Earthworks (archaeology)

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Offa's Dyke, Britain

In archaeology, earthworks are artificial changes in land level, typically made from piles of artificially placed or sculpted rocks and soil. Earthworks can themselves be archaeological features, or they can show features beneath the surface.[1]

Types

Earthworks of interest to

  • Hill forts, a type of fort made out of mostly earth and other natural materials including sand, straw, and water, were built as early as the late Stone Age and were built more frequently during the Bronze Age and Iron Age as a means of protection.[3] See also Oppidum
    .
  • Henge earthworks are those that consist of a flat area of earth in a circular shape that are encircled by a ditch, or several circular ditches, with a bank on the outside of the ditch built with the earth from inside the ditch. They are believed to have been used as monuments for spiritual ritual ceremonies.[4]
  • A mound is a substantial manmade pile of earth or rocks that was frequently created to mark burial sites [5]
  • Platform mounds are pyramid or rectangular-shaped mounds that are used to hold a building or temple on top.[6]
  • An effigy mound is a pile of earth, often very large in scale, that is shaped into the image of a person or animal, often for symbolic or spiritual reasons [7]
  • An enclosure is a space that is surrounded by an earthwork.[8]
  • Long barrows are oblong-shaped mounds that are used for burials.[9]
  • A tumulus or barrow is a mound of earth created over a tomb.[10]
  • A cross dyke or cross-ridge dyke is a bank and ditch, or sometimes a ditch between two banks, that crosses a ridge or spur of high ground. Found in Europe and often belonging to the later Bronze Age or Iron Age.[11] Often marked on Ordnance Survey maps in the UK.[12]
  • Ridge and furrows are sets of parallel depressions and ridges in the ground formed primarily through historic farming techniques.[13]
  • Mottes are mound structures made of earth and stone that once held castles. They are an important part of the motte-and-bailey castle, a castle design during early Norman times in which the castle is built on the motte, and surrounded by a ditch and a bailey, which is an enclosure with a stone wall.[14]
  • A round barrow is a mound that is in a rounded shape that was used during Neolithic times as a burial mound.[15]
  • Geoglyph, a large design or motif

Size

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 miles (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).

Detection

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.[16] Similarly, earthworks may be more visible after a frost or a light dusting of snow.[17]

Earthworks can be detected and plotted using Light Detection and Ranging (

GIS
) to produce three-dimensional representations of the earthworks.

Interpretation

A survey of a Hopewell enclosure; Newark Earthworks in Ohio, U.S.

An accurate

excavation.[19] For example, earthworks from deserted medieval villages
can be used to determine the location, size, and layout of lost settlements. Often these earthworks can point to the purpose of such a settlement, as well the context in which it existed.

Examples

Great Serpent Mound
in Ohio

Earthworks in North America include

Citrus County, Florida.[23] The earthworks at Poverty Point occupy one of the largest-area sites in North America, as they cover some 920 acres (320 ha) of land in Louisiana.[24]

Military earthworks can result in subsequent archaeological earthworks. Examples include Roman marching forts which can leave small earthworks. During the American Civil War, earthwork fortifications were built throughout the country, by both Confederate and Union sides.[25] The largest earthwork fort built during the war was Fortress Rosecrans, which originally encompassed 255 acres (103 ha).[26][relevant?]

In northeastern Somalia, near the city of Bosaso at the end of the Baladi valley, lies an earthwork 2 to 3 km (1.2 to 1.9 mi) long.[27][28] Local tradition recounts that the massive embankment marks the grave of a community matriarch. It is the largest such structure in the wider Horn region.[28]

interlacustrine region of southwestern Uganda. On the south shore of the Katonga river, the Bigo earthworks consist of a series of ditches and berms comprising an outer arch that encompasses four interconnected enclosures. When combined, the Bigo earthworks measure more than 10 km (6 mi) long.[29] Radiometric dates from archaeological investigations at Bigo date the earthworks to roughly AD 1300–1500, and they have been called Uganda's "largest and most important ancient monument".[30]

The Steppe Geoglyphs, discovered in 2007 using Google Earth, are an example of earthworks in Central Asia.

Gallery

Citations

  1. ^ Muir, 77
  2. excavation
  3. ^ Scott, Willie. "How Earthwork Forts were Built". Retrieved 13 April 2012.
  4. ^ "The Definition of a Henge". Retrieved 13 April 2012.
  5. ^ "Mound". Retrieved 13 April 2012.
  6. ^ "Platform Mound". Retrieved 13 April 2012.
  7. ^ "Effigy Mound". Answers.com. Retrieved 13 April 2012.
  8. ^ "Enclosure". Answers.com. Retrieved 13 April 2012.
  9. ^ "West Kennet Long Barrow". Retrieved 13 April 2012.
  10. ^ "Tumulus". Retrieved 13 April 2012.
  11. .
  12. ^ Ordnance Survey 1:50,000 Landranger series.
  13. ^ "Ridge and Furrow". Answers.com. Retrieved 13 April 2012.
  14. ^ "Motte". Retrieved 13 April 2012.
  15. ^ "Round Barrow". Retrieved 13 April 2012.
  16. ^ Wilson, 38
  17. ^ Aston, 14
  18. ^ EID; crater beneath canopy
  19. ^ Taylor, 59–60
  20. ^ Feder, 344
  21. ^ a b Feder, 54
  22. ^ Crystal, Ellie. "Mounds of North America". Retrieved 12 April 2012.
  23. ^ Weisman, Brent (1995). "Crystal River: A Ceremonial Mound Center on the Florida Gulf Coast". Florida Archaeology. 8: i-86.
  24. ^ Kidder, Tristram R.; Ortmann, Anthony L.; Arco, Lee J. (November 2008), "Poverty Point and the Archaeology of Singularity", Society for American Archaeology Archaeological Record, 8 (5): 9–12
  25. ^ Earl J. Hess (2005). "Field Armies and Fortifications in the Civil War". UNC Press. Archived from the original on 1 March 2013. Retrieved 20 May 2013.
  26. ^ Ed Bearss (1960). "Fortress Rosecrans Research Report". National Park Service. Retrieved 17 May 2013.
  27. .
  28. ^ a b Ali, Ismail Mohamed (1970). Somalia Today: General Information. Ministry of Information and National Guidance, Somali Democratic Republic. p. 295.
  29. ^ Sutton, John (2000). "Ntusi and Bigo: Farmers, cattle-herders and rulers in western Uganda, AD 1000–1500". Azania: Archaeological Research in Africa.
  30. ^ Posnansky, Merrick (1969). "Bigo Bya Mugenyi". The Uganda Journal.

General and cited references

External links