Ancient Cycle of Italy's Volcanic Giant Seems to End in a Large Eruption



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Sitting within the Bay of Naples in southern Italy is Campi Flegrei, a vast and restless volcanic caldron. The history of this sleeping colossus includes two massive eruptions, 39,000 and 15,000 years ago, that left deep calderas in the landscape. Its last significant volcanic event a 1538 eruption known as Monte Nuovo that spawned a small new mountain. Since then, it has been curiously eruption-free.

Today, 1.5 million people live within the volcano'S caldera and its surroundings, and the cache of magma that could make it one of the most hazardous areas on earth. In a study published Wednesday in Science Advances, volcanologists report that Campi Flegrei is at the beginning of an eruption cycle, one that may result in a massive outburst at some point in the likely distant future.

The researchers arrived at this conclusion by the 60,000-year-long history of the volcano, which reveals what appears to be a rhythm at Campi Flegrei's upsurges. Fortunately, there are no signs that an eruption is imminent. And because the volcano is one of the world's most closely monitored, scientists are likely to pick up on any warning signs.

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Previous studies of Campi Flegrei have focused on one or a handful of its eruptions. But the new study, led by Francesca Forni, a postdoctoral researcher at Nanyang Technological University in Singapore, who conducted the work at ETH Zurich, used fresh geological samples taken from 23 eruptions across its history, both larger and smaller, to see how the chemistry of the magma changed over deep time. Her team also used computers to simulate what may have happened to the volcano since the last caldera-forming eruption 15,000 years ago.

The team found Campi Flegrei has gone through stages. First, a massive eruption occurs, resulting in the formation of a caldera. Then the volcano enters a period of regular, small eruptions as magma escapes through new fractures in the crust.

Finally, the volcano enters a pre-caldera phase. Minor eruptions become infrequent, and magma accumulates in the subterranean reservoir. As it pools, the magma evolves into a water-rich, gassy form, and the most drunk, bubble-rich patches gather at the top. This magma buildup may eventually culminate in another major eruption, and the cycle would begin anew.

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