Tom Charles is an Archaeologist in the South Carolina. He has been heading up the petroglyph survey in SC since 1997. I have been assisting in the survey since the beginning. At last count we had recorded about 75 of these same line and circle glyphs. He has written several papers on them. They are a well known style of petroglyph. Up until our survey it was generally accepted that the glyphs were used for lye leaching or tar extraction. But a lot of the ones we recorded were basically non functional for that use. Either they were way to small for any kind of yield, or on vertical rock faces, grooves way to shallow etc... Anyway the design is fairly common in North American rock art. They are some guys out in the Four Corners region chasing these things down also. They call them Waterglyphs. You can look it up on the web. I personally believe these are prehistoric, but the early settlers tried to find a use for them. They are easier ways to extract tar than this! These are part of an mystery that stretches almost completely across America. As no one has yet come up with a good answer for what they are.