A New Zealand-led team has completed the fullest investigation to date into January’s eruption of the underwater Tongan volcano. Hunga-Tonga Hunga-Ha'apai (HT-HH) emitted the biggest atmospheric explosion recorded on Earth in more than 100 years.
New Zealand's National Institute for Water and Atmospheric Research (NIWA) has discovered that almost 10km3 of seafloor was displaced – the equivalent to 2.6 million Olympic-sized swimming pools and a third more than initial estimates – with two-thirds coming from the summit and the rest from the surrounding flanks.
Three-quarters of this material was deposited within 20km of the volcano. This leaves almost 3.2km3 unaccounted for.
The project leader, NIWA marine geologist Kevin Mackay, said this missing debris could be partly explained by aerial loss.
“This is why we didn’t notice the loss until we had mapped everything. The eruption reached record heights, being the first we’ve ever seen to break through into the mesosphere. It was like a shotgun blast directly into the sky. The volume of this ‘shotgun’ plume is estimated to be 1.9km3 of material, which has been circulating in our atmosphere for months, causing the stunning sunsets we saw following the eruption. This goes some way to explaining why we’re not seeing it all on the seafloor,” said Mackay.
Despite the huge displacement of material, the volcano’s flank remains surprisingly intact. However, the caldera, or crater, is now 700m deeper than before the eruption.
Further evidence from the caldera shows signs that HT-HH is still erupting. A robot boat remotely operated from the UK by SEA-KIT International detected active venting from newly formed cones, explaining why glass fragments formed from cooled molten lava were picked up during NIWA’s earlier survey.
Text excerpted from a NIWA media release on 21 November 2022. Read the full article here.