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.

In the Hebrides, it was customary to remove the thatch from the "black houses" every spring, and spread it on the fields as fertilizer, improved by the soot which it retained.

Dark earth over 7 hectares (17 acres) has been found in the Viking city of Björkö (today called Birka), in central Sweden, close to modern Stockholm.

[citation needed] Dark earths occur around ruins in the Upper Guinean forests of Ghana, Guinea, Liberia and Sierra Leone.

[8][9] For a period of at least 700 years, West African farmers have enriched the rain forest soils around their towns with compost derived from kitchen, animal, agricultural, and fire waste to produce a signature dark earth.