Mount Fuji: a deep dive into Japan's iconic stratovolcano
Mount Fuji is one of the few mountains whose shape is so recognisable it has become shorthand for an entire country. Its 3,776-metre cone sits on the boundary of three tectonic plates — Pacific, Philippine and Eurasian — and is the youngest of three superimposed volcanoes that have built and rebuilt the peak over hundreds of thousands of years.
A young cone on an old foundation
The Fuji we see today is "New Fuji," built up since roughly 10,000 years ago on top of the older Komitake and Ko-Fuji edifices. The symmetrical cone owes its form to a long series of basaltic-andesite eruptions that buried earlier structures under fresh lava and tephra. On clear days the unbroken slope from base to summit is unmistakable.
The Hōei eruption of 1707
Fuji's most recent eruption began on 16 December 1707 and lasted about two weeks. It did not flow lava, but produced a massive ash column that fell on Edo (Tokyo) and opened a new vent — the Hōei crater — on the southeast flank. That crater is still visible from the air and along the Subashiri trail.
Three hundred years of silence
Since 1707, Fuji has not erupted. The volcano is classified by Japan's Coordinating Committee for Prediction of Volcanic Eruptions as active, and a 2021 update of hazard maps significantly enlarged the modelled flow paths to account for new lava-flux estimates. There is no imminent warning, but the silence is not a guarantee.
The Yamanashi and Shizuoka prefectures
Fuji sits on the boundary between Yamanashi to the north and Shizuoka to the south. The Fuji Five Lakes (Fuji-go-ko) — Yamanaka, Kawaguchi, Sai, Shōji, Motosu — fill depressions carved by older lava flows; they are the classic photographic foregrounds. To the south, the Hakone caldera and Izu Peninsula complete the volcanic landscape.
Climbing season
Fuji is one of the world's most climbed mountains. The official climbing season runs from early July to early September. There are four trails — Yoshida, Subashiri, Gotemba and Fujinomiya — each ending at the rim. Many climbers begin in late afternoon, sleep at a hut on the upper slope, and reach the summit for sunrise (goraikō).
In art and culture
Fuji has been painted, written about and photographed more than almost any other mountain on Earth. Hokusai's "Thirty-six Views" and Hiroshige's prints established the visual vocabulary. The mountain is listed by UNESCO as a Cultural rather than Natural site, on the basis of its inspirational role rather than its geology.
Monitoring and forecasting
The Japan Meteorological Agency runs continuous monitoring with seismometers, GPS, tiltmeters and gas instruments. The 2011 Tōhoku earthquake produced detectable strain changes inside the volcano, and small earthquake swarms in the years since have been carefully analysed; none has so far suggested imminent eruption.
Why Fuji matters
Fuji is the cone that defines what a stratovolcano looks like in the popular imagination. It is also a working laboratory for understanding how a quiet volcano in a megacity's backyard ages between eruptions — and how one would prepare 35 million people for the day it stops being quiet.
On the map
Open the map and find Fuji about 100 kilometres southwest of Tokyo, on the line where the Pacific and Philippine plates dive under the Eurasian. The Izu volcanic arc trails south through the islands of Ōshima, Miyakejima and Hachijōjima.