The eruption of an underwater volcano near Tonga has been confirmed as the largest ever recorded, researchers revealed on Monday.
The underwater Hunga-Tonga-Hunga-Ha'apai volcano, 65 kilometres north of Tonga's capital Nuku'alofa, erupted in January, sending a gigantic cloud of ash and gas into the sky.
A New Zealand-led team has completed the fullest investigation to date into the eruption.
National Institute for Water and Atmospheric Research (NIWA) discovered that the equivalent to 2.6 million Olympic-sized swimming pools of seafloor was displaced - a third more than initial estimates.
Three-quarters of the material was deposited within 20 kilometres of the volcano.
NIWA marine geologist Kevin Mackay said the 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."
The plume sent debris into the sky, where it has been circulating in our atmosphere for months, Mackay said.
Despite the huge displacement of material, the volcano's flank remained largely intact. However, the caldera, or crater, is now 700 metres deeper than before the eruption.
Further evidence from the caldera shows signs that the volcano is still erupting.
NIWA scientists have also unravelled one of the biggest unknowns of the eruption – the pyroclastic flows.
Pyroclastic flows are currents made up of dense lava, volcanic ash and gases which can reach temperatures of 1,000 degrees Celsius and speeds of 700 kilometres per hour.
Pyroclastic deposits were found some 80 kilometres away from the volcano.
Emily Lane, NIWA Principal Scientist - Natural Hazards, believes they could have travelled as far as 100 kilometres.
"They are also what caused both the domestic and international communications cables to break, with the domestic cable now being buried under 30m of eruptive material."
