Japan's Mount Fuji may erupt? Will it have an impact on my country?

According to a report by Japan's Jiji Press on the 19th, the National Police Agency of Japan has begun to make comprehensive preparations for the possible eruption of Mount Fuji. According to people familiar with the matter, the National Police Agency of Japan will purchase dust masks and distribute them to local police departments. The National Police Agency believes that if Mount Fuji erupts, volcanic ash may not only fall in the area near Mount Fuji, but also in the Tokyo metropolitan area.

Why might Mount Fuji erupt? What effects might it have?

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It has been 315 years since Mount Fuji last erupted

Mount Fuji is 3,776 meters high and is located in the south-central 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 news reports that Mount Fuji has begun to show signs of activity. However, according to Zheng Jingyun, a researcher at the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, the last large-scale eruption of Mount Fuji was in the early 18th century.

According to historical records, the last time Mount Fuji erupted was in 1707, 315 years ago. The data shows that the volcano erupted for 16 consecutive days, thousands of square kilometers of the surrounding area were filled with volcanic ash, the entire Edo area (now Tokyo) was almost dark, and the air was filled with the smell of fire and sulfur.

"The eruption of Mount Fuji in 1707 may have had a greater impact on local Japan, but its impact on the global climate was not particularly typical," Zheng Jingyun told Science and Technology Daily.

Why is it possible that a volcano that has been dormant for more than 300 years may "wake up" this time?

In response to this issue, Chu Guoqiang, a researcher at the Institute of Geology and Geophysics of the Chinese Academy of Sciences, said that volcanic eruptions are normal due to internal geological activities.

If it erupts, what impact will it have on our country?

Zheng Jingyun told reporters that if Mount Fuji erupts, it will cause serious air pollution in the area. Volcanic ash will not only affect human health, but also have a serious impact on local water resources and the ecological environment. At the same time, the large amount of extremely high-temperature magma brought by the volcanic eruption will surge to the ground, which will also damage the surrounding geological and ecological environment.

"However, the direct impact of the eruption of Mount Fuji on my country may not be significant," Zheng Jingyun explained. This is because my country is in the "upwind zone" of Mount Fuji, and the wind blows from west to east, so the volcanic ash produced by the eruption will not "drift" over. But if the eruption of Mount Fuji is a "strong volcanic eruption", it may affect my country's cooling and rainfall 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), medium (level 3), medium-large (level 4), large (level 5), very large (level 6), huge (level 7), and super (level 8). With each increase in level, the total volume of the eruption increases 10 times.

Zheng Jingyun said that strong volcanic eruptions inject a large amount of sulfur-containing gases into the atmosphere. These gases undergo a series of chemical reactions to form sulfide aerosols in the lower stratosphere. The aerosols mix with water vapor to form volcanic clouds, which affect cooling and rainfall. "In layman's terms, this cloud blocks solar radiation, which causes cooling. If it has enough water vapor, it will bring rainfall."

Related research shows that volcanic clouds will spread rapidly around the world within 2 to 3 weeks along with atmospheric circulation, affecting regional and even global climate. Usually, a strong volcanic eruption will cause the average surface temperature of the hemisphere or the world to drop by about 0.3℃ within 1-2 years.

The impact area is smaller than that of volcanic eruptions in low-latitude areas.

Taking into account the movement of atmospheric circulation, Zheng Jingyun said that Mount Fuji is located in the mid-latitude zone, and the impact of its eruption is generally smaller than that of volcanoes in the equatorial region. The atmospheric movement in the equatorial region is from low latitudes to mid-latitudes and then to high latitudes, and there is a "three-circle circulation" phenomenon. Volcanic ash, aerosols and other volcanic eruptions that rush into the stratosphere can reach farther places and have a wider impact range. However, volcanic eruptions in the mid-latitude zone flow to high latitudes and are not easy to flow to low latitudes, so the impact range is smaller.

"The specific impact will depend on the eruption situation," said Zheng Jingyun.

Zheng Jingyun also shared with reporters a study on the significant impact of volcanic eruptions in low-latitude areas - the eruption of Mount Tambora.

In April 1815, Mount Tambora in Indonesia (located at 8°15′ south latitude), near the equator, erupted with a VEI index of 7, which greatly affected the world's climate. The volcanic clouds caused by the eruption weakened the solar radiation energy reaching the ground, and the low temperature caused a significant harvest failure of major crops such as rice and buckwheat in my country from 1815 to 1817. In addition, Europe and North America were generally cold and famine-stricken at the same time, so 1816 was also called the "Year Without Summer."

In fact, the intensity of cooling caused by strong volcanic eruptions at different latitudes varies significantly. Studies have shown that 1-2 years after strong volcanic eruptions at different latitudes, my country's temperature is basically falling, and there are significant regional and seasonal differences in the intensity of cooling.

In addition, in the third year after the strong volcanic eruption, some areas experienced a second cooling phenomenon, with the drop even greater than the first one.

Source: Science and Technology Daily

◎ Sun Yu, intern reporter of Science and Technology Daily

Editor: Liu Yiyang

Review: Julie

Final judge: Wang Yu