Natural in archaeology is a term to denote a layer (stratum) in the stratigraphic record where there is no evidence of anthropogenic activity. While there may be "natural" layers interbedded with archaeologically interesting layers, such as when a site was abandoned for long periods of time between occupations by man, the top (the horizon) of the natural layer below which there is no anthropogenic activity on site, and thus where the archaeological record chronologically begins, is the sought-for point to terminate digging. This final natural layer is often the underlying geological makeup of the site that was formed by geological processes. It is the goal of complete excavation to remove the entirety of the archaeological record all the way to the final "natural", thus leaving only the natural deposits of pre-human activity on site. If the excavation is related to development, the impact assessment may stipulate excavation will cease at a certain depth, because the nature of the development will not disturb remains below a certain level; such an excavation may not reach a natural or sterile layer. Thus one always has to overdig a site (dig past the top of the natural) in order to establish the natural.