Glacial Geomorphology around the Migimata, Gamata Valley, Northern Japanese Alps

Abstract

Several cirques and glacial throughs around the Migimata, Gamata Valley on the western slope of the Yari-Hotaka Range have been studied by some geomorphologists (IMAMURA, 1940; SHIKI, 1970, etc.; IOZAWA, 1972, etc.). The author has newly investigated this area in detail. The distribution of glacial topography in this area, clarified through field survey and aerophoto-interpretation, is shown in Fig. 2, 4 and 5. Judging from the location of terminal moraines, the difference of the degree of dissection of glacial landforms, four stages could be recognized. They are named, from older to younger, Takitani, Yaridaira, Hidazawa I and II stages respectively. They seem to be synchronous to the stages which were proposed by KOBAYASHI, 1958 or by IOZAWA, 1972 in the Yarisawa Valley and Yokoo Valley at the eastern side of the Yari-Hotaka Range. The altitude of the reconstructed glacial snout is same at the both sides of the Yari-Hotaka Range in the early two stages, while it is higher at the western side in the later two. The difference in the direction to the snow bearing wind should be main factors which cause the altitudinal difference of glacial snouts at the both sides of the Yari-Hotaka Range. At the western (windward) slope, most of snow was blown out by the strong wind, while at the eastern (lee) slope, snow accumulation was much more favorable. During the later stages when the snowline had relatively raised, the difference of conditions on the both side of slopes mentioned above should have played a decisive role for determining the glacial distribution.