The mountain of Hakone with its distinctive 11km diametercaldera is known as a triple volcano, and has been active from about 400,000 years ago to the present day, with its activity roughly divided into 4 stages.

Stage 1 of the Volcanic Activity
	The volcano began its life about 400,000 years ago. As a consequence of continuously repetative eruptions, a straitified volcano of some 2700m in the shape of Mt. Fuji was created about 200,000 years ago and is known as Mt. Furuhakone.
The First Caldera Lake
		About 200,000 years before the end of this activity, the center of the mountain caved in creating a huge caldera. It is thought that the huge lake was the result of water filling the caldera.
Stage 2 of the Volcanic Activity
	Following the collapse of the first caldera was the beginning of the second stage of the volcanic activity. This activity occured between from about 200,000 - 80,000 years ago when lava spread thickly within the caldera forming a gently sloping shield-shaped volcano.
Stage 3 of the Volcanic Activity
		From about 50,000 years ago explosive volcanic activity began and with this eruption a new caldera was formed as the western side of the shield-shaped volcano caved in. The second caldera filled with water, in the same way as the first caldera, and a lake was formed.
Stage 4 of the Volcanic Activity
		Following this was the fourth stage where volcanic eruptions continued on a small scale, forming Mt.Kami, Mt. Komagatake, Mt. Futago and Mt. Kammrigatake. Lake Sengokuhara and Lake Ashi Around about 20,000 years ago in the middle of this stage, lava gushing out from Mt. Kami made a lake in the Sengokuhara region by stopping the flow of the Haya River. The lake of this stage is called Lake Sengokuhara.
Last Eruption - Birth of Lake Ashi
		About 3000 years ago, a vaporous eruption of Mt. Kamiyama resulted in the birth of Owakudani Valley and Lake Ashi. The washout caused by this eruption blocked the Haya River close to Kojiri, creating Lake Ashi.