Tsunami advisories issued for parts of B.C. as undersea volcano erupts in Pacific

Tsunami advisories issued for parts of B.C. as undersea volcano erupts in Pacific

An undersea volcano erupted in spectacular fashion near the Pacific nation of Tonga on Saturday, sending tsunami waves crashing across the shore and people rushing to higher ground.

There were no immediate reports of injuries or the extent of the damage because all internet connectivity with Tonga was lost at about 6:40 p.m. local time, said Doug Madory, director of internet analysis for the network intelligence firm Kentik.

Tonga gets its internet via an undersea cable from Suva, Fiji, which presumably was damaged. Southern Cross Cable Network, the company that manages the connection, does not know yet “if the cable is cut or just suffering power loss,” chief technical officer Dean Veverka said, adding he assumed the eruption was responsible.

Tonga’s Islands Business news site reported that a convoy of police and military troops evacuated King Tupou VI from his palace near the shore. He was among the many residents who headed for higher ground.

Warnings issued

The Tonga Meteorological Services said a tsunami warning was declared for all of the archipelago, and data from the Pacific Tsunami Warning Center said waves of 80 centimetres were detected.

In Canada, a tsunami advisory was issued for parts of the B.C. coast — specifically the north coast and Haida Gwaii, the central coast and northeast Vancouver Island, the outer west coast of Vancouver Island and the Juan de Fuca Strait coast.

Officials in Saanich, on Vancouver island, said there is no need to evacuate — that the potential risk is limited to increased tidal currents — but they urged people to avoid beaches and marinas.

Residents in Hawaii, Alaska and along the U.S. Pacific coast were also advised to move away from the coastline to higher ground and to pay attention to specific instructions from their local emergency management officials, said Dave Snider, tsunami warning co-ordinator for the National Tsunami Warning Center in Palmer, Alaska.

Authorities in the nearby island nations of Fiji and Samoa also issued warnings, telling people to avoid the shoreline due to strong currents and dangerous waves.

In New Zealand, officials warned of possible storm surges from the eruption. The country’s private forecaster, Weather Watch, tweeted that people as far away as Southland, the southernmost region, reported hearing sonic booms from the eruption. Others reported that many boats were damaged by a tsunami that hit a marina in Whangarei, in the Northland region.

‘Darkness blanketing the sky’

On Tonga, home to about 105,000 people, video posted to social media showed large waves washing ashore in coastal areas, swirling around homes, a church and other buildings. Satellite images showed a huge eruption, with a plume of ash, steam and gas rising like a mushroom above the blue Pacific waters.

New Zealand’s military said it was monitoring the situation and remained on standby, ready to assist if asked.

A Twitter user identified as Dr. Faka’iloatonga Taumoefolau posted video showing waves crashing ashore.

“Can literally hear the volcano eruption, sounds pretty violent,” he wrote, adding in a later post, “Raining ash and tiny pebbles, darkness blanketing the sky.”

The explosion of the Hunga Tonga-Hunga Ha’apai volcano was the latest in a series of spectacular eruptions.

Earth imaging company Planet Labs PBC had watched the island in recent days after a new volcanic vent there began erupting in late December.

Satellite images captured by the company show how drastically the volcano had shaped the area, creating a growing island off Tonga.

An island created by the underwater Hunga Tonga-Hunga Ha’apai volcano is shown just before a massive eruption on Saturday. (Planet Labs PBC via AP)

“The surface area of the island appears to have expanded by nearly 45 per cent due to ashfall,” Planet Labs said days before the latest activity.

Earlier, the Matangi Tonga news site reported that scientists observed massive explosions, thunder and lightning near the volcano after it started erupting early Friday. Satellite images showed a five-kilometres-wide plume rising into the air to about 20 kilometres.

The Hunga Tonga-Hunga Ha’apai volcano is located about 64 kilometres north of the capital, Nuku’alofa. In late 2014 and early 2015, a series of eruptions in the area created a small new island and disrupted international air travel to the Pacific archipelago for several days.

Water can add explosivity to volcanoes

There is not a significant difference between volcanoes underwater and on land, and underwater volcanoes become bigger as they erupt, at some point usually breaching the surface, said Hans Schwaiger, a research geophysicist with the Alaska Volcano Observatory.

With underwater volcanoes, however, the water can add to the explosivity of the eruption as it hits the lava, Schwaiger said.

This satellite image taken by Himawari-8, a Japanese weather satellite, shows an undersea volcanic eruption, to the right, near the Pacific nation of Tonga on Saturday. (Japan Meteorology Agency/The Associated Press)

Before an explosion, there is generally an increase in small local earthquakes at the volcano, but depending on how far it is from land, that may not be felt by residents along the shoreline, Schwaiger said.

In 2019, Tonga lost internet access for nearly two weeks when a fibre-optic cable was severed. The director of the local cable company said at the time that a large ship may have cut the cable by dragging an anchor. Until limited satellite access was restored people couldn’t even make international calls.

Southern Cross Cable Network’s Veverka said limited satellite connections exist between Tonga and other parts of the world, but he did not know if they might be affected by power outages.

Published at Sat, 15 Jan 2022 08:00:57 +0000