Mono Lake, Tufa on Blue, California

(Click image to enlarge)

Mono Lake formed at least 760,000 years ago as a terminal lake in a basin with no outlet. The lack of an outlet causes high levels of salts to accumulate over time, which makes the water alkaline. The tufa formations seen in this photograph are made of calcium carbonate. They form when calcium-rich groundwater enters the alkaline lake water causing calcium carbonate to precipitate. This slowly forms a calcium carbonate tube or pipe around the groundwater's entry point. Tufa towers stop growing when their tops become exposed, either because they reach the lake's surface or because lake level drops.

In this case the level of Mono Lake began dropping in 1941 when the city of Los Angeles diverted water from freshwater streams flowing into the lake. As a result the lake's area was reduced by 31%, alkaline sands and formerly submerged tufa towers became exposed as the water salinity doubled. Mono Lake's Negit Island became a peninsula, which made all of the bird nests on it accessible to coyotes and other predators. This was catastrophic because 95% of all California Gulls in California (one fifth of the world's population), in addition to many other migratory birds, nested on Negit Island. The Mono Lake Committee formed in response and won a legal battle in 1983 that forced Los Angeles to partially replenish the lake level. Current drought conditions in the west in addition to increased evaporation from higher temperatures, both fueled by climate change, make it nearly impossible to maintain the water levels in Mono Lake today.

This photograph was made possible by a crystal clear blue sky, a fairly wide angle lens, a polarizing filter, and Kodachrome ISO 25 film. Due to the wide angle of the lens, polarization increases toward the bottom of the image. That increasingly eliminates reflections like that of the blue sky from the water's surface. The corresponding exposure reduction caused by increased polarization in addition to light attenuation by the water and the film's low dynamic range renders the lake bottom nearly black, except for the area just above the leftmost pieces of tufa. This is better seen in the larger version of the image, available by clicking on the image above.