The large-scale eruption of an undersea volcano in the South Pacific has set off waves in global public opinion. Listen to scientists in various fields to interpret the process and effects of volcanic eruptions from a professional perspective.
On January 15, a massive volcanic eruption occurred off the south Pacific island nation of Tonga, triggering a tsunami that affected the entire Pacific Rim. This "accidental" volcanic eruption has made the South Pacific island nation with a total population of 100,000 instantly become the focus of global attention.
▲ On January 15, satellite images taken by the Japanese meteorological satellite "Haima 8" showed that the undersea volcano erupted in Tonga to form an eruption column of up to 20 kilometers and spread hundreds of kilometers at the top (Image source/Visual China)
Some experts speculate that this volcanic eruption is the most powerful on Earth in the past 30 years. Secondary disasters caused by volcanic eruptions not only caused Tonga to be "lost" for a time, but may continue to have unpredictable impacts on the global ecological environment and climatic environment.
Due to the suddenness and historical rarity of volcanic eruptions, large-scale humanitarian relief was followed by discussions and questions from the public and professionals about relevant scientific issues. The reporter interviewed professionals in geology, climate, oceanography and other fields, and interpreted the process and impact of volcanic eruptions from a scientific perspective.
Why can undersea volcanic eruptions "blend water and fire"?
As we all know, water and fire are the existence of "water and fire". However, in the volcanic eruption of Tonga, the sea waters of the vast Pacific Ocean not only failed to "extinguish" the volcano, but even contributed to the power of the eruption.
First of all, it needs to be clear, what exactly is the eruption of submarine volcanoes? At first glance, it does look like a "spitfire", but in fact it is not fire, but magma, a molten substance like molten steel.
Magma originates from the Earth's asthenosphere, is the melting state of rock, is flowing, and has a temperature of up to thousands of degrees Celsius. Due to the high temperature and high pressure environment under the earth's crust, a large amount of magma is stored. When plate movement is frequent, magma will break through the earth's crust under high pressure and gush outward, forming volcanic eruptions.
Fire is formed by the violent oxidation between the incendiary and the air, and the principle that water can extinguish the fire is to cool down and the other is to isolate oxygen. Without oxygen, the combustion can not continue oxidation activities, and the combustion naturally stops.
The magma is not the same, its eruption is caused by the high pressure of the ground, itself does not need combustibles and incendiary substances, hot magma after contact with the cold seawater, the high temperature makes the nearby seawater quickly become water vapor, this is the "water and fire fusion" when the violent scene.
▲From the remote sensing image of the mainland Gaofen-1 B satellite, it can be seen that there are a large number of red and brown pumice stones floating in the tens of kilometers around Hong Aha Apay Island, and the length ranges from a few meters to more than 10 kilometers. Pumice is formed by the contact between volcanic lava and seawater, its main component is usually silica, soft texture, small specific gravity, gathered together under the action of the waves, can form a large area of pumice, not only will affect the navigation of ships, fish resources in the sea will also die because of the accidental swallowing of pumice (Source: CCTV News)
Submarine volcanic eruptions are not the same medium as land volcanic eruptions (one is seawater, the other is air). Since the resistance of air is less than that of seawater, it is reasonable to say that volcanic eruptions of the same size will erupt more violently on land. But the truth is that undersea volcanoes sometimes erupt more intensely. This is because magma eruptions can cause seawater to boil rapidly, producing high temperatures and large amounts of gas in a very short period of time, so submarine volcanic eruptions are prone to violent explosions.
Of course, some submarine volcanic activities are relatively mild, and during the contact between seawater and magma, the seawater continues to boil, the magma continues to cool, and eventually the magma will cool into a solid state covering the seabed. The more lava erupts, it piles up and emerges to become an island.
How difficult is it to warn of a volcanic eruption?
As things stand, most scientists believe that the magnitude of the Tongan eruption is relatively strong, VEI5 or VEI6 (i.e., the Volcano Explosivity Index, volcanic eruption index). At a time when technology is highly developed, why is such a strong volcanic movement still unable to be warned in advance?
At present, the monitoring of volcanic eruptions, especially submarine volcanoes, is very difficult.
Volcanoes are the product of magmatic activity, and when the magma in the deep underground is subjected to great pressure, it will erupt from the surface to form volcanoes. If the volcano is located at the bottom of the ocean, it is called a submarine volcano. It is estimated that there are about 20,000 submarine volcanoes on the earth, mostly distributed in areas with plate tectonics and active magmatic activity, such as mid-ocean ridges and island arcs. Some of the 20,000 volcanoes are dying, some are still young and active, and others are dormant. For example, the famous Hawaiian Islands are actually archipelagos formed by volcanic eruptions.
The most volcanically active region in the world is precisely the Pacific Ocean, and geologically there is a "Pacific Ring of Volcanic Belt", which roughly surrounds the entire Pacific Ocean, with a total length of more than 40,000 kilometers and more than 500 active volcanoes, and Tonga Volcano is just one of them.
With so many volcanoes in the world, submarine volcanoes are distributed in the vast ocean, with the existing geological research and marine exploration level of human beings, it is difficult to achieve intuitive monitoring of the activities of submarine volcanoes, basically can only be "resigned".
▲ Monitoring distribution map of active volcanoes in the mainland. Jilin Changbaishan Volcano, Longgang Volcano, Heilongjiang Wudalianchi Volcano, Jingpo Lake Volcano, Yunnan Tengchong Volcano and Hainan Qiongbei Volcano have been included in the China Volcano Monitoring Network. A variety of monitoring methods, including earthquakes, gravity, deformation, fluids, etc., have been used in real-time monitoring of these active volcanoes (Source: Sichuan Online)
For submarine volcanoes, the current common method is to calculate the next possible active period and time based on the existing eruption data, but the scientific accuracy of this data is not high, and the method is relatively primitive.
