Volcanic ash, tsunamis... What is the impact of an undersea volcanic eruption in Tonga?

Source: Xinhua Viewpoint

A recent volcanic eruption occurred on the island of Hong Aha Apai in the South Pacific island nation of Tonga. According to the analysis of many experts in Australia and New Zealand, this may be the world's largest submarine volcanic eruption in 30 years, the scale of the tsunami it triggered is huge, and the volcanic ash will have different degrees of impact on the surrounding atmosphere, ocean currents, fresh water, agriculture and people's health, etc. The specific situation needs to be further evaluated.

This imposition photo shows a satellite image of Aha Apayee Island in Tongahun taken by the Worldview02 satellite on April 11, 2021 (left) and a satellite image of the island after the volcanic eruption taken by the Gaofen I satellite on January 17, 2022, with an orange curve showing the original outline of the island according to geographical coordinates. Xinhua News Agency (Courtesy of Xinhua Satellite News Laboratory)

Oliver Nebel, associate professor of high-temperature geochemistry at Monash University in Australia, told Xinhua News Agency on the 17th that Tonga is located in the Pacific Ring Of Volcanic Seismic Zone, and due to the collision of crust plates, volcanoes located in the subduction zone will erupt violently. He introduced that this volcanic eruption is not caused by a single event, but a continuous accumulation of underground energy, so it is difficult to predict the volcanic eruption.

Nebel believes that the replenishment of magma under the volcano is an ongoing process, and the volcano on Hong Aha Apai Island may erupt again in the near future, but because this eruption is already very violent, if the next eruption occurs in the next few days, weeks or months, it is unlikely to be as violent and destructive as this time, because a large amount of magma underground has already been erupted.

For the secondary disaster caused by this submarine volcanic eruption, Neibel said that in addition to the tsunami, it is followed by volcanic ash, and a volcanic eruption of this scale will allow a large amount of volcanic ash to enter the atmosphere.

Professor Shaun Cronin, a volcanologist at the University of Auckland in New Zealand, introduced to the media on the 17th that the explosive lateral spread of the volcanic eruption in Tonga showed that it may be the largest global scale since the eruption of Pinatubo Volcano in the Philippines in 1991.

Located about 65 kilometers north of The Capital of Tonga, Nuku'alofa, The Island of Hong Aha Apai began to erupt on the morning of the 14th and erupted again on the afternoon of the 15th. Volcanic eruptions cause large amounts of ash, gas and water vapor to enter the sky to form huge clouds, which erupt to a height of 20 kilometers. After the eruption on the 15th, in addition to Tonga, fiji, Samoa, Vanuatu and other parts of the country also had abnormal seawater activity, and these countries urgently issued tsunami warnings. In addition, Japan, the United States, Canada, New Zealand, Australia and Chile have issued tsunami warnings.

Dr. Emily Lane, an expert in fluid dynamics and tsunami research at the New Zealand Institute of Atmospheric and Water Resources, said in an interview with local media on the 17th that most tsunamis are caused by underwater earthquakes, but only about 5% of tsunamis are caused by volcanic eruptions, and "volcanic tsunamis" are extremely rare. She said the tsunami triggered by the Tonga eruption was enormous. A similar event previously documented was a tsunami triggered by the eruption of Mount Krakatoa in Indonesia in 1883.

At present, volcanic ash over parts of Tonga has subsided, but there are still large amounts of volcanic ash floating in the air. Neibel said that unlike the ash after the wood is burned, the volcanic ash is actually tiny rock particles, and if the aircraft passes through it, the windshield will be damaged, and the particles of volcanic ash will also melt and crystallize in the aircraft engine, which may cause the engine to stop, which is dangerous, so the volcanic ash will affect air traffic.

Professor Cronin also introduced that volcanic ash may also have a serious impact on Tonga's freshwater supply and agriculture. Volcanic ash not only endangers people's health, but also produces acid rain and leachate, which can damage crops. Acid rain can corrode crops, such as stems and leaves and leafy vegetables, and drinking water contaminated with volcanic ash can lead to stomach upset and other health problems, he said.

Fiji's environment department warned on the 17th that satellite data show that the increase in the concentration of sulfur dioxide in the atmosphere of Tonga and neighboring countries may lead to acid rain, and people should stay at home as much as possible when it rains, and take measures to prevent rainwater from polluting drinking water.

The volcanic eruption in Tonga also caused damage to the submarine cables connecting the South Pacific island nation to the outside world, and Tonga's external communications are now largely interrupted. Tonga Cable Co., Ltd., which owns the cable, told the media that repairing the cable could take weeks.