A team from the University of Tokyo and the Mount Fuji Institute of Science in Yamanashi Prefecture in Japan said on the 30th that it has been confirmed that Mount Fuji erupted at least six times between 4,000 and 5,000 years ago, which was previously thought to be a gap in activity. Volcanic ash formed by unknown eruptions was found at the bottom of Lake Yamanaka at the foot of the Yamanashi prefecture side of the mountain. The research result was published in an international scientific journal.
It was analyzed as a high frequency eruption with an interval of one or two hundred years, and University of Tokyo professor Yukinori Yokoyama (earth system science) said, “It can be said that there has been activity that cannot be underestimated, and it may be used for future disaster prevention plans and evacuation route development.”
The team investigated 8,000 years of strata at the bottom of the lake and surrounding land, collecting and analyzing carbon samples that could be used for dating and emitting very weak radiation. the samples of strata at the bottom of the lake collected in 1998 contained only a very small amount of radiocarbon, which was difficult to use for technical dating, but the analysis with the latest equipment allowed for more precise dating of the strata.
In addition, a detailed investigation of whether the strata contain volcanic ash revealed that strata from 4,000 to 5,000 years ago contain basaltic volcanic ash, which is representative of Mount Fuji. Based on the carbon dating method, it was determined that the ash was formed by a total of six eruptions between 5050 and 3900 years ago. It is expected that investigations will be conducted on the surrounding lakes and other areas.
It has been confirmed that Mount Fuji has erupted about 180 times since 5,600 years ago, the latest being the Hoyaga eruption in 1707 during the Edo period.