natural disasters

Eruption of Undersea Volcano Near Tonga Triggers Tsunami Warnings Across Pacific

Satellite image of eruption of the Hunga Tonga Hunga Ha’apai volcano on Saturday. Photo: Himawari-8/Japan Meterological Agency

The spectacular eruption of an undersea volcano near the ​​South Pacific kingdom of Tonga on Saturday generated a tsunami which apparently struck Tongatapu, the main island of the country’s archipelago, which is just 40 miles from the volcano. The event also triggered tsunami warnings and advisories for numerous countries across the Pacific, including for Hawaii and the U.S. West Coast from California to Alaska.

The Eruption

The Hunga Tonga Hunga Ha’apai volcano first erupted Friday, sending an enormous plume of ash up to 12 miles into the air, and then erupted again on Saturday at 5:26 p.m. local time. The dramatic event and the shockwaves it produced were captured by meteorological satellites:

The eruption was reportedly heard across the South Pacific, as far away as New Zealand and Australia. Volcano experts said that a shockwave from the eruption moved across the region at something like 600 miles per hour, not far off the speed of sound in air.

It also produced an intense lightning storm:

Satellite imagery shows that a large portion of the island that had been created by the volcano was destroyed prior to the large event on Saturday.

On Sunday, New Zealand Prime Minister Jacinda Ardern said the country has not received any reports of deaths or injuries in Tonga related to the eruption. Still, Pacific nations and humanitarian groups have struggled to establish communications with the island archipelago. “The tsunami has had a significant impact on the foreshore on the northern side of [the Tongan capital of] Nuku’alofa with boats and large boulders washed ashore,” she told reporters. “There are parts of Tonga where we just don’t know yet… we just haven’t established communication.” The United Nations children’s agency, in coordination with Australia and New Zealand, said it was preparing emergency supplies to fly into Tonga.

It’s not yet clear how powerful the eruption was or what long-term impact it could have. Volcanologists have developed a scale that describes the size of explosive volcanic eruptions based on magnitude and intensity — the volcanic explosivity index, or VEI. Prior eruptions from the undersea volcano near the nation of Tonga were 2. (For context, Krakatoa’s 1883 eruption, which was one of the most deadly volcanic eruptions of modern history, had a VEI of 6.)

But while some experts predict Saturday morning’s eruption could be, at least, a VEI of 4, it’s too soon to tell. “Until we know how much material has been ejected (made harder by the underwater component), we can’t use the scale,” volcanologist Jess Phoenix tweeted. “This means that while we know this eruption is consequential, we won’t have all the info on it for a while.” Since the eruption is still ongoing, there could be more explosions, collapses, and tsunamis to come — or this could be it for a while.

The Tsunami

A tsunami warning was declared for all of Tonga after the eruption on Saturday evening. Before communication with Tonga was lost a little more than an hour after the eruption on Saturday, images and videos of large tsunami waves striking the shoreline and inundating coastal communities in were shared on social media. The extent of the damage in the country, which is home to some 105,000 people, remains unclear.

Radio New Zealand reported that Tonga’s King Tupou VI was evacuated from the Royal Palace after the tsunami flooded the capital city of Nuku’alofa.

The Impact on Other Countries, Including the U.S.
Tsunami warnings were issued in Australia, New Zealand, Japan, and other Pacific nations. New Zealand’s National Emergency Management Agency said some parts of the country could expect “strong and unusual currents and unpredictable surges at the shore following a large volcanic eruption.”

Tsunami advisories were also issued for Hawaii and the U.S. West Coast on Saturday morning. In the Hawaiian Islands, the waves ranged from a foot to just under three feet. “We are relieved that there is no reported damage and only minor flooding throughout the islands,” the Pacific Tsunami Warning Center said, prior to canceling the Hawaii-based tsunami alert. On Twitter, a user created a depiction of the pressure wave associated with the Tonga eruption as it moved across the U.S. today.

The tsunami also caused minor flooding in California, prompting officials to temporarily close several beaches and arenas from Orange County to the Bay Area. “If you are located in this coastal area,” the National Weather Service said, “move off the beach and out of harbors and marinas. Do not go to the coast to watch the tsunami. Be alert to instructions from your local emergency officials.”

One- to three-foot waves were expected along the Oregon coast:

Tonga Volcano Eruption Triggers Pacific Tsunami Warnings