Petroglyphs are carved, pecked,chipped or abraded pictures in stone. The outer patina is removed exposing the lighter color underneath. Petroglyphs are found world wide in almost every culture. In the US, the southwest is famous for its petroglyphs. Many theories abound as to their purpose. There are astronomy maps and soltice markers, others act as a historic descriptive narrative including comets, train wrecks, generations, many are maps, and some are symbols, ritualistic and religious in nature. Simply, they are important and beautiful.