30 million years ago divergent plate boundaries formed two mountain ranges and a basin was formed. Eventually water became trapped in the basin and Lake Otero was formed.
11,000 years ago as the climate became warmed after the ice age, rain and snow melt carried (erosion) dissolved gypsum into the lake.
As the climate continued to get warmer the lake dried up. Selenite crystals formed on Alkali flat and strong winds began to break apart the crystals into fine, white grains.
These brilliantly white dust grains were constantly pushed by strong winds.
Eventually, the sand accumulated into large dunes.
Periodically, Lake Otero fills with water, then evaporates, leaving selenite crystals behind. Wind and water break down these crystals into progressively smaller and smaller particles until they are fine grains of white gypsum sand and eventually dust.