Present Condition of Limnology in Japan

Abstract

The festooned Japanese islands were formed during and H. Tanakadate Japan). 2) Ordinary crater lakes of moderate size are numerous on volcanoes and in volcanic regions. Several crater lakes, including Ohata-ike and Onami-ike on the Kirisima Volcanic group in Kyusyu, are good examples of this kind. 3) Volcano-tectonic lakes (lakes of compound origin); one of this type is Inawasiro-ko, situated in the northeastern part of the main island of Japan. 4) Maars are not wanting in our country, Unagi-ike in the southern part of Kyusyu and several Megatas of the Oga peninsula in the northeastern part of the main island, being examples of them. 5) Lakes dammed up by volcanoes, lava streams, and mud flows (this might be classified under lakes formed by accumulation). Yamanaka-ko, Kawaguti-ko, and Motosu-ko, all situated at the northern foot of Huzi-san (Mt. Fuji) are some examples. It is well known that the three lakes, Hibara, Akimoto, and Onogawa were formed in this manner as the result of avalanches from-the explosion of Bandai-san in 1888. A lake with a crescentt shape, such as Asino-ko in Central Japan, belongs to a compound type, being a caldera lake dammed up by its own central cone. III. Erosion lakes. It is very rare that a lake is formed by erosion alone. Lakes of small size occupying the glacial cirques that crown the tops of the lofty peaks of the Japanese Alps in Central Japan come within this category. Noga-ike, on Kiso-Komagadake, is an example of this type. IV. Lakes formed by accumulations. 1) Ox-bow lakes. Typical examples of these are those lakes scattered about the Isikari river plain in Hokkaido. 2) Lagoons are numerous in Japan, especially on the coast of Sakhalin island as well as in the eastern half of Hokkaido. Hatiro-gata (223.29 sq. km) in the northeastern part of the main island and Taraika-ko (180.06 sq., km) in Sakhalin, are two large lagoons. 3) A compound type of lake that is formed by several genetical forces such-as erosion, land subsidence and accumulation, drowned valleys or basins closed by sand bars are plenti