A cuesta is a ridge with steep cliff on one side and gentle slope on the other. The reason for this formation is that sedimentary rocks of interchanging layers of sandstone and shale are made to rise and bend by orogenic movements. The bent layers are eroded by the waves while the bottom layers are softer and collapse inward from erosion and the top layers are harder and less vulnerable to erosion. However, as the soft bottom rocks are completely washed away, the hollow becomes larger and the top rocks lose support and fall. The result is a cuesta with asymmetrical slopes. The rocky coasts in Beiguan feature rocky coasts with wave-cut platforms and cuesta. These areas are now designated as the Northeast Coast and Yilan National Scenic Area.