What Moves Gravel-Size Gypsum Crystals Around the Desert?
Bassel Nasr
Wind, water and a little help from salt explain a strange desert mystery.
In some deserts, crystals the size of gravel seem to wander across the ground. Researchers wanted to know why.
Time-lapse cameras and weather sensors showed that rare rains create shallow pools. When strong winds blow across the wet surface, the crystals slide and roll, leaving faint trails.
It is a reminder that even the quietest landscapes are slowly on the move.