アイスランドの融氷河流扇状地の位置づけ : 沖積扇状地の定義の確立に向けて

概要

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Not only outwash fans but also stream-flow fans have been discussed as to whether or not they are involved in alluvial fans. In this study the Skeidara outwash fan in Iceland is examined by checking various definitions on alluvial fans. The criterion that alluvial fans are steeper than 1.5 degrees is not acceptable in humid regions, because there is no gap between depositional slopes ranging from 0.5 to 1.5 degrees. Gentle stream-flow fans with mean slopes steeper than 2‰ or 0.11 degrees in Japan are recognized as alluvial fans ; therefore, the Skeidara outwash fan with a mean slope of 3.9‰ or 0.22 degrees can also be regarded as an alluvial fan on the basis of its longitudinal profile. Although the apex is around the valley mouth of Morsardalur, it is at the front of the Vatna glacier. Therefore, the fan is not considered to be an alluvial fan in the narrow sense that it is formed at the valley mouth. However, the possibility of it being an alluvial fan in a narrow sense remains because of the following probable events-the main fan body had been built at the valley mouth, and the body was modified subsequently by outwash flow. The problem is whether or not such events occurred.
社団法人東京地学協会の論文
2006-08-25