More Extreme Rainstorms Might Mean More Volcano Eruptions, Study Finds

Major volcanic eruptions can alter weather patterns around the world, a fact that has shaped the course of human history and set off mass extinctions in the deep past.

Now, scientists have discovered that the reverse is also true: Weather—specifically heavy rainfall—can trigger volcanic activity, according to a study published on Wednesday in Nature.

The extensive eruptions of Hawaii's Kīlauea volcano in 2018 “strongly suggest a correlation between rainfall and volcanic activity,” said the study, which was led by volcanologist Jamie Farquharson, a postdoctoral researcher at the University of Miami.

Farquharson and co-author Falk Amelung, a professor of geophysics at the University of Miami, emphasized that human-driven climate change is expected to boost precipitation in some regions, which may increase the odds of rainfall-triggered volcanic phenomena around the world.

“We can’t necessarily extrapolate from this single example,” Farquharson said in an email.

“But the fact that more extreme precipitation is anticipated in the future in many parts of the globe suggests that understanding the potential coupling between the hydrological cycle and volcanism is an important area of research moving forward.”

“The kind of volcanoes we are interested in exploring further would be highly active systems that have shown evidence in the past of being affected by external forces, and would likely be located in parts of the globe that currently experience or highly variable rainfall,” he added.

Farquharson and Amelung are not the first scientists to propose a link between rainfall and volcanic activity—past studies have suggested that eruptions at Mount St Helens, Piton de la Fournaise, and Soufrière Hills Volcano may have been activated by rainfall.

However, the new study introduces extensive evidence from the Kīlauea eruption that bolsters the correlation and reveals, for the first time, the role precipitation might play in stirring up deep magmatic activity beneath a volcano.

Kīlauea, located on the southeast corner of Hawaii’s Big Island, has been in an active phase since 1983. But beginning in May 2018, the volcano went into overdrive for several months, spilling lava across more than a dozen square miles and forcing hundreds of people to evacuate.

By the time the lava flows finally sputtered out later that year, it had become the most destructive volcanic event in the US since the 1980 eruption of Mount St. Helens.

Kīlauea is a complex volcano and its percolations are driven by multiple natural forces. That said, the 2018 eruption was preceded by extraordinary downpours equal to about 2.5 times the average rainfall for the season and area. On a single day in mid-April, Kauai Island, northwest of the Big Island, was doused in 1.26 meters (4.1 feet) of precipitation, “a record not only for Hawai‘i but for the entire United States,” the study notes.

As the rainwater seeped into Kīlauea, it helped pump up the fluid pressure underneath the volcano to the highest level recorded in nearly 50 years. The team suggests that the deluge caused a pressure wave beneath the volcano that weakened its edifice, triggering the eruption and collapse of the summit caldera.

The notion that the eruption was set off by extreme rainfall is also backed up by the volcano’s past. “Historical precipitation records show that Kīlauea’s May 1924 eruption—the previous extraordinary eruption—also followed extremely wet conditions,” the researchers said in the study.

“The 2018 eruption echoed many features of 1924 (for example, major summit explosions and a drop in lava lake level), suggesting that not only the timing of intrusions and eruptions but also the eruptive style of Kilauea is influenced by rainfall,” they added.

Constraining the exact relationship between rainfall and volcanoes could help scientists generate more accurate predictions about the timing of big eruptions, enabling communities to better anticipate these disasters. This could prove to be especially important to people living in volcanically active regions that are projected to receive more rainfall in the future due to anthropogenic climate change—though it’s not yet clear where those hotspots might be.

“Currently we are trying to work out where this example fits within a broader context,” Farquharson explained, citing the previous studies about rainfall-triggered eruptions. “Are these cases anomalies, or are they symptomatic of a larger-scale trend? If so, what are the commonalities between volcanoes that exhibit this phenomenon?”

“There is still a great deal of research to be done before we can answer these questions conclusively,” he said.