Convict Lake is dammed by a recessional moraine of the Tioga glaciation in the eastern Sierra Nevada. The mountain in the distance is composed of marble and slate of Paleozoic age; they are the rocks that existed prior to the intrusion of the Sierra Nevada batholith in Mesozoic time.
Mono Lake is a remnant of the ice age pluvial lakes that once extended across much of the Basin and Range Province. It was once a freshwater lake hundreds of feet deep, but today is saltier than seawater. It hosts only two life forms, fairy shrimp and brine flies, but these two species support several million migratory birds which pass through the region every year.
Violet-green Swallows live and nest in the tufa towers that are found around the lake. The tufa towers (below) are composed of calcium carbonate (calcite), and form where freshwater springs flowed into the lake. They were exposed as the lake level dropped 50 feet when Los Angeles started diverting streams that once replenished the lake in 1941. The diversions threatened to destroy the complex ecosystem, which is international in scope (some of the migratory birds travel 15,000 miles). Efforts are now ongoing to raise lake level to about where it was in 1963, roughly midway between the 1941 level and the low point in the 1980's.
More pictures can be accessed here. Do you have pictures of the trip? Send them along, and I'll post them!