It’s a big dry lake bed, made up of a vast flat “playa” of dried mud. During the winter when it’s cold, windy, and wet, the rocks slide around on the surface. No one has seen them move, but the tracks they leave behind are left in the dry mud to see in better weather. Each rock takes a different course across the playa, some straight, some curvy, some zigzag. Most of the sliding rocks are on the southern end of the playa.