According to related reports, this is the largest volcanic eruption in 30 years, and its volcanic explosivity index (VEI) may reach 5 or even 6. A large amount of gas is wrapped by volcanic ash, forming a huge mushroom cloud with an eruption height of at least 20,000 meters. In the 20th century, there were only two similar volcanic eruptions, one was Mount Pinatubo in the Philippines in 199 1 and the other was Mount San hellens in the United States in 1980. Strong volcanic eruptions of magnitude 5 and above are rare on the earth, with *** 1 1 times since the 9th century.
Volcano disaster is one of the most violent and extreme natural disasters on earth. Large-scale volcanic eruption will not only greatly change the landform within dozens of kilometers around the volcano, but also the volcanic ash and volcanic gas produced by its eruption will enter the stratosphere, which can change the local climate in a short time.
From the satellite image, Tonga volcanic eruption is a typical Pliny volcanic eruption, which is the largest and most violent of all volcanic eruptions. Characterized by the eruption of a large number of pyroclastic and volcanic ash, a very violent gas explosion occurs, and the volcanic gas and volcanic ash injected into the stratosphere form a mushroom-like volcanic ash column, usually accompanied by a loud noise.
According to Pei Fu Rong, as the strongest volcanic eruption in recent 30 years, Tonga's volcanic eruption will have many impacts on the environment, among which the tsunami is the most obvious and direct one. About 20 minutes after the eruption, Tabu Island, about 65 kilometers away from the volcanic eruption point and where Tonga's capital is located, was hit by a tsunami and lost contact. Then the tsunami quickly reached Fiji and Vanuatu, and even Japan, 654.38+0000 kilometers away, issued a tsunami forecast. Secondly, volcanic eruption releases a lot of gases such as volcanic ash, carbon dioxide and sulfur dioxide, which may cause acid rain and air pollution in the nearby area, and cause "parasol effect" and "greenhouse effect". Volcanic eruptions will also pollute the sea and bring destructive effects to fish and coral reefs. What is slower is the influence of volcanic structure on regional geological environment.
Pei Fu Rong believes that the impact on the environment should be only regional in terms of the intensity of Tonga volcano eruption. "At present, our understanding can only be partial, and further research work is needed to understand it scientifically."
On the one hand, volcanic disasters have caused great losses to human society, on the other hand, they have also brought a variety of resources.
Dr Weasion Wei from the Institute of Mineral Resources of the Chinese Academy of Geological Sciences said that volcanoes played a great role in the formation of the earth. Due to volcanic eruption, the atmosphere and hydrosphere suitable for life have evolved on the earth, and finally life and human beings have evolved. If the submarine volcano erupts above sea level, it will form a volcanic island. The 170 islands that make up the kingdom of Tonga are roughly divided into two rows in the north-south direction, with volcanic islands in the west and coral reefs in the east. Volcanic landforms formed by volcanic eruption are important tourism resources, and tourism is one of the three pillars of Tonga's national economy.
Pei introduced that in terms of mineral resources, many mineral deposits, whether metallic or nonmetallic, are formed by volcanism, so many mineral deposits are called volcanic deposits. From the perspective of land-sea mineralization, he explained the global ocean-circumterrestrial, ocean-continental and land-sea metallogenic background. Submarine volcanism mainly forms copper, gold, pyrite and barite. The thermal energy released by volcanic eruption can also form geothermal resources, which are generally found in places with volcanoes.
Tonga is located in the subduction zone where plates converge, and its volcanic activity is active, which is conducive to the formation of mineral resources. According to relevant information, there are basically no mineral resources on Tonga's land, but there should be some mineral resources on the seabed. It is reported that in May 2008, Nautilus Mining Company of Canada began mineral exploration in Tonga's waters, and announced the discovery of massive polymetallic sulphides in Tonga's territorial waters, including copper, zinc, gold and silver. On February 20 10, American modular energy company signed an agreement with Tonga, and was allowed to explore oil and gas resources in Tonga's waters, and began exploration and drilling in Tonga's waters in 20 15. In order to protect domestic resources, Tonga promulgated the seabed minerals law in August 20 14.