Mt.Fuji sits on the foundation of Mt.Komitake, a vokano that erupted hundreds of thousands of years ago. Approximately 100,000 years ago, Older Fuji began to erupt on Komitake’s southern incline, Older Fuji erupted repeatedly and explosively, scattering large volumes of volcanic ash over a broad area, Finally, some 10,000 years ago, the structure of