Thursday 5/21 Petroglyphs are rock carvings (rock paintings are called pictographs) made by pecking directly on the rock surface using a stone chisel and a hammerstone. When the desert varnish (or patina) on the surface of the rock was chipped off, the lighter rock underneath was exposed, creating the petroglyph. Archaeologists have estimated there may be over 25,000 petroglyph images along the 17 miles of escarpment within the monument boundary. It is estimated 90% of the monument's petroglyphs were created by the ancestors of today's Pueblo people. Puebloans have lived in the Rio Grande Valley since before 500 A.D., but a population increase around 1300 A.D. resulted in numerous new settlements. It is believed that the majority of the petroglyphs were carved from about 1300 through the late 1680s. ACTIVITY Find a rock, Try to make a lasting image on it with simple/rudimentary tools. How will you go about doing this? What are the steps in your process, be c