27:
517:, or development because of the nutrient-poor, shallow soil and difficult slopes. For this reason downland often survived uncultivated when other, more easily worked land was ploughed or reseeded. This shallow soil structure makes downland ecosystems extremely fragile and easy to destroy. With modern machinery and fertilising techniques, it has become possible to use some previously uncultivated downland for farming, and the decline of extensive grazing has meant that many areas of downland, neither cultivated nor grazed, revert to
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or other less rare habitat, essentially destroying the delicate calcareous grassland. The UK cover of lowland calcareous grassland has suffered a sharp decline in extent since the middle of the twentieth century. There are no comprehensive figures, but a sample of chalk sites in
England surveyed in
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can occur where water emerges from the porous chalk or the underlying greensand. Along this line, settlements and farms were often built, as on the higher land no water was available. This is demonstrated very clearly beneath the scarp of the
655:
Butler, A.P.; Hughes, A.G.; Jackson, C.R.; Ireson, A.M.; Parker, S.J.; Wheatear, H.S.; Peach, D.W. (2012). "Advances in modelling groundwater behaviour in Chalk catchments". In
Shepley, M.G.; Whiteman, M.I.; Hulme, P.J.; Grout, M.W. (eds.).
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rich surface layer which grades through a lighter brown hillwash containing small pellets of chalk, to the white of the chalk itself. This is largely because of the purity of the chalk, which is about 98%
474:
Steep slopes on chalk downland develop a ribbed pattern of grass covered horizontal steps a foot or two high. Although subsequently emphasised by cattle and sheep walking along them, these
526:
found that over 50% had been lost between the mid-1950s and the early 1990s. Much remaining chalk downland has been protected against future development to preserve its unique
831:
627:
Clayton, C.R.I.; Matthews, M.C. (1987). "Deformation, diagenesis and the mechanical behaviour of chalk". In Jones, M.E.; Prescott, R.M.F.; Prescott, R.M.E. (eds.).
411:. The practice of extracting water from this aquifer, in order to satisfy the increasing demand for water, may be putting some of these streams under stress.
414:
In the valleys below the downs at the base of the chalk layer, greensand or gault clay comes to the surface and at the interface at the top of the gault a
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effects included significant amounts of dissolution of the chalk and the modification of existing valleys due to a combination of frozen ground and
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in chalk hills rises in winter and falls in summer. This leads to characteristic chalk downland features such as dry valleys or
325:. Later erosion has produced the characteristic ridges of the downland landscape. The landscape was further modified during the
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where chalk is exposed at the surface. The name "downs" is derived from the Celtic word "dun", meaning "fort" or "
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698:
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30:
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699:"The geological history of the Isle of Wight: an overview of the 'diamond in Britain's geological crown'"
78:" (and by extension "fortified settlement", from which it entered English as "town", similar to Germanic
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384:
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is relatively soft porous white chalk with only poorly-defined bedding. The chalk is classified as a
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478:(commonly known as sheep tracks) were formed by the movement of soil downhill, a process known as
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427:. In many chalk downland areas there is no surface water at all other than artificially created
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chalk layer in southern
England is typically tilted, chalk downland hills often have a marked
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293:. The fracturing has greatly increased the chalk's permeability, such that it is a major
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period by the area's proximity to the southern edge of the ice sheets formed during the
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1966 and 1980 showed a 20% loss in that period and an assessment of chalk grassland in
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86:), though the original meaning would have been "hill", as early forts were commonly
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Downland develops when chalk rock becomes exposed at the surface. The chalk slowly
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slope on the other. Where the downs meet the sea, characteristic white chalk
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This article is about the geographical feature. For the ship anchorage, see
631:. Geological Society, Special Publications. Vol. 29. p. 55–62.
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70:. This term is used to describe the characteristic landscape in southern
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Since its deposition, the chalk in southern
England has been uplifted,
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454:. Unlike many soils in which there are easily distinguished layers or
450:. Weathering of the chalk has created a characteristic soil known as
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263:. The Chalk Group either directly overlies the impermeable uppermost
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665:
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and wild animals. Chalk downland is often unsuitable for intensive
761:"Down to earth – the unique soil of the South Downs National Park"
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Chalk deposits are generally very permeable, so the height of the
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mud. Small amounts of silica were also deposited, mainly from
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The largest area of downland in southern
England is formed by
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497:(L.) Lady's Bedstraw, a typical English chalk downland plant
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minerals which are abundant, for example, in valley floors.
660:. Geological Society, Special Publications. Vol. 364.
443:
of chalk downland in
England is a thin soil overlaying the
375:
slope on one side, which is very steep, and a much gentler
658:
Groundwater
Resources Modelling: A Case Study from the UK
367:
to form characteristic rolling hills and valleys. As the
791:
458:, a chalk rendzina soil consists of only a shallow dark
90:- compare Germanic "burg" (fort) and "berg" (mountain).
