probability showed these still posed a threat.

Joyce warned the consequences of even a small eruption coming into contact with groundwater could include hot, wet ash falls, dangerous gases and ash blown into the air, damage to animals and the environment, and pollution in water systems.

Other geohazards
But Dr Wally Johnson, head of the geohazards division at Geoscience Australia told ABC Science Online that Australia's government geological science organisation was more concerned about hazards posed by fires, storms and earthquakes than volcanoes.

"Australians are more likely to face risks from volcanoes when flying to Southeast Asia or the South Pacific and ash from volcanoes getting into the jets and causing problems with aircraft," said Johnson.

While Johnson said that Joyce did a good job raising awareness of the risks posed by volcanoes, he said there were other hazards with higher priorities.

"If Mt Gambier did erupt it would impact on local communities," Johnson said. "But any changes to the state of these volcanoes would be noticed early on, either through earthquakes, or in the case of Mt Gambier an increase in the temperature of the water.

"We know that volcanoes do provide a fair bit of warning. In most cases this would be months or even years. You might get a volcano way out in western Victoria where you might not notice the warning signs but in most cases you'll get advance warning from geological phenomena," he said.

Advance warnings could include an increase in seismic activity, a change in the temperature of surface soils, or even smoking fumaroles, small eruptions from the side of a volcano that indicate that a major eruption was imminent.