The monsoon climate of Penghu forms a great natural power. Wind is the main power of the formation of wind piled terrain. Under the blow and attack of wind, the bulged landscape formed by wind’s moving and piling up is sand hill. Sand hills in Magong City are the most complete ones. Following the slop of landscapes, wind carried sand to here and sand hills were formed by the stop of wind and the slop of landscapes, just like skiing lands.

The components of sand hills mostly come from coral fragments, shells and basalt fragments etc. that were brought by the waves’ washing and invasion. Shihli sand hills appear on the foot of basalts steep slop in Chaonan. It is estimated that the southwest airflow in summer blew sands from beach toward the north, and the sands were stopped by the terrain. When the Northeast monsoon came in winter, it blew the sand toward the south, and the speed was slowed down suddenly forming the phenomenon of piling up in the sheltered side.