Editing Grantham (section)

===Topography and geology===
The town lies in the [[valley]] of the [[River Witham]], its core at the Witham's confluence with the Mowbeck (or Mow Beck).<ref name="Lane2011-9">{{Harvnb |Lane |2011 |p=9}}.</ref> The Witham flows south–north through Grantham.<ref>{{Harvnb |White |1979 |pp=1–2}}.</ref> The Mowbeck, which rises from springs at Harlaxton about {{convert|3|mi|km}} to the south-west of the town,<ref>[https://www.google.com/maps/dir/52.8859015,-0.6823101/Grantham/@52.8888804,-0.6827709,1483m/data=!3m1!1e3!4m9!4m8!1m0!1m5!1m1!1s0x487820d7b8e18acd:0xec445ad0df69f289!2m2!1d-0.643582!2d52.912524!3e2 "Harlaxton to Grantham"], ''[[Google Maps]]''. Retrieved 14 December 2020.</ref> is [[culvert]]ed behind Westgate and Brook Street<ref name="Lane2011-9"/> until it joins the Witham at White Bridge.<ref>[https://www.granthammatters.co.uk/grantham-underground/ "Grantham Underground"], ''Grantham Matters'', 21 March 2019. Retrieved 14 December 2020.</ref>

The floor of the Witham valley – 50–60 m above [[sea level]] in the town centre – is underlain by [[mudstone]] of the [[Charmouth Mudstone Formation|Charmouth formation]] of the [[Lower Jurassic]] period (199–183 million years ago). This formation is overlain by Belton sand and gravel laid down in estuaries and rivers in the [[Quaternary|Quaternary period]] up to 3 million years ago. The river courses are overlain by Quaternary [[alluvium]] and to the north by [[Fluvial terrace|river terrace]] deposits.<ref name="BGS">[http://mapapps.bgs.ac.uk/geologyofbritain3d/ "Geology of Britain 3D"] {{Webarchive|url=https://web.archive.org/web/20200523052912/http://mapapps.bgs.ac.uk/geologyofbritain3d/ |date=23 May 2020 }} ([[British Geological Survey]]). Retrieved 14 December 2020.</ref> The [[soil]] around the route of the Witham is wet, acidic, sandy and loamy; its fertility is poor.<ref name="soilscapes">[http://www.landis.org.uk/soilscapes/ "Soilscapes Map"], Landis.org.uk. Retrieved 14 December 2020.</ref>

As the ground rises on the town's eastern and southern fringes, it is underlain by Jurassic [[Marl]]stone rocks of ferruginous [[sandstone]] and [[ironstone]] formed 190–174 million years ago, and then by [[Whitby Mudstone]] of 174–183 million years ago. The land rises sharply to form the [[Lincoln Cliff]] that marks the edge of the urban area and start of the [[Lincoln Heath]] and Kesteven Uplands, which are capped by Jurassic [[Oolite|Oolitic Limestone]],<ref name="BGS"/><ref name=":6">{{Harvnb |Robinson |2001 |pp=8–9}}.</ref><ref>{{Harvnb |South Kesteven District Council |2007 |pp=37, 44}}.</ref> mostly overlain by shallow, free-draining, [[Lime (material)|lime]]-rich soils.<ref name="soilscapes"/>

To the west, the town is near the edge of the low-lying [[Vale of Belvoir]]<ref>{{Harvnb |Measom |1861 |p=145}}.</ref> but fringed by an [[escarpment]]<ref>{{Harvnb |Robinson |2001 |p=9}}.</ref> rising in places to over 100 m to form the hills on which sit Barrowby, Great Gonerby, the Green Hill and Earlesfield suburban areas and the business parks off Trent Road. These hills are of siltstone and mudstone of the Jurassic [[Dyrham Formation]], which line the edges of the Witham and Mowbeck valleys and the shallow valley of [[Barrowby Stream]]. At its highest the scarp is capped by Jurassic ferruginous sandstone and ironstone rocks of the Marlstone formation. There are some [[Head (geology)|head deposits]] and [[pleistocene]] [[glaciofluvial]] deposits of sand and gravel east of Barrowby.<ref name="BGS"/> The soil in the lower areas is slowly [[Permeability (Earth sciences)|permeable]], seasonally wet and slightly acidic, though [[Base-richness|base-rich]]. On higher ground it tends to be slightly acidic and base-rich, but freely draining and highly fertile.<ref name="soilscapes"/>

[[Grantham Canal]], which opened in 1797,<ref>[http://www.granthamcanal.org/history/ "History"], ''Grantham Canal Society''. Retrieved 14 December 2020.</ref> closely follows the route of the Mowbeck from Echo Farm into the town. West of there it cuts through a valley north of Harlaxton into the Vale of Belvoir, eventually reaching [[West Bridgford]] near [[Nottingham]].<ref name="bing">[https://www.bing.com/maps/?v=2&cp=52.752459~-0.69762&style=r&lvl=11&sp=Point.52.752459_-0.69762_River%20Witham___ "Grantham"], ''[[Bing Maps]]''. Retrieved 14 December 2020. Toggle the [[Ordnance Survey]] layer for contours.</ref>