Recently, a large-scale volcanic eruption occurred in Tonga, an island country in the South Pacific, which triggered a tsunami that affected the entire Pacific coast. Several countries issued tsunami warnings, and the subsequent impact of the disaster attracted global attention. Tonga is located on the subduction boundary of the southwest Pacific plate, in the strong crustal activity area of the circum Pacific seismic belt, and has the "second deepest Tonga Trench on earth". Based on such a special geological location, volcanoes and earthquakes occur frequently in this area. The eruption of hongaha ApaI island volcano has been very active in history. In recent 100 years, there have been small-scale eruptions in 1912, 1937, 1988, 2009 and 2014. Judging the impact of a volcanic eruption depends first on its intensity. It is reported that the volcanic column ejected by Tonga volcano is more than 20 kilometers. Combined with the sound of volcanic eruption and the scale of tsunami, it is preliminarily judged that its volcanic eruption index (VEI) may be between 5-6. VEI is an index to comprehensively measure the intensity of volcanic eruption based on the volume of volcanic debris, the height of volcanic ash exceeding the peak or entering the atmosphere, and the type of volcanic eruption. It is divided into 8 levels. Each level increases, the corresponding energy will increase 10 times. Volcanic eruptions above VEI level 6 are rare. The largest recorded eruption was the Tambora volcano in Indonesia in 1815, with an intensity of VEI level 7. At that time, the volcanic ash ejected spread all over the world with the atmospheric flow, resulting in the average temperature of the whole earth falling by about 0.5 degrees Celsius. Therefore, 1816 was called "a year without summer" in European and American countries. Second, it depends on its duration. Generally speaking, volcanic eruptions need to have three conditions: first, the material basis, that is, the magma inside the earth; The second is the eruption channel; The third is the eruption power, that is, the energy that can promote magma to eject from the earth's interior along the channel to the surface. How long a volcanic eruption can last also depends on these three conditions. Volcanic eruptions are mostly intermittent. For example, the eruption of La Palma, Spain, which has just ended, lasted intermittently for nearly three months. At present, it is impossible to judge how long the Tonga volcanic eruption will last, which needs continuous attention. Volcanic eruptions are common to the earth, but close attention needs to be paid if they are close to human activity areas. Hongaha ApaI island volcano is located on the seabed. The eruption first triggered a tsunami in the local area. It can be seen from the report that not only the air and water sources are polluted, but also the communication and transportation are affected, resulting in the inability of aircraft to land and large ships to approach. Water supply has become a problem that needs to be paid attention to at present. In addition, the volcanic eruption triggered tsunami warning in neighboring countries, such as Fiji, New Zealand and Australia, Japan and the United States. According to the latest monitoring results of the tsunami early warning center of the Ministry of natural resources, tsunami waves were detected in China's coastal waters in the early morning of the 16th, with a maximum tsunami amplitude of about 20 cm. Although the impact is small, the coastal areas of Southeast China also need to strengthen prevention. In addition, volcanic eruptions may also have a potential impact on the climate. After the sulfur dioxide emitted by the volcano enters the stratosphere above the earth's surface, it forms sulfate aerosol through chemical reaction, so as to block solar radiation, play a "parasol effect" and change the climate. In 1991, Pinatubo volcano erupted in the Philippines, spraying about 20 million tons of sulfur dioxide into the stratosphere. The "parasol effect" led to the earth's cold winter in the following two years. At present, the sulfur dioxide emitted by Tonga volcano is only 400000 tons, which is only equivalent to 2% of Pinatubo volcano. It is too early to draw a conclusion on the geometry of global climate impact. There may be cooling in some areas, which needs further continuous observation. Natural disasters do not know national boundaries. To deal with large-scale volcanic eruptions, we need to strengthen prediction, prevention and response. At present, accurate prediction of volcanic eruption is a worldwide problem. With the development of earth science to deep space, deep earth and deep sea, scientists are expected to have a deeper understanding of volcanoes, an active crustal activity. (Xinhua News Agency)