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Peeling Back the Layers Over time, soils and the residues of human existence are buried, leaving a map, of sorts, for archeologists to follow. A man builds a house, for example, that one day burns, then collapses. Water from rain or flooding rivers washes dirt over the debris, gradually burying all evidence of the house. Wind pushes more dirt on top, and, as centuries pass, a layer cake of different dirts develops on the spot. The deeper one digs, theoretically, the older the layers are. Archeologists call such layers strata, and identify them by color, thickness, composition, texture, and by stains and artifacts from human activity. Ideally, the layers are easily distinguished from one another, and appear in sequence from the most recent on top to the oldest at the bottom. In reality, however, the sequence is often disturbed by erosion, earthquakes, frigid temperatures, root growth, toppled trees, and burrowing animals. People, by digging graves, pits, and trenches, and through plowing, also churn and shift the layers. Artifacts, like layers, can also become dislodged from their original placement because of burrowing animals, decaying plant roots, or human digging These disturbances complicate the science of stratigraphy, charting soil layers and interpreting what those layers mean. Stratigraphy is a relative dating technique, allowing archeologists to compare time periods. Relative dating methods supplement absolute dating methods such as carbon-14 testing. Unfortunately, however, understanding soil layers is rarely easy because layers are not only often jumbled, they are also often so similar that they are nearly indistinguishable, requiring careful observation and judgment. Occasionally, archeologists do find in the Southeast an undisturbed, stratified site with many artifacts. Gregg Shoals, uncovered during the Russell studies, was such a place. The excavation at the north Georgia site was exceptionally deep, eventually reaching 14 feet below ground, an unexpected challenge. Special equipment was called for and designed by archeologist James Michie. He devised a boom equipped with a hand-turned winch to help speed the digging. Platforms and ladders gave the crew safe access down below.
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