Editing Canadian Shield (section)

== Geographical extent ==
The Canadian Shield is a [[Physiographic region|physiographic division]] comprising four