Scientists seem to be taking a step closer to predicting volcanic eruptions – a problem that has vexed volcanologists for decades. Research published last week in Nature Geoscience found that using satellite observations to calculate the rate at which molten underground rock, or magma, is accumulating beneath volcanoes could predict certain eruptions weeks or months in advance.
“Any type of information that we can use to get forecasts is going to be important because the more time you have to warn people that they can take action, the more you can reduce the impacts of eruptions,” the volcanologist said. Michael Poland. of the United States Geological Survey told VOA. “That’s all we have, really, in terms of lessening blowout impacts – to get out of the way.”
Most volcanoes do not erupt without warning. They swell, trigger small earthquakes and release gas leading to an eruption – what volcanologists call “unrest”. But while volcanoes rarely erupt completely out of the blue, it’s also not uncommon for unrest to set in without erupting.
“The challenge is to understand when these changes in these monitoring parameters will lead to an eruption, and when they will not,” Federico Galetto, a volcanologist at Cornell University and first author of the new study, told VOA. .
Currently, the gold standard for predicting eruptions involves highly localized observation of individual volcanoes, Poland said. But most volcanoes are not closely monitored on the ground. In contrast, deformation – how volcanoes bulge and deform during unrest – can be measured from space, even for the most distant volcanoes.
“The satellite warping technique has really shown that a lot of these volcanoes inflate and deflate, and that allows us to help come up with that kind of ‘holy grail’ prediction in some places where there’s no ground data,” Poland said. .
Unfortunately, deformation alone cannot reliably predict eruptions. But Galetto and his colleagues thought magma flow, which can be calculated using deformation data, might work better.
To find out, they looked at 45 episodes of unrest in basalt calderas – common volcanoes that generally look like wide, flat shields of dark basalt, including volcanoes in Hawaii, Iceland and the Galápagos Islands. Basalt calderas are considered relatively easy to study thanks to relatively shallow magma chambers – pools of molten rock beneath the Earth’s surface – and frequent eruptions, and they have been observed for a long time.
“They picked a subset where we have a lot of information and a lot of observations, these basalt calderas,” Poland said. “These types of volcanoes we have a lot of experience with…they tend to be large laboratories.”
Galetto’s analysis found that magma flow reliably predicted whether the Unrest would end with a rupture of the magma chamber – which usually causes an eruption – or simply die out.
All of the volcanoes in the dataset with magma discharges greater than a tenth of a cubic kilometer per year—about 40,000 Olympic pools—ruptured their magma chambers within a year. Flows 10 times lower did not lead to a magma chamber rupture in 89% of cases, and never before more than a year of unrest. Volcanoes with average flows were harder to predict, with factors like rock type and magma chamber size coming into play.
“It’s really promising,” Galetto said. ” It seems [be] works very well in these types of volcanoes.”
Calculations by Galetto and his team suggest that low magma flows do not tend to cause eruptions because slowly-filling magma chambers behave much like viscous putty or molasses, seeping outward to accommodate a slow trickle of incoming magma without breaking. Rapid flows increase pressure abruptly enough to crack magma chambers instead of just squeezing them.
“It makes sense,” Poland said. “The faster you inflate the balloon, the more likely it is to burst.” But he also warned that it would be difficult to use the new results to predict specific volcanoes.
“In volcanology, there is always a level of local expertise for your volcano that is needed, because every volcano is different,” he said. “But we can learn some general trends…that can help point us in the right direction when we look at these specific systems that we’re trying to predict.
Based on his findings, Galetto thinks magma flow could help predict eruptions weeks or months ahead for basalt calderas. But there is still work to be done. Refining forecast calculations with volcano-specific data, as described by Poland, will be important to make good forecasts, he said, as will collecting and analyzing better data from deformation of satellites.
“My article is just a starting point, not the end point,” Galetto said. “We should start… to see if this relationship can be found in other volcanoes. Because the other point is to try to extend these results not only to the group of volcanoes that I studied but also to try to extend these results to other groups of volcanoes, and it will be much more complicated.