Formed more than 700,000 years ago, Mono Lake is one of the oldest in North America. ~~~~~~~~ The mineral content of the water is so high that only algae, brine shrimp, and the pupae of the ephydra fly find it habitable. ~~~~~~~~ The lake level has dropped more than 40 feet since LA has diverted stream water in 1941, exposing the eerie tufa towers (formations of calcium carbonate).