Mount Fuji | Facts, Height, Location, & Eruptions | Britannica

Origin

1 of 2

2 of 2

According to tradition, the volcano was formed in 286 bce by an earthquake. The truth is somewhat more complex. The age of Fuji is disputed, but it seems to have formed during the past 2.6 million years on a base dating from up to 65 million years ago; the first eruptions and the first peaks probably occurred sometime after 700,000 years ago. The earliest precursors to Mount Fuji were Komitake (which forms the mountain’s north slope) and Ashitaka-yama (which sits southeast of the mountain). Mount Fuji is a stratovolcano that rose sometime after 400,000 years ago between the peaks of Komitake and Ashitaka-yama. The present-day mountain is a composite of three successive volcanoes: at the bottom is Komitake, which was surmounted by Ko Fuji (“Old Fuji”) about 100,000 years ago and, finally, by the most recent, Shin Fuji (“New Fuji”). Over the millennia, the lava and other ejecta from Ko Fuji covered most of Komitake, although the top of the latter’s cone continued to protrude from the slope of Ko Fuji. Shin Fuji probably first became active about 10,000 years ago and has continued ever since to smolder or erupt occasionally. In the process it has filled in the slopes of its predecessors and added the summit zone, producing the mountain’s now nearly perfect tapered form.

The base of the volcano is about 78 miles (125 km) in circumference and has a diameter of some 25 to 30 miles (40 to 50 km). At the summit of Mount Fuji the crater spans about 1,600 feet (500 metres) in surface diameter and sinks to a depth of about 820 feet (250 metres). Around the jagged edges of the crater are eight peaks—Oshaidake, Izudake, Jojudake, Komagatake, Mushimatake, Kengamine, Hukusandake, and Kusushidake.

Japanese: Fuji-san (Show more) Also spelled: Fujisan (Show more) Also called: Fujiyama or Fuji no Yama (Show more) See all related content Britannica Quiz All About Mountains Quiz

Mount Fuji is part of the Fuji Volcanic Zone, a volcanic chain that extends northward from the Mariana Islands and the Izu Islands through the Izu Peninsula to northern Honshu. Geologists note that the subduction of the Pacific Plate beneath the Philippine Plate at the Nankai Trough, which extends along Japan’s southern coast, likely drives Mount Fuji’s volcanic activity. Large eruptions occur about every 500 years. Accounts of the most recent major eruption, in December 1707, note that ash darkened the midday sky as far as Edo (present-day Tokyo) and buried temples and dwellings near the mountain. Geologists report that the eruption was triggered by a magnitude-8.4 earthquake, which struck the region 49 days earlier. Mount Fuji’s volcanic activity since 1707 has been limited mostly to small earthquakes; however, a magnitude-6.4 aftershock struck the mountain’s southern flank in the days following the Great Sendai Earthquake of 2011.