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.
Quick Answer. The world's largest sand dunes in terms of square miles are the Simpson Dunes in Australia. They cover more than 65,000 square miles of land area. The tallest roving sand dunes are found in the Namib Desert in Namibia, where a dune exceeds 1,200 feet.