Dark earth

In geology and archaeology, dark earth is a substratum, up to 1 metre (3 ft 3 in) thick, that indicates settlement over long periods of time. The material is high in organic matter, including charcoal, which gives it its characteristic dark colour; it may also contain fragments of pottery, tile, animal bone and other artefacts. It is interpreted as soil enriched with the sooty remains of thatched roofs from houses without chimneys, with other waste materials. In some areas it appears to give the soil added fertility.

London's dark earth was originally called 'black earth' by archaeologists. It was renamed 'dark earth' because of confusion with the chernozem (black earth soils in Russia), whose dark colour is traditionally (not universally) thought to come from humus, rather than soot.