579:
Rural
England: An Illustrated History of the Landscape
202:. Similar chalk hills are also found further north in
501:
The dominant habitat in chalk downland is typically
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and other fine-grained fossil debris in a matrix of
780:
UK Lowland calcareous grassland habitat action plan
317:leading to the formation of structures such as the
650:
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138:. To the northeast, downlands continue along the
738:. Cambridge University Press. pp. 153–154.
832:Salisbury Plain & West Wiltshire Downs AONB
190:. To the southeast the downlands continue into
629:Deformation of Sediments and Sedimentary Rocks
467:, and the consequent absence of soil-building
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305:during the Triassic to Early Cretaceous were
8:
759:South Downs National Park Authority (2020).
581:. Oxford University Press. pp. 27–49.
170:. To the east downlands are found north of
114:. To the southwest, downlands continue via
706:Proceedings of the Geologists' Association
25:
556:
792:South Downs Virtual Information Centre
7:
407:, and seasonally-flowing streams or
736:The Periglaciation of Great Britain
102:Downland areas in southern England
14:
228:The Chalk Group is a sequence of
797:South Downs information gateway
852:Mountains and hills of England
505:, formed by grazing from both
289:by the distant effects of the
1:
718:10.1016/j.pgeola.2011.09.007
607:Online Etymology Dictionary
878:
221:
21:The Downs (ship anchorage)
18:
272:Upper Greensand Formation
323:Portland-Wight Monocline
259:and accumulated to form
210:where they are known as
16:Area of open chalk hills
802:North Wessex Downs AONB
577:. In Thirsk, J. (ed.).
126:and southwards through
498:
360:
274:above the Gault Clay.
103:
41:
734:; Harris, C. (1994).
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385:White Cliffs of Dover
358:Belle Tout Lighthouse
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255:, which moved during
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503:calcareous grassland
573:Bettey, J. (2002).
425:Vale of White Horse
243:, with microscopic
817:Isle of Wight AONB
697:Hopson P. (2011).
545:North Wessex Downs
499:
383:form, such as the
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299:Sedimentary basins
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59:are areas of open
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812:Surrey Hills AONB
465:calcium carbonate
421:White Horse Hills
319:Wealden Anticline
146:through parts of
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230:Upper Cretaceous
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235:. The dominant
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156:Buckinghamshire
140:Berkshire Downs
132:Hampshire Downs
116:Cranborne Chase
108:Salisbury Plain
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786:External links
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712:(5): 745–763.
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575:"1. Downlands"
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291:Alpine Orogeny
222:Main article:
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186:, forming the
184:Greater London
168:Cambridgeshire
144:Chiltern Hills
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540:List of downs
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764:. Retrieved
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610:. Retrieved
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528:biodiversity
515:horticulture
500:
495:Galium verum
494:
473:
441:soil profile
438:
423:, above the
413:
398:
362:
331:last ice age
276:
227:
204:Lincolnshire
182:and part of
164:Bedfordshire
124:Dorset Downs
110:, mainly in
105:
94:Distribution
56:
52:
48:
44:
43:
31:Devil's Dyke
822:Dorset AONB
511:agriculture
476:terracettes
401:water table
389:Beachy Head
356:cliffs and
354:Beachy Head
335:periglacial
224:Chalk Group
200:South Downs
196:East Sussex
192:West Sussex
188:North Downs
152:Oxfordshire
68:North Downs
53:chalk downs
39:South Downs
841:Categories
766:10 October
551:References
480:soil creep
416:springline
369:Cretaceous
327:Quaternary
301:formed by
268:Gault Clay
257:diagenesis
245:coccoliths
241:biomicrite
233:limestones
35:dry valley
684:140713528
612:9 October
507:livestock
395:Hydrology
345:Formation
311:Paleogene
283:fractured
237:lithology
212:the Wolds
208:Yorkshire
172:the Weald
166:and into
148:Berkshire
134:onto the
128:Hampshire
112:Wiltshire
88:hillforts
84:"burough"
49:chalkland
862:Prairies
857:Plateaus
534:See also
452:rendzina
429:dewponds
339:snowmelt
333:. These
321:and the
307:inverted
76:fastness
55:or just
45:Downland
486:Habitat
405:coombes
315:Miocene
303:rifting
295:aquifer
279:faulted
249:micrite
218:Geology
198:as the
130:as the
122:as the
72:England
37:in the
742:
682:
672:
635:
603:"down"
585:
524:Dorset
445:parent
381:cliffs
365:erodes
287:folded
261:flints
176:Surrey
120:Dorset
80:"burg"
847:Hills
702:(PDF)
680:S2CID
519:scrub
460:humus
448:chalk
373:scarp
118:into
64:hills
61:chalk
57:downs
768:2020
740:ISBN
670:ISBN
633:ISBN
614:2020
583:ISBN
469:clay
439:The
435:Soil
387:and
285:and
206:and
194:and
180:Kent
142:and
33:, a
714:doi
710:122
662:doi
377:dip
313:to
174:in
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708:.
704:.
678:.
668:.
647:^
605:.
559:^
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513:,
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341:.
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82:/
23:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
