Cropmarks or crop marks are a means through which sub-surface archaeological, natural and recent features may be visible from the air or a vantage point on higher ground or a temporary platform. Such marks, along with parch marks,[1]soil marks and frost marks, can reveal buried archaeological sites that are not visible from the ground.
Sketched diagram of a negative cropmark above a wall and a positive cropmark above a ditchCrop marks in Gloucestershire. Cereal crop left, beans right. The relative intensity in the crops was reversed in the near infra-red.
Crop marks are due to the principle of differential growth. One of the factors controlling the growth of vegetation is the condition of the soil. A buried stone wall, for example, will affect crop growth above it, as its presence channels water away from its area and occupies the space of the more fertile soil. Conversely, a buried ditch, with a fill containing more organic matter than the natural earth, provides much more conducive conditions and water will naturally collect there, nourishing the plants growing above.
The differences in conditions will cause some plants to grow more strongly and therefore taller, and others less strongly and therefore shorter. Some species will also react through differential ripening of their fruits or their overall colour.
Particularly effective crops that exhibit differential growth include cereal crops, peas, and potatoes.
Differential growth will naturally follow any features buried below. Although the growth differences may appear small close up, from the air the pattern they make is more visible, as the small changes can be seen as marked differences in tone or colour in the context of the normally growing surrounding vegetation. When the sun is low to the horizon, shadows cast by the taller crops can also become visible.
By their nature crop marks are visible only seasonally and may not be visible at all except in exceptionally wet or dry years. Droughts can be especially useful to cropmark hunters, as the differential growth can become apparent in normally hardy species such as grass. The drought of 2010 produced particularly good conditions for observing crop marks in the UK.[2] Pre-parching stress in crops and grass, and others factors that may affect plant health, can be captured in near infra-red photography.
Near infra-red kite aerial photo at Rufford Abbey, Nottinghamshire, UKRoman Road – The Via Julia, Clifton Down, Bristol
An alternative approach is thermal imaging, where differential water loss (which is dependent of the availability of water at the roots) can create temperature differences, which result in thermal crop marks that are potentially visible at any time during crop growth.[3] Thermal imaging can also reveal archaeological residues as a result of thermal inertia (storage heater effect) or differential evaporation. The interaction of the processes involved can be complex and the prediction of optimal imaging time, for a given site, further complicated by environmental conditions including temperature variation and relative humidity.
Kite aerial thermogram of Statford Court Playingfields, Stroud, Gloucestershire, UK.
Thermal inertia and differential transpiration/evaporation are involved.[4]
The usefulness of cropmarks to archaeologists has largely been a fruit of inspection from aircraft, but the possibility was suggested by Rev. Gilbert White in The Natural History of Selborne (1789), in a note appended to his Letter VI, to Thomas Pennant, apropos of local people's success in searching for bog oak for house construction, by discovering these trees "by the hoar frost, which lay longer over the space where they were concealed, than on the surrounding morass." To White it suggested the query "might not such observations be reduced to domestic use, by promoting the discovery of old obliterated drains and wells about houses; and in Roman stations and camps lead to the finding of pavements, baths and graves, and other hidden relics of curious antiquity?"
Examples
After a long hot dry period, cropmark on a lawn from a line of flagstones overgrown and buried by grass
Examples of archaeological sites where cropmarks have been observed are Balbridie and Fetteresso in Scotland.
In 2009, investigation of crop marks near Stonehenge revealed a variety of 6,000-year-old prehistoric subterranean structures.[5]
Another example is the rediscovery of the Roman city Altinum, a precursor to the city of Venice, from a combination of visible and near-infrared photos of the area taken during a drought in 2007, which stressed the maize and soy crops. [6]
The multi period site at Mucking was discovered as a result of aerial photographs showing cropmarks and soil marks. The earliest photographs to reveal the site were taken by the Luftwaffe in 1943.[7] The importance of the site was recognised following photographs taken by Kenneth Joseph in 1959[7] (published in 1964).[8] In 1982, Margaret Jones (site director at the Mucking excavation) said that some sites were being interpreted on crop mark evidence alone. She said that some features do not produce crop marks and that some crop marks, when excavated, turn out not to be what they seem.[9][full citation needed]
Wilson, D. R . 2000 Air photo interpretation for archaeologists (2nd edn.), London.
Agache, R. 1963. Détection des fossés comblés sur terrains sans végétation grâce à l'humidité rémanente des remblais. Bulletin de la société préhistorique française, 1963, vol. 60, n°9–10, p. 642–647
Lasaponara R., N. Masini. 2007. Detection of archaeological crop marks by using satellite QuickBird multispectral imagery. In: Journal of Archaeological Science, 34(2), pp. 214–221
^. Archived from the original on 2018-12-15. Retrieved 2012-12-05.
^James Owen (2009-06-15). "Huge Pre-Stonehenge Complex Found via "Crop Circles"". National Geographic.
^ Ninfo A., Fontana A., Mozzi P., Ferrarese F. 2009. The Map of Altinum, Ancestor of Venice. Science 31 July 2009: Vol. 325 no. 5940 p. 577
^ abClark, A. 1993. Excavations at Mucking, Volume 1: The Site Atlas (English Heritage Archaeological Report 20)
^JK St Joseph, Air reconnaissance: recent results (Antiquity, vol 38, pp 217-218)
^Jones, Margaret. "Jottings from Mucking post-excavation". Panorama. 25.
