Editing Wiltshire (section)

==Geology, landscape and ecology==
{{See also|List of hills of Wiltshire|List of rivers of Wiltshire}}
[[File:Cherhillwhitehorse.jpg|left|thumb|[[Cherhill White Horse]], east of Calne ]]

Two-thirds of Wiltshire, a mostly [[Rural area|rural]] county, lies on [[chalk]], a kind of soft, white, porous limestone that is resistant to erosion, giving it a high [[downland|chalk downland]] landscape. This chalk is part of a system of chalk downlands throughout eastern and southern England formed by the rocks of the [[Chalk Group]] and stretching from the [[Dorset Downs]] in the west to [[Dover]] in the east. The largest area of chalk in Wiltshire is [[Salisbury Plain]], which is used mainly for [[agronomy|arable]] agriculture and by the [[British Army]] as training ranges. The highest point in the county is the [[Tan Hill, Wiltshire|Tan Hill]]–[[Milk Hill]] ridge in the [[Vale of Pewsey|Pewsey Vale]], just to the north of Salisbury Plain, at {{cvt|295|m}} above sea level.<ref>{{cite book |last=Bathurst |first=David |year=2012 |title=Walking the county high points of England |location=Chichester |publisher=Summersdale |isbn=978-1-84-953239-6 |pages=138–147}}</ref>

The chalk uplands run north-east into [[West Berkshire]] in the [[Marlborough Downs]] ridge, and south-west into Dorset as [[Cranborne Chase]]. Cranborne Chase, which straddles the border, has, like Salisbury Plain, yielded much Stone Age and Bronze Age [[archaeology]]. The Marlborough Downs are part of the [[North Wessex Downs AONB]] (Area of Outstanding Natural Beauty), a {{convert|1730|sqkm|abbr=in|adj=on}} conservation area.

In the north-west of the county, on the border with [[South Gloucestershire]] and [[Bath and North East Somerset]], the underlying rock is the resistant [[oolite]] [[limestone]] of the [[Cotswolds]]. Part of the Cotswolds AONB is also in Wiltshire, in the county's north-western corner.

Between the areas of chalk and limestone downland are [[clay]] [[valley]]s and [[River valley|vale]]s. The largest of these vales is the [[River Avon, Bristol|Avon Vale]]. The Avon cuts diagonally through the north of the county, flowing through [[Bradford-on-Avon]] and into [[Bath, Somerset|Bath]] and [[Bristol]]. The Vale of Pewsey has been cut through the chalk into [[Greensand]] and [[Oxford Clay]] in the centre of the county. In the south west of the county is the [[Vale of Wardour]]. The south-east of the county lies on the sandy soils of the northernmost area of the [[New Forest]].

Chalk is a [[porous]] rock, so the chalk hills have little surface water. The main settlements in the county are therefore situated at wet points. Notably, Salisbury is situated between the chalk of Salisbury Plain and marshy flood plains.

=== Green belt ===
{{main|Avon Green Belt}}
The county has a [[Green belt (United Kingdom)|green belt]] mainly along its western fringes as a part of the extensive [[Avon Green Belt]]. It reaches as far as the outskirts of Rudloe/[[Corsham]] and Trowbridge, preventing [[urban sprawl]] particularly from the latter in the direction of [[Bradford-on-Avon]], and affording further protection to surrounding villages and towns from Bath in Somerset.