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The eruption of an underwater volcano off Tonga, which triggered a tsunami warning for several South Pacific island nations, is seen in an image from the NOAA GOES-West satellite taken at 05:00 GMT January 15, 2022. Image Credit: via REUTERS

Dubai: On Saturday (January 15, 2022), a powerful undersea volcanic explosion near Tonga islands sent plumes of ash, steam and gas 20km skyward.

The volcano, known as "Hunga-Tonga-Hunga-Ha’apai", erupted for about 8 minutes, creating a spectacular plume of ash and volcanic debris visible from space.

It set off walls of tsunami in the Pacific with waves reaching the coasts of Peru, the US West Coast, Australia and Japan. Two more eruptions followed in the next three days. The eruption triggered a tsunami on Tonga's largest island, Tongatapu, with 1.2-metres waves lashing areas near Nuku'alofa city.

Tonga, an island nation composed of more than 170 islands with a surface are 750 km2 (about the size of Singapore) in the South Pacific — has been covered in volcanic ash.

The story so far:

What's the extent of the damage?

Tonga volcano
Image Credit: Seyyed dela Llata / Gulf News

After the volcanic eruption, tsunami warnings were issued across Pacific Island nations, including Fiji, Samoa and Vanuatu, besides Hawaii, Alaska, British Columbia and much of North America's West Coast.

In Hawaii, four-foot waves were recorded, residents warned to stay away from coastline, move to higher ground. In Japan, four-foot waves also reported in the remote southern island of Amami Oshima. The eruption was so powerful that a booming sound was heard in New Zealand — 1,100 miles southwest of the main island of Tongatapu.

In Peru, two women died in Lambayeque due to "anomalous waves."

What’s the immediate impact?

Tonga, an island nation in the South Pacific (population: 105,000), is covered in ash, which has been falling from the sky from Saturday evening. The nation has appealed for “immediate aid” after the eruption caused significant damage in Nuku'alofa, capital.

The main island, Tongatapu, is home to the capital of Nuku’alofa and most of the country’s inhabitants. The thick film of volcanic dust raised concerns about drinking water. Communications were still out in much of the Pacific island nation.

What neighbours, UN said

No mass casualties have been reported so far, but the extent of the destruction is unknown. Signs of “significant damage” from the eruption and resulting tsunami were reported, Prime Minister Jacinda Ardern of New Zealand said on Sunday. Conditions were otherwise “stable” and power had been restored to some parts of the main city.

Contact with more remote parts of the country had not yet resumed. Ardern said official damage assessments were not yet available because of the difficulties with communication.

Aid organisations are worried about contaminated air and access to clean water for 100,000 residents of Tonga, a Polynesian country of more than 170 South Pacific islands. Air surveillance efforts by Australia and New Zealand could not be carried out due to the ash cloud.

Australia and New Zealand have offered the country aid. A New Zealand Navy vessel will also soon depart for the country, 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 neighbours.”

“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.”

TONGA DISASTERS
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 has reported just one case of the coronavirus. But it 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.

What happens when a submarine volcano erupts?

Submarine volcanoes are underwater vents or fissures in the Earth's surface from which magma can erupt. Many are located near areas of tectonic plate formation, known as "mid-ocean ridges". However, submarine volcanoes are not as well studied as the ones above ground.

1million

Estimated number of undersea volcanoes

There are an estimated 1 million undersea volcanoes — most are extinct. According to the Global Foundation for Ocean Exploration group, about 75% of all volcanic activity on Earth actually occurs underwater”.

In general, during major volcanic eruptions, large amounts of volcanic gases, aerosol droplets and ash are injected into the stratosphere, where volcanic gases like sulfur dioxide can cool the climate.

The stratosphere is the layer of the earth’s atmosphere above the troposphere, extending to about 50 km above the earth's surface (the lower boundary of the mesosphere.

The stratosphere starts just above the troposphere — which starts at the Earth's surface and extends 8 to 14.5 kilometers — and goes 50 kilometers high.

