Pictographs vs. Petroglyphs

Many people are familiar with Lascaux Cave, with its iconic images of swirling horses, deer, and other figures. These pictures give scientists a fascinating snapshot into a vanished culture that existed around 20,000 years ago. Less famous, but equally compelling are the pictographs and petroglyphs of the American Southwest, dating back 10,000-15,000 years. Their haunting imagery hints at a collective culture that spanned thousands of miles, had an intimate understanding of astronomy, and a complex belief system.

What’s in a Name?

Archaeologists use the term rock art to describe both pictographs and petroglyphs.

Pictographs are painted, usually on a flat rock surface. Images were painted with small brushes made of yucca fibers or animal hairs; utensils have been discovered in places like Chaco Canyon and Mesa Verde. Paints were made from readily available mineral sources such as charcoal (black pigment), gypsum (white pigment), or ocher/hematite (red pigment). These minerals were then mixed with animal fats. Because of the fragile nature of pictographs, only those protected in caves or by overhangs have survived centuries (or even millennia) of weather and erosion damage.

Petroglyphs are images that have been cut out of a rock surface by a variety of techniques (chipping, pecking, or etching). This labor-intensive imagery is enhanced as it ages by something called desert varnish. Anywhere from millimeter to several centimeters thick, desert varnish is a form of chemical oxidation that coats rock surfaces of the desert in a black or reddish brown patina. Petroglyphs are etched through this layer of darker rock to the lighter surfaces below. Since the carved portions also darken with desert varnish as they age, petroglyphs are easier to date than pictographs. Unless rocks are physically damaged, petroglyphs are also more resilient to decay.

Many rock art images share common themes or even identical images, despite being separated by thousands of miles. Humans, animals and various objects (like spirals, handprints/footprints, geometric patterns and undulating lines) are the most common. Then there are images that have no real-life equivalent. Animal-like figures are called zoomorphs and human-like ones are called anthropomorphs.

How old are they?

While advances have been made in dating pictographs and petroglyphs through scientific analysis, the locations of the rock art and their unique designs also give clues to their age. Historians have developed the following classifications:

  • Archaic: 500 BCE to 300 CE

  • Basketmaker: 1,000 BCE to 750 CE (oldest Ancestral Puebloan [formerly known as Anasazi] rock art)

  • Fremont: 500 CE to 1,400 CE (found mostly in Utah, some in Colorado)

  • Ancestral Puebloan: 200 CE to 1,600 CE (found mostly in northern Arizona and northwestern New Mexico)

  • Hohokam: 300 CE to 1,400 CE (southern Arizona)

  • Mogollon Red: 500 CE to 1,250 CE (southeastern Arizona and southwestern New Mexico)

  • Historic: Begins approximately 1,540 CE (after European contact, evidenced by horse figures; horses did not live in North America until introduced by the Spanish in the 1,500s)

What do they mean?

No one can say for sure what these mysterious images mean. Some think they’re nothing more than ancient graffiti, works of art that exist only because of an artist’s passion.

University of New Mexico professor Greg Cajete refers to petroglyphs and pictographs as image writing, similar to Chinese writing or Egyptian hieroglyphics. He believes a majority of rock art functions like storyboards which depict key scenes or maps to important ancient locations.

Others see symbolic or religious meanings, especially in commonly repeated symbols. One of these is the circle. It has been alternately interpreted to represent the universe, a shield, the sun, nearby water or an eye. Another is the spiral, which modern Puebloan people interpret to represent migration. The spiral portrays their people’s history from creation through the many twists and turns of their cultural and physical journeys throughout the Southwest.

Despite the many mysteries still enshrine these images, petroglyphs and pictographs are haunting reminders of thousands of years of human existence that predate most people’s conception of American history. Ancient rock art is a testament to both the creativity and endurance of the human spirit and instills in us a careful humility about our own lifespan on this earth.

Because these ancient treasures are incredibly delicate, always follow petroglyph/pictograph etiquette when viewing rock art. A guide to proper procedures can be found here: https://www.nps.gov/petr/learn/historyculture/takecare.htm


For further reading:

Armstrong, Wayne P. Desert Varnish. http://www.abdnha.org/TSP-desert-varnish.html. Summer 2008.

Chino, Conroy. Petroglyphs of the Southwest : a Puebloan perspective. Tucson, Arizona Western National Parks Association, 2012. Print.

De Pastino, Blake. Ancient Rock Art in Texas Yields ‘Surprising’ New Finds. http://westerndigs.org/ancient-rock-art-in-texas-yields-surprising-new-finds/. October 14, 2015.

North America's Oldest Known Petroglyphs Discovered In Nevada. NPR: All Things Considered. http://www.npr.org/2013/08/16/212569006/n-americas-oldest-known-petroglyphs-discovered-in-nevada. August 16, 2013.

Slifer, Dennis. Kokopelli : the magic, mirth, and mischief of an ancient symbol. Layton, Utah: Gibbs Smith, 2007. Print.

Zentner, Joe. Petroglyphs and Pictographs. https://www.desertusa.com/desert-activity/desert-rock-art.html