Mt. Fuji is the most famous mountain in Japan. Formed approximately 100,000 years ago, Mt. Fuji is a composite volcano (volcanic cone). After repeating volcanic activities, it became the largest mountain in Japan. The eruption in 1707 continued for as long as 16 days, and there remain records that massive amounts of volcanic ash and lapilli traveled as far as present-day Tokyo area 100 kilometers away.
And this eruption led to the formation of Mt.Hoei-zan (2,963 m) which is a parasite volcano of Mt. Fuji. Mt.Hoei-zan’s huge mouth of the crater can be seen from Shizuoka Prefecture.
Other products of this eruption include the numerous caves located in Aoki-ga-hara, also known as the Sea of Trees (Jukai), which is a 3,000-hectare virgin woodland growing over the lava flow. Also formed at the mountain foot were five lakes which are known as Fuji-go-ko, or the Five Lakes of Fuji. These lakes are considered to share the same subterranean water veins, and at times of heavy rainfall, a sixth lake called Aka-ike (Red Pond) sometimes emerges.
Mt. Fuji is also blessed with abundant spring water. The piled-up snow takes many years to be filtered through the layers of earth, producing mellow water with high mineral contents. Especially famous for abounding spring water flowing from Mt. Fuji are the eight ponds known as Oshino Hakkai in the village of Oshino-mura in Yamanashi Prefecture.