Jiuzhaigou's best-known feature is its dozens of blue, green and turquoise-colored lakes. The local Tibetan people call them "Haizi" in Chinese, meaning "son of the sea". Originating in glacial activity, they were dammed by rockfalls and other natural phenomena, then solidified by processes of carbonate deposition. Some lakes have a high concentration of calcium carbonate, and their water is very clear so that the bottom is often visible even at high depths. The lakes vary in color and aspect according to their depths, residues, and surroundings.