The common archaeological term for petroglyphs and pictographs is “Rock Art”. Some scholars call them “Rock Paintings”. I call them “Rock Writings” because I believe that they serve a similar communicative function to the hand and arm sign language gestures that allowed Native American tribes of differing languages to communicate in fundamental ways. The primary difference is that petroglyphs and pictographs are presented visually through rock and stone and utilize more complex symbolic meanings than typical sign language. For an in-depth view of this perspective read le Van Martineau’s book When The Rocks Begin To Speak.
www.rock-art.com/books
www.geocities.com/Athens/Olympus/6381
www.rockart.org
www.jqjacobs.net/rock_art
http://bancroft.berkeley.edu/collections/rockart.html
www.rupestre.net/tracce