The eruption of a giant underwater volcano in the Pacific Ocean has triggered tsunami warnings, including for some of Australia's east coast.
Here's what we know about the volcano at Hunga Tonga-Hunga Ha'apai and why it erupted.
What is Hunga Tonga-Hunga Ha'apai?
Technically, the volcano that erupted at Hunga Tonga-Hunga Ha'apai is classified as an underwater volcano, said Emeritus Professor Richard Arculus from the Australian National University.
But as Professor Arculus points out, and as you can see in the image below, the vent or crater of the volcano is above water.
It sits nested in between two landmasses, Hunga Tonga and Hunga Ha'apai.
NASA says these landmasses are "young" and were born out of eruption.
Has it erupted before?
Yes. And Professor Arculus said it's been "fairly active in the last 15 years".
A 2015 eruption made headlines after its ash cloud forced several airlines to cancel flights in and out of Tonga.
At the time, New Zealand Civil Aviation Authority meteorologist Peter Lechner told Radio New Zealand the volcano was sending volcanic ash more than 9,000 metres into the air.
He also said the volcano had erupted in 2009, 1988, 1937 and 1912.
When the Hunga Tonga-Hunga Ha'apai volcano erupted in 2015, scientists did not expect the land mass it formed to last.
Its landscape has eroded and changed over the past few years.
So what happened this time?
Professor Arculus described it as a "major vent-clearing explosion".
Satellite imagery of the eruption shows the explosion at sea surface "spreads somewhat laterally".
This surge turns into a "shock wave ring".
Tsunamis are generated by the rebound of inrushing seawater into the cavity made in the Earth's crust by the explosion.
Professor Arculus said the ash cloud, seen from outer space, was the result of water and hot fragmented matter interacting.
How powerful was this eruption?
As a comparison, Professor Arculus said it "would be many times more powerful than White Island".
The White Island volcano erupted in December 2019, and killed 22 tourists visiting the island, including 17 Australians.
New Zealand's Ministry of Foreign Affairs and Trade said there were no official reports of deaths or injuries in Tonga, but communications remain limited.
The island nation was hit by a metre-high tsunami after the eruption, with witnesses saying the eruption shook the earth for several minutes.
The Bureau of Meteorology has issued marine warnings for NSW, Lord Howe Island and Norfolk Island.
Chile's National Emergency Office ordered the evacuation of several coastal regions due to a minor Tsunami.
Claudio Aldea, Deputy Director of Operations of The National Emergency Office of the Ministry of the Interior asked people in the regions of Coquimbo and Los Rios to evacuate to safe zones at least 30 metres above sea level.
Tsunami warnings were issued for New Zealand, Japan, Hawaii, Alaska and the Pacific coast of the United States.
What happens next?
Grace Legge, a Senior Meteorologist for Australia's Bureau of Meteorology warned the situation was dangerous and changing.
An underwater eruption was much harder to predict than atmospheric weather patterns or earthquakes, she said.
Professor Arculus said volcanic activity could continue for weeks or months but it was hard to predict if or when another powerful explosion would happen again.
"This might not be over," he said.
But you can expect to see a reminder of the eruption soon on Australian shores.
Professor Arculus said pumice, which is lightweight volcanic rock, will be washing up on our east coast in the months ahead.
Pumice floats and can crumble in your hand, it's grey and full of holes.
ABC / wires
