There was evidence of civilization. The Lucero brothers in the late 1800s had cattle ranches in the area and needed wells to water the cattle. Some of the equipment it still around.
The lake bed is covered in gypsum, a sulfate rock that is very soft and comes apart easily.You can actually scratch it with your finger nail.
The ranger explained how the gypsum is eroded down to grains of white sand... which is why the White Sand Dunes are on the other side of the lake.
I figured that God had actually taken the salt shaker from the banqueting table in heaven and shaken it out until there was enough dune to make it worth our while.