Lebanon, Kornet es Saouda 付近の周氷河現象
1971 年 80 巻 6 号 p. 354-362
詳細
1971 年 80 巻 6 号 p. 354-362
In this present paper, the authors discuss about periglacial activities around Mt. Kornet es Saouda, during late Quaternary by our on-the-spot investigations. The most characteristic periglacial phenomena, here we observed, are the developments of nivation hollows and patterned ground.
At first, the distribution of nivation hollows is widely scattered above 2300 m on the slopes in this area and strictly controlled by the accumulation patterns of snow (snow patch). And more or less these accumulation patterns are related with total precipitations in winter and micro-relief of topography.
By our observations, the melting water from snow patches on limestone bedrocks, which is very sensitively resoluble into CO2 rich water even at low temperature, penetrated through cracks and joints into rocks. And alternations of temperature caused freezing-thawing cycles of absorbed water.
These cycles caused intensive destructions of bedrocks and produced flakey gravels and small particles (fine sand, silt).
As transporting function, melting water transport small particles as suspension materials. These processes of developments of nivation hollows may be distinguished under periglacial environments.
Patterned ground, especially sorted circles develop widely above 1900 m on the gentle slopes. But one of the most important factors to the formation of sorted circles in this area is the thickness of weathered materials on bedrocks. As mentioned above, limestone bedrocks produce a large amount of small particles by frost shattering, and these fine weathered materials accumulate on gentle slopes. By extrusive forces during a cold time, the layers of fine weathered materials develop on weathered mantles of limestone bedrock.
These periglacial features develop under some restricted conditions, climatic conditions and bedrock behaviours to weathering processes. So in this area, about periglacial phenomena, we must consider the relationships between periglacial environment and bedrocks properties to frost action in addition to climatic conditions.
