By: Jason Shen

In 2022, an underwater volcano in the South Pacific island nation of Tonga made a new record for the highest lightning ever recorded. It spewed a plume of ash and water up to 30 kilometers (higher than most planes fly). It also launched a tsunami as tall as the Statue of Liberty. Now, scientists find that it triggered lightning at the highest altitudes ever seen.

Most often, lightning is born from clouds, but lightning can also be formed inside a volcano’s eruption plume. That plume is made of tiny bits of ash, gas and dust. When these tiny bits bump into each other, they make static electricity. Once enough static electricity builds up, lightning rushes through the plume.

Alexa Van Eaton led a team that looked at how high the Tonga eruption’s lightning was. She’s a volcano scientist at the U.S. Geological Survey’s Cascades Volcano Observatory in Vancouver, Washington. To estimate the lightning’s height, Van Eaton’s team looked at a few different types of data. One was radio waves created by the lightning. They also examined satellite images of the eruption plume and infrared light from the flashes.

The data revealed that the lightning started more than 12 miles above sea level. Normally, lightning doesn’t start from that high up (1 mile above sea level), but the air pressure at that height is usually too low to form lightning leaders. These leaders are the channels of hot plasma that make up the lightning in thunderstorms.