The Hunga Tonga Hunga Ha’apai eruption was only a surprise in its violence – the volcano has been erupting for years.

When the Hunga Tonga Hunga Ha’apai volcano in Tonga exploded on Saturday, it caused a meter-high tsunami that spanned the entire Pacific ocean and a shock wave that went twice around the world. The massive cloud of ash and steam was photographed from space, where it looks larger than New Zealand.

As of Wednesday, the known death toll of the eruption is only five people. Three in Tonga, and two fishermen in Peru whose boat was overturned by the powerful wave. This despite the fact that on three Tongan islands, nearly every building was destroyed. But this was the second eruption of Hunga Tonga Hunga Ha’apai in less than a month – a smaller eruption on December 20 2021 made enough of an ash plume that air traffic was diverted, and the volcano grew overnight.

Before 2009, Hunga Tonga and Hunga Ha’apai were two small, inhabited islands, about 40 miles north of Tongatapu, the main island of Tonga. An eruption in 2009 saw the rise of a massive cinder cone between the two islands, merging them into one island four times the size either had been previously. Both islands were part of the rim of an ancient caldera of the same volcano.

In the wake of the eruption, most of the conjoined island has been destroyed, leaving only two tiny landmasses, each about the size of a tennis court, around a new crater. The tsunami was likely caused by the massive landslides as the volcanic cone self-destructed.

The eruption made communication with Tonga very difficult for several days. The underwater landslides severed the deep sea communication cables, while ash and dirty lightning made satellite communication unreliable. Planes couldn’t reach the island, and it wasn’t safe to bring boats through the falling, caustic ash. But on Friday, communications were partially restored.

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