Tufa towers in Mono Lake, California, USA. The lake has no outlet, which makes it highly saline. The city of Los Angeles has taken water from Mono Lake in recent years, substantially lowering the water level. All tufa at Mono Lake forms underwater. Beneath Mono Lake, calcium-rich freshwater springs seep up from the lake bottom and mix with lake water rich in carbonates. As the calcium comes in contact with the carbonates in the lake, a chemical reaction occurs, resulting in calcium carbonate, or limestone.