“Rock art” is the collective term for a variety of forms of visual representation made on natural rocky surfaces (boulders, cliff faces, cave walls, etc.) and are found throughout the world. Pictographs and petroglyphs represent the two main techniques used to make rock art. Pictographs are made through an additive process, where they are applied to the rock surface, and include paintings, charcoal drawings, stencils, prints. Petroglyphs are made by a reductive process, in which they are cut into the rock by engraving, pecking, incising or abrasion.