I recently took a one-day photo safari with my 19 year-old grandson, who will be reporting to the US Navy on 30 March. It was a great drive and a great time doing something we both enjoy, photography. It was generally a nice day, but the lighting was all over the place as we went from complete overcast to mostly sun, and everything in between.

(Per the park website)
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 (think baking soda). As the calcium comes in contact with the carbonates in the lake, a chemical reaction occurs, resulting in calcium carbonate, or limestone. The calcium carbonate precipitates (settles out of solution as a solid) around the spring, and over the course of decades to centuries, a tufa tower will grow. Tufa towers can grow to heights of over 30 feet underwater.

The reason visitors see so much tufa around Mono Lake today is because the lake level fell dramatically after excessive water diversions by the Los Angeles Department of Water & Power began in 1941. Once above the waterline, tufa can no longer grow and are susceptible to erosion.

Tufa towers are not the only form of tufa at Mono Lake. Calcium carbonate crystals will also precipitate out of lake water far from springs and coat lake bottom surfaces like pumice boulders, dead vegetation, and anything else that might end up in the lake (instant fossils!).

Another way tufa is formed is through biogenesis, the biological activity of organisms like the alkali fly. When an adult alkali fly emerges from an underwater pupae case it leaves behind a tiny deposit of calcium carbonate, a waste product from its earlier life stage beneath the salty, alkaline water. Alkali flies, on a small scale, actually contribute to the growth of underwater tufa towers.