Earthwork (archaeology)

In archaeology, earthworks are artificial changes in land level, typically made from piles of artificially placed or sculpted rocks and soil. Earthworks are often known as barrows in England, and mounds in North America. Earthworks can themselves be archaeological features, or they can show features beneath the surface.

Earthworks of interest to archaeologists include hill forts, henges, mounds, platform mounds, effigy mounds, enclosures, long barrows, tumuli, ridge and furrow, mottes, round barrows, and other tombs.

Earthworks can vary in height from a few centimetres to the size of Silbury Hill at 40 metres (130 ft). They can date from the Neolithic to the present. The structures can also stretch for many tens of kilometres (e.g. Offa's Dyke and Antonine Wall). In area, they can cover many hectares; for example, Maiden Castle, which is 19 hectares (47 acres).

Shallow earthworks are often more visible as cropmarks or in aerial photographs if taken when the sun is low in the sky and shadows are more pronounced. Similarly, earthworks may be more visible after a frost or a light dusting of snow.

Earthworks can be detected and plotted using Light Detection and Ranging (LIDAR). This technique is particularly useful for mapping small variations in land height that would be difficult to detect by eye. It can be used to map features beneath forest canopy and for features hidden by other vegetation. LIDAR results can be input into a geographic information system (GIS) to produce three-dimensional representations of the earthworks.

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