Editing British Isles (section)

==Geography==
{{See also|Geography of England|Geography of Wales|Geography of Scotland|Geography of Ireland|Geography of the United Kingdom|Geography of the Isle of Man|Geography of the Channel Islands}}

[[File:British-Isles-NW-European-shelf.png|thumb|alt=An image showing the geological shelf of the British Isles.|The British Isles in relation to the north-west [[Geography of Europe|European]] [[continental shelf]]]]

The British Isles lie at the juncture of several regions with past episodes of tectonic mountain building. These [[Orogeny|orogenic belts]] form a complex geology that records a huge and varied span of Earth's history.<ref>{{Cite book| last=Goudie| first=Andrew S.|author2=D. Brunsden| title=The Environment of the British Isles, an Atlas| year=1994| publisher=Clarendon Press| location=Oxford| page=2}}</ref> Of particular note was the [[Caledonian orogeny]] during the [[Ordovician]] and [[Llandovery epoch|early Silurian]] periods, when the [[craton]] [[Baltica]] collided with the [[terrane]] [[Avalonia]] to form the mountains and hills in northern Britain and Ireland. Baltica formed roughly the north-western half of Ireland and Scotland. Further collisions caused the [[Variscan orogeny]] in the [[Devonian]] and [[Carboniferous]] periods, forming the hills of [[Munster]], south-west England, and southern Wales. Over the last 500&nbsp;million years the land that forms the islands has drifted north-west from around 30°S, crossing the [[equator]] around 370&nbsp;million years ago to reach its present northern latitude.<ref><!--Goudie, ''The Environment of the British Isles, an Atlas''-->Ibid., p. 5.</ref>

The islands have been shaped by numerous glaciations during the [[Quaternary Period]], the most recent being the [[Devensian]].<ref>{{cite journal |last1=Jacobi |first1=Roger |last2=Higham |first2=Tom |title=12 - The Later Upper Palaeolithic Recolonisation of Britain: New Results from AMS Radiocarbon Dating |doi=10.1016/b978-0-444-53597-9.00012-1 |publisher=Elsevier |journal=Developments in Quaternary Sciences}}</ref><ref>{{cite book |last1=Bradley |first1=Raymond S. |title=Paleoclimatology |chapter=Insects and Other Biological Evidence from Continental Regions |edition=Third |date=2015 |pages=377–404 |doi=10.1016/b978-0-12-386913-5.00011-9 |publisher=Academic Press |isbn=9780123869135}}</ref> As this ended, the central [[Irish Sea]] was deglaciated and the English Channel flooded, with sea levels rising to current levels some 8,000 years ago, leaving the British Isles in their current form.

There are about [[List of the British Isles by area|136 permanently inhabited islands]] in the group, the largest two being Great Britain and Ireland. Great Britain is to the east and covers {{convert|83,700|sqmi|km2|abbr=on}}.<ref name="Calder-1995">{{cite web |last=Calder |first=Joshua |title=100 Largest Islands of the World |url=http://www.worldislandinfo.com/LARGESTV1.html |website=WorldIslandInfo.com}}</ref> Ireland is to the west and covers {{convert|32,590|sqmi|km2|abbr=on}}.<ref name="Calder-1995"/> The largest of the other islands are to be found in the [[Hebrides]], [[Orkney]] and [[Shetland]] to the north, [[Anglesey]] and the Isle of Man between Great Britain and Ireland, and the [[Channel Islands]] near the coast of France. The most densely populated island is [[Portsea Island]], which has an area of {{convert|9.5|mi2|km2|abbr=on}}<ref>{{Cite book |last=Naldrett |first=Peter |url=https://www.worldcat.org/oclc/1257549460 |title=Treasured Islands: The Explorer's Guide to Over 200 of the Most Beautiful and Intriguing Islands Around Britain  |date=2021 |publisher=Conway |isbn=978-1-84486-593-2 |location=[S.l.] |oclc=1257549460}}</ref> but has the third highest population behind Great Britain and Ireland.<ref>{{Cite web|date=11 November 2019|title=These are Britain's biggest islands|url=https://www.independent.co.uk/travel/news-and-advice/britain-islands-biggest-uk-coastline-lewis-harris-portsea-isle-wight-skye-anglesey-a9197726.html|access-date=9 September 2021|website=The Independent}}</ref>

