By Sid Perkins
Molten rock moving up through a volcano’s plumbing prior to an eruption can heat up substantially, an unexpected finding that could affect scientists’ models of the eruption process.
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Magma crystallizes as it slowly loses heat to the environment, a process in which minerals with the highest melting points are the first to solidify. However, magma can also crystallize when volatile substances such as water and carbon dioxide bubble out suddenly, causing pressure within the lava to drop, says Kathy Cashman, a volcanologist at the University of Oregon in Eugene. When pressure drops slowly, the first minerals to solidify give up large amounts of heat that warms the remaining molten rock, Cashman and her colleagues report in the Sept. 7 Nature.