After the mountain building process thrust sedimentary sandstone and shale formations upward to form the island of Taiwan, wave action along the coast undercut the rock, causing the seaward sides of the mountains to collapse into the water.
傾斜的岩層因下層受到海浪侵蝕掏空凹陷，失去支撐力量而崩落，形成陡峭的剝蝕坡，並和原本的構造坡形成不對稱的地形。