The Formation of Lake Towada
1. Approximately 200,000 years ago
The Towada volcano was formed and erupted molten lava and ash, creating a conical volcano. This formation of alternate layers of ash and lava is called a stratovolcano.
2. Approximately 30,000 years ago
A major eruption occurred in which the volcano spewed enormous amounts of pumice. Two geological faults surrounding the area moved, causing the center of the volcano to begin to collapse in on itself.
3. Three more eruptions occurred, sending pumice into the air. The volcano continued to collapse, eventually creating a square-shaped basin which formed Lake Towada.
4. Approximately 10,000 years ago
A new stratovolcano with a central depression formed to the south of the lake.
5. Approximately 4,000 years ago
The central crater erupted, spewing ash and pumice into the air.
6. The eruption created a bowl-shaped depression in which a new lake, called the nakanoumi (or inner lake) formed.
7. The shore of the lake continued to erode as the volume of water increased, eventually breaching the rim wall and creating the Oirase Gorge. This marked the completion of the shape of the lake today.
8. Approximately 2,000 years ago
A small parasite volcano formed a small dome at the head of Ogura Peninsula, which is known as the Ogurayama Lava Dome.