Mount Fuji's Magma at 1707 Levels... Fears of a Super-Eruption

Currently, the amount of magma in Mount Fuji's magma chamber is at the same level as during the great eruption of Mount Fuji in 1707. In particular, with gas sealed inside the magma without leakage, there is a constant risk that accumulated pressure could lead to a super-eruption.

Professor Kim Ki-bum explained, "The amount of magma in Mount Fuji's magma chamber is enough to cause an eruption of the same scale as in 1707, and even more concerning, there is no gas leakage. This could lead to a super-eruption." He also warned of the potential danger by mentioning the Kikai Caldera eruption, which was 100 to 1,000 times larger than Mount Fuji.

That experience raised considerable awareness in Japanese society and significantly influenced subsequent disaster preparedness attitudes.

Recently, during the Noto Peninsula Earthquake in January 2024, significant damage occurred even in the western coastal areas, which were considered relatively safe. As a result, Japan is now approaching disaster preparedness by assuming the worst-case scenarios, without distinguishing between severity.

Professor Kim Ki-bum stated, "During the Great East Japan Earthquake, there was absolutely no preparation, and they faced that huge disaster, which then led to a great awakening." He added that based on the understanding that no region is safe from disaster, a nationwide preparedness system is now being established.

The Japanese government transparently shares information with the public that there is an 80% probability of a large-scale earthquake occurring within 30 years. This is done proactively, with even the Prime Minister involved in producing and distributing simulation videos.

Professor Kim Ki-bum said, "So, in Japan, even the Prime Minister comes out and says there's this much probability here. They even create and show the public those absurd simulation videos." He explained that this open attitude contributes to raising public awareness, despite societal repercussions such as declining apartment prices.

The case of Mount Fuji erupting 49 days after the 1707 Hoei earthquake is considered strong evidence that earthquakes can trigger volcanic eruptions. This is because seismic vibrations affect the magma chamber, separating dissolved carbon dioxide from the magma.

Professor Kim Ki-bum explained, "At that time, a large earthquake caused vibrations in the magma chamber beneath Mount Fuji. Magma contains an enormous amount of dissolved gas. When vibrations are applied, the dissolved carbon dioxide starts to escape." He added that through this mechanism, the possibility of a chain of earthquakes and volcanoes is accepted as common knowledge in Japanese society.

The interconnectedness of earthquakes and Mount Fuji eruptions frequently appears in Japanese popular culture. Especially in films depicting the sinking of Japan, scenarios always show Mount Fuji erupting simultaneously with large-scale earthquakes, deeply imprinting the inevitable link between earthquakes and Mount Fuji eruptions in the Japanese consciousness.

Professor Kim Ki-bum mentioned, "In films about Japan sinking, Mount Fuji always erupts at the same time," emphasizing that mass media has greatly influenced the formation of this perception.

This magma is currently sealed without gas leakage.

Professor Kim Ki-bum explained, "It has also been revealed that the amount of magma already present beneath Mount Fuji is enough to cause an explosion of the same magnitude as in 1707."

The sealed state without gas leakage is similar to shaking a carbonated drink, implying a greater risk that a rapid separation of gas within the magma during an earthquake could lead to a super-eruption.

This caldera is known to have caused a large eruption about 7,300 years ago and is currently preparing for re-eruption.

Professor Kim Ki-bum announced, "Researchers at Kobe University in Japan confirmed a large magma reservoir of about 220 km³ beneath the Kikai Caldera on the seabed south of Kyushu," explaining that this super-large magma reservoir suggests the possibility of a future large-scale eruption.

Volcanoes in the Kyushu region have the potential to erupt on a much larger scale (VEI 7-8) than Mount Fuji (VEI 5), which could have significant implications for the Korean Peninsula. Records indicate that volcanic ash fell on the southeastern Korean Peninsula about 10 times during large eruptions in the Kyushu region over the past 100,000 years.

Notably, Japanese volcanic ash 10-20 cm thick has been found in the Hapcheon Chogye Basin, suggesting that such a thickness of ash in the southeastern region could completely paralyze urban functions.

