A team of US scientists have found evidence a mega tsunami hit Tonga in the past few thousand years and said another giant wave could strike the region again.
The scientists from the University of Texas studied massive boulders of coral found up to 400 metres from the shoreline on Tonga's main island Tongatapu.
Team leader Dr Matthew Hornbach said it was likely the boulders were deposited when a nearby underwater volcano caused a land-slip, resulting in a tsunami.
"We think there was a fl, with a slide-related tsunami ... It is really tricky to say whether that was an eruption versus a slide-event," Hornbach said.
"We think that it is possible that they (the boulders) were put in place within the last few thousand years," he said.
The huge boulders washed ashore during the event weigh up to 1,600 tonnes, more than twice the size of the largest rocks deposited on land when Indonesia's Krakatoa volcanic island erupted in 1883, causing a huge tsunami.
"The energy involved in the wave at least at this zone, in this region where the wave came on shore, was potentially more powerful than what we saw at Krakatoa," he said.
Hornbach believes a volcanic chain situated 30-35km to the west of Tonga was the most likely cause of the event, adding the region's volcanoes probably have minor eruptions every year, with larger events every 25-50 years.
He said people living in Tonga and surrounding countries should consider plans in case the event was repeated.
"For volcanic eruptions and submarine slides in this area you only have a few minutes before a wave would likely arrive on shore, because of the close proximity and the deep water," he said.
"The closer the islands are, the more I would be concerned."
Hornbach said it was difficult to know how high the mega tsunami might have been without more data.
