The magma is fragmented by volcanic eruption into a rock layer cemented by debris with grains less than 2mm. The composition of debris includes glass particles, rock fragmentscrystals, which are composed under different proportions. The main locationswhere tuffs are exposed includeCingluo Village, Chiyu, MaanshanIsletDragon Sea-eroded Platform in Qimei Township. Small volcanic debris such as tuffs is fast-condensing lava,most of the tuffs seen in Penghu are brown-redgray. The tuff at the bottom of Chiyu is about 1 to 2 meters thick. Its texture is loosethe panning degree is good. It is mainly composed of gray-whitebrown-red coarse-grained minerals. In addition to the horizontal bedding, there is also a structure of granular layers, whose upper layer is finerlower layer is coarser.And theless the gray-white minerals are, the higher they go up.Tuff contains vitreous fragmentscrystalscrystal fragments, which are almost all composed of quartz. Most of the vitreous fragments undergo alteration to form chloriteother clay minerals. Its rock layers have normalreverse fault structures. This specimen was collected from Chiyu, HuxiTownship.