February 3, 2012
Studies Suggest Volcanic Eruptions Can Be Predicted
New research suggests that eruptions at some of Earth's largest volcanoes could be predicted decades before the event actually occurs, potentially making it easier for experts to monitor danger zones and conduct pre-emptive evacuations to keep residents out of harm's way.
In one study, published Thursday in the journal Nature, scientists investigate "caldera-forming volcanic eruptions," or eruptions that discharge such massive amount of magma that it can create a large depression in the planet's surface and leave behind a crater-like substance known as a caldera, BBC News Science and Health Reporter Neil Bowdler reported.
"Because no such eruption has been monitored during its long build-up phase, the precursor phenomena are not well understood," the research team behind the study wrote in their study. "Geophysical signals obtained during recent episodes of unrest at calderas such as Yellowstone, USA, and Campi Flegrei, Italy, are difficult to interpret, and the conditions necessary for large eruptions are poorly constrained."
As a result, lead researcher Tim Druitt of Blaise Pascal University in France and his colleagues studied the "pre-eruptive magmatic processes" from the Minoan caldera-forming eruption at Greece's Santorini volcano more than in the late 1600s BC. In the course of their work, they discovered that most of the crystals in that volcano's magma record occurred no earlier than 100 years before the eruption occurred.
"Recharge of the magma reservoir by large volumes of silicic magma (and some mafic magma) occurred during the century before eruption, and mixing between different silicic magma batches was still taking place during the final months," they wrote. "Final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period, with major growth phases immediately before eruption. These observations have implications for the monitoring of long-dormant, but potentially active, caldera systems."
According to Charles Q. Choi of OurAmazingPlanet, by definition, Santorini is not a "supervolcano" since it is not capable of producing at least 120 cubic miles of magma at once. Nonetheless, Druitt told Choi that the eruption evaluated was similar in nature to supervolcano eruptions, and similar processes would have taken place.
By looking at about 300 crystals of a mineral known as feldspar, while serve as pre-eruption activity records beneath the Greek volcano, they discovered that "large changes in magma composition could occur quite abruptly prior to these large eruptions," according to OurAmazingPlanet's February 1 report.
"The changes in composition of the crystals with time provide little histories of how the magma itself has evolved," Druitt told Bowdler on Wednesday. "What we found was that all the crystals in the magma grew within a few decades of the eruption."
"What we're saying is that all caldera volcanoes, even those in remote regions of the globe, should be monitored using highly sensitive modern instruments in order to pick up these deep signals which may suggest reactivation," he added. "If you had a big eruption of this sort, let's say in the middle of Europe today, the effects would be enormous and a few months might not be enough to get your act together."
A similar study, published this month in the journal Geophysical Research Letters, looked at Ubehebe Crater in California's Death Valley. By studying beryllium in the rocks at the volcano -- which is about a half a mile wide, 700 feet deep, and an estimated 10,000 years old -- the scientists were able to determine that it last erupted just 800 years ago, according to USA Today's Elizabeth Weise.
"Ubehebe Crater is the result of what's known as a phreatomagmatic eruption. That means that it has a huge pocket of molten rock, or magma, deep below it. When it begins to push to the surface and comes into contact with water, superhot steam is created, building up pressure until it explodes," Weise wrote.
While previously experts believed that the eruptions could only occur during wet climate periods, the dry conditions at Death Valley and U.S. Geological Survey (USGS) data showing that the current water table may just be 500 feet below the crater's surface now suggest otherwise, Weise said. As a result, the underground magma could is most likely still hot, and if it comes into contact with water, it could produce a massive, explosive eruption.
Another area of concern for scientists as a result of these studies, USA Today reported, is the fear that some caldera volcanoes, "such as Mount Pinatubo in the Philippines and Krakatoa in Indonesia, may be able to blow much more quickly than previously believed."
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