Editing Geography of Ireland (section)

==Geological development==
{{Main article|Geology of Ireland}}
[[File:SlieveLeague1.jpg|thumb|[[Slieve League]] in western [[Banagh]]|alt=See caption]]
The geology of Ireland is diverse. Different regions contain rocks belonging to different geological periods, dating back almost 2 billion years. The oldest known Irish [[Rock (geology)|rock]] is about 1.7 billion years old and is found on [[Inishtrahull Island]] off the north coast of [[Inishowen]]<ref>{{cite web|title=Site Synopsis (Inishtrahull) |publisher=National Parks and Wildlife Service |url=http://www.npws.ie/en/media/Media,3875,en.pdf |access-date=30 January 2008 |archive-url=https://web.archive.org/web/20090327121447/http://www.npws.ie/en/media/Media%2C3875%2Cen.pdf |archive-date=27 March 2009 |url-status=dead }}</ref><ref>{{cite book |title=Geological History of Britain and Ireland |last=Woodcock |first=N. H. |year=2000 |publisher=Blackwell Publishing |isbn=978-0-632-03656-1 |page=57 |url=https://books.google.com/books?id=dTkKn8Ufzd4C |access-date=16 October 2015 |archive-date=1 May 2023 |archive-url=https://web.archive.org/web/20230501044017/https://books.google.com/books?id=dTkKn8Ufzd4C |url-status=live }}</ref> and on the mainland at Annagh Head on the [[Mullet Peninsula]].<ref>{{Cite journal |last=Daly |first=J. Stephen |title=Pre-Caledonian History of the Annagh Gneiss Complex North-Western Ireland, and Correlation with Laurentia-Baltica |journal=Irish Journal of Earth Sciences |volume=15 |pages=5–18 |publisher=[[Royal Irish Academy]] |location=Dublin |year=1996 |jstor=30002311}}</ref> The newer formations are the [[drumlin]]s and glacial valleys as a result of the last ice age, and the sinkholes and cave formations in the limestone regions of Clare.<ref>{{cite book |title=Geology and Environment in Britain and Ireland |last=Woodcock |first=N. H. |year=1994 |publisher=CRC Press |isbn=978-1-85728-054-8 |page=13 }}</ref><ref>{{cite book |title=A New History of Ireland |last=Moody |first=Theodore William |author2=Francis John Byrne |author3=Francis X Martin |author4=Art Cosgrove |year=2005 |publisher=Oxford University Press |isbn=978-0-19-821737-4 |page=37 |url=https://books.google.com/books?id=SJSDj1dDvNUC |access-date=16 October 2015 |archive-date=1 May 2023 |archive-url=https://web.archive.org/web/20230501044027/https://books.google.com/books?id=SJSDj1dDvNUC |url-status=live }}</ref>

