In Death Valley, Badwater Pool takes its name from a surveyor who found that his mule would not drink from the spring and labeled it "bad water," a name that remained. The pool is not poisonous but salty, as shown by the presence of pickleweed, aquatic insects, larvae, and the Badwater Snail, one of Death Valley's rarest animals, a tiny mollusk found only in a few springs at the edge of the valley's salt flats. The pool is fed year-round by ancient water, much of it originating as Ice Age snow and rain hundreds of miles away in the mountains of central Nevada, then seeping into porous limestone bedrock and traveling underground through a regional aquifer before emerging at Badwater along the faultline at the mountain's base. As this water rises, salts dissolve from old deposits and reach the surface, giving the spring its salty character. By the 1930s, the area around the pool had been damaged by visitors who trampled the salt crust and threw debris into the water.