Over the weekend, the volcanic island of Hunga Tonga-Hunga Ha’apai erupted in the south Pacific. People as far away as Alaska heard the sound. Here in Indiana, we did not. But we were able to detect the shock wave from the explosion as a rapid pressure change.

In fact, you can watch it cross the continental US by plotting the pressure changes, as Daryl Herzmann did.

A little after midnight, the pressure wave came around from the other side of the globe. Alerted to this possibility by Daniel Dawson, I grabbed the graph from my weather station again.

I don’t have much to add. It’s just a neat example of how our planet works. Some of the satellite imagery is absolutely mesmerizing. Unfortunately, it sounds like the damage to nearby islands may be catastrophic. The BBC reported that some islands may have been completely covered by seawater. Tonga is already gravely threatened by rising sea levels, and disasters like this can only make the situation worse.

Edited 17 January 2022 at 3pm EST to say the pressure wave came from the other direction, not around again. Thanks to Shelley Melchior for the correction.