Tonga tsunami: huge waves batter coast after underwater volcanic eruption

An incredible satellite image showed the moment an underwater volcano erupted yesterday, causing rolling tsunami waves and downpours of water-clogged ash to pound the Pacific island nation of Tonga.

On the ground the afternoon skies turned dark within minutes after plumes of gas, smoke and ash ripped through the ocean surface and spiralled into vast debris clouds more than ten miles high.

Terrified residents fled by foot and car for higher terrain. Some thought bombs had exploded as sonic booms crackled during the eight-minute eruption.

The explosion was heard across the South Pacific before tsunami waves several feet high lashed the island chains of Fiji and Vanuatu.

Depictions of the eruption and its aftermath were picked up by weather satellites in the region. The most spectacular — which also showed the outline of Australia more than 2,000 miles away — came from Himawari-8, operated by the Japan Meteorological Agency.

The extent of the destruction and casualties remained unclear after communications collapsed on the main island of Tongatapu. All internet connectivity was lost at around 6.40pm local time.

New Zealand prime minister Jacinda Ardern said there had so far been no reports of injury of death from the country’s embassy in the capital Nuku’alofa but warned that Tonga was in need of water supplies due to contamination caused by the ash cloud.

“The tsunami has had a significant impact on the foreshore on the northern side of Nuku’alofa with boats and large boulders washed ashore,” Ardern said.

“Nuku’alofa is covered in a thick film of volcanic dust but otherwise conditions are calm and stable.”

The New Zealand military offered assistance and may fly reconnaissance missions at first light on Monday if the cloud allows. Local airfields were reported to be out of action.

Troops evacuated Tupou, the Tongan king, from his palace near the shore as water surged into its grounds in the capital Nuku’alofa, 40 miles south of the eruption of the Hunga Tonga-Hunga Ha’apai volcano.

“You could just hear screams everywhere, people screaming for safety, for everyone to get to higher ground,” Mere Taufa, a Tongan resident, told the New Zealand website Stuff. She said her brother initially thought they had heard a series of bomb blasts, but then water poured into their home.

Mary Fonua, a journalist in the Tongan capital, described a series of “huge explosions” as the volcano erupted. “You’ll forgive the wobble in my voice because we’ve had a very frightening hour,” she told 1News in New Zealand.

She said the eruption was followed about 15 minutes later by “huge, rolling” waves which hit waterfront settlements.

“This long white wave, we could see coming from the horizon. After about three waves it had come over the road and into our garden,” she added.

Fonua said she could see lightning flashing in the direction of the volcano. There have been intermittent eruptions by the volcano since last month. Tonga has a population of about 105,000 people, more than two thirds of whom live on Tongatapu, one of 45 inhabited islands out of 171 that make up the nation.

The Tonga Meteorological Service announced that a tsunami warning was declared for all of the archipelago. Hours later waves of 2.5ft reached California and flooded beach car parks, the US National Weather Service reported.

In the Fijian capital Suva, more than 500 miles away, officials described “loud thunder sounds” as they issued tsunami alerts and opened emergency evacuation centres after urging residents of low-lying communities to leave their homes.

In New Zealand, 1,500 miles away, the authorities issued storm surge warnings.

In Australia swimmers in New South Wales were advised to leave the water and move away from the water’s edge in case of a tsunami.

Around 230,000 residents in Japan were advised to evacuate as waves of more than a metre hit coastal areas, including some affected by the deadly 2011 tsunami.

Across the ocean in Hawaii, Alaska and along the US Pacific coast, residents were asked to seek higher ground, said Dave Snider, of the National Tsunami Warning Centre in Palmer, Alaska. “We don’t issue an advisory for this length of coastline as we’ve done — I’m not sure when the last time was,” he said. “I hope that elevates the importance and severity for citizens.”

The vast majority of Earth’s volcanic activity takes place under the sea. Across the ocean floor, where tectonic plates collide into each other, huge pressures and destructive forces play out, creating new land. Most submarine volcanoes are prevented from explosive eruptions that breach the surface due to the seawater and high pressure. When underwater volcanoes near the surface erupt, the heat and pressure can result in explosive eruptions causing dramatic changes in the surrounding sea level and triggering tsunamis. Destructive waves can also be caused by the collapsing slopes of volcanic islands slipping into the sea.

Hunga Tonga–Hunga Ha’apai lies underwater between two islands from which it gets its name. The area is highly active and part of the Pacific Ring of Fire. It has been the scene of a number of eruptions in recent years.

The Indian Ocean tsunami, also known as the Christmas or Boxing Day tsunami, which struck on the morning of December 26, 2004, was triggered by a magnitude 9.1 underwater earthquake.

Within 20 minutes the first of several enormous waves hit the coast of Banda Aceh in Sumatra, Indonesia, killing more than 100,000 people. Subsequent waves crashed over shorelines in Thailand, India, Sri Lanka and South Africa. Nearly 230,000 people died.