Mudstone is a sedimentary rock composed of fine muddy sediments below 1/16mm,its color is gray to dark gray, sometimes yellow-brown due to weatheringiron staining. Mudstone is rich in clay minerals therefore, when coming into contact with water, it is easy to swelldispersecondensebecome deeply viscousplastic. When exposed to the earth surface, it can be easily eroded by rainseawater due to its fragile lithology. As its soil is sticky, it is difficult for plants to growis thus called "bad land". Because of its shape like a barren lunar surface, it is also known as the "Moon World". The Hsiaomen Islet Geopark in Hsiaomen Village of Siyu Township is well known for its badland-like terrain, which contains tuffaceous sandmudstone under the combined effect of wind erosionmarine erosion for many centuries. The specimens collected by this center are from Dongping Village located on Dongyupingyu of Wang-an Township.