Excessive and sustained rainfall caused the massive eruption of the Kīlauea volcano in Hawaii two years ago by softening the rock, according to a new study.
US researchers say the dramatic eruption in 2018, which destroyed hundreds of homes, was due to wet volcanic rock, which breaks easily under pressure.
Local rainfall patterns contributed to the timing and frequency of the chaotic eruption at Kīlauea and perhaps at other volcanoes, they say.
Increased levels of rainfall caused by climate change could also mean more dramatic volcanic events in the future, not just in Hawaii, they warn.
Scroll down for video
Lava erupts from a fissure east of the Leilani Estates subdivision during ongoing eruptions of the Kilauea Volcano in Hawaii, US, May 13, 2018. UM Rosenstiel School scientists have showed that the eruption was likely initiated by prolonged, and at times extreme, rainfall in the months leading up to the event
Outbreaks of lava fountains up to 300 feet (90 metres) high caused hundreds of homes to be lost in the Puna district on Hawaii’s biggest island
‘Interestingly, when we investigate Kīlauea’s historical eruption record, we see that magmatic intrusions and recorded eruptions are almost twice as likely to occur during the wettest parts of the year,’ said Dr Jamie Farquharson at the Rosenstiel School of Marine and Atmospheric Science, University of Miami.
‘If we can identify regions of the globe where this kind of coupling between rainfall and volcanism exists, it could go a long way towards advanced warning of associated volcanic hazards.
‘It has been shown that the melting of ice caps in Iceland led to changes of volcanic productivity.
‘As ongoing climate change is predicted to bring about changes in rainfall patterns, we expect that this may similarly influence patterns of volcanic activity.’
The team say the water’s intrusion started in the Pu’O O’o area of the volcano in the east rift zone.
Sustained periods of rainfall trigger volcanic eruptions, because wet rock breaks easier than dry rock when under pressure from the magma below.
‘We knew that changes in the water content in the Earth’s subsurface can trigger earthquakes and landslides,’ said co-author of the study Falk Amelung, also at the University of Miami.
‘Now we know that it can also trigger volcanic eruptions.’
The unprecedented eruption of Kīlauea, one of Hawaii’s most active volcanoes, destroyed more than 500 homes.
Although erupting continuously for decades, the 2018 eruption in the Puna district of the state’s largest island entered an extraordinary new phase on May 3, 2018.
Incandescent lava was shot nearly two hundred feet in the air and spewed over 13 square miles across the well-populated east coast of Hawaii’s biggest island.
The Hawaiian government reported high levels of toxic sulfur dioxide in the area, which affected some of the first responders.
Power lines were reported to have melted off poles because of the heat, with other reports describing streams of lava running through woods and down roads.
Lava flows at a lava fissure in the aftermath of eruptions from the Kilauea volcano on Hawaii’s Big Island, on May 12, 2018 in Pahoa, Hawaii
To learn more about the cause, using ground-based and satellite measurements of rainfall, researchers modelled the fluid pressure within the volcano’s edifice over time.
Fluid pressure can directly influence the tendency for mechanical failure in the subsurface, ultimately driving volcanic activity.
‘An eruption happens when the pressure in the magma chamber is high enough to break the surrounding rock and the magma travels to the surface,’ said Professor Amelung.
‘This pressurisation causes inflation of the ground by tens of centimetres.
‘As we did not see any significant inflation in the year prior to the eruption we started to think about alternative explanations.’
Fluid pressure was the highest in almost half a century prior to the eruption, which likely facilitated magma movement below the volcano.
While small steam explosions and volcanic earthquakes have been linked to rainfall infiltration at other volcanoes in the past, this is the first time this mechanism has been used to explain deeper magmatic processes.
The authors have warned that if this process can be detected at Kīlauea, then it is likely to occur elsewhere as well.
May 12, 2018, the ash plume of Kīlauea is visible drifting across the island as a large bank of rainclouds encroaches on the northern coast
‘Having established the evidence for rainfall-triggered eruptions at Kīlauea, it will be fascinating to investigate other volcanoes,’ said Farquharson.
The study used Earth-observing satellites and precipitation information from NASA and the Japanese Space Exploration Agency, as well as ground deformation observations from the European Space Agency.
The findings are published in the journal Nature.