More than half of the world’s volcanoes are basaltic. Most basaltic eruptions tend to ooze their magma out in a relatively benign way, producing a thick, sticky flow. But occasionally they go off with a big bang, like the eruption of Mount Vesuvius in AD79, which destroyed the Roman town of Pompeii. Now a study reveals what makes some basaltic eruptions so explosive.

By cooking up miniature volcanoes in the lab, analysing rock samples flung from explosive basaltic eruptions and numerically modelling the eruption process, Dr Fabio Arzilli, from the University of Manchester, and colleagues showed that low temperature magma and fast ascent up the pipes are key conditions for an explosive basaltic eruption.

That’s because cooler magma is closer to crystallisation temperature. And if cool magma is whooshed rapidly upwards it chills it fast, enabling lots of crystals to form quickly. The findings, which are reported in Nature Geoscience, describe how this change of state from molten magma to fragmented magma can occur in just a couple of minutes. Some basaltic volcanoes, like Vesuvius, are recognised for their explosive nature, but the findings indicate that, given the right conditions, all basaltic volcanoes have the potential to produce highly explosive eruptions.



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