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.
What are the conditions necessary for the formation of sand dunes? Hi, Dunes are formed by interaction with the wind. Wind speeds of 10 to 20 mph,. are necessary for sand to start saltating under the direct pressure of the wind.