Wave erosion terrain is formed by natural power, the destructive effect of water movement on land. Along the cost of Magong City, the wave erosion platform exposed at downs becomes the place for residents to do tidal flat activities. The places such as Shihwei, Chungkung, Kuanyin Pavilion and Sokang etc. are all typical landscape of wave erosion platform. The wave erosion gap and wave erosion cavity terrain of Fengkuei Neighborhood are also ones of the scenic spots in Magong City. Whenever the water is up, the wave push one after another, and the waves flow along wave erosion gap pouring on rock cavity. After the air in the cavity is squeezed, it will make sounds from fissures sometimes with the ejection of water pillars. There is a wave erosion arch on the south side of Sokang’s wave erosion platform and another one on the foot of Shangshui’ West Mountain.

These wave erosion terrains are mostly composed of basalts. The formation of wave erosion platform comes from that the waves continually washed away the coast. Over a long period of time, the cliffs collapsed and became a flat tableland almost as high as the sea level. They are mostly basalts or volcanic breccia with a lot of holes. Wave erosion gap is that rocks along the coast were eroded from the part of joints surface that was more easily eroded by wave invasion and therefore expanded gradually. If the wave eroded in aspect, it can be eroded into a trench like oceanic trench. And the formation of wave erosion cavity is because that the rocks are weaker, such as deposited rocks, or the rocks with more joints. Waves invaded deeply along the weak area of the rocks and therefore formed the terrain. Furthermore, the wave erosion arch is formed because the both sides of the rocks which stretching into the sea were eroded and the wave erosion cavities on both sides were passing through.