The dunes in southern New Mexico cover over 140,000 acres. They consist of gypsum crystals called gelenite. Unlike sand, they are pure white, continually shift and blow and do not convert sunlight into heat. So kids slide down the dunes on saucers in shorts and bare feet while nearby snow plows keep the roads open. An eight mile road into this geologic anomaly is provided by the White Sands National Monument. Nearby is a missile range where the first atom bomb was detonated.