fengcong (peak cluster depression, or cone karst) is composed of the rock peaks with their foundation linked together and the depression closed in between. the rock peaks are always in taper shape, and there are mostly bare rocks or thin soil on the bottom of the depression, where the aven may be formed. the bottom is often altered into farmland. the height difference between the crest of peak and the bottom ranges from 50m~500m or more. the embedded depth of underground water is deep and the underground river is formed.
fenglin （peak forest plain or tower karst）is orderly and separately located on the slightly undulant or basically flat ground. the typical peak is in pagoda shape with steep side slope, and its surrounding areas are plain, with bare bedrock or thin terra rossa covering the ground. the embedded depth of underground water is shallow and is often close to the ground.