Chlorofluorocarbons or CFCs are a chemical compound containing carbon, chlorine, and fluorine. Throughout the 20th century, CFCs were mass produced for their popularity in refrigeration and spray cans. In the 1970s, evidence began to show the harmful effects of CFCs on Earth.
Originally created as Great Sand Dunes National Monument on March 17, 1932, Great Sand Dunes National Park and Preserve was established by an act of the United States Congress on September 13, 2004.
The magnificent sand dunes are, of course, the main attraction at Great Sand Dunes National Park. Scientists believe that the sand that comprises the dunes has been in the San Luis Valley for 35 million years. They are a product of winds blowing predominately in opposite directions. 2  Star dunes: The many arms of star dunes are shaped by winds blowing in all directions. 3  Parabolic dunes: Oblong designs are formed when vegetated sand prevents parts of the dune from migrating.