Mount Fuji Eruption: 319 Years of Silence

When Mount Fuji Last Erupted

The Hōei eruption began on December 16, 1707 and ran into early 1708. It is the most recent confirmed eruption in our record and, at VEI 5, the largest Fuji has produced in historical time. Unusually, it did not come from the summit. It opened on the southeast flank, building the crater still visible today as Hōeizan — a gouge in Fuji's otherwise famously perfect cone that you can see from the Shinkansen.

The eruption ejected roughly 1.7 km³ of material(equivalent to about 0.7 km³ of magma) and it did so as ash and pumice rather than lava. Prevailing westerlies carried the plume straight over the Kantō plain. Ash fell on Edo — modern Tokyo — about 100 km away, and reached the Bōsō Peninsula beyond it. Contemporary accounts describe daytime darkness in the city and residents sweeping ash off roofs for weeks. The agricultural damage on the volcano's eastern flank was worse and longer-lasting than the immediate disruption: farmland buried in ash stayed unproductive for decades, and the resulting silt fed repeated flooding of the Sakawa River.

One detail is routinely cited and worth stating carefully: Hōei began 49 days afterthe enormous Hōei earthquake of October 28, 1707, one of the largest ever recorded in Japan. The sequence is real and the physical mechanism — a great subduction earthquake changing stress on a nearby magma system — is plausible and actively studied. What it is not is proof of a rule. One well-timed pair is a hypothesis, not a forecasting tool, and treating it as one is how “the next big earthquake will set off Fuji” headlines get written.

Fuji's Full Eruption Record

Our Smithsonian GVP record holds 67 eruption entries for Fujisan — 58 confirmed and 9 flagged uncertain — with the oldest dated to roughly 8540 BCE. Twenty-nine of the confirmed eruptions fall in the Common Era. Of the 30 confirmed eruptions carrying a VEI grade, the breakdown is: three VEI 5, two VEI 4, five VEI 3, nineteen VEI 2 and one VEI 1. Fuji is mostly a modest erupter that occasionally does something serious.

Selected eruptions from the 29 Common-Era entries in our GVP record. Full profile and complete list on the Fujisan data page, or filter every VEI 4+ eruption on our eruption timeline.

Two entries deserve more than a table row. The Jōgan eruption of 864 CE was a flank eruption whose lava flows poured northwest into a large lake called Senoumi, filling most of it and splitting what remained into today's Lake Sai and Lake Shōji. The flow hardened into roughly 30 km² of bare basalt with almost no soil — the ground the Aokigahara “sea of trees” spent the next thousand years colonising. If you have walked in Aokigahara, you have walked on an eruption. The Enryaku eruption of 800–802 CE was large enough (VEI 4) to close the Ashigara pass, the main road between the capital region and eastern Japan, forcing traffic onto an alternative route — a rare case of an eruption redrawing a national road network.

Is Fuji Overdue? The Arithmetic, Honestly

“Fuji is 300 years overdue” is one of the most-repeated claims about any volcano on Earth. Here is the actual arithmetic from our record, and it is more interesting than the headline.

So: 319 years is more than five times the average, which is why the “overdue” claim feels obviously true. But Fuji has already sat silent for 352 years once before, between 1083 and 1435 CE, and then resumed normally. The current quiet spell is not unprecedented — it is the second-longest in the record, and still about 33 years short of the record holder.

That is the honest version, and it cuts both ways. It defuses the “centuries overdue, could go any second” framing. It also means Fuji is genuinely in unusual territory, with only one precedent in two thousand years of records. Averages do not schedule eruptions — we make the same argument about Yellowstone and Katla — but a repose this long is a reasonable thing for a government to plan around, and Japan is doing exactly that.

What Japan Is Actually Preparing For: Ash, Not Lava

The mental image of a Fuji eruption is lava pouring toward Tokyo. That is not the scenario Japan plans for, because it is not the realistic one. Tokyo is roughly 100 km away and lava does not travel remotely that far. The hazard that reaches the capital is ash — and ash turns out to be the thing that breaks a modern megacity.

