“It was clear right away that this was going to be a showstopping scientific event,” said Alexa Van Eaton, a volcanologist at the U.S. Geological Survey. “It’s several orders of magnitude larger than anything we’re used to looking at … This eruption clearly was going to teach us something new.”
The climatic awakening of the Hunga Tonga — Hunga Haʻapai submarine volcano lasted less than a day and took the lives of a handful of people, including as far away as Peru.
The volcano has already broken several records: The powerful blast was bigger than any U.S. nuclear explosion. Tsunami waves overwhelmed shores. Ash flew up into the third layer of Earth’s atmosphere, higher than any other recorded volcanic eruption. An unprecedented amount of water, enough to fill nearly 60,000 Olympic-size swimming pools of water, shot up in the atmosphere and could warm our atmosphere in the future.
Now, a new study led by Van Eaton reveals more details of this puzzling event by analyzing lightning data. Researchers found the plume created its own massive weather system — and the most intense lightning storm ever recorded.
At least 2,600 lightning bolts each minute were detected during peak activity, shattering rates from any other weather system, storm or volcanic eruption recorded in Earth’s history. Using the data, the team also determined that the eruption lasted for 11 hours, several hours longer than previously estimated.
Even using satellites in space, Van Eaton said the ash cloud from the eruption obscures the region around the volcano.
“You can’t drill down through the cloud and see what’s going on at the event,” Van Eaton said. “Lightning can help us do that … we were able to basically match up the lightning rates with the plume height to reconstruct the timeline of the Jan. 15 activity.”
The intense eruption lodged volcanic material and ash 36 miles high, a world record. Van Eaton said that momentum from the fragmentation of the magma drove a strong upward current of air at the ground level, which is typically seen in thunderstorms. Volcanoes are known to create their own weather system like this, but she said “this was on another level” and created intense lightning.
Lightning in volcanoes isn’t necessarily new. Lightning is caused by an imbalance of electrical charges in the atmosphere. In volcanoes, ash particles scraping against one another, along with hail and ice-forming processes, can electrify airborne particles.
“It may be that larger particles were going one direction and smaller particles were going in another, and that helped create the charge separation that leads to electrical discharges,” Van Eaton said.
Nearly 200,000 lightning flashes were detected in the volcanic plume during the entire eruption, according to ground and satellite sensors. Some of the lightning occurred between 12 and 19 miles above sea level, the highest-altitude flashes on record. The lightning also appeared in ring formations expanding and contracting around the center of the volcano, which the authors had not seen before.
At the peak of the eruption, half of the lightning detected around the globe at the time was occurring at the volcano, said co-author Chris Vagasky, a meteorologist and lightning data expert. The peak lightning rate — 2,600 lightning bolts in a minute — was more than eight times higher than the next highest volcanic lightning event, from the Mount Redoubt eruption in April 2009.
The authors say this peak rate might even be an underestimate because instruments may have missed many bolts. Van Eaton said one lightning sensor network basically “blew itself up” because it was detecting so much lightning and became saturated.
The lightning also occurred even when other remote, infrared and seismic data were quiet, indicating that the eruption continued for hours longer than scientists had initially thought.
“The Hunga Volcano eruption was a truly extreme event that created conditions that don’t occur in traditional thunderstorms or other volcanic eruptions,” said Vagasky, the manager of the Wisconsin Environmental Mesonet. “It was unlike any lightning event that I’ve ever seen before, and it will be difficult to surpass.”
Geoscientist Sam Purkis, who was not involved in the research, said the study elegantly illuminates how volcanoes interact with the atmosphere. Scientists had already suspected that the eruption was a focal point for lightning, but the paper pinpoints how extreme it really was.
“This is a fascinating study and shows how the Tongan eruption influenced the Earth system in ways that you might not immediately associate with a volcanic explosion,” Purkis, a professor at the University of Miami, wrote in an email.
These insights, the authors say, will help researchers better understand future volcanic eruptions as they are happening.
“Ultimately, we want to be able to do this type of study in near real time to understand what’s happening during an eruption that could be impacting aviation, could be impacting human infrastructure downwind, and basically to try to keep people out of harm’s way,” Van Eaton said.
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