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Tonga volcanic eruption and its impact

  The Tonga Trench is located east of the Tonga Islands in the central and southern Pacific Ocean (latitude 22°0’s south, longitude 173°0′ west), starting from the Samoa Islands in the north and connecting to the Kermadec Trench in the south, with a total length of 1,375 kilometers and a width of about 80,000 kilometers. Meter.
Why did the Tonga volcano erupt?

  Tonga is a small country in the South Pacific, consisting of more than 170 islands, with a land area of ​​747 square kilometers and a population of 104,000. On January 15, 2022, Beijing time, the country’s Hongaha Apay Island volcano (20.536° south latitude, 175.382° west longitude) erupted violently, triggering a strong earthquake and tsunami, causing network and communication signals throughout Tonga The interruption caused great harm to the local area and neighboring areas, and also had a certain impact on the local ecological environment and climate… This news shocked the whole world.
  Why did Tonga have such a strong volcanic eruption?
  Volcanic eruptions are closely related to their geological environment. The Tonga Volcanoes are part of the Tonga-Kermadec volcanic arc, which is at the junction of the Pacific and Oceania plates (usually, where the two different plates meet are areas of intense tectonic activity). Here is the Earth’s second-deepest Tonga Trench (10,882 meters deep, second only to the world’s deepest Mariana Trench in eastern Japan at 11,034 meters), through which the plate subduction zone passes. The geological tectonic activity here is quite strong, and volcanic eruption and seismic activity are the main manifestations of geological tectonic activity, so volcanic eruptions and earthquakes often occur here. In recent years, the Hongaha Apai Volcano has erupted several times. The eruptions that can be monitored on the surface include several in 2009, 2014 and 2021, but the previous eruptions were not as strong as this time.

Tonga Trench structural map
What are the characteristics of this Tonga volcanic eruption?

  The scale of the Tonga volcanic eruption is relatively large and the level is not low. Volcanic eruptions are usually divided into 8 levels. According to the available information, I believe that the Tonga volcanic eruption index is about 5, which is at a medium level. Even so, this is the strongest volcanic eruption on Earth that has been observed by humans in the past 30 years. There have only been two volcanic eruptions of the same scale in the 20th century: one was the eruption of Mount Pinatubo in the Philippines in 1991, the most recent large-scale eruption, with a volcanic eruption index of 6; the other was the 1980 St. Helens in the United States Volcano eruption.
  The damage caused by the Tonga volcanic eruption is relatively extensive, mainly caused by earthquakes and tsunamis. The earthquake had a significant impact on Fiji, which is 800 kilometers away, and was felt farther away; the eruption of the Tonga volcano also triggered a tsunami in the pan-Pacific region, Vanuatu, the coast of the North Island of New Zealand and 10,000 kilometers away from the Tonga volcano. Tsunami waves of more than 1.5 meters were monitored along the coast of Chile; tsunami waves of about 1 meter were also monitored along the coasts of the Hawaiian Islands of the United States and Kyushu Island of Japan.
  The Tonga volcano eruption is a submarine volcanic eruption, where the seawater is at least several kilometers deep. The magma, ash and gas ejected by the volcano must first be blocked, cooled, diluted or absorbed by the seawater. Reduced the explosiveness and hazard of volcanoes. Even so, the volcanic ash from this volcanic eruption washed up to an altitude of 20 kilometers through the water body, and caused a relatively strong earthquake and a large-scale tsunami, indicating that the scale of the eruption was still large. However, hot magma, volcanic ash and volcanic gases can quickly boil, evaporate and “explode” seawater, so the huge volcanic clouds seen in the air are mostly water vapor.

Tonga’s submarine volcanic eruption also caused relatively strong earthquakes and large-scale tsunamis
Will Tonga Volcano Eruption Affect Global Climate?

