Today Today the canyon is 1,000 feet deep with massive walls of peach colored De Chelly sandstone. Large parts of these walls are covered with a dark blackish coating called desert varnish . Desert varnish is caused by manganese and iron oxides staining the rock. Manganese and iron are two chemical elements that are found in nature. It these elements are in contact for a long period of time, a chemical reaction occurs called oxidation .
Oxidation can sometimes change the color of the element that is reacting with the water and air.
By itself, iron changes to an orange color, which we call rust. The combination of iron and manganese together changes to a black color. Early Native Americans would chip off the desert varnish and make pictures on the rock called petroglyphs . We can see these pictures today when we visit the canyon. Some petroglyphs are pictures of people and animals, others are simple geometric shapes, but no one knows for sure whether they were created for religious reasons or were just a unique form of art.