The spectacular eruptions of the Kīlauea volcano in Hawaii in 2018 were triggered by extreme rainfall in the preceding months, research suggests.
Scientists say the finding raises the possibility that climate breakdown, which is causing more extreme weather, could lead to an increase in eruptions around the world.
The 2018 Kīlauea eruptions were one of the most extraordinary sequences in at least 200 years, according to the scientists, with rifts opening, summit explosions and collapses, and a magnitude 6.9 earthquake. But the trigger was not known.
However, several months of unusually high rainfall preceded the eruption, with one 24-hour period setting a record for the entire US. This flood of water would have percolated down into fissures and pores in the rocks of the volcano, as far as 1.8 miles (2.9km) below the surface.
The scientists calculated this pushed up the pore pressure inside the rocks to the highest level in almost 50 years, weakening them and allowing magma to push up from below.
The scientists also looked at eruptions of Kīlauea since 1790 and found that these historical events were twice as likely to happen in the rainy season. Such a link has long been thought possible – JD Dana, one of the first geologists to visit Hawaii in the late 1800s, suggested the idea.
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