Oshima(redirected from Ooshima)
a peninsula in Japan, in the southwestern part of Hokkaido, bounded by the Pacific Ocean, the Sea of Japan, and the Tsugaru Strait.
The peninsula is joined to the rest of Hokkaido by the Shiribeshi Isthmus. It is more than 100 km long, with average elevations ranging from 500 to 1,000 m and a maximum elevation of 1,520 m (inactive Karibo volcano). It has two active volcanoes, Komagatake and Esan. There are large deposits of sulfur. The peninsula has a temperate monsoon climate. On the slopes grow broadleaf forests with an admixture of southern coniferous species, such as cryptomeria. The main economic activities are fruit growing, sericulture, fishing, and animal husbandry. The chief port is Hakodate.