Professor Kim Ki-bum emphasized, "The volcanoes that erupted here were all of magnitudes 7-8. These were volcanoes that erupted 100 to 1,000 times larger than Mount Fuji," warning of the ripple effects of Kyushu's volcanic activity on the Korean Peninsula.

The Kikai Caldera eruption 7,300 years ago destroyed Japan's Jomon civilization, recorded as a historical case of civilization annihilation similar to the Pompeii disaster.

Professor Kim Ki-bum stated, "They say Baekdu Mountain's millennium eruption was the second largest in history, but this (Kikai Caldera) is an amount that could happen twice." He added that actual volcanic ash deposits found in the Ulsan region's strata prove the impact of past large-scale eruptions on the Korean Peninsula.

Japan anticipates massive human and economic damage from a Nankai Trough earthquake, one of the worst-case disaster scenarios it faces. This major earthquake is suggested to trigger a Kikai Caldera eruption, based on the same logic as a Mount Fuji eruption.

Professor Kim Ki-bum mentioned, "A Kikai Caldera eruption could also occur if a large earthquake happens in the Nankai Trough," warning that seismic vibrations could stimulate the magma chamber and lead to a large-scale volcanic eruption.

Professor Kim Ki-bum explained, "The amount of magma Kikai Caldera holds is 220 cubic km. The magma under Mount Fuji is about 1 cubic km, so it has 220 times more." He emphasized that Kikai Caldera's potential eruption scale is incomparably larger than Mount Fuji's.

Kyushu, Shikoku, and southwestern Japan, as well as Tokyo and the Tohoku region, could be extensively affected.

The Korean Peninsula would also not be immune to volcanic ash fall, with Gyeongsang provinces, Jeju Island, and South Jeolla Province likely to suffer damage from volcanic ash.

Professor Kim Ki-bum warned, "If a volcanic ash event occurs, almost the entire Japanese archipelago will be within the volcanic ash fall zone. Our Korean Peninsula, including Gyeongsang provinces, Jeju Island, and South Jeolla Province, could also be included in the volcanic ash fall zone," suggesting the need for international disaster preparedness.

Plinian eruptions, which are powerful volcanic explosions, create massive eruption columns like a nuclear bomb, with volcanic ash reaching high into the upper atmosphere. Volcanic ash that rises into the stratosphere then moves according to the Earth's atmospheric circulation patterns.

Professor Kim Ki-bum explained, "When a volcano erupts, if it explodes very powerfully, like a nuclear bomb, a huge eruption column is created, and volcanic ash rises very high into the upper atmosphere."

Because westerlies always blow steadily in the stratosphere, volcanic ash that reaches this layer tends to move predominantly eastward with the westerlies.

Professor Kim Ki-bum stated, "Even when an eruption occurred at Baekdu Mountain, it went eastward on the westerlies. It's named Baekdu Mountain Tomakomai volcanic ash." He cited evidence that the impact of Baekdu Mountain volcanic ash was more significantly confirmed in the eastern region of Japan than in the western region of China.

The 2022 Tonga volcanic eruption, where ash reached the mesosphere and affected the entire world, demonstrates this.

Professor Kim Ki-bum explained, "It goes up to an altitude of 35 km, into the mesosphere. The westerlies don't blow there. Volcanic ash spreads in all directions, at the same distance, centered around the volcano."

Therefore, volcanic ash that reaches the mesosphere does not move in a single direction due to the westerlies but instead spreads uniformly in all directions—east, west, north, and south—from the volcano's center.

It is confirmed that volcanic ash from this massive eruption fell as far as the northern regions of the Korean Peninsula.

Professor Kim Ki-bum mentioned, "The last eruption at Aso Mountain about 100,000 years ago is considered VEI 8. That's 10 times the scale of Baekdu Mountain's millennium eruption. At that time, volcanic ash even fell in North Korea..." emphasizing the widespread impact of Aso Mountain's past eruption on the entire Korean Peninsula.