The eruption of the Hunga Tonga-Hunga Ha’apai volcano in Tonga on 15 January was the most powerful of the 21st century so far.
The volcano, which is 20 kilometres wide at its base and mostly lies underwater north of Tonga’s main island, Tongatapu, erupted with a making it the most explosive eruption since that of Mount Pinatubo in the Philippines in 1991. The blast shot ash 57 kilometres into the sky.
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Tsunami waves caused by the explosion were initially and were still up to 18 metres high by the time they reached some parts of Tonga, says at the University of Auckland in New Zealand, who went to Tonga to assess the damage in March.
On Mango Island, north-east of Tongatapu, he saw “every single house and every single building washed up and squashed against the back hill”, while on the western side of Tongatapu, “there were about 12 resorts that were absolutely smashed – you could only see the foundations left”, he says.
Four people in Tonga were killed by the tsunami. The reason the death toll wasn’t higher is that Tongans are very aware of tsunami risk, and most people swiftly evacuated to the highlands when they saw and heard the volcano erupting, says Cronin.
In May, Cronin visited the volcano to assess whether it was still active. “It was a bit dangerous, but we went out with a small crew and worked night and day to collect information as quickly as possible and minimise the time we spent there,” he says.
The measurements they took in May, and more that were taken in October, suggest that the volcano is becoming less active and should enter a dormant period.
Previous mega-volcanic eruptions, like the Mount Pinatubo eruption and the 1883 eruption of Krakatoa, cooled Earth slightly by ejecting large amounts of gases and particles that reflect sunlight back into space. Hunga Tonga-Hunga Ha’apai , which could have a small, temporary warming effect because water traps heat.
“But we don’t know the climate impact yet because it’s still too soon,” says Cronin.
