begin quote from:https://www.nytimes.com/live/2022/01/15/us/tsunami-california-tonga
Live Updates: Signs of ‘Significant’ Tsunami Damage Are Seen in Tonga
Communications were still out Sunday in much of the South Pacific nation, a day after an undersea volcano erupted nearby, triggering warnings across the Pacific.
An underwater volcano erupted on Saturday near the remote Pacific nation of Tonga, triggering tsunami warnings across the South Pacific and for the West Coast of the United States, and causing strong waves and currents in many coastal areas.
The volcano’s eruption was dramatic, sending plumes of gas and ash thousands of feet into the atmosphere, though early reports of damage were limited.
A four-foot tsunami wave was reported to have hit Tonga’s capital, Nuku’alofa, sending people rushing to higher ground, and witnesses said ash had fallen from the sky. There were no immediate official reports on the extent of injuries or damages, but internet service in the country was disrupted, according to The Associated Press, making it difficult to assess.
Despite Tonga’s geographical isolation, a booming sound after the initial eruption was heard as far away as New Zealand, 1,100 miles southwest of the archipelago’s main island of Tongatapu.
In the United States, officials urged residents of coastal areas in much of the West Coast, Alaska and Hawaii to stay away from the coastline and move to higher ground.
In Japan, the country’s meteorological agency reported that a four-foot wave had reached the remote southern island of Amami Oshima, according to Reuters, and that smaller surges had hit other areas along Japan’s Pacific Coast.
Across the Pacific warnings were sounded. New Zealand’s National Emergency Management Agency advised people in the coastal areas to expect “strong and unusual currents and unpredictable surges at the shore.” And on their Facebook pages, the meteorological services for Fiji and Samoa also issued alerts, advising people to stay away from low-lying coastal areas.
The volcano, Hunga Tonga-Hunga Ha’apai, which is about 40 miles north of Tongatapu, had been relatively inactive for several years. It began erupting intermittently in December but by Jan. 3 the activity had decreased significantly, according to a report by the Smithsonian Institution’s Global Volcanism Program.
Satellite imagery of the eruption on Saturday, shared on Twitter by New Zealand’s National Institute of Water and Atmospheric Research, showed a “brief spike in air pressure as the atmospheric shock wave pulsed across New Zealand.”
Henry Fountain and Sophie Kasakove contributed reporting.
A day after the volcanic eruption off Tonga’s shores, communications were still out in much of the Pacific island nation, but there were signs of significant damage from the eruption and resulting tsunami, Prime Minister Jacinda Ardern of New Zealand said on Sunday.
Ms. Ardern, whose country has close ties to Tonga, said the tsunami had had “a significant impact on the foreshore on the northern side of Nuku’alofa,” the Tongan capital, “with boats and large boulders washed ashore.”
“Shops along the coast have been damaged and a significant cleanup will be needed,” she said at a news conference.
The tsunami was caused by an eight-minute eruption of the undersea volcano Hunga-Tonga-Hunga-Ha’apai, located about 40 miles north of Tongatapu, Tonga’s main island, on which about 70 percent of the population live.
Contact with Tonga was still extremely limited on Sunday afternoon, and communication with more remote parts of the country had not yet resumed. Ms. Ardern said official damage assessments were not yet available because of the difficulties with communication.
Nuku’alofa was covered in a thick film of volcanic dust, she said, but conditions were otherwise stable and power had been restored to some of the city.
“A clear indication that has come from Tonga is a need for water,” Ms Ardern said. “The ash cloud has, as you can imagine, caused contamination. That’s on top of already a challenging environment, in terms of water supply.”
Countries including Australia and New Zealand have offered the country aid, and a New Zealand Defense Force reconnaissance flight was set to deploy on Monday morning, subject to conditions, including ash fall. A New Zealand Navy vessel will also soon depart for the country, Ms. Ardern said.
In a post on Twitter, the United States secretary of state, Antony J. Blinken, offered his condolences: “Deeply concerned for the people of Tonga as they recover from the aftermath of a volcanic eruption and tsunami. The United States stands prepared to provide support to our Pacific neighbors.”
