The wonder cliffs in Red Rock, thousands feet high, are made of Aztec sandstone. This formation, dating from around 180 to 190 millions of years, includes dunes of lithified sand that formed a huge desert that covered a large part of the southwestern United States during the Jurassic period. The lithification is the process that turns a soft sediment into a sedimentary rock. Huge slanting stratifications, specific to the wind deposits, are the result of changes in the direction of the wind in the Jurassic dune field, and can be seen in the Aztec sandstone of the outcrops.
Photo: James Fraleigh