From the sea urchin fossils embedded in the rock, you can surmise that before geologic activity caused these mountains to rise, Taiwan was once under the sea. More proof of this can be seen from the coastal plants that grow here, which prove that the land of Chihshan Park was once a small island.
例如這裡的地質非常特殊，從石頭裡鑲崁的海膽化石來說，可以推溯到地球的造山運動以前、台灣島還沈積在海底的時代，再佐證以公園裡原生的一些濱海植物，說明瞭芝山公園以前是一個小島，而如今，最近的海岸距離這裡至少二十多公里，可見滄海桑田的變化之劇。