Because Tonga is located on the edge of a tectonic plate it does get frequent earthquakes, though they are usually tremore and nothing to worry about. However, Tonga is also located on what is known as the Pacific Ring of Fire (cool name, I know!), which is basically a massive area of submarine volcanic activity.
A couple of days ago, a new eruption occured from the Hunga caldera, which has not erupted since 1988. You can see the plume of smoke from the waterfront road here in Nuku'alofa.
Tonga is amazing for this kind of stuff - new islands appear, hang around for a bit, and then are pulled back into the ocean never to be seen again. It's quite eerie in a way, especially having come from a country which has been solid, virtually unchanged land mass for millenia!
Thanks to whoever posted these pics of the Hunga erruption - taken on a flight south to Tongatapu from Vava'u!