The following information and definitions may help you appreciate and understand more about the nature and study of petroglyphs at Petroglyph National Monument.


Ancestral Pueblo

Ancestral Pueblo peoples are the ancestors of the people living in the 19 modern New Mexico Pueblos and at Hopi in northeastern Arizona. Many of the petroglyphs at Petroglyph National Monument are believed to have been created by these ancestral people.

In addition to the Ancestral Puebloan associated images, other rock carvings may have been created by the ancestors of the Navajo and Apache, whose descendants also still reside in New Mexico and Arizona.

Desert Varnish

Desert Varnish, sometimes called rock varnish, is a thin coating (patina) of clay particles that are deposited on rocks in desert environments. These clay particles are attached to rock surfaces by bacteria that live there. The presence of manganese with the clay particles gives desert varnish a dark color, while the presence of iron causes it to appear red. After an underlying area is exposed by pecking or scratching, the color of the exposed interior gradually becomes more like the color of the surface because of the rock varnish's regrowth, or repatination.


A glyph is a symbol or image that is incised or carved in relief.


The patina on a boulder is the thin coating of color, also referred to as desert varnish or rock varnish.


Petroglyphs are images and designs made by engraving, carving or scratching away the dark layer of rock varnish on a rock's surface to reveal the lighter rock underneath. Images can be of varying depths and thicknesses. Images can be pecked, carved, incised, scratched, or abraded.

We do not know the exact method used to make the petroglyphs at Petroglyph National Monument. There are several possible techniques that could have been used. In general, archeologists believe that stone hammers and other stone tools were used to create the petroglyphs. A stone hammer could have been used directly on the boulders, or it may have been that two tools were used like stone versions of a hammer and chisel. Archeologists refer to these methods of production as direct and indirect percussion.

It is estimated that there are nearly 20,000 petroglyphs within Petroglyph National Monument.


Pictographs are images and designs made by painting on rocks or in caves. Colorful plants and minerals were ground up and mixed with protein based liquids such as egg, blood, or urine to make different colors of paint. The pigments were applied using sticks, brushes, fingers or hands.

Only a very small number (less than 0.1%) of rock images in Petroglyph National Monument are pictographs. An inventory of rock images begun in 1997 has found only a handful of images that can be called pictographs.


Repatination refers to the re-coloration, or the re-growth of the desert varnish after a petroglyph image has been created. Repatination occurs at various rates and degrees. A close examination of the degree of repatination can give a relative idea of how old an image may be. A great degree of repatination (darkening) indicates greater age than an image that shows only slight repatination.

Rock Art

Rock Art is a term we generally do not use at Petroglyph National Monument. The images on the rocks are more than just art. In fact, Native American languages generally do not have words that describe things in artistic terms. When you do see the term "rock art" used it is a general reference that includes both pictographs and petroglyphs.


When were the petroglyphs and pictographs made?

Images have been carved and painted onto rocks for many thousands of years. In North America and Mexico, some rock images may be as much as 10,000 to 12,000 years old. Other rock images are probably less than a few hundred years old. To many Native people in North America, the petroglyphs are immeasurably old. They are considered an integral and inseparable part of the landscape created at the beginning of time.

There is currently no widely accepted method of exact dating for petroglyphs and pictographs. Some attempts have been made to extract DNA from pictographs where organic materials were used to adhere the paints. In general, through relative dating based on pottery styles and Pueblo murals, there have been attempts to place images into general blocks of time.

Relative Dating by Depiction

We know when the time periods related to the widespread use of the atlatl (spear thrower) and the bow and arrow. If these images are depicted we know approximately when the image may have been made. The atlatl, a stick used for throwing spears, was used for thousands of years prior to the introduction of the bow and arrow. The bow and arrow came into use in the Southwest approximately A.D. 500. A petroglyph panel showing bow and arrow use tells us that the image's creation was after A.D. 500. Contact with the Spanish dates to after A.D. 1540. An image of a horse or horse and rider would place that image into a time period after the arrival of the Spanish. In this way, looking at the subject matter of a petroglyph panel can provide a relative or approximate date for the creation of the images depicted.

Most of the petroglyphs at Petroglyph National Monument are believed to have been created by Ancestral Pueblo peoples between A.D. 1300 and 1600; though some could be as much as 2,000 to 3,000 years old, while others date to the Spanish colonial period.

Who made the petroglyphs?

Petroglyphs and pictographs have been created by people all over the world. Many of them were made hundreds and thousands of years ago, although in some areas of the world people still produce these images in the old ways following ancient traditions.

Native Americans made most of the images in North America. This is also true at Petroglyph National Monument, however some rock images within the monument were made by early Spanish settlers or Indians living in the area during the Colonial Period (A.D. 1540-1821). Some of the presumed Spanish influenced images depict horses, livestock brands, and Christian crosses.

Interpreting Images on Stone

There were probably many reasons for making the petroglyphs. We do not always understand why an image was placed in a particular location, or what it may mean. We do know that the images are more than just art or imitation of the natural world. We leave the interpretation to the individual.

It is likely that the carved and pecked images are important cultural symbols that reflect the complex society and beliefs of Native American peoples today and in the past. There are hundreds of different kinds of images. All told, we believe that more than 25,000 images exist within Petroglyph National Monument. Today there are more than 20 Native American pueblos and tribes culturally affiliated with the monument, therefore many different beliefs and practices may be represented by the petroglyphs.

We usually do not try and interpret the images or assign specific meanings. Some meanings were not meant to be known or understood today. Some meanings were not meant to be known or understood by the uninitiated. Some images were possibly made for religious purposes. They probably all have a deep spiritual significance and may be considered prayers by some people. Current speculation has led some researchers to believe that some petroglyphs or pictographs may tell a story, mark a trail, or commemorate an event. Some images may have been made to ensure fertility or successful hunting, or may have also been used to keep track of the seasons. In some instances the image may represent a clan or family.

What an image appears to be on the surface though, may be very different from the meaning it had for the person who pecked the image into the rock. Today, when we examine the images carved on stone we can only speculate what their significance was. We may never know for sure what the maker intended. It is likely that meanings have been obscured by time and distance. Some meanings are still known, others have been forgotten, but they are still respected. The petroglyphs' deepest meanings are closely guarded by today's Native peoples.

Studying Petroglyphs and Pictographs

Archeologists, art historians, cultural geographers, and others study petroglyphs and pictographs and the cultural landscapes in which they reside.

Since 1997 an inventory of the petroglyphs in the monument has been underway. As of May 2002 over 21,000 actual images have been recorded and documented in a systematic way. At the current rate of recording, with several highly concentrated areas left to record, monument staff are predicting that close to 25,000 images will ultimately be documented. These data are available for management and research purposes.

When studying and recording petroglyphs and pictographs, many aspects are considered. Similarities and differences are noted. Their position and spatial relationship to each other is recorded as that may be of importance. Their specific appearance is described by identifying visual characteristics of the image called elements. Elements can be representational (depicting animals, people or plants) or abstract lines, spirals and dots. Single or multiple elements are sometimes repeated to cover a large surface. Complex panels may combine numerous representational and abstract elements.

Researchers also classify petroglyph and pictograph styles according to elements, figures, compositions, and techniques that are consistent within a geographic area and time period. This is how relative dates and periods may be assigned through style and similarities to objects and features that can be dated, such as pottery and architecture. Once a style is defined, it is used to associate images with specific cultural groups and histories.

Last updated: March 31, 2012

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