Birthed by Volcanoes: The Underwater Calderas of Kinkowan Bay
Volcanic activity and diastrophism—the deformation and movement of the earth’s crust—created the caldera sea that is Kinkowan Bay. The Aira caldera, which filled with seawater after being formed during a major volcanic eruption around 29,000 years ago, forms the innermost bay. The older Ata caldera, at the mouth of the bay, was formed approximately 110,000 years ago.
Because of these calderas, Kinkowan Bay is unusually deep, with an average depth of 117 meters. Tokyo Bay, by comparison, has an average depth of 17 meters. While most bays become steadily shallower closer to the shore, Kinkowan Bay gets progressively deeper, reaching depths of up to 206 meters not far from the innermost shore.