added by archaeologs One of the main agents by which plant litter, humus and minerals are incorporated and mixed in soil. Earthworms are responsible for the maintenance and stability of various types of soil, especially the Brown Forest soils. The character of a soil may change markedly if the plant litter produced by the vegetation changes to a kind which is unpalatable to earthworms (seepodzol). The effects of earthworm sorting may be seen on archaeological sites in the blurring of layers and the development of worm-sorted layers in the top of buried soils, where a line of stones marks the lower limit of worm activity.
The Macmillan dictionary of archaeology, Ruth D. Whitehouse, 1983