Tonga, a nation of about 105,000 people, has experienced successive natural disasters in recent years. In 2018, more than 170 homes were destroyed and two people killed by Cyclone Gita, a Category 5 tropical storm. Two years later, in 2020, Cyclone Harold caused an estimated $111 million of damage, including extensive flooding.
The country, which has reported just one case of the coronavirus, has struggled economically during the pandemic. It closed its borders in March 2020, effectively cutting off all tourism to the country, which had previously made up about 12 percent of its GDP.
“We stand ready to support the government and the people of Tonga,” a spokesperson for the United Nations in the Pacific said in a post on Twitter. “Unfortunately this is not over, and more eruptions and consequent tsunamis may follow.”
Tsunami warnings around the Pacific Ocean were downgraded on Saturday and Sunday, as waves set off by the eruption off Tonga hit coastlines thousands of miles away but did not appear to cause major damage or loss of life.
The Pacific Tsunami Warning Center in Honolulu said shortly before 5 p.m. local time on Saturday that “the tsunami threat from this volcanic explosion has now lifted.”
“We are relieved that there is no reported damage and only minor flooding throughout the islands,” the agency said on Twitter.
Japan, which suffered a devastating tsunami in 2011, downgraded its warnings on Sunday morning but urged coastal residents to remain cautious.
Russia also dropped a tsunami alert for the Kuril Islands in the country’s far east, which saw tsunami waves of about eight inches, the Tass news agency reported on Sunday.
The United States lifted tsunami advisories for Alaska, Hawaii, Washington, Oregon and parts of California, although two remained in effect for stretches of the central and Northern California coasts on Saturday evening.
The U.S. National Weather Service said that by midday Saturday, the highest waves from the tsunami had been recorded in Port San Luis, Calif., at 4.3 feet. Two other locations in California, Arena Cove and Crescent City, recorded waves of 3.7 feet.
The authorities warned that abnormal currents, coastal flooding and sea level fluctuations above and below normal tide levels could continue for several hours after the threat of a tsunami had passed.
Ben Dooley contributed reporting.
Tsunamis are created when large amounts of water — in the ocean, a bay or even a lake — are quickly displaced, usually through earthquakes or volcanic activity.
The four-foot tsunami that hit the South Pacific nation of Tonga on Saturday was caused when a nearby undersea volcano about 40 miles north of the archipelago’s main island erupted in spectacular fashion, sending ash into the sky, and creating an explosive plume visible from space.
The tsunami that killed hundreds of people on Sumatra and Java in Indonesia in December 2018 also appeared to have been caused by volcanic activity. There had been an eruption on the volcanic island of Anak Krakatau about half an hour before.
In an earthquake, displacement of water can occur when the ground moves as a fault breaks. This was the mechanism by which a 9.1 magnitude earthquake on Dec. 26, 2004, off Aceh Province in northern Indonesia, spawned large waves that traveled across the Indian Ocean and killed 225,000 people.
Many other tsunamis have also followed earthquakes, including those in September 2018 that devastated the city of Palu on the Indonesian island of Sulawesi after a 7.5 magnitude quake.
Volcanic activity creates a tsunami differently. One possibility is an explosive eruption, or general weakening of the flanks of a volcano by hot magma passing through. Either way, part of the volcano can collapse, creating a landslide that displaces water.
Another possible mechanism is the collapse of a magma chamber below the volcano as it empties during an eruption.
Volcano-related tsunamis are not uncommon. An eruption in 1792 in Japan created waves that were several hundred feet high. Landslides during the 1980 eruption of Mount St. Helens in Washington spawned large waves in a lake nearby.
Perhaps the most famous volcanic disaster in history, the 1883 eruption of Krakatau, also called Krakatau, triggered tsunamis that killed tens of thousands of people. (Anak Krakatau island has built up in place of Krakatau, which was obliterated in the 1883 event.)
The volcano that erupted on Saturday and sent tsunamis rippling across the Pacific Ocean had been relatively inactive for several years.
Named Hunga Tonga-Hunga Ha’apai, the volcano lies partly submerged about 40 miles north of Tongatapu, the main island in the nation of Tonga. It began erupting intermittently in December, but by Jan. 3, the activity had decreased significantly, according to a report by the Smithsonian Institution’s Global Volcanism Program.
