Discovery of a Storm Deposit with Small, Glassy Spheres in Hakodate Bay, Hokkaido

The youngest graded gravel to sand bed in Hakodate Bay was discovered to contain abundant glassy spheres 0.5-2.0mm in diameter. The stratigraphic distribution and the processes of formation and supply of the glassy spheres, and the history of natural and anthropogenic events influencing Hakodate Bay, lead to the following conclusions: 1. The glassy spheres may have been formed by explosions of large steamships in the east head of the bay during World War II (July, 14, 1945). 2. During Typhoon Toyamaru in 1954, the storm surge and associated currents could have carried abundant sediment, including the glassy spheres, seaward and deposited them as the youngest graded bed in Hakodate Bay. The storm bed may be useful as a key bed that can be used to understand depositional processes and environmental changes in Hakodate Bay.