Ireland's geological history includes a wide range of elements, from [[volcanism]] and tropical seas to the [[last glacial period]]. Ireland was formed in two distinct parts, which slowly joined, [[Iapetus Suture|uniting]] about 440 million years ago. As a result of tectonics and the effect of ice, the sea level has risen and fallen. In every area of the country, the rocks which formed can be seen as a result. Finally, the impact of the glaciers shaped the landscape seen today.<ref>{{cite book | last = Foster | first = John Wilson |author2=Helena C. G. Chesney | title = Nature in Ireland: A Scientific and Cultural History | publisher = McGill-Queen's Press | year = 1998 | page = 16 | url = https://books.google.com/books?id=SG8sbdTzUdgC&q=esker+riada | isbn = 978-0-7735-1817-9 }}</ref> The variation between the two areas, along with the differences between volcanic areas and shallow seas, led to a range of soils. There are extensive [[bog]]s and free-draining brown earths. The mountains are [[granite]], [[sandstone]], [[limestone]] with [[karst]] areas, and [[basalt]] formations.<ref>{{cite web |title=Bog of Allen |work=Ask About Ireland |publisher=[[Department of the Environment, Community and Local Government]] |url=http://www.askaboutireland.ie/enfo/irelands-environment/county-focus/kildare/bog-of-allen/ |access-date=22 November 2013 |archive-date=4 June 2013 |archive-url=https://web.archive.org/web/20130604061826/http://www.askaboutireland.ie/enfo/irelands-environment/county-focus/kildare/bog-of-allen/ |url-status=live }}</ref><ref>{{cite web | title = Giant's Causeway and Causeway Coast | publisher = [[World Heritage Site|Unesco World Heritage Sites]] | url = https://whc.unesco.org/en/list/369 | access-date = 23 January 2008 | archive-date = 19 January 2008 | archive-url = https://web.archive.org/web/20080119193930/http://whc.unesco.org/en/list/369 | url-status = live }}</ref><ref>[https://archive.today/20110813062050/http://www3.interscience.wiley.com/cgi-bin/abstract/61005289/ABSTRACT Brittle tectonism in relation to the Palaeogene evolution of the Thulean/NE Atlantic domain: a study in Ulster] (Subscription required) Retrieved on 10 November 2007</ref><ref>{{cite news |last=Deegan |first=Gordon |title=Blasting threatens future of stalactite |newspaper=[[Irish Examiner]] |date=27 May 1999 |url=http://archives.tcm.ie/irishexaminer/1999/05/27/ihead.htm |access-date=23 January 2008 |archive-url=https://web.archive.org/web/20110629130315/http://archives.tcm.ie/irishexaminer/1999/05/27/ihead.htm |archive-date=2011-06-29 }}</ref>

Most of Ireland was probably above sea level during the [[Cenozoic|last 60 million years]]. As such its landscapes have been shaped by [[erosion]] and [[weathering]] on land.<ref name="SimmsCoxon" /> Protracted erosion also means most of the [[Paleogene]] and [[Neogene]] sediments have been eroded away or, as known in a few cases, buried by [[Quaternary]] deposits.<ref name="Mitchell1980">{{cite journal |last1=Mitchell |first1=G.F. |date=1980 |title=The search for Tertiary Ireland |journal=Journal of Earth Sciences Royal Dublin Society |volume=3 |pages=13–33 }}</ref> Before the [[Quaternary glaciation]]s affected Ireland the landscape had developed thick weathered [[regolith]] on the uplands and karst in the lowlands.<ref name="SimmsCoxon" /> There has been some controversy regarding the origin of the [[planation surface]]s found in Ireland.<ref name="Mitchell1980" /><ref>{{cite journal |last1=Miller |first1=A.A. |date=1955 |title=The origin of the South Ireland Peneplane |journal=Irish Geography |volume=3 |issue=2 |pages=79–86 |doi= 10.1080/00750775509555491}}</ref> While some have argued for an origin in marine planation, others regard these surfaces as [[peneplain]]s formed by weathering and [[cycle of erosion|fluvial erosion]]. Not only is their origin disputed but also their actual extent and the relative role of [[eustacy|sea-level change]] and tectonics in their shaping.<ref name="Mitchell1980" /> Most river systems in Ireland formed in the Cenozoic before the Quaternary glaciations. Rivers follow for most of their course [[structural geology|structural]] features of the [[geology of Ireland]]. Marine erosion since the [[Miocene]] may have made Ireland's western coast retreat more than 100&nbsp;km. Pre-Quaternary relief was more dramatic than today's [[glacial erosion|glacier-smoothened]] landscapes.<ref name="SimmsCoxon">{{cite book |last1=Simms |first1=Michael J.|last2=Coxon|first2=Peter |date=2017|chapter=The Pre-Quaternary Landscape of Ireland |title=Advances in Irish Quaternary Studies|editor-last=Coxon|editor-first=Peter|editor-last2=McCarron|editor-first2=Stephen|editor-last3=Mitchell|editor-first3=Fraser |publisher=Atlantis Press |pages=19–42 |series=Atlantis Advances in Quaternary Science|isbn=978-94-6239-219-9 }}</ref>