: N2 =
Tertiary sedimentary rocks; αN2 = Tertiary volcanic rocks; αQ1 =
Komitake volcano; α-δQ1 =
Ashitaka volcano; βQ2 = Older Fuji volcano; αβQ2 = Younger Fuji volcano. Mount Fuji is located at a
triple junction trench where the
Eurasian Plate,
North American Plate, and
Philippine Sea Plate meet. These three plates form the western part of Japan, the eastern part of Japan, and the
Izu Peninsula respectively. The Fuji triple junction is only from the
Boso triple junction. Fuji's main crater is in diameter and deep. The bottom of the crater is in diameter. Slope angles from the crater to a distance of are 31°–35°, the
angle of repose for dry gravel. Beyond this distance, slope angles are about 27°, which is caused by an increase in
scoria. Mid-flank slope angles decrease from 23° to less than 10° in the
piedmont. Pre-Komitake started erupting in the
Middle Pleistocene in an area north of Mount Fuji. After a relatively short pause, eruptions began again, which formed Komitake Volcano. These eruptions ended 100,000 years ago. Ashitaka Volcano was active from 400,000 to 100,000 years ago and is located southeast of Mount Fuji. Mount Fuji started erupting 100,000 years ago, with Ko-Fuji (old-Fuji) forming 100,000 to 17,000 years ago, but it is now almost completely buried. A large
landslide on the southwest flank occurred about 18,000 years ago. Shin-Fuji (new-Fuji) eruptions in the form of
lava,
lapilli, and
volcanic ash have occurred between 17,000 and 8,000 years ago, between 7,000 and 3,500 years ago, and between 4,000 and 2,000 years ago. Flank eruptions, mostly in the form of parasitic
cinder cones, ceased in 1707. The largest cone,
Omuro-Yama, is one of more than 100 cones aligned NW-SE and NE-SW through the summit. Mt. Fuji also has more than 70
lava tunnels and extensive lava tree molds. Two large landslides are at the head of the Yoshida-Osawa and Osawa-Kuzure valleys. Since then, no signs of an eruption are recorded. On the evening of March 15, 2011, however, a
magnitude 6.2 earthquake at shallow depth occurred a few kilometres from Mount Fuji on its southern side.
Recorded eruptions About 11,000 years ago, a large amount of lava erupted from the west side of the top. This lava formed new Fuji, which is the main body of Mount Fuji. Since then, the tops of ancient Fuji and new Fuji have been side by side. About 2,500–2,800 years ago, the top part of ancient Fuji was destroyed in a large
sector collapse and only the top of Shin-Fuji remained. Ten known eruptions can be traced to reliable records.
Current eruptive danger Following the
2011 Tōhoku earthquake, media speculated that the shock might induce volcanic unrest at Mount Fuji. In September 2012, mathematical models created by the National Research Institute for Earth Science and Disaster Prevention (NRIESDP) suggested that the pressure in Mount Fuji's
magma chamber could be 1.6
megapascals higher than before its 1707 eruption. This was interpreted by some media outlets to mean that an eruption of Mount Fuji could be imminent. Absent any method of directly measuring the pressure of a volcano's magma chamber however, indirect calculations of the type used by NRIESDP remained speculative and unverifiable. Other indicators suggestive of heightened eruptive danger, such as active
fumaroles and recently discovered
faults, are typical occurrences at this type of volcano. Eruption fears continued into the 2020s. In 2021, a new hazard map was created to help residents plan for evacuation, stoking fears because of its increased estimate of lava flow and additional vents. Soon afterwards, a 4.8 magnitude earthquake hit the area. The Japan Meteorological Agency however, assured the public that the earthquake did not increase the eruption risk. In 2023, a new evacuation plan was developed to account for the 2021 hazard map update. == Aokigahara forest ==