the surface with a harder stone to create an artificially smoothed and flattened area contrasting with the naturally rough-textured rock. Pecked designs were sometimes further smoothed by abrading.
A few Pacific Northwest petroglyphs were made by scratching the rock with a sharp stone flake or piece of metal to produce a light-colored line on the dark surface. Some shallow scratches are now nearly invisible, having weathered over several hundred years. Others were deepened to form distinct incisions still readily apparent. A few petroglyphs show a combination of techniques; most common are animal figures with abraded bodies and scratched legs, horns, or antlers.
Columbia Plateau petroglyphs are most often made on basalt, a hard, dense volcanic stone. The weathered surface of basalt is a dark, reddish-brown to black patina, or “crust,” several millimeters thick. Underneath this patina the stone is a lighter color, ranging from yellowish brown to dark grey. Prehistoric artists engraved deep enough to reveal this un-weathered interior stone so that designs would stand out against the darker background. Reweathering of designs exposed in this way provides a clue to help in dating some petroglyphs.
Pictographs
Pictographs are rock paintings. On the Columbia Plateau these are most often in red, but white, black, yellow, and even blue-green pigments were sometimes used. Polychrome paintings are uncommon, but a few do occur throughout the region. Most frequent are the red and white polychromes of the lower Columbia River and Yakima valley.
Pigment was made from various minerals. Crushed iron oxides (hematite and limonite) yielded red—ranging from bright vermilion to a dull reddish brown—and yellow colors. Sometimes these ores were baked in a fire to intensify their redness. Certain clays yielded white pigment, and copper oxides blue green. Both charcoal and manganese oxide produced black. Early descriptions indicate that Indians mixed crushed mineral pigment with water or organic binding agents, such as blood, eggs, fat, plant juice, or urine, to make paint.
Pigment was most commonly applied by finger painting: finger-width lines compose the large majority of pictographs throughout the area. Some paintings, done with much finer lines, indicate the use of small brushes made from animal hair, a feather, or a frayed twig. Still others were drawn with lumps of raw pigment (much like chalk on a blackboard) or grease-paint “crayons.” These pictographs have a characteristic fine-line appearance, but the pigment appears somewhat unevenly applied in comparison with the small brush paintings.
How this paint has survived on open exposed cliff faces, where pictographs are usually found, has long been the subject of scientific debate. Early scholars, presuming that the paint would fade rapidly, argued that all of these paintings had been done during the last two hundred years. Several reported significant fading at some sites, and even suggested that none of these paintings would last beyond a few more years. Fortunately, they have been proven wrong: scientists have recently discovered evidence that the paintings are not disappearing, as originally thought. Photographs taken at several sites over spans of as much as seventy-five to one hundred years indicate that pronounced fading is not usually a problem. Often, “faded” pictographs are found to have been destroyed by road construction, inundated by reservoirs, or covered by road dust or lichen. When affected only by natural weathering, paintings at hundreds of sites remain as bright today as when they were first discovered.
Recent research by Canadian scientists (Taylor et al. 1974, 1975) has demonstrated why these rock art pigments are so durable. When freshly applied, the pigment actually stains the rock surface, seeping into microscopic pores by capillary action as natural weathering evaporates the water or organic binder with which the pigment was mixed. As a result, the pigment actually becomes part of the rock.
Mineral deposits coating many cliff surfaces provide a further “fixative” agent for these paintings. Varying types of rock contain calcium carbonates, aluminum silicates, or other water-soluble minerals. Rain water, washing over the surface of the stone or seeping through microscopic cracks and pores, leaches these naturally occurring minerals out of the rock. As the water evaporates on the cliff surface, it precipitates a thin film of mineral. This film is transparent unless it builds up too thickly in areas with extensive water seepage. In these instances the mineral deposit becomes an opaque whitish film that obscures some designs, the reason that some pictographs do actually fade from view. However, microscopic thin section studies show that, in most instances, staining, leaching, and precipitation have actually caused the prehistoric pigment to become a part of the rock surface, thereby protecting it from rapid weathering and preserving it for hundreds of years.
Anthropomorph, Zoomorph
Anthropomorph and zoomorph derive from the Greek words morphe, “form”; anthropos, “man”; and zoon, “animal.” Thus, anthropomorphs have human form, zoomorphs have animal form. These words are often used instead of “human” and “animal” in the professional literature to communicate a specific meaning because scientists cannot be sure that the original artist intended a specific figure to represent an actual human (or animal), or merely the concept of humanness, or even the personification of a spirit or other nonliving thing. However, in this book, the terms “human,” “human figure,” “animal,” and “animal figure” are more readily understood, and fine distinctions of meaning are not required.
On the other hand, I have used these two terms when it is obvious that the prehistoric artist did not intend to represent a real human or animal, yet used undeniably human or animal features in a design. Multiple-headed beasts, faces that combine some features of both humans and animals, or otherwise abstract designs incorporating clearly recognizable body parts are categorized as anthropomorphic or zoomorphic, depending on which features are primary. Thus, a grinning human face with a fish tail would be anthropomorphic, while a three-headed animal figure with hands in place of hooves or paws would be referred to as zoomorphic. For the most part, however, if a figure closely resembles a human or an animal (given stylistic conventions), I refer to it using the simpler terms.
Rock Art Style and Rock Art Tradition
Rock art style and rock art tradition are also technical terms with specific meanings. Researchers world-wide define rock art style as a group of recurring motifs or designs (e.g., rayed arc, human figure) portrayed in typical forms (e.g., alternate red and white rays, stickman), which produce basic recognizable types of figures. Usually these various figures are associated with one another in structured relationships, leading to an overall distinctness of expression. Thus, we can define the Yakima polychrome style and easily distinguish classic examples of it from the central Columbia Plateau style, which used the same rayed arc motif and stick figure humans, but in significantly different forms, numbers, and structured relationships.
The characteristics of styles vary across space and through time, however, and some blending occurs between neighboring styles. For instance, some highly abstract anthropomorphic figures that are undoubtedly in the Long Narrows† style are executed as elaborate polychrome paintings more like characteristic Yakima polychrome motifs. Likewise, a few of the rayed arcs characteristic of the western Columbia Plateau style occur in the eastern part of the region, although not as an important motif. This blending occurs to some extent between almost all art styles that are contemporaneous and geographically associated, and sometimes artists will even copy motifs from much older styles, thereby bridging the gap of time.
The greatest blending, however, occurs among styles whose makers are culturally related and who have regular contact with one another. The result is a rock art tradition, extending through time in a defined area, which has two or more styles that are more similar to each other than to any neighboring style. Such is the Columbia Plateau rock art tradition, where stick figure humans, simple block-body animal forms, rayed arcs and circles, tally marks, abstract spirit beings or mythical figures, and geometric forms are combined to produce an art that is recognizably distinct from that of the neighboring areas of the Northwest Coast, Great Basin, or northwestern Plains.
Rock art styles have been generally identified as naturalistic, stylized, and abstract (Grant 1967). Naturalistic art depicts actual things, such as humans and animals, in a reasonably realistic or natural manner. Stylized art renders recognizable forms in a highly conventionalized or nonrealistic manner. Finally, abstract art shows forms that are unrecognizable