Photo/Illutration Mount Fuji seen from Lake Yamanakako (Provided by Shinya Yamamoto)

Researchers found evidence of six previously unknown major eruptions of majestic Mount Fuji between 4,000 and 5,000 years ago.

The discovery may lead to a review of conventional studies on volcanic event intervals and scales, said scientists from Yamanashi Prefecture’s Mount Fuji Research Institute and the Atmosphere and Ocean Research Institute of the University of Tokyo.

“Our accomplishment could change the existing interpretation of Mount Fuji’s volcanic activity,” said Shinya Yamamoto, a chief researcher of geochemistry at the Mount Fuji Research Institute.

“We will be clarifying what kind of eruptions happened each time throughout history, with the goal of contributing to the development of better countermeasures against volcanic disasters.”

The team’s research results were published in the international academic journal Quaternary Science Advances at (https://doi.org/10.1016/j.qsa.2023.100091) on June 30.

Geological formations were traditionally examined for traces of volcanic ash and other substances spewed from past eruptions of Japan’s highest peak, enabling the latest findings to be made through their analysis.

However, these markers can disappear over time due to erosion and other elements.

With this in mind, the researchers studied nearby Lake Yamanakako since traces of past eruptions were thought to lay undisturbed on the lakebed.

The lake is situated 13 kilometers northeast of the summit of Mount Fuji. Debris from past eruptions came down in the lake.

The scientists first applied carbon dating to sedimentary specimens collected from the lake bottom via an earlier drilling survey in 1998. A new excavation study was carried out around the lake as well.

The outcomes revealed six geological layers dating back 5,050 to 3,900 years, showing signs of volcanic events. All the confirmed markers were previously unknown on the northeastern side of Mount Fuji, according to the team.

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