日本アルプスにおける氷河の高度分布特性と類型化

Abstract

Glaciations during the Last Glacial in the Japanese Alps can be classified “azonal glaciation” and “zonal glaciation”. The ELAg (geomorphological equilibrium line altitude) of each former type of glacier is determined by Hs (height of summit), and is depressed by microclimatological phenomena such as drifted snow. The vertical/horizontal distribution of this type of glacier is azonal and sporadic. On the other hand, the ELAg of the latter type of glacier remains constant with Hs, and reflects the regional air temperature. In the case, the mountain ridge is higher than the regional equilibrium-line altitude, the vertical/horizontal distribution of glaciers belonging to this type becomes zonal and continuous. Modern examples of these two types of glaciation can be found in Kamchatka Peninsula, the Altai Mountains, and the Caucasus Mountains. These facts suggest that this classification is applicable to spatial and temporal variations of glaciation. Most of the Last Glacial glaciers in the Japanese Alps are classified into the “azonal glaciation” type. The glaciers belonging to the “zonal glaciation” type are located in the Northern Japanese Alps that have high altitudes. Some of the “zonal glaciation type” that existed during the Last Glacial Maximum stage were changed to “azonal glaciation” type during the Late Glacial stage. From this point of view, the Last Glacial glaciers in the Japanese Alps existed as a spatio-temporal transition between these two types. Paying attention to the “azonal glaciation” which is controlled by local conditions, is important for reconstructing the palaeoclimate based on the glacial landforms and their ELAs.