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Volcanologist Shane Cronin is the first overseas scientist allowed into Tonga to investigate January's powerful undersea volcanic eruption and tsunami which caused massive disruption and damage.
Water supply and agriculture were affected in the fallout from the eruption and the explosions of Hunga Tonga-Hunga Ha'apai could be heard as far away as New Zealand and Alaska.
It is now known to be the largest volcanic explosion ever recorded - double that of the next largest, Mount Pinatubo in the Philippines more than 30 years ago.
Photo: Supplied / Shane Cronin, University of Auckland
Professor of Volcanology at the University of Auckland, Shane Cronin has examined ash from the explosion, video footage and aerial images.
His working theory is that the side of the volcano collapsed, vastly expanding the already explosive interactions between magma and water.
Professor Cronin is now in Tonga to investigate further.
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