Rock art, or rock imagery, is to be found throughout much of the world, with especially high concentrations in the region known as the American Southwest.
Interestingly, there is valid speculation that these designs continue to be created by Southwestern tribal groups, as they have been for hundreds if not thousands of years.
Generally, there are four basic types of rock art: Pictographs, which are painted on the rock surface; petroglyphs, which are pecked or incised into the rock; geoglyphs, designs made of rocks arranged on the ground, typically on a very large scale; and also cupules, small holes, often found in clusters. Petroglyphs seem to be the most common type in the Southwest. There, rocks are often covered by a veneer known as ‘desert varnish’.
Mineral deposits such as iron oxide adhere to rock surfaces over time and eventually stain the rock. This natural varnish ranges from a rust color to a brown so dark that at first it appears to be black. Almost invariably, it covers a lighter colored rock such as sandstone, which is found throughout the Southwest. By scratching, incising or pecking away at the desert varnish, perhaps with an antler chisel, the artist would reveal the lighter sandstone beneath, thus creating a negative image.
The designs themselves vary, but there are a few general types that are repeatedly found. Aside from the geometric designs, there are typically two others: anthropomorphs, or human images; and zoomorphs, depictions of animals. Sometimes these two motifs are combined, such as humans with animal heads or perhaps vise versa. Also, two different animals may sometimes be combined in a similar manner.