Sunday, January 17, 2010


It seems to be almost universal that people writing about petroglyphs assume that they are produced by indirect percussion – the use of a hammerstone to hit some form of chisel which carves the image into the rock surface. I have even seen a number of artist’s impressions showing a Native American holding some form of chisel against the cliff with one hand and holding the hammerstone in the other hand. Just a little reasoning tells us that this cannot possibly be correct. If such a stone-age culture wanted to build a chisel they would have to use a sharpened stone blade with a bone, horn, or wood shaft, assembled with lashings and possibly low quality natural adhesives.

Newton’s second law of motion (conservation of momentum) tells us that as much or more of the force from pounding on such a chisel with the hammerstone would be absorbed by that chisel than would be transferred to the rock surface. This technique would very quickly destroy the joints in the chisel leaving the rock surface essentially untouched (if the rock surface is soft enough, a deer or elk antler tine used as a chisel, a hard, tough material which would probably be successful because it would have no joints to fail under repeated impacts).

Bird Rattle carving petroglyph,1924, Writing-on-Stone,
Blackfeet, from James Keyser,Art of the Warriors
Univ. of UT Press, Salt Lake City.

It is obvious to anyone with any firsthand experience in carving stone and the required tools, that petroglyphs must have been created with direct percussion – hitting the rock surface directly with a harder hammerstone. Indeed I have found many of the hammerstones used to create petroglyphs lying on the ground at the base of the decorated rock or cliff. People with no first-hand experience generally assume that direct percussion is extremely difficult, requiring heavy blows, and that accuracy is very hard to achieve. This is, in fact, incorrect. Moderate, easily controlled blows are best, and they can be applied with considerable accuracy.

We must remember that much of the great stonework of the ancients was created in exactly this way. Egyptian stone for temples, pyramids, and obelisks was quarried from the bedrock by pounding with hammerstones. Mayan and Aztec architecture was created by pounding with a hammerstone, as was the cyclopean stone work of the Incas. Indeed, the multitude of Easter Island statues were quarried and carved with direct percussion of a hammerstone. With all of these marvelous examples why do we still question the ability of direct percussion to create the petroglyphs?

Hammerstone below petroglyph panel,
Wild Horse Draw, Canyon Pintado, CO.
Photo: Peter Faris.

I think it is because our image of carving stone comes from Hollywood style presentations of Michelangelo carving large blocks of marble with a swinging mallet and a chisel. Metallurgical technology has given us chisels made from tempered steel that can hold up to the repeated blows of the mallet and to the surface of the stone. Our cultural technological focus tends to carve with the indirect percussion of a hammer or mallet and a chisel. We have a cultural bias toward expecting the use of a chisel in carving a hard substance.

Native American Rock Art, Yvette La Pierre,
1994, Thomasson-Grant, Charlottsville, VA.,
illustrations by Lois Sloan, p.22

There is a marvelous book for children about rock art. Native American Rock Art, by Yvette La Pierre, 1994, illustrated by Lois Sloan, has two nicely painted illustrations in it which show the creation of petroglyphs correctly using direct percussion. The irony in this is that they have it correct while so many experts get it wrong. Perhaps La Pierre and Sloan are actually the experts in this. Well, with this book to show them correctly the children growing up to be the next generation of rock art experts may get it right.

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