An Experimental Examination of Trampling Effects on the Lateral Movement of Surface Artifacts

An often cited but little understood archaeological disturbance process is the effect of a site's occupants walking across the surface. Human foot traffic will move and alter archaeological materials, artifacts, in characteristic ways. How surface items will respond to trampling is dependent on a variety of factors. These factors will determine the extent and dimensions available for movement. By controlling for some of the relevant variables, the effects of other variables can be examined.

In this thesis, experiments are described that identify each of the variables that influence or may possibly influence how surface artifacts respond to foot traffic. The application of the experimental method allows most of these to be controlled so that the effects of other factors can be studied. These factors, trampling pattern, artifact distribution, artifact size and trampling duration, were each determined to have a significant impact on the movement of surface items.

Ceramic tiles of three size grades were placed in a regular pattern at known locations. These were laid on a prepared soil surface. The surface was constructed to accentuate lateral and decrease vertical displacement. The sediment exhibited a high clay content. The surface was flat, dry and compact with no extant vegetation or detritus. Each test consisted of four individuals walking across the surface in a proscribed pattern. After each test, tile locations were mapped and the test was repeated. This yielded beginning and ending Cartesian coordinates for each item for each bout.

A model of artifact displacement as a function of trampling disturbance was generated based on the significant factors. This allowed for the determination of the impact of each of these factors. Most displacement will occur soon after deposition. A non-restricted walking pattern will move materials more that if the pattern is constrained. Material high density areas are more resistant to trampling disturbance than low density areas. Larger artifacts are more liable to move, but they will not move as far as small artifacts. This model, while accounting for only some of the relevant variables, serves as solid baseline for further research.