China News Agency, Beijing, January 16 Question: Why can the strongest submarine volcanic eruption in this century cause a transoceanic tsunami?
China News Agency reporter Ruan Yulin
On the 15th, the underwater volcano of Hongahaapai Island in the South Pacific island country Tonga erupted violently, triggering a transoceanic tsunami that affected the entire Pacific coast.
How did the strongest submarine volcanic eruption in this century have such a large-scale tsunami impact?
Experts from the Tsunami Warning Center of the Ministry of Natural Resources of China accepted an exclusive interview with a reporter from China News Agency on the 16th, and analyzed the scope, duration and causes of the tsunami's impact.
Triggered tsunami across the Pacific Ocean
At 12:27 on January 15, 2022, Beijing time, the Hongaha Apay Island volcano (20.5 degrees south latitude, 175.4 degrees west longitude) in Tonga waters erupted and triggered a large-scale tsunami.
According to the latest monitoring results by the Tsunami Warning Center of the Ministry of Natural Resources of China, the volcanic eruption triggered a transoceanic tsunami that affected the entire Pacific coast.
Countries such as Chile, Japan and New Zealand on the Pacific coast have observed significant tsunami waves, with a maximum tsunami wave amplitude of 1.5 meters.
According to global water level monitoring data, the eruption triggered a transoceanic tsunami that affected the Pacific coast.
As of 11:30 on January 16, 2022 (Beijing time), tidal stations in Chile, Japan and other countries along the Pacific coast have monitored tsunami waves ranging from 30 cm to 150 cm. Tsunami waves were detected in the coastal waters of China in the early morning of the 16th. Among them, the largest tsunami wave at Zhejiang Shipu Station is about 20 cm.
The Pacific Tsunami Warning Center (PTWC) has issued multiple tsunami warnings for the volcanic tsunami, and issued tsunami warnings for areas around the volcanic eruption. It is expected that the tsunami may cause disastrous effects.
Countries including New Zealand, Tonga, Fiji, Japan, Vanuatu, Chile and Australia also issued tsunami warnings for the event.
The volcanic tsunami had a disastrous impact on Tonga's capital, Nuku'alofa, flooding parts of the country.
Why does the tsunami affect thousands of miles away?
According to reports, tsunamis of more than 1 meter have occurred along the coasts of Japan and California, which are thousands of miles away from the crater.
Wang Peitao, an associate researcher at the Tsunami Warning Center of the Ministry of Natural Resources of China, said in an interview with a reporter from China News Agency that the Tsunami Warning Center of the Ministry of Natural Resources of China relies on the global real-time tsunami monitoring network to obtain live tsunami information as soon as possible. As of noon on the 16th, this time Transoceanic tsunamis caused by volcanic eruptions are relatively rare in a wide range of impacts, affecting the pan-Pacific region.
"At present, the cause of the tsunami is not particularly clear, and more observational data is needed for a comprehensive analysis," Wang Peitao said. According to preliminary judgments, first of all, the submarine landslide caused by the eruption of the submarine volcano in Tonga was one of the main factors leading to the tsunami. one.
But in general, it is relatively rare for a landslide tsunami to generate such a large-scale transoceanic tsunami.
According to local media reports, the Tonga submarine volcano erupted very violently. The volcanic ash shot up 20 kilometers into the sky, and the waves nearly 1 meter high poured into the local houses.
Secondly, from the current satellite cloud images, the atmospheric pressure disturbance caused by the volcanic eruption and the resulting meteorological tsunami is another important factor that aggravates the scale of the tsunami, but it is very rare to trigger a pan-Pacific tsunami.
The Hongahaapai volcano is located on the subduction boundary of the Pacific Plate and the Indo-Australian Plate and is part of the Tonga-Kermadec Archipelago Volcanic Arc.
The volcano was formerly a submarine volcano, which formed new islands after erupting in 2009.
The volcano has erupted several times in 2014, 2015, 2019 and 2021.
Third, the submarine volcano on Hongahaapai Island is relatively active and has erupted several times in recent years, the most recent eruption occurred on December 20, 2021.
However, the eruption of the Hongahaapay Island volcano this time was very strong and was the strongest volcanic eruption in the past 30 years.
"Meteorological tsunamis caused by volcanic eruptions are very similar to landslide tsunamis and are difficult to distinguish," said Wang Peitao.
Why can tsunamis travel so far?
The expert pointed out, "This is a remarkable feature of tsunamis. The wavelength of tsunamis can reach hundreds of kilometers, or even hundreds of kilometers. If there is no blocking, tsunami waves can travel tens of thousands of kilometers in deep water with little energy attenuation."
As of January 16, 2022, the volcanic eruption continues.
According to the tsunami warning center of China's Ministry of Natural Resources, based on statistical analysis of historical volcanic events, the current eruption may last for weeks or months.
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