Cross-section of Lake Towada
The word “caldera” comes from the Spanish word for “cauldron” or “cooking pot,” because the crater is formed by a sharp drop from the rim to a broad flat central floor. Lake Towada is a rare water-filled caldera, and rarer still because it is a double caldera, created by the main shallow basin (the perimeter caldera) and a deep basin (the central caldera). The summit of Mikado-ishi visible in the lake is a parasite volcano created approximately 4,000 years ago.
Lake Bottom Topography
The main lake basin is approximately 100 meters deep in most spots. The deepest point is in the central nakanoumi caldera, which is 327 meters deep. The deep valley within the lake was caused by powerful underwater currents aggressively eroding the lake bottom.