Mono Lake tufa towers. You can think of them as petrified springs. Mono Lake lies in a basin with no outlets. Rainfall from the surrounding mountains flows into the lake and carries with it dissolved minerals. Since there's no outflow (other than evaporation) the saline content of the lake is greater than ocean water. The lake has also become highly alkaline so the water has a soapy feel to it. Fresh water springs under the lake surface carried dissolved calcium which reacted with carbonate in the lake water forming calcium carbonate or limestone structures. In the 1940's water was diverted from the Mono Lake basin to feed the Los Angles aqueduct. The lake level dropped and exposed the limestone structures known as tufa towers.