The Tonga volcano caused powerful waves that kept ringing through the atmosphere following the eruption of Hunga Tonga–Hunga Haapai is unlike anything else seen. Volcanoes are rare to occur but are usually very powerful and deadly when they do.

Scientists are racing to unravel a perplexing series of massive ripples in the Earth’s atmosphere caused by the weekend eruption of the Tongan volcano. Satellite data show that the event, which some fear could have wiped out the Pacific-island nation, caused an unusual pattern of atmospheric gravity waves. Previous volcanic eruptions did not generate such a signal, leaving experts perplexed.

‘Nice concentric wave patterns,’

“This instrument has been running for about 20 years, and we’ve never seen such nice concentric wave patterns before,” Hoffmann adds.

When air molecules in the atmosphere are disturbed vertically rather than horizontally in the air column, atmospheric gravity waves occur. This can happen when the wind picks up speed as it rises over a mountaintop, or when convection occurs in local weather systems.

The up-and-down waves transport energy and momentum through the atmosphere, and their effects are frequently visible in the way they cause high clouds to form in a series of ripples.

Tonga volcano
The US National Oceanic and Atmospheric Administration’s GOES-West satellite captured the explosive eruption of Tonga volcano Haʻapai.Credit: NOAA

“It’s truly one-of-a-kind.” “We’ve never seen anything like this before in the data,” says Lars Hoffmann, an atmospheric scientist at Germany’s Jülich Supercomputing Centre.

The discovery was made in images collected by NASA’s Aqua satellite’s Atmospheric Infrared Sounder (AIRS) in the hours following the 14 January eruption of the Hunga Tonga–Hunga Haapai volcano.

They depict dozens of concentric circles, each representing a fast-moving wave in the atmosphere’s gases stretching over 16,000 kilometres. The waves travelled from the ocean’s surface to the ionosphere, and researchers believe they circled the globe several times.

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