  Volcanic eruptions can have two effects on the climate.
  On the one hand, volcanic eruptions can trigger a “parasol effect” that causes cooling and rain in local areas. The volcano spews a lot of volcanic ash and volcanic gas, which will form an aerosol layer high in the sky, as if holding an umbrella in the air. The “parasol” will block solar radiation, so that the sun’s heat received by the earth’s surface is reduced, the temperature may be lowered, and cloudy and rainy days may increase. As far as this Tonga volcanic eruption is concerned, although the “parasol effect” will cause cooling and raining in local areas for a period of time, it is not enough to have a decisive impact on the global climate.
  Climate is the sum of changes in weather. The accumulation of weather over a long period of time is called climate. We generally say “weather forecast”. It is no problem to forecast for three or five days, but if it is forecast for three to five months, it may not work. This volcanic eruption may have an impact on the weather, but not the climate. Therefore, the so-called “volcanic eruption will alleviate global warming” seems to be exaggerated. NASA records also show that since 1880, the world has experienced several large-scale volcanic eruptions, all within the magnitude of 6. Although large-scale volcanic eruptions are often accompanied by a drop in global temperature, from a long-term perspective, the temperature fluctuations caused by volcanic eruptions are not significantly different from those in other periods.
  Volcanic eruptions, on the other hand, can trigger a “greenhouse effect” caused by localized warming due to increased greenhouse gases. Volcanic eruptions can create a layer of greenhouse gases above the Earth’s surface. The greenhouse gas layer will make it difficult for the heat released from the earth’s surface to spread to higher space, which will heat up the local area, thereby producing the greenhouse effect.
  The impact of the Tonga volcanic eruption on the climate should be mainly based on the “parasol effect”, the “greenhouse effect” is not obvious, and the impact on the climate is also short-term. Some people worry, will it cause a “year without summer” like the eruption of Mount Tambora in 1815? In my opinion, this is impossible. Because the Tonga eruption is much smaller than the Tambora eruption, it will not have a significant impact on the global climate.

What is the impact of Tonga’s volcanic eruption on our country?

  Will the tsunami and volcanic ash spewed by this volcanic eruption affect my country?
  The tsunami will not have a significant impact on our country. Because the scale of this volcanic eruption is not too large and it is too far from our country (nearly 10,000 kilometers), even if the tsunami comes, it is already “the end of the force” and the power has been greatly weakened. What’s more, there is an island arc chain from the Philippines to Japan on the periphery of mainland China, which acts as a barrier to tsunamis, making it almost impossible for tsunamis to reach the mainland of my country directly, and only has a certain impact on Taiwan Island.
  Tonga volcanic eruption released a large amount of volcanic ash and gas, which will cause great harm to the ecological environment, buildings and people’s lives. I once inspected the site of the volcanic eruption, and my personal experience was that the ash was filled with ash and nothing could be seen. Volcanic gases contain substances such as carbon monoxide, carbon dioxide and hydrogen sulfide, some of which are toxic and have toxic effects on living things. In the volcanic area, if you don’t wear a gas mask, if you breathe too much of these poisonous gases, you will be poisoned, and even if you are far away from the volcano, you will feel uncomfortable. Volcanic ash falling on the ground will destroy vegetation ecology and even endanger human life. For example, the eruption of Mount Vesuvius in Italy in AD 79, several meters of ash bury a Pompeii city, and many people died. According to reports of this volcanic eruption, the thickness of the volcanic ash ground cover is three to five centimeters. Even if it is thicker, it will not cause great harm to people. The volcanic ash that can really float to China, even if there is, is very little, so it has little impact on our country.
Can volcanic eruptions be predicted?

  At present, the earth is in a period of relatively active geological tectonic movements. From the second half of the 20th century to the beginning of the 21st century, the frequency and intensity of volcanic eruptions and earthquakes will increase significantly. A Japanese scholar said that the Changbai Mountain volcano will erupt in 2034. I am skeptical about this, but I do not deny that the Changbai Mountain volcano will erupt in the future. Because it had a major eruption 1,000 years ago, which is larger than the Tonga eruption, and the geological background of the original eruption still exists, so it has the conditions for another eruption.
  Volcanic eruptions are theoretically predictable, especially those on land. There have been relatively successful predictions. However, there are still many technical difficulties in monitoring and early warning of submarine volcanic eruptions.
  Natural disasters know no borders and should be predicted, prevented and responded to in a timely manner. Like earthquake prediction, volcanic eruption prediction mainly includes three parameters: time, location and intensity. Unlike earthquakes, the location, timing and intensity of terrestrial volcanic eruptions can now be basically grasped, but submarine volcanoes have not yet reached the level of accurate prediction. Now earth science is developing towards deep space, deep earth and deep sea, and volcanism is closely related to these three aspects, so we should make great efforts in this area.

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