In archaeology, prehistoric rock art is human made markings placed on natural stone. A global phenomenon, prehistoric rock art is found in many regions of the world. It has been produced in many contexts throughout human history, although the majority of rock art that has been ethnographically recorded has been produced as a part of ritual. Such artworks are often divided into three forms: petroglyphs, which are carved into the rock surface, pictographs, which are painted onto the surface, and earth figures, formed on the ground. The oldest known rock art dates from the Upper Palaeolithic period, having been found globally. Archaeologists studying these artworks believe that they likely had magical and or religious significance.