The climate in Penghu area is with high temperature, few rains, and strong monsoon. Dark color basalts are easy to have spheroidal weathering under long time illumination of sunlight and the blow of monsoon. Tungpan Islet and Huchin Islet are most spectacular. Moreover, there also has this weathering terrain on the north coast of Hsiwei. If the weathering effect happens along the joints or cracks, it will have a color lines weathering landscape on the joints that have not formed into spheroidal shape such as the joints weather terrain in Tungpan Islet. Moreover, some rocks have holes on them looking like honeycomb and they are called MaoChiang Stone in this county. They were formed by the different weathering on the basalt’ s surface and the erosion of flows, wind, waves and creatures. This phenomenon happens mostly in Tungpan Islet and Huchin Islet.

The main reason to cause spheroidal weathering happen is that there are often pillar joints and nearly horizontal slate cracks in the dense basalts. The edges and corners of the joints and cracks more easily disperse than central parts since they are both weathered, then edges and corners disappear and become red brown soil or so-called red soil. The weathering texture generally is alkaline basalts, which has more iron and magnesium minerals. This kind of rock is most easily to form the weathering texture on the joints surface that has not yet become spheroidal joints. However, the MaoChiang Stone appears in Tungpan Islet and Huching Islet is a kind of basalts. And because the different stone characteristic, it is formed with a shape of honeycomb and called the honeycomb rock.