In January 2022, the Hunga volcano in Tonga began to rumble and its explosive activity increased to a climax on January 15, when it ejected ash, water and magma gas into the mesosphere at least 58 km away. The eruption lasted at least 11 hours and caused a record number of lightning bolts. New information gathered about the eruption can be used to better monitor aviation hazards resulting from this type of eruption.
Hunga is an underwater volcano in the South Pacific Ocean. Researchers tracked lightning flashes and estimated their height based on data from sensors that measure light and radio waves. They found that Hongi’s eruption caused just over 192,000 flashes consisting of nearly 500,000 electrical pulses. The flashes peaked at 2,615 per minute and reached heights of 12 to 19 miles (20 to 30 kilometers), something never seen before.
“This eruption produced a powerful thunderstorm the likes of which we have never seen before,” said Alexa Van Eaton, lead author of the study. “It turns out that volcanic eruptions can produce stronger lightning than any other storm on Earth.”
The volcano plume pushed so much mass into the mesosphere that waves formed in the volcanic cloud, very similar to the ripples that occur in a pond when a rock is thrown into it. It was observed that lightning “slid” over these waves, moving outward in huge rings 150 miles (250 km) long.
Getting reliable information about volcanic plumes at the beginning of a volcanic eruption, especially from underwater volcanoes, can be difficult. According to the researchers, the information obtained from the eruption of the Hunga volcano can be used to better monitor aviation hazards during a major volcanic eruption in the future.
This is the first time that a large volume of magma has been observed erupting through water, known as the Freatoplin eruption, using modern instruments. Until now, scientists have only seen evidence of Freatoplin eruptions in the geological record.
“It was like digging up a dinosaur and seeing it walk on four legs,” Van Eaton said. “It kind of takes your breath away.”
The information about the Hongi eruption can be used to more accurately monitor aviation hazards caused by volcanic eruptions. It also expands our knowledge of how volcanic plumes can affect atmospheric phenomena such as lightning, and how Freatoplin eruptions occur.