FORMATION OF SOUTH-FACING BALD MUDSTONE SLOPES IN SOUTHWESTERN TAIWAN

In the southwestern part of Taiwan, most foothills are covered by muds tones. The mudstone, formed during Miocene to Pliocene and Pleistocene , is a young and weak sedimentary rock. When subjected to water, slaki ng of the mudstone can easily take place and in dry seasons, severe sh rinkage can occur. Thus, erosion of mudstone slopes is easily induced by rainfalls. Heavily eroded natural mudstone slopes in southwestern T aiwan frequently become ''bald'' (i.e. not covered by any plants or bu shes) and are very susceptible to geologic damages such as mudflow and slope failure. One interesting observation of the mudstone slopes in southwestern Taiwan is that most of the bald slopes are south-facing. The causes of this directional variation are thoroughly examined in th is paper. It is concluded that solar radiation, rather than the direct ion of typhoons, is the main reason for forming bald slopes in the sou th-facing direction.