On January 15, 2022, Hunga Volcano in Tonga produced the most violent eruption in the modern satellite era, sending a water-rich plume at least 58 km (36 miles) high. This plume created record-breaking amounts of volcanic lightning observed both from space and by radio antennas on the ground thousands of kilometers away. New research shows that the eruption created more lightning — 2,615 flashes per minute at peak intensity — than any storm yet documented on Earth, including supercells and tropical cyclones. The peak lightning rate is significantly higher than the second most intense lightning event ever detected — 993 flashes per minute — in a thunderstorm over the southern United States in 1999.
Hunga Tonga-Hunga Ha’apai volcanic eruption captured at December 30, 2021. Image credit: Tonga Geological Services.
An explosive eruption began on December 19, 2021 near the remote islands of Hunga Tonga and Hunga Ha’apai in the South Pacific Ocean.
These two islands are small peaks on the rim of a much larger submarine caldera volcano known as Hunga Volcano.
The explosive activity intensified on January 13, 2022, followed by the climactic eruption on January 15 that sent a water-rich volcanic plume into the mesosphere of our planet.
In addition to significant local impacts on the Kingdom of Tonga, the eruption created global-scale acoustic waves, tsunamis, ionospheric and geomagnetic disturbances, and warmed the climate due to water vapor injection.
The event continues to push the boundaries of our understanding of how explosive volcanism impacts the broader Earth system.
“This eruption triggered a supercharged thunderstorm, the likes of which we’ve never seen,” said lead author Dr. Alexa Van Eaton, a volcanologist at the U.S. Geological Survey.
“These findings demonstrate a new tool we have to monitor volcanoes at the speed of light and help the U.S. Geological Survey’s role to inform ash hazard advisories to aircraft.”
“The storm developed because the highly energetic expulsion of magma happened to blast through the shallow ocean.”
“Molten rock vaporized the seawater, which rose up into the plume and eventually formed electrifying collisions between volcanic ash, supercooled water and hailstones. The perfect storm for lightning.”
Combining data from sensors that measure light and radio waves, Dr. Van Eaton and colleagues tracked lightning flashes and estimated their heights.
The eruption produced just over 192,000 flashes (made up of nearly 500,000 electrical pulses), peaking at 2,615 flashes per minute.
Some of this lightning reached unprecedented altitudes in Earth’s atmosphere, between 20 to 30 km (12-19 miles) high.
“With this eruption, we discovered that volcanic plumes can create the conditions for lightning far beyond the realm of meteorological thunderstorms we’ve previously observed,” Dr. Van Eaton said.
“It turns out, volcanic eruptions can create more extreme lightning than any other kind of storm on Earth.”
The lightning provided insight into not only the duration of the eruption, but also its behavior over time.
“The eruption lasted much longer than the hour or two initially observed,” Dr. Van Eaton said.
“The January 15 activity created volcanic plumes for at least 11 hours. It was really only from looking at the lightning data that we were able to pull that out.”
The researchers saw four distinct phases of eruptive activity, defined by plume heights and lightning rates as they waxed and waned.
“The insights gained from linking lightning intensity to eruptive activity can provide better monitoring and nowcasting of aviation-related hazards during a large volcanic eruption, including ash cloud development and movement,” Dr. Van Eaton said.
“It’s a significant challenge to get reliable information about volcanic plumes at the beginning of an eruption, especially for remote, submarine volcanoes.”
“Harnessing all the long-range observations available, including lightning, improves early detection to keep aircraft and people out of harm’s way.”
The authors were also puzzled by the concentric rings of lightning, centered on the volcano, that expanded and contracted over time.
“The scale of these lightning rings blew our minds. We’ve never seen anything like that before, there’s nothing comparable in meteorological storms. Single lightning rings have been observed, but not multiples, and they’re tiny by comparison,” Dr. Van Eaton said.
Intense, high-altitude turbulence was again responsible.
The plume injected so much mass into the upper atmosphere that it sent out ripples in the volcanic cloud, like dropping pebbles in a pond.
The lightning appeared to ‘surf’ these waves and move outward as 250-km-wide rings.
As if all that weren’t enough to make this eruption fascinating, it represents a style of volcanism known as phreatoplinian, which occurs when a large volume of magma erupts through water.
Previously, this eruption style was only known from the geological record and had never been observed with modern instrumentation. The Hunga eruption changed all that.
“It was like unearthing a dinosaur and seeing it walk around on four legs. Sort of takes your breath away,” Dr. Van Eaton said.
“The eruption of Hunga Volcano was the largest volcanic explosion since Krakatau in 1883,” said co-author Dr. Sonja Behnke, a researcher at Los Alamos National Laboratory.
“Lightning observations such as these reveal detail about the evolution of an eruption over time, which is particularly valuable when cloud-cover obscures satellite observations of a plume.”
The team’s paper was published in the journal Geophysical Research Letters.
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Alexa R. Van Eaton et al. Lightning Rings and Gravity Waves: Insights Into the Giant Eruption Plume From Tonga’s Hunga Volcano on 15 January 2022. Geophysical Research Letters, published online June 20, 2023; doi: 10.1029/2022GL102341