Because of this, it is impossible to determine when the current volcanic eruption in Tonga will end, because volcanic activity is on geological time scales, not on human time scales, and it is possible to last for several days, weeks or even months, and it can only be said that the intensity of subsequent eruptions may be weakened. This is similar to how aftershocks last for years or even decades after an earthquake.
Volcanic eruptions will cause a "summerless year" of global cooling?
After the eruption of the Tonga volcano, some speculation about the impact of volcanic ash on the climate involved people's nerves - a large amount of volcanic ash could not settle for a long time after entering the stratosphere, resulting in a "parasol effect", which would cause a "summerless year" of global temperature decline. Is there a scientific basis for this claim? Volcanic eruptions do correlate with falling global temperatures. But so far, the impact of Tonga's volcano on global temperatures has not been significant.
Volcanoes do cause the Earth to "cool down," mainly because they inject sulfur-laden aerosols into the atmosphere, which, when they enter the stratosphere, reflect more sunlight, creating a cooling effect within the atmosphere. In the past 100 years, there have been three large-scale low-latitude volcanic eruptions, namely Agung Volcano in Indonesia (2019), El chitron Volcano in Mexico (1982), and Mount Pinatobo in the Philippines (1991). In the winter of the year after their eruption, temperatures were low in most parts of the mainland except the northeast and Xinjiang.
But when it comes to climate impacts, the scale of volcanic eruptions is a key factor that must be considered, the Eruption of Pinatubo Volcano in the Philippines, which caused the global average temperature to drop by 0.5 °C, was VEI of 6, and it released 20,000 kilotons of sulfur dioxide from the eruption in 1991; the estimated VEI of the Tonga volcano is 5 to 6, but the release of sulfur dioxide on the first day of the eruption is only 62 kilotons, and the impact on global temperature will not be large.
▲ According to the observations of the Mainland Fengyun-4 B satellite, most of the mineral particulate matter in the volcanic ash cloud hovers around the volcanic eruption point and gradually settles, while the light-colored clouds in the volcanic cloud gradually separate and gradually spread westward. After analysis, this part of the cloud is mainly composed of acidic gases such as sulfur dioxide (image source: CCTV News)
A series of studies have shown that volcanic eruptions generally have a sustained impact on the global and East Asian climate in the next 1 to 2 years, causing a certain cooling effect. For the mainland, volcanic eruptions may also weaken the intensity of east Asian summer winds the following year, which in turn will lead to the southward summer rain band of the continent, affecting the rainfall throughout the flood season.
Is it a blessing or a curse for marine ecology?
After the eruption of Tonga's submarine volcano, a huge amount of volcanic ash, magma, and sulfides fall into the sea and drift with the ocean currents, what will be the impact of marine life? Will it damage the coastal ecological environment of the mainland?
At the moment of the eruption of the submarine volcano, the surrounding seawater will rapidly heat up and boil, which will cause devastating blows to nearby marine life; the magma emitted by the volcano will cover the seabed, causing a large number of seabed organisms to die; and the large amount of sulfide carried in the lava is also toxic to marine life farther away.
The indirect effects of volcanic eruptions are long-term and widespread. Due to the large amount of volcanic ash blocking the sunlight, the photosynthesis of the algae in the seawater is weakened. Algae are primary producers in marine ecosystems that produce oxygen through photosynthesis, supply organic matter, and feed other marine animals or microorganisms. Once the algae are reduced, the biomass of the sea area will decrease, which may lead to radical changes or even collapse of the community structure in the ecosystems of the region.
Volcanic eruptions will also cause increased turbidity of seawater in a certain area, which will not only further affect the photosynthesis of algae, but also attach or cover coral reefs with turbid particulate matter, blocking the breathing and filter feeding holes of reef organisms, and killing reef habitats such as corals.
Affected by the tsunami caused by the volcanic eruption on the tonga seabed, a total of about 30 fishing boats in Japan have capsized or sunk, and there have been damage to fishing and aquaculture equipment in many places (Source: Global Network)
From another point of view, volcanic eruptions lead to an increase in the temperature of the sea and an increase in toxic and harmful substances, which may trigger an accelerated rate of genetic mutation in marine organisms.
A few days ago, the news about the "harvest of wild yellow croakers" brushed the screen, and some netizens believed that this was related to the eruption of the undersea volcano in Tonga, in fact, the scientific basis for this suspicion was insufficient. The yellow croaker is one of the main economic fish in China's offshore waters and was not driven from the open ocean by volcanic eruptions. The fact that fishing boats can catch so many large yellow croakers in a single net is mainly the result of the summer fishing moratorium on the mainland for many years and the strengthening of marine environmental protection measures. Coupled with the significant increase in the fishing capacity of fishing vessels and the radar detection and tracking capabilities of fish populations, the fish in wintering grounds (waters where fish and shrimp groups are concentrated for wintering).
As for whether the fish concentration is related to the earthquake and tsunami caused by the volcanic eruption on the tonga seabed, this is unlikely, but it cannot be completely ruled out that the larger yellow croaker will form a large fish school in a short period of time due to the spread of seismic waves and tsunami waves to the coast of China.
Producer: Popular Science Central Kitchen
Producer: Beijing Science and Technology News | Beike Media
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