Hunga Tonga-Hunga Ha’apai (hung-uh tahng-uh-hung-uh ha-ah-PIE) is an underwater volcano in Tonga, a nation of 170 islands in the Pacific Ocean. In December 2021, it started erupting on and off. Then, on January 15, 2022, it exploded, blasting a huge plume of ash, rocks, and water vapor into the air. This eruption had major effects around the globe.

Scientists studied data from satellite videos, seismometers, which measure vibrations in Earth’s crust, and other tools. They learned that the eruption produced powerful vibrations in the air called pressure waves. These vibrations suddenly moved a large amount of water, forming ocean waves called tsunamis. Large tsunamis damaged hundreds of buildings on Tonga, including many homes. Small tsunamis even formed in the Caribbean Sea—11,000 kilometers (7,000 miles) away!

This was the first evidence that pressure waves from a large eruption could cause far-reaching tsunamis. Researchers hope to use data from the eruption to improve tsunami warning systems.