The Tokyo Metropolitan Government's ashfall modelling of a Hōei-scale eruption with the wind in the worst direction puts 2 to 10 cm or more of ash across most Tokyo wards. The Cabinet Office's 2025 simulation video, released for Volcano Disaster Prevention Day, put about 20 cm on Sagamihara in Kanagawa, 60 km from the crater, and more than 5 cm on Shinjuku at 100 km, two days after the eruption starts.

What makes those numbers serious is how little ash it takes to break infrastructure — especially once it rains and dry dust becomes heavy, conductive grey sludge:

Thresholds as published in Japanese government ashfall preparedness materials, 2025–2026.

The preparedness push has been unusually visible. Japan's Cabinet Office released a computer-generated simulation showing Tokyo in mid-afternoon darkness, ash-laden trains stopped and roofs sagging, aimed squarely at the roughly 37 million people in the greater Tokyo area — a campaign some commentators called alarmist and the government defended as overdue. Working groups through 2026 have been tackling the unglamorous questions: keeping water and power running, informing residents, and where the ash actually goes. Household guidance now recommends stocking goggles, N95-equivalent masks and plastic sheeting for electronics.

The JMA has also moved on warnings. An expert committee compiled a report introducing a volcanic ash warning, issued by municipality when cumulative ashfall of 3 cm or more is expected, and a volcanic ash advisory at 0.1 mm or more — the first time Japan has treated ash depth as a formal, municipality-level warning product rather than a footnote to eruption alerts.

Aviation is the part that would go global fastest. A sustained ash plume over the Kantō plain would close Haneda and Narita, and volcanic ash melts inside jet engines at cruise temperatures. Eyjafjallajökull in 2010 grounded European aviation for six days from a far smaller eruption in a far emptier place. Fuji sits under one of the densest air corridors on the planet.

Is Mount Fuji Showing Signs of Erupting Now?

This distinction gets lost constantly, and the Cabinet Office simulation made it worse — a dramatic CG video of Tokyo under ash reads like a warning about something imminent. It isn't. Japan runs one of the densest volcano-monitoring networks on Earth, and a dormant volcano reawakening magmatically announces itself first: rising magma cracks rock on the way up, so you get earthquake swarms, measurable ground deformation and changing gas output before anything reaches the surface. Nothing of that kind is being reported at Fuji.

One honest caveat, because Japan learned it the hard way. That warning window applies to magmatic eruptions. A phreaticeruption — groundwater flashing to steam with no new magma involved — can arrive with almost none. Mount Ontake killed 63 hikers in 2014 in exactly that way, at a volcano sitting at Alert Level 1 on a clear autumn Saturday. It is the reason “Level 1 means safe” is the wrong reading of the scale anywhere in Japan. Level 1 means nothing unusual is being detected, which is not the same claim.

For comparison, the volcano in Japan that is actually erupting regularly is Sakurajima, which explodes hundreds of times a year and coated Kagoshima in ash in June 2026. Fuji is the famous one; Sakurajima is the busy one. Our volcanoes in Japan hub covers the full picture.

Climbing Mount Fuji in 2026

The official season runs July 1 to September 10, 2026. The rules changed significantly and catch people out:

• A ¥4,000 permit fee per climber now applies, with advance online reservation generating a digital permit you show at the gate.
• The Yoshida Trail has a daily cap of 4,000 climbers. Some slots are held back for same-day booking, but the gate closes once the cap is hit.
• Entry between 2 p.m. and 3 a.m. is barred unless you hold a mountain hut reservation — introduced to stop “bullet climbing,” the practice of ascending overnight without rest, which was producing a steady stream of hypothermia and exhaustion cases.
• Outside the official season the trails and huts are shut, and the mountain becomes a serious winter alpine climb that kills experienced mountaineers most years.

The volcano is not the danger here. At 3,776 m, altitude sickness is common even for fit climbers, summit temperatures can sit near freezing in August with strong wind, and the descent's loose volcanic gravel causes more injuries than the ascent. Our volcano hiking guide covers the checks worth doing before climbing any active volcano, and guided volcano tours are worth considering if it is your first high-altitude climb.

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