The eruption of a giant underwater volcano in the Pacific Ocean near Tonga has triggered tsunami warnings across the Pacific. Here’s what we know about the volcano at Hunga Tonga-Hunga Ha’apai and why it erupted.
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, the vent or crater of the volcano is above water. It sits nested in between two landmasses, Hunga Tonga and Hunga Ha’apai. 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 9,000m 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.
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.
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.
Tsunami warnings were issued for New Zealand, Japan, Hawaii, Alaska and the Pacific coast of the United States.
For more information, go to www.abc.net.au/news/2022-01-16/how-the-volcanic-eruption-near-tonga-unfolded/100759528