In a paper published in Nature, the international team of scientists describe their analysis of geophysical changes that took place in the long-dormant volcano prior to its eruption.

‘Several months of unrest preceded the eruptions, with magma moving around downstairs in the plumbing and making noise in the form of earthquakes,’ said one of the study’s authors, Kurt Feigl of the University of Wisconsin-Madison.

The researchers used a combination of satellite imagery and GPS surveys to track the deformation of the volcano’s edifice. The results showed that the volcano swelled for 11 weeks before it first began to erupt, expanding by more than 15 centimetres as magma flowed into shallow chambers beneath the mountain.

After the initial eruption, the researchers believe that the fresh magma came into contact with a different type of magma, perhaps left over from the last eruption, which took place 200 years ago. The differences in temperature, composition and gas content probably triggered the more explosive second eruption.

The researchers are now using data from an array of sensors around the volcano to map the chambers and other structures within it. ‘We’re a long way from being able to predict eruptions, but if we can visualise the magma as it moves upwards inside the volcano, then we’ll improve our understanding of the processes driving volcanic activity,’ Feigel said.

January 2011