As if earthquakes were not bad enough on their own there’s the tsunamis – giant waves in the ocean – generated by off-shore earthquakes.

In some respects the devastation from a tsunami can beat that of a quake, simply because the latter’s destruction is usually restricted to a few hundred square miles at worst, whereas the tsunami can smash thousands of miles of coastlines, and do so at great distances from the source of the tsunami.

We’ve actually seen two of the worst tsunamis in our lifetime and both in the still-young 21st century. First with the terrible Indian Ocean tsunami of 2004, one wave of which is pictured here, and the 2011 Japanese event.

But now there’s a new type to think about – ones caused by underwater volcanic eruptions. Ever since Krakatoa’s famous destruction in 1883 and the subsequent tsunami, people have been aware that volcanoes can cause them, even if nowhere near as common as earthquake-generated ones.

But the Tonga eruption earlier this year has, after considerable analysis, provided yet another method of tsunami generation:

The initial tsunami wave created by the eruption of the underwater Hunga Tonga Ha’apai volcano in Tonga in January 2022 reached 90 meters in height, around nine times taller than that from the highly destructive 2011 Japan tsunami, new research has found.

The article points out that detection of volcanic-tsunamis is “30 years behind” that of earthquake-based events. Fortunately the volcano-based ones are a lot less common. I also found this interesting:

The research team found that the tsunami was unique as the waves were created not only by the water displaced by the volcano’s eruption, but also by huge atmospheric pressure waves, which circled around the globe multiple times. This ‘dual mechanism’ created a two-part tsunami—where initial ocean waves created by the atmospheric pressure waves were followed more than one hour later by a second surge created by the eruption’s water displacement.

Well, there’s a start on a warning system.