Long ago, an ancient sea covered most of the southwestern United States. It was during this time that layers of gypsum were deposited on the seafloor. The rise and fall of the sea level millions of years ago started the process of making the gypsum sand that covers the monument today. Many factors, including the latest ice age, had an effect on the formation of this magnificent landscape. The following journey through time shows the gradual transformation from sea to sand, and the amazing factors that allow this dune-field to exist.