In northwest Australia, the Great Sandy Desert holds great geological interest as a zone of active sand dune movement and noticeable fire scars.
Although a variety of dune forms appear across the region, this astronaut photograph features numerous linear dunes (about 25 meters high) separated in a roughly regular fashion (0.5 to 1.5 kilometers apart). The dunes are aligned to the prevailing winds that generated them, typically blowing from east to west.
Where linear dunes converge, dune confluences point downwind. When you fly over such dune fields—either in an airplane or the International Space Station—the fire scars stand out. Where thin vegetation has been burned, the dunes appear red from the underlying sand; dunes appear darker where the vegetation remains.
Image courtesy of NASA.