Petroglyphs are engravings or carvings into the rock panel.
Stylistically they normally relate to other types of sculpture from the culture and period concerned, and except for Hittite and Persian examples they are generally discussed as part of that wider subject.Normally found in literate cultures, a rock relief or rock-cut relief is a relief sculpture carved on solid or "living rock" such as a cliff, rather than a detached piece of stone.They are a category of rock art, and sometimes found in conjunction with rock-cut architecture.In several regions, it remains spiritually important to indigenous peoples, who view it as a significant component of their cultural patrimony.It also serves as an important source of cultural tourism, and hence as economic revenue in certain parts of the world.The archaeological sub-discipline of rock art studies first developed in the late-19th century among Francophone scholars studying the Upper Palaeolithic rock art found in the cave systems of Western Europe.
Rock art continues to be of importance to indigenous peoples in various parts of the world, who view them as both sacred items and significant components of their cultural patrimony.
Once the pigments had been obtained, they would be ground and mixed with a liquid, such as water, blood, urine, or egg yolk, and then applied to the stone as paint using a brush, fingers, or a stamp.
Alternately, the pigment could have been applied on dry, such as with a stick of charcoal.
In some societies, the paint itself has symbolic and religious meaning; for instance, among hunter-gatherer groups in California, paint was only allowed to be traded by the group shamans, while in other parts of North America, the word for "paint" was the same as the word for "supernatural spirit".
One unusual form of pictograph, found in many, although not all rock-art producing cultures, is the hand print.
Some archaeologists also consider pits and grooves in the rock, known as cups, rings or cupules, as a form of rock art.