Sydney, November 12 Scientists, who conducted a study of bubbles trapped in pumice rock, have suggested that it's a lot easier for volcanoes to erupt than we think.

According to a report in ABC Science, the study was carried out by geologists Dr Heather Wright and Dr Roberto Weinberg of Monash University in Melbourne.

Geologists have long known that volcanic explosions are caused by fast-flowing magma.

Magma acts like silicone putty. It is very viscous and can flow gently like a fluid, but if it is pushed out of the earth under high pressure it can snap like a solid, according to Wright.

Scientists have developed models to help predict when a volcano will erupt. These models assume an eruption will occur when the magma flow reaches a certain critical threshold speed.

The absolute speed depends on a number of factors, such as composition of magma.

But Wright and Weinberg's latest findings suggest the models are too simplistic.

"Conventional volcano models assume that the magma behaves in a homogenous way," said Wright.

But, Wright and Weinberg's findings suggest magma is much more complex and eruption can occur at much lower average speeds than previously thought.

Wright and Weinberg's study shows the speed of magma varies greatly within a volcano.

"There can be rapidly flowing magma in one place and a millimetre away it can be flowing very slowly," said Wright.

She said that this makes it is too simplistic to talk about "averages speeds".

"Nothing is behaving in an average way," said Wright.

She said that as long as magma in one part of the volcano is flowing at the threshold speed, eruption will occur, even if the average speed is lower than this.

"Because things are so spatially variable, you can reach the critical threshold at a lower average speed," said Wright.

Wright and Weinberg based their study on magma flow from the Cerro Galan volcano in north-western Argentina, which exploded in a 'supervolcanic' eruption about 2 million years ago.

"Close examination of the bubbles in the pumice (solid magma) from the eruption showed that when they are round, they rub against each other and slow down magma flow," said Wright.

She said that when the bubbles are elongated and flat, they slide against each other and speed up magma flow.

"The complex pattern of round and elongated bubbles in the pumice reflects enormous variabilities in magma speed," said Wright. (ANI)