Mt. Kamiyama and Hummocky Hills
Around 3,000 years ago, the northwest flank of Mt. Kamiyama ( the highest peak of the Mt. Hakone volcanic complex ) collapsed and produced a landslid e that swept down the slope.
Owakudani was created in the source area of the landslide, near Mt. Kamiyama peak.
This landslide phenomenon is called a “debris avalanche.” A well-known example of such an avalanche occurred during the 1980 eruption of Mt. St. Helens in the USA.
This area contains many blocks of collapse material that were transported by the debris avalanche.
The irregular topography of this area is described as “Hummocky Hills” in the terminology of volcanology.
Lake Ashinoko was formed when the m aterial of the debris avalanche dammed the Hayakawa river.