Qualla: Historic Eruptions of Mount Fuji

Historic Eruptions of Mount Fuji: Introduction

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Public domain. The mountain that appears on every postcard, every airline screensaver, every meditation app -- that perfectly symmetrical cone of white and blue -- is a loaded weapon. Mount Fuji is an active volcano. Its last eruption, in 1707, flung ash almost 100 kilometers to blanket the streets of Edo, the city now called Tokyo. Sixteen eruptions have been recorded since 781 AD, and scientists monitoring the magma chamber know that the internal pressure has been climbing since the massive Tohoku earthquake of 2011. Mount Fuji is not a relic. It is a geological event in progress, and the serene profile that defines Japan's skyline is simply the current frame in a 700,000-year story of fire and collapse.

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Historic Eruptions of Mount Fuji: Three Mountains in One

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Public domain. What most people see as a single peak is actually three volcanoes stacked on top of each other. The oldest, the Komitake volcano, became active 700,000 years ago. Its remnant peak sits about halfway up Mount Fuji's north face, at the approximate elevation of the fifth station whe...

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Historic Eruptions of Mount Fuji: The Night Aokigahara Was Born

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Public domain. In 864 AD, the sixth year of the Jōgan era, Mount Fuji's northeast side erupted and did not stop for ten days. The summit ejected immense quantities of cinders and ash while lava poured down the western flank and into the lowlands below. A large lake called Se-no-umi, which had e...

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Historic Eruptions of Mount Fuji: The Earthquake That Lit the Fuse

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Public domain. The Hōei eruption of 1707 was not a sudden event -- it was a chain reaction triggered by seismic forces that had been building for years. On October 28, 1707, the Great Hōei earthquake, measuring 8.7 on the Richter scale, devastated Osaka and compressed the magma chamber 20 kilom...

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Historic Eruptions of Mount Fuji: Ash Over Edo

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Public domain. The eruption that followed was remarkable for its reach. Volcanic ash and scoria rained down across the provinces of Izu, Kai, Sagami, and Musashi, depositing material almost 100 kilometers from the summit. In Edo -- a city of over a million people, the seat of the Tokugawa shogu...

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Historic Eruptions of Mount Fuji: The Pressure Beneath

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Public domain. Mount Fuji is not dormant. After the devastating 2011 Tohoku earthquake and tsunami, scientists found that the internal pressure of Fuji's magma chamber had increased to an estimated 1.6 megapascals. Researchers monitor the volcano by measuring CO2 emissions in its deeper regions...

Image: Public domain