Petroglyph

A petroglyph (Greek petros, a stone, and glyphe, carving) is an image that has been pecked, chiseled, grooved, or scratched into a rock surface. Petroglyphs were usually made by rubbing or striking a stone against the drawing surface. Sometimes, to achieve greater control, the chisel-stone was placed against the rock and then struck with a heavier hammer-stone. The end result was to wear away or knock off the darker oxidized exterior or patine, exposing a lighter undersurface. Petroglyphs vary greatly, from thinly scratched doodlings and scrawls, to more deeply etched stylized representations of the natural world, to carefully conceived designs. Noble 1981, p 10