ASU Research E-Magazine: Viewing the Rocks

More than 1,500 petroglyphs cover the eastern slope of Hedgpeth Hills in North Phoenix. They have puzzled archaeologists, inspired artists and musicians, and provided local Indian tribes with a potential connection to their ancestors.

The petroglyphs also should delight visitors to the new Deer Valley Rock Art Center, which opened in December. The center is operated by ASU’s department of anthropology in consultation with the Hopi, Yavapai, and Gila River Indian tribes.

Director Peter Welsh says the center will show how complicated petroglyph interpretation can be. An ASU assistant professor of anthropology, Welsh explains that any symbol can have different meanings in different contexts.

“For example, the numeral ‘7’ has different meanings depending on whether it appears on a Phoenix Suns jersey, in an arithmetic problem, or on a sign in Las Vegas,” Welsh says.

Exhibits at the new center explain that petroglyphs are created by chipping through the dark layer of material that covers the rocks to reveal the lighter rock underneath. Deposited by natural processes over hundreds of years, the dark material is called rock varnish.

The exhibits also discuss the various methods used to study petroglyphs. Researchers use dating techniques, classify petroglyphs by design style, rely on Native American interpretations, or classify them within the context of other archaeological evidence.

“Different approaches offer different perspectives,” Welsh says. “We emphasize an openness and respect for all of them.”

The new center is one of the few visitor centers and resesearch facilities in the world dedicated to rock art. The U.S. Army Corps of Engineers built Adobe Dam in 1980. That work led to a decision to build a center to house archaeological findings from the area. A means to protect the petroglyphs from urban expansion also was needed.

Federal law requires that steps be taken to preserve archaeologically significant sites threatened by development. The Corps of Engineers recognized its Phoenix and Vicinity Flood-Control Project as a rare opportunity to promote research, education, and preservation at the same location.