The islands are at relatively low altitudes, with central Ireland and southern Great Britain particularly low-lying: the lowest point in the islands is the [[North Slob]] in [[County Wexford]], Ireland, with an elevation of {{convert|-3.0|m|feet}}. The [[Scottish Highlands]] in the northern part of Great Britain are mountainous, with [[Ben Nevis]] being the highest point on the islands at {{convert|1345|m|0|abbr=on}}.<ref name="Ordnance Survey Blog-2016" /> Other mountainous areas include Wales and parts of Ireland, although only seven peaks in these areas reach above {{convert|1000|m|0|abbr=on}}. Lakes on the islands are generally not large, although [[Lough Neagh]] in Northern Ireland is an exception, covering {{Convert|150|sqmi|km2}}.{{citation needed|date=January 2012}} The largest freshwater body in Great Britain (by area) is [[Loch Lomond]] at {{convert|27.5|sqmi|km2|0}}, and [[Loch Ness]] (by volume) whilst [[Loch Morar]] is the deepest freshwater body in the British Isles, with a maximum depth of {{convert|1017|ft|abbr=on|order=flip}}.<ref name="Gazetteerfor Scotland,Morar">[http://www.scottish-places.info/features/featurefirst2408.html Gazetteer for Scotland] Morar, Loch.</ref> There are a number of major rivers within the British Isles. The longest is the [[River Shannon|Shannon]] in Ireland at {{convert|224|mi|0|abbr=on}}.<ref>[http://www.osi.ie/Education/Secondary-Schools/Teacher-Resources/Facts-%281%29.aspx Ordnance Survey (Ireland) Educational Facts].</ref><ref>{{cite web |url=https://www.britannica.com/place/River-Shannon |title=River Shannon |last=Ray |first=Michael |website=Encyclopædia Britannica |publisher=Encyclopædia Britannica, inc. |access-date=11 February 2020 |quote="about 161 miles (259 km) in a southerly direction to enter the Atlantic Ocean via a 70-mile (113-kilometre) estuary below Limerick city"}}</ref> The [[river Severn]] at {{convert|220|mi|0|abbr=on}}<ref>{{cite web |url=https://www.britannica.com/place/River-Severn |title=River Severn |last=Wallenfeldt |first=Jeff |website=Encyclopædia Britannica |publisher=Encyclopædia Britannica, inc. |access-date=11 February 2020 |quote=about 180 miles (290&nbsp;km) long, with the Severn estuary adding some 40 miles (64&nbsp;km) to its total length}}</ref> is the longest in Great Britain.

===Climate===
The [[climate of the British Isles]] is mild,<ref>{{Cite web |url=https://www.bgs.ac.uk/discoveringGeology/geologyOfBritain/iceAge/home.html |title=Ice and our landscape {{!}} Geology of Britain {{!}} British Geological Survey (BGS)|website=www.bgs.ac.uk |access-date=19 November 2019}}</ref> moist and changeable with abundant rainfall and a lack of temperature extremes. It is defined as a temperate oceanic climate, or ''Cfb'' on the [[Köppen climate classification]] system, a classification it shares with most of north-west Europe.<ref>{{cite journal |author1=Peel, M. C. |author2=Finlayson B. L. |author3=McMahon, T. A. |year=2007 |title= Updated world map of the Köppen&ndash;Geiger climate classification | journal=Hydrol. Earth Syst. Sci. |volume=11 |issue=5 |pages=1633–1644 |url=http://www.hydrol-earth-syst-sci.net/11/1633/2007/hess-11-1633-2007.html |issn=1027-5606 |doi=10.5194/hess-11-1633-2007 |bibcode=2007HESS...11.1633P |doi-access=free}} ''(direct: [http://www.hydrol-earth-syst-sci.net/11/1633/2007/hess-11-1633-2007.pdf Final Revised Paper])''.</ref><ref>{{cite web|url=http://www.met.ie/marine/marine_climatology.asp|title=Marine Climatology|publisher=Met Éireann|access-date=30 January 2008}}</ref> The [[North Atlantic Current|North Atlantic Drift]] ("Gulf Stream"), which flows from the Gulf of Mexico, brings with it significant moisture and raises temperatures {{convert|11|C-change||abbr=on}} above the global average for the islands' latitudes.<ref>{{Cite book |last=Mayes |first=Julian |author2=Dennis Wheeler |title=Regional Climates of the British Isles |url=https://archive.org/details/regionalclimates00whee |url-access=limited |year=1997 |publisher=Routledge |location=London |page=[https://archive.org/details/regionalclimates00whee/page/n36 13]}}</ref> Most Atlantic [[Low-pressure area|depressions]] pass to the north of the islands; combined with the general [[Westerlies|westerly circulation]] and interactions with the landmass, this imposes a general east–west variation in climate.<ref><!--Mayes, ''Regional Climates of the British Isles''-->Ibid., pp. 13–14.</ref> There are four distinct climate patterns: south-east, with cold winters, warm and dry summers; south-west, having mild and very wet winters, warm and wet summers; north-west, generally wet with mild winters and cool summers; and north-east with cold winters, cool summers.<ref>{{Cite web |title=UK Climate Factsheet |url=https://www.rgs.org/CMSPages/GetFile.aspx?nodeguid=4abef83d-916e-4b81-b156-286947cc5de3&lang=en-GB |website= |publisher=[[Royal Geographical Society]] |type=PDF}}</ref><ref>{{Cite web |title=The climate of the UK |url=https://www.bbc.co.uk/bitesize/guides/zpykxsg/revision/3 |access-date=19 November 2019 |website=[[BBC Bitesize]]}}</ref>