Owing to various reasons, there are many strip mounds under the water of Jiuzhaigou. When water rich in CaCO2 run through these mounds, the speed gets slowed down but the sediment of calcium carbonate speeds up. At both sides of them, flat gradients come up. While the sediment continues, the mounds under the water keep on growing until they are slightly above the water. Then, seeds brought by water, wind or birds start to grow over them and aquatic plants grow by them as well. Once plants start growing, the sediment becomes faster. As a result, most of the mounds will grow above the water.