Beautiful white rock formations leading to Aztec Sandstone in the Valley of Fire. These formations were exposed where older rocks of Cambrian age (about 500 million years old) were pushed sideways on a thrust fault over younger rocks (Jurassic, about 160 million years old) of the Aztec Sandstone. The sandstone was originally laid down in a colossal, long-lived sandy desert much like today's Sahara. Before the area was a dry desert, it was an inland sea. The red color is from the presence of iron oxides in the sand.