Mount Fuji is the tallest volcano and the highest mountain in Japan. Mount Fuji is still considered an active volcano. The current volcano, which erupted about ten thousand years ago, covers two older volcanos, Komitake Fuji and Old Fuji.

Mount Fuji is the tallest volcano and the highest mountain in Japan. It straddles the boundary of Shizuoka and Yamanashi Prefectures just west of Tokyo, from where it can be seen on a clear day. It is located near the Pacific coast of central Honshu. Three small cities surround it, Gotemba (East), Fuji-Yoshida (North) and Fujinomiya (Southwest).

Mount Fuji has five lakes around it: Lake Kawaguchi, Lake Yamanaka, Lake Sai, Lake Motosu and Lake Shoji. They—along with nearby Lake Ashi—provide excellent views of the mountain. It is part of the Fuji-Hakone-Izu National Park.

Mount Fuji is the tallest volcano in Japan, and also the volcano with the greatest volume. It is believed to have grown greatly in volume in the last 100,000 years, so it can be classified as a "young volcano." Scientists have identified four distinct phases of volcanic activity in the formation of Mount Fuji. The first phase, called Sen-komitake, is composed of an andesite core recently discovered deep within the mountain. Sen-komitake was followed by the "Komitake Fuji," a basalt layer believed to have been formed several hundred thousand years ago. Approximately 100,000 years ago, "Old Fuji" was formed over the top of Komitake Fuji. The modern, "New Fuji" is believed to have formed over the top of Old Fuji by around ten thousand years ago.

The mountain as it appears now is the "New Fuji volcano," which began to erupt about 10,000 years ago. Under the "New Fuji volcano" lie the "Komitake volcano," and the "Old Fuji volcano."

There has been volcanic activity in the vicinity of Mount Fuji for several million years. About 700,000 years ago, in the location occupied by the current Mount Fuji, a volcano known as Mount Komitake, became active. The peak of the ancient volcano, Komitake, can be seen from the north face of Mount Fuji at the fifth station, about 2,300 meters above sea-level. Around 100,000 years after becoming inactive, Komitake entered another period of activity. The volcano of this period is known as Old Fuji and was characterized by explosive eruptions which threw out large quantities of scoria, volcanic ash and lava to form a large mountain which reached a height of 3,000 meters.

Following the Old Fuji period, there were about four thousand years of inactivity, ending when Mount Fuji became active again around five thousand years ago; this period is known as New Fuji and continues to the present day. Eruptions of New Fuji exhibit phenomena such as lava flows, magma, scoria, volcanic ash, collapses and side eruptions. Ash from New Fuji is often black, and eruptions are new in terms of geological layers. Valuable data on the activity of Mount Fuji, exhibiting a range of representative eruptions, is recorded in Japanese historical documents dating from the eighth century onwards.

About 2,300 years ago the east face of the volcano collapsed, and liquid mud flowed down to Gotenba area as far as the Ashigara plain in the east and the Suruga bay across Mishima city in the south. This incident is now called the Gotenba mud flow.

In 684 (the sixth year of the Jogan era) there was an eruption on the northeast side of Mount Fuji, which produced a great amount of lava. Some of the lava filled up a large lake which existed at the time, dividing it into two lakes, Saiko and Shojiko. This is known as the Aokigahara lava and at present is covered by forest.

The latest eruption, in 1707, was known as the great Hoei eruption. It began 49 days after the Hoei earthquake, which was on the largest scale found in Japan. This eruption spread a vast amount of volcanic ash and scoria over a region as far away as Edo (Tokyo). A new crater, along with a second peak, named Hoei-zan after the era name, formed halfway down the side of Mount Fuji.

The volcano is currently classified as active with a low risk of eruption. The last recorded eruption occurred in 1707, during the Edo period. At this time, Mount Fuji is located at the point where the Eurasian Plate, the Okhotsk Plate, and the Philippine Plate meet. Those plates form the western part of Japan, the eastern part of Japan, and the Izu Peninsula respectively.

credited to New World Encyclopedia and flickr: straightfinder