The third pitch, Mrs....

Dow Williams - Oct 18, 2006 3:12 pm - Hasn't voted

yes, but the area around Zion National Park is slowly but surely being converted from sedimentary rock to sand dunes. Over 200 million years ago the area where Zion National Park is today was a desert basin. Over vast amounts of time the mountains there eroded. The material was carried by slow moving streams and rivers and laid down in the vast basin, filling it with sand. Time passed and the sea covered the dunes as the environment changed. Calcium carbonate cemented loose grains of sand making hard sandstone. It turned the seabed to limestone and mud and clay to mudstone and shale, forming the sweeping diagonal cross-bedding that Zion National Park is famous for. It is slowly being turned back to dunes by the wind erosion. Cheers