Tufa formations, Mono Lake, California, USA. Diversion of the lake's water supply to the Los Angeles Aqueduct in 1941 produced a gradual drop of 46 feet in elevation. As the lake level has lowered, the former lake-bed, eroded by wind, is revealed. These other-worldly formations are the fossil records of hot volcanic, calcium rich water rising through the submerged lake-bed sands. As the spring water meets the carbonate rich lake water, a natural cement, calcium carbonate, or tufa, is formed.