Jun 25, 2023 - Science

Tonga volcano eruption triggered most intense lightning on record

An umbrella cloud generated by the underwater eruption of the Hunga Tonga-Hunga Ha’apai volcano on Jan. 15, 2022. Credits: NASA Earth Observatory image by Joshua Stevens using GOES imagery courtesy of NOAA and NESDIS

The underwater eruption of the Hunga Tonga-Hunga Ha’apai volcano last year generated a supercharged storm — and the most intense lighting event on record.

Why it matters: Observations of the eruption-induced storm could help efforts to one day monitor the hazards from volcanoes using real-time lightning data, according to the researchers who led the study.

Details: The underwater eruption created a plume of ash, water and volcanic gas that reached 58 km, or about 36 miles, above sea level and into the stratosphere.

  • It then expanded as an umbrella cloud and created powerful gravity waves that rippled outward from the plume, followed by flashes of lightning in a similar ring-shaped pattern that the researchers detected by combining data from sensors for radio waves and light.
  • Lightning occurred high in the volcanic cloud, about 20 to 30 km (about 12 miles to 18.5 miles) above sea level, researchers reported in Geophysical Research Letters.
  • The storm lasted 11 hours and generated more than 2,600 lightning flashes per minute at its peak intensity, "an astonishing rate of volcanic lightning" and "the most intense lightning rates ever documented in Earth's atmosphere," they write.

The researchers propose a combination of a very large eruption rate, a fast-expanding umbrella cloud and vaporized seawater in the plume contributed to the unique event.

  • It "eventually formed electrifying collisions between volcanic ash, supercooled water and hailstones," per a press release.

The intrigue: The massive lighting event suggests lightning can be triggered in conditions beyond those typically seen on Earth.

  • The volcanism in this eruption involved magma erupting through water — what's called phreatoplinian. Until now it had been known to exist only through geological records, according to the release.
  • “It was like unearthing a dinosaur and seeing it walk around on four legs,” Alexa Van Eaton, a volcanologist at the United States Geological Survey who led the study, said in the press release.
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