What causes a tsunami? An ocean scientist explains the physics

Waltham (Massachusetts): On January 15, 2022, the Hunga Tonga-Hunga Ha’apai volcano in Tonga erupted, sending a tsunami racing across the Pacific Ocean in all directions.

As word of the eruption spread, government agencies on surrounding islands and in places as far away as New Zealand, Japan and even the U.S. West Coast issued tsunami warnings. Only about 12 hours after the initial eruption, tsunami waves a few feet tall hit California shorelines more than 5,000 miles away from the eruption.

I’m a physical oceanographer who studies waves and turbulent mixing in the ocean. Tsunamis are one of my favourite topics to teach my students because the physics of how they move through oceans is so simple and elegant.