The volcano had erupted in 2014, spawning a new island that eventually became home to blossoming vegetation and barn owls, according to the BBC.
Satellite imagery of the eruption on Saturday, shared on Twitter by New Zealand’s National Institute of Water and Atmospheric Research, showed a “brief spike in air pressure as the atmospheric shock wave pulsed across New Zealand.”
In a thread on Twitter, Dr. Janine Krippner, a volcanologist at the Smithsonian Institution, noted that “the majority of the volcano is submarine.”
The strength and potential impact of an eruption is estimated using a volcanic explosivity index, or V.E.I., which takes into account the volume of material ejected during the eruption and how high the plume reaches.
The V.E.I. of the eruption Saturday has not been estimated yet, but before the eruption, the volcano was estimated to be able to produce an eruption with a maximum V.E.I. of 2.
Eruptions with a V.E.I. of 6 or higher send so much gas and particles so high into the atmosphere that they can have a cooling effect on the climate for several years, by reflecting more sunlight away from the Earth’s surface. But eruptions of that magnitude occur very rarely. The latest was Mount Pinatubo in the Philippines in 1991.
Henry Fountain and Sophie Kasakove contributed reporting.
Since 2001, there have been 296 tsunami events, according to data from the National Oceanic and Atmospheric Administration.
But destructive tsunamis are rare occurrences. According to the Global Historical Tsunami Database, tsunamis that cause damage or deaths near their source occur only about twice per year. Tsunamis that cause damage or deaths on distant shores more than 620 miles away happen about twice per decade.
These are some of the largest ones:
Indian Ocean in 2004
On Dec. 26, 2004, after a 9.1 magnitude underwater earthquake struck near the Indonesian island of Sumatra, walls of water traveled thousands of miles across the Pacific, killing more than 250,000 people in half a dozen countries across South and Southeast Asia, with thousands more missing.
The earthquake set off tsunamis that built up speeds of as much as 500 miles per hour, then crashed into coastal areas of Sri Lanka, India, Thailand, Indonesia, the Maldives and Malaysia as 40-foot-high walls of water.
Japan in 2011
A 8.9-magnitude earthquake near the east coast of Honshu, Japan, set off a devastating tsunami, sending massive waves crashing over coastal cities in northern Japan on March 11, 2011.
According to the National Oceanic and Atmospheric Administration, the tsunami was “observed all over the Pacific and caused tremendous devastation locally.” The tsunami even triggered tidal gauges in parts of South America.
The highest wave from the tsunami was 127 feet in the Iwate Prefecture, a region over 300 miles north of Tokyo.
Indonesia in 2018
Two tsunamis within months of each other caused major destruction in parts of Indonesia.
On Sept. 28, 2018, a tsunami triggered by a 7.5 magnitude earthquake destroyed thousands of homes and killed more than 1,200 people on the island of Sulawesi in Indonesia.
The damage was particularly destructive because Indonesia’s early warning system for tsunamis did not go off. The open water tsunami buoys had not worked since 2012 because of vandalism and a lack of maintenance.
Three months later, on Dec. 22, an undersea landslide caused by volcanic activity set off a second tsunami that mostly hit areas around the Sunda Straight, including beaches in Pandeglang District, Serang, and South Lampung according to the NOAA.
Chile 1960
In 1960, a 9.5-magnitude earthquake, thought to be the largest of the 20th century, hit near Chile’s coast outside the city of Valdivia, causing a tsunami. The disaster left about 1,600 people dead, with the tsunami responsible for 1,000 of those deaths. That tsunami also killed 60 people on the Hawaiian Islands and 200 people in Japan, according to NOAA.
Japan 1792
One of the most destructive tsunamis happened in Japan in the late 18th century. The accounts of the disaster in Japanese literature are somewhat contradictory, especially with respect to dates, but it is estimated that sometime in the winter of 1791 and 1792, there was a strong eruption of the Mount Unzen Volcano on Kyushu Island, the southwestern most point in Japan, that lasted for months.
At the end of the eruption, the side of the mountain collapsed and caused the tsunami, which was thrown to the east, toward the city of Kumamoto. The disaster is recorded as having killed 15,000 people, and a third of those were killed by the wave.
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