The purpose of this simulation was to help viewers understand some fundimental concepts relating to pecked (chipped) petroglyphs. The intent is to have this simulation shown on a projector in the information center at petroglyh sites such as The Edge of the Cedars in Blandin, Utah, or the Jeffers Petroglyph Site near Jeffers, Minnesota.
Petroglyphs are carvings on rocks and are found in virtually every corner of the world (Antartica excepted). All human cultures seem to have shared a common urge to make near permanent marks on stone.
Carving on stone, epecially without modern tools, is a difficult and time consuming endeavor. I wanted to help casual visitors to understand how much of an investment the original artists had made.
Traditionaly glyphs are chipped from the stone face by striking the face with another, hand-held (and hopefully harder) stone. This is an imperfect technique and small errors are common. The stone might miss the exact target causing a slightly out-of-line flake. The stone might strike a wak spot resulting in a larger than intended flake. I tried to mimic these variables in the simulation.
By giving the participant only a tiny "flake" for each tap (or click if a mouse is used insteadof a touch-screen) a significant investment must be made. In testing this also had the benefit of discouraging sureptitious graffiti artists. Drawing with a mouse is vastly different than drawing with a pencil, and even participants with significant drawing experience find that they must "learn" this new technique of tapping to make a serial line of flakes.
Archaologists try to date petroglyphs. There are a number of ways to do this, for instance one might compare carved symbols to the stories told by indigenous people, but in many cases the glyph carving culture has been supplanted by more recent cultures.
One way to date glyphs relative to each other is to compare the gradually darkeing "desert varnish" that naturally occurs as rock weathers, natural chemical staining slowly continues, and lichens grow on protected surfaces. For this simulation I have the rock surface darken very slowly. A participant will not notice the darkening whle they work, but when they return from exploring the site and the museum they will see that thier glyphs have darkened along with the rock, and more recent glyphs are lighter in color.