External links
August 29, 2023
cropmark, other, uses, crop, mark, crop, marks, means, through, which, surface, archaeological, natural, recent, features, visible, from, vantage, point, higher, ground, temporary, platform, such, marks, along, with, parch, marks, soil, marks, frost, marks, re. For other uses see Crop mark Cropmarks or crop marks are a means through which sub surface archaeological natural and recent features may be visible from the air or a vantage point on higher ground or a temporary platform Such marks along with parch marks 1 soil marks and frost marks can reveal buried archaeological sites that are not visible from the ground Cropmarks at a protohistoric site at Grezac France Contents 1 Description 2 Examples 3 See also 4 References 5 External linksDescription Edit Sketched diagram of a negative cropmark above a wall and a positive cropmark above a ditch Crop marks in Gloucestershire Cereal crop left beans right The relative intensity in the crops was reversed in the near infra red Crop marks are due to the principle of differential growth One of the factors controlling the growth of vegetation is the condition of the soil A buried stone wall for example will affect crop growth above it as its presence channels water away from its area and occupies the space of the more fertile soil Conversely a buried ditch with a fill containing more organic matter than the natural earth provides much more conducive conditions and water will naturally collect there nourishing the plants growing above The differences in conditions will cause some plants to grow more strongly and therefore taller and others less strongly and therefore shorter Some species will also react through differential ripening of their fruits or their overall colour Particularly effective crops that exhibit differential growth include cereal crops peas and potatoes Differential growth will naturally follow any features buried below Although the growth differences may appear small close up from the air the pattern they make is more visible as the small changes can be seen as marked differences in tone or colour in the context of the normally growing surrounding vegetation When the sun is low to the horizon shadows cast by the taller crops can also become visible By their nature crop marks are visible only seasonally and may not be visible at all except in exceptionally wet or dry years Droughts can be especially useful to cropmark hunters as the differential growth can become apparent in normally hardy species such as grass The drought of 2010 produced particularly good conditions for observing crop marks in the UK 2 Pre parching stress in crops and grass and others factors that may affect plant health can be captured in near infra red photography Near infra red kite aerial photo at Rufford Abbey Nottinghamshire UK Roman Road The Via Julia Clifton Down BristolAn alternative approach is thermal imaging where differential water loss which is dependent of the availability of water at the roots can create temperature differences which result in thermal crop marks that are potentially visible at any time during crop growth 3 Thermal imaging can also reveal archaeological residues as a result of thermal inertia storage heater effect or differential evaporation The interaction of the processes involved can be complex and the prediction of optimal imaging time for a given site further complicated by environmental conditions including temperature variation and relative humidity Kite aerial thermogram of Statford Court Playingfields Stroud Gloucestershire UK Thermal inertia and differential transpiration evaporation are involved 4 The usefulness of cropmarks to archaeologists has largely been a fruit of inspection from aircraft but the possibility was suggested by Rev Gilbert White in The Natural History of Selborne 1789 in a note appended to his Letter VI to Thomas Pennant apropos of local people s success in searching for bog oak for house construction by discovering these trees by the hoar frost which lay longer over the space where they were concealed than on the surrounding morass To White it suggested the query might not such observations be reduced to domestic use by promoting the discovery of old obliterated drains and wells about houses and in Roman stations and camps lead to the finding of pavements baths and graves and other hidden relics of curious antiquity Examples Edit After a long hot dry period cropmark on a lawn from a line of flagstones overgrown and buried by grassExamples of archaeological sites where cropmarks have been observed are Balbridie and Fetteresso in Scotland In 2009 investigation of crop marks near Stonehenge revealed a variety of 6 000 year old prehistoric subterranean structures 5 Another example is the rediscovery of the Roman city Altinum a precursor to the city of Venice from a combination of visible and near infrared photos of the area taken during a drought in 2007 which stressed the maize and soy crops 6 The multi period site at Mucking was discovered as a result of aerial photographs showing cropmarks and soil marks The earliest photographs to reveal the site were taken by the Luftwaffe in 1943 7 The importance of the site was recognised following photographs taken by Kenneth Joseph in 1959 7 published in 1964 8 In 1982 Margaret Jones site director at the Mucking excavation said that some sites were being interpreted on crop mark evidence alone She said that some features do not produce crop marks and that some crop marks when excavated turn out not to be what they seem 9 full citation needed See also EditArchaeological field survey Aerial archaeology Crop circle Shadow marksReferences EditWilson D R 2000 Air photo interpretation for archaeologists 2nd edn London Agache R 1963 Detection des fosses combles sur terrains sans vegetation grace a l humidite remanente des remblais Bulletin de la societe prehistorique francaise 1963 vol 60 n 9 10 p 642 647 Lasaponara R N Masini 2007 Detection of archaeological crop marks by using satellite QuickBird multispectral imagery In Journal of Archaeological Science 34 2 pp 214 221 Parch marks at Rufford Abbey Near infra red KAP Archived from the original on 2018 12 15 Retrieved 2012 12 05 BBC news reporting English Heritage Thermal prospecting on vegetation PDF Archived from the original PDF on 2017 03 21 Retrieved 2017 03 21 Archaeological Aerial Thermography and Near Infrared Photography James Owen 2009 06 15 Huge Pre Stonehenge Complex Found via Crop Circles National Geographic Ninfo A Fontana A Mozzi P Ferrarese F 2009 The Map of Altinum Ancestor of Venice Science 31 July 2009 Vol 325 no 5940 p 577 a b Clark A 1993 Excavations at Mucking Volume 1 The Site Atlas English Heritage Archaeological Report 20 JK St Joseph Air reconnaissance recent results Antiquity vol 38 pp 217 218 Jones Margaret Jottings from Mucking post excavation Panorama 25 External links EditKite Aerial Photographers Archaeology Retrieved from https en wikipedia org w index php title Cropmark amp oldid 1170688169, wikipedia, wiki, book, books, library,