The “updraft” from the Tongan eruption is expected to enter the stratosphere.

75%

estimated percentage of magma output on Earth from volcanoes at mid-ocean ridges.

Why underwater eruptions are highly explosive

Underwater volcanic eruptions tend to be highly explosive, although seawater should technically cool the magma down. It doesn't happen that way, as the magma blasted out is actually full of volcanic gas. "When magma enters the water rapidly, any steam layers are quickly disrupted, bringing hot magma in direct contact with cold water," a report in the Conversation said. Researchers call this "fuel-coolant interaction" and likens it to weapons-grade chemical explosions.

During major volcanic eruptions, large amounts of volcanic gases, aerosol droplets and ash are injected into the stratosphere, where volcanic gases like sulfur dioxide can cool the climate.

The stratosphere starts just above the troposphere — which starts at the Earth's surface and extends 8 to 14.5 kilometers — and goes 50 kilometers high. The “updraft” from volcanic eruption enters the stratosphere.

Will the volcanic eruption help cool the earth?

No, say experts. Volcanic eruptions are often discussed in relation to climate change. Volcanoes release CO2(and other gases) into our atmosphere. However, human contributions to the carbon cycle are more than 100 times those from all the volcanoes in the world — combined, according to Nasa.

Volcanic eruptions do cause an increase in atmospheric CO2, according to the USGS. The climactic eruption of Mt Pinatubo on June 15, 1991 was the largest sulfur dioxide cloud ever observed in the stratosphere since the beginning of such observations by satellites in 1978.

It caused what is believed to be the largest aerosol disturbance of the stratosphere in the 20th century, though probably smaller than the disturbances from eruptions of Krakatau in 1883 and Tambora in 1815. Consequently, it was a standout in its climate impact and cooled the Earth's surface for three years following the eruption, by as much as 1.3 degrees F at the height of the impact, USGS said.

By comparison, human activities emit a Mt Pinatubo-sized eruption of CO2 twice daily, and a Mount St. Helens-sized eruption of CO2 every 2.5 hours.

Climate scientists bring up volcanic eruptions to better understand and explain short periods of cooling in our planet’s past. Every few decades or so, there is a volcanic eruption (e.g., Mounts Krakatoa/Krakatau, Pinatubo, El Chichón) that throws out a huge amount of particles and other gases into the stratosphere. These will effectively shield us enough from the Sun to lead to a short-lived global cooling period.

The largest possible eruptions are from “super volcanoes”, which erupt very rarely, about every 100,000 to 200,000 years or more. On the other hand, the total annual CO2 emissions from human activities is like one or more Pinatubo super eruptions going off every year, said Nasa.

“Essentially, CO2 emissions from human activities dwarf those of volcanoes,” the agency said.

The particles and gases typically dissipate after about 1 to 2 years, but the effect is nearly global. Comparatively speaking, greenhouse gas warming coming from human activities (primarily driven by the human burning of fossil fuels) will endure for millennia, even longer than nuclear waste.

TIMELINE: Hunga Tonga-Hunga Ha’apai

 

The Hunga Tonga-Hunga Ha’apai submarine volcano is located 64 km north of Tongatapu, main island of Tonga in the Pacific.

History of eruptions:

December 2021: Though relatively inactive for several years, it began erupting intermittently in December.

January 3, 2022: The activity had decreased significantly, according to a report by the Smithsonian Institution’s Global Volcanism Program.

January 15, 2022: Just before sunset, the underwater volcano made a violent eruption.

TSUNAMI FROM EARTHQUAKE VS ERUPTION
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 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 Krakatoa 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.

Tsunamis typically follow earthquakes. An example is the September 2018 tsunami 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 common. 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.

The most famous volcanic disaster in history, the 1883 eruption of Krakatoa triggered tsunamis that killed tens of thousands of people. ("Anak Krakatoa" island has built up in place of Krakatoa, which was obliterated in the 1883 event.)