When coastal geologist Ian Goodwin went surfing at Avalon Beach at sunrise on Sunday, he could feel the after-effects of the tsunami that had ripped through Tonga only hours earlier.

“Paddling out was tough, the waves were smaller and choppier,” he said. “There was a sizeable swell running and unusual currents. It was like the ocean was completely confused.”

The first ripple of tsunami waves hit Sydney’s shores after 8pm Saturday, after an explosive underwater volcano violently erupted off Tonga, blanketing the island in a plume of ash that rose 20 kilometres into the air, sending shockwaves rolling around the world.

On Sunday night, there were reports it had contaminated vital water supplies and had severely increased the air pollution of the island.

“This is an extremely rare event with only a handful of similar scale eruptions in the past century,” Australian National University climate scientist Nerilie Abram said. “The atmospheric pressure wave travelled around the globe and was heard as far away as Alaska. This kind of volcanic eruption could have a major impact on our climate in coming years, but it will take a few days until we have the data to understand that.”

Professor Abram said a similar event to the explosion of the Hunga Tonga-Hunga Ha’apai volcano had not occurred since the 1991 Mount Pinatubo eruption in the Philippines.

An undersea volcano eruption of the Pacific nation of Tonga Saturday, January 15, 2022. Credit:NICT

“If it has put enough matter into the stratosphere, then we could see cooler temperatures for the next year or so,” she said.

Dramatic footage showed waves rolling through coastal Tongan homes, causing havoc and sending residents of the Pacific island nation rushing to higher ground. There have been no immediate reports of casualties, and the full extent of damage is not yet known, but multiple communication lines were wiped out.

In late 2014 and early 2015, a series of eruptions in the area, about 60 kilometres north of the capital, created a small island and disrupted international air travel to the Pacific archipelago for several days.

On Sunday, the Bureau of Meteorology issued renewed tsunami alerts and marine threat warnings for all of Australia’s east coast, with lifesavers closing all beaches affected by the warning. NSW beaches remained closed on Sunday evening.

Bondi Beach was open on Sunday morning and then closed again due to a tsunami warning.Credit:Edwina Pickles

Meteorologist Sarah Scully said warnings were expected to be cancelled into Sunday evening, with the highest wave recorded at 1.27 metres on Norfolk Island.

“So an enormous amount of energy was released by the volcanic eruption, and that was trapped by the oceans,” she said, noting a 0.82-metre wave was recorded on the Gold Coast and a 0.77-metre wave at Twofold Bay.

For a tsunami warning to be cancelled, an area would need to have no significant wave height for six hours, Ms Scully said.

The eruption generated large waves in several South Pacific islands and triggered multiple global tsunami warnings, from New Zealand to the west coasts of the United States and South America. Reverberations were felt in Mount Hood in Oregon in the US. An evacuation order was issued for Californian beaches and surge waves hit the Santa Cruz harbour, submerging boats and swamping parking lots.

The ironman and ironwoman series held at Bondi Beach were cancelled.Credit:Getty

From Bondi to Newport, many surfers chose to remain in the water, but Bondi’s ironman series was called off.

University of Newcastle coastal scientist Hannah Power said geological evidence from massive eruptions shows the events are not “usually one-off” and often come in multiples.

“Tsunami waves come in clusters,” Associate Professor Power said.

“We might see another eruption in days, weeks or even years. Often the first wave is not the biggest, so people can become complacent.

An undersea volcano eruption, right, at the Pacific nation of Tonga on Saturday.Credit:NICT

“The last time we saw tsunami waves this big hit Australia’s east coast was in 1960. The tsunami waves that we’ve seen here have been about a metre high, and everyone thinks ‘well I surf or swim in that.’ But waves we see every day on our coastline arrive every 10 seconds. Tsunamis are different in that they arrive every 10 to 30 minutes.”

Dr Power said forceful and unusual currents of water were being “pushed upstream in estuaries, and then pulled back downstream” as the tsunami waves propagate into and out the estuary system.

“Even as far as 8000 kilometres away, on the west coast of the United States, we are seeing significant damage from this event,” said Dr Power, noting Tonga sits on the Ring of Fire in the Pacific, which is rimmed in tectonic plate boundaries, where more than 90 per cent of the world’s earthquake activity occurs.

“The Tonga-Kermadec trench, in the western Pacific Ocean, is a really active part of the world where two tectonic plates meet. It is an area that is prone to volcanoes and earthquakes and one event could mean months or years of more activity to come.”

The explosion on Saturday off Tonga, with lightening seen nearby.Credit:Nine

New Zealand Prime Minister Jacinda Ardern said on Sunday that while there were no official reports of death or injury, further volcanic activity could not be ruled out, and the ash plumes from the eruption had contaminated Tonga’s water supply.

“We have … aircraft ready to deploy and are looking at the deployment of a Navy vessel should it be required,” she said.

“The clear view is that we want to be in Tonga on the ground as soon as we can. For flights that looks like tomorrow. [By sea], we’re already preparing to take those steps as we speak,” Ms Ardern said, noting the satellite images brought home the severity of the eruption and potential damage for the closest islands. “We’re able to deploy within eight hours, but we need to know from Tongan authorities what it is they need to make sure we are providing.”

Australia’s International Development Minister Zed Seselja said Prime Minister Scott Morrison and Ms Ardern had spoken earlier on Sunday and agreed it was important “Australia and New Zealand co-ordinate very closely in any responses.”

A tsunami hitting the shores of Tonga on Saturday.Credit:ABC News

“The Tongan government has agreed to an offer for assistance from the Australian government of a P8 surveillance flight, which we hope will be able to deploy [Monday] morning,” Mr Seselja said.

Pending ash and weather, the flight will assess damage to critical infrastructure such as roads, ports and powerlines, which will determine the next phase of the response.

University of Auckland Professor Shane Cronin, a volcanologist, told New Zealand’s RNZ radio the umbrella ash cloud from the explosion was 300 kilometres wide at some point.

“The cloud covered the [nearest] island, that’s why it went completely dark. The ash doesn’t let any light through,” he said.

The eruption of an underwater volcano off Tonga, which triggered a tsunami warning for several South Pacific island nations Saturday.Credit:

Professor Cronin said there would “almost certainly be more eruptions” in the next few days and weeks.

ANU’s earthquake and tsunami scientist Professor Phil Cummins said while Australia’s east coast had historically avoided large tsunamis, the number of southern volcanoes along the Tonga-Kermadec trench do pose risks.

“If that trench had a large earthquake or a volcanic flank collapse [then] that could cause a significant tsunami on Australia’s eastern coast.”

University of NSW’s coastal researcher Mitchell Harley said the one-metre tsunami waves that hit Sydney’s shores over the weekend generated strong currents, making surfing and boating hazardous.

“To the naked eye it’s not easy to see. But if you can imagine high and low tide coming up and down at hyper speed, that is what is happening. It’s not a huge wave, just a slow process, and it’s this speeding up that is causing strong rips.”

with AP and Mike Foley

A guide to the environment, what’s happening to it, what’s being done about it and what it means for the future. Sign up to our fortnightly Environment newsletter here.

Most Viewed in National

From our partners

Source: Read Full Article