TechnologyDaily intern reporter Sun Yu
Why Mt. Fuji might erupt? What might be the impact?
Mount Fuji has been around since the last eruption315 years
Mount Fuji, 3776 meters high, is located in the central and southern part of Honshu Island, Japan, about 80 kilometers east of Tokyo. It is the highest peak in Japan and an active volcano.
In recent years, there have been continuous news reports that Mount Fuji has begun to act. In the impression of Zheng Jingyun, a researcher at the Institute of Geographical Sciences and Natural Resources Research of the Chinese Academy of Sciences, the last large-scale eruption of Mount Fuji was in the early 18th century.
According to historical records, the last eruption of Mount Fuji was in 1707, 315 years ago. According to the data, the volcano erupted continuously for 16 days, and thousands of square kilometers of surrounding area were filled with ash. The entire Edo area (today’s Tokyo) was almost invisible, and the air was filled with the smell of fire and sulfur.
“The eruption of Mount Fuji in 1707 may have a relatively large impact on the local area of Japan, and the impact on the global climate is not particularly typical.” Zheng Jingyun told the Science and Technology Daily reporter.
Why is the volcano that has been sleeping for more than 300 years “awakened” this time?
For this issue,Chu Guoqiang, a researcher at the Institute of Geology and Geophysics of the Chinese Academy of Sciences, said,Affected by internal geological activities, volcanic eruptions are normal.
If it erupts, how will it affect our country?
Zheng Jingyun introduced to reporters,If Mount Fuji erupts, it will bring serious air pollution to the local area.Volcanic ash will not only have an impact on human health, but also have a serious impact on local water resources and ecological environment. At the same time, a large amount of extremely high temperature magma brought by the volcanic eruption poured to the ground, which will also damage the surrounding geological and ecological environment.
“but,The direct impact of the eruption of Mount Fuji on our country may not be large. “Zheng Jingyun explained that this is because our country is in the “upwind zone” of Mount Fuji, the wind blows from west to east, and the volcanic ash produced by the eruption will not “drift” over.However, if the eruption of Mount Fuji is a “strong volcanic eruption”, it may affect the cooling and rainfall of our country through atmospheric circulation.
A strong volcanic eruption refers to an eruption event with a volcanic eruption index VEI ≥ 4. The VEI index reflects the size of a volcanic eruption. The index is measured by the total volume of volcanic material produced by an eruption. There are 8 levels in total, namely micro (level 1), small (level 2), and medium (level 3). ), medium and large (level 4), large (level 5), very large (level 6), huge (level 7), super (level 8), each additional level increases the total eruption volume by 10 times.
Zheng Jingyun said that strong volcanic eruptions injected a large amount of sulfur-containing gas into the atmosphere. These gases formed sulfide aerosols in the lower stratosphere through a series of chemical reactions, and the aerosols mixed with water vapor to form volcanic clouds, which affected cooling and rainfall. “In layman’s terms, the cloud blocks solar radiation, causing cooling, and if there is sufficient water vapor, it will bring rain.”
Relevant studies have shown that volcanic clouds will rapidly spread to the world within 2 to 3 weeks with atmospheric circulation, affecting regional and even global climates.Under normal circumstances, a strong volcanic eruption will cause the average temperature of the hemisphere or the global surface to drop by about 0.3°C within 1-2 years.
The area of influence is smaller than that of volcanic eruptions in lower latitudes
Considering the movement of atmospheric circulation, Zheng Jingyun said,Mount Fuji is located in the mid-latitudes, and its eruptions generally have less impact than volcanoes in the equatorial regions.Atmospheric movement in the equatorial region ranges from low latitudes to mid-latitudes and then to high latitudes. There is a phenomenon of “three-circle circulation”. Volcanic eruptions such as volcanic ash and aerosols that rush into the stratosphere can reach farther places and have a larger impact. . The volcanic eruptions in the middle latitudes flow to the high latitudes, and it is not easy to flow to the low latitudes, and the impact range is small.
“The specific impact depends on the eruption.” Zheng Jingyun said.
Zheng Jingyun also shared with reporters a study on the significant impact of volcanic eruptions in low latitudes – the eruption of Mount Tambora.
In April 1815, the Indonesian volcano Tambora (located at 8°15′ south latitude) near the equator erupted with a VEI index of 7, which greatly affected the world climate. The volcanic cloud caused by the eruption weakened the solar radiation energy reaching the ground, and the low temperature caused the major crops such as rice, buckwheat and other crops to fail in my country from 1815 to 1817. Combined with the widespread cold and famine in Europe and North America during the same period, 1816 is also known as the “Year without Summer”.
In fact, the cooling intensity caused by strong volcanic eruptions at different latitudes varies significantly.Some studies have pointed out that in the 1-2 years after strong volcanic eruptions at different latitudes, the temperature in my country is mainly decreased, and there are significant regional and seasonal differences in the cooling intensity.
The significant cooling areas after high-latitude volcanic eruptions occurred in the northeast and southeast regions, with a temperature drop of 1.2°C in the winter half year and a 2.0°C drop in the summer half year;
After the volcanic eruption at the middle and low latitudes, the significant temperature drop areas in the winter half year occurred in the Qinghai-Tibet, southeast and east-central regions, with an amplitude of 1.3-2.2°C, and the temperature drop in the summer half year was smaller than that in the winter half year;
After the equatorial volcanic eruption, the areas where the temperature dropped significantly in the winter half year occurred in the northeast, southeast and Qinghai-Tibet regions, and the temperature drop was greater than 1.2°C.
In addition, in the third year after the strong volcanic eruption, there was a second cooling phenomenon in some areas, even more than the first time.