Onuma Quasi-National Park

This quasi-national park is located in the southwest of Hokkaido, in the southern part of the Oshima Peninsula. It was designated in 1958 (Showa 33). Its area is 90.83 square kilometers. It consists of the active volcano Mount Komagatake (1,131 meters) and the Onuma, Konuma, and Junsainuma swamps at its southern foot. Made of andesite, Mount Komagatake was a stratovolcano similar to Mount Fuji, but repeated eruptions have changed the mountain's shape since about 10,000 years ago. The summit has collapsed, leaving a large U-shaped crater to the east. Near the summit, there are alpine plants such as rock lilies and Polygonum salicina, and on the middle slopes and below, there are many broad-leaved trees such as mountain willow, poplar, white birch, and Mizunara oak. Lake Onuma, Lake Konuma, and Lake Junsai were formed when mudflow from Mt. Komagatake dammed up the Orito River. They are home to smelt and carp, and produce water shield. The lake has a complex shoreline, with 126 small islands scattered throughout. There are walking trails, and the lake is a popular spot for strolling along the lake, boating, hiking, camping, and skating throughout the year.

[Hideyoshi Segawa]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

北海道南西部、渡島(おしま)半島南部にある国定公園。1958年（昭和33）の指定。面積90.83平方キロメートル。活火山の駒ヶ岳(こまがたけ)（1131メートル）とその南麓(なんろく)の大沼、小沼、蓴菜沼(じゅんさいぬま)からなる。安山岩からなる駒ヶ岳は富士山型の成層火山であったが、約1万年前から噴火を繰り返して山体を変えた。山頂部は崩壊し、東に開いたU字形の大火口がある。山頂付近にはイワブクロ、ウラジロタデなどの高山植物、中腹以下にはミネヤナギ、ドロノキ、シラカバ、ミズナラなどの広葉樹が多い。大沼、小沼、蓴菜沼は駒ヶ岳の泥流が折戸(おりと)川をせき止めてできた湖沼で、ワカサギやコイが生息し、ジュンサイを産す。湖岸線は複雑で、湖沼中には126の小島が点在する。遊歩道なども整備され、湖畔散策、ボート遊び、登山、キャンプ、スケートなど四季を通じてにぎわう。

［瀬川秀良］

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