十和田湖
Lake Towada occupies the caldera of a stratovolcano still regarded as an active volcano. This volcano became active around 200,000 years ago, and through repeated eruptions and pyroclastic flows, especially 55,000 and 36,000 and 15,000 years ago, created an 11 kilometer diameter caldera with the proto-Lake Towada. From approximately 15,000 to 12,000 years ago, intermittent eruptions formed a small stratovolcano within this caldera (Mount Goshikiiwa). Intermediate eruptive activity continued and at least eight eruptions of magma occurred from 11,000 years ago to the present. The Ogurayama Lava Dome was formed approximately 7,600 years ago on the northeastern slope of the Goshikiiwa volcano. The Mikadoishi Lava Dome is estimated to be within 12,000 and 2,800 years ago. The collapse of these secondary lava domes approximately 5400 years ago give the lake its distinct shape and the inlet between its two peninsulas (called the “Nakaumi”) is the remnant of a secondary caldera which erupted and collapsed.