A New Zealand-led team has confirmed that last January’s massive underwater Tongan volcano eruption was the loudest ever recorded on earth.
New Zealand’s National Institute for Water and Atmospheric Research (NIWA) determined that the Hunga-Tonga Hunga-Ha’apai volcano emitted the biggest atmospheric explosion recorded on Earth in more than 100 years.
NIWA scientists found that almost 10 cubic kilometers (2.4 cubic miles) 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/12.4 miles of the volcano. This leaves almost 3.2 cubic kilometers/0.77 cubic miles unaccounted for, according to NIWA.
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 [0.46 cubic miles] 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.”
Despite the huge displacement of material, the volcano’s flank remains surprisingly intact. However, the caldera, or crater, is now 700m/2,297ft 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.
To learn more, check out the video below.