THE huge eruption of Kilauea volcano on Hawaii in 2018 was triggered by extremely heavy rains, according to a new analysis. The water caused pressure to build up deep inside the volcano, fracturing the rock and allowing hot magma to rise.
The finding bolsters the idea that rainfall can affect volcanoes and thus that climate change could lead to more eruptions.
Kilauea began erupting at the end of April 2018, when the floor of its lava lake collapsed. The volcano crumbled and huge volumes of magma flowed over the landscape, eventually reaching the coast. The eruption continued for months.
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Why it happened was unclear. The volcano didn’t expand in the weeks before, which would have indicated new magma entering from below. Instead, the upper rocks that keep the magma trapped must have been weakened, allowing it to escape.
Jamie Farquharson and Falk Amelung at the University of Miami in Florida noticed that Hawaii had unusually heavy rain in early 2018. On 14 to 15 April, 1.26 metres of rain fell within 24 hours – a US record. In the first three months of 2018, Kilauea had 2.25 metres of rain, when it would normally get 0.9 metres.
Previous research suggests that passing storms can cause small explosions when they interact with unstable material on the surface of a volcano, says Farquharson. For instance, the Soufrière Hills volcano on Montserrat in the Caribbean erupts more after heavy rain.
“Our study goes further,” says Farquharson. He and Amelung used rainfall data to calculate how much pressure built up inside the volcano as a result of increased groundwater, finding that, in early 2018, the pressure was at its highest for almost 50 years. They suggest that pressure fractured the rock, letting magma rise and erupt (Nature, DOI: ).
This is backed by historical evidence. The pair found that about 60 per cent of Kilauea’s reported eruptions since 1790 began during the five-month rainy season. Notably, a spectacular eruption in May 1924 was preceded by extreme rain. Furthermore, magma seems to be more likely to ooze into the volcano from below when internal pressure is high.
“It’s definitely a possibility of explaining this eruption,” says Carolina Pagli at the University of Pisa in Italy. She says previous claims of “volcano weather” haven’t stood up to scrutiny, but here the historical data is “particularly convincing”.
The finding could help improve eruption warning systems for Kilauea, says Pagli.
“I am not at all surprised,” says Bill McGuire at University College London, who has long that climate change will trigger more volcanic eruptions, earthquakes and tsunamis as melting ice sheets and extreme rainstorms alter the pressures that control geological phenomena.
“The fact that tropical cyclones are already getting much wetter, and will become more so, could mean that they will provide increasingly effective triggers for eruptions at tropical volcanoes that are primed and ready to go,” says McGuire.
Farquharson says this may be the case, but every volcano is unique. “The study is concerned solely with Kilauea volcano and cannot necessarily be applied more generally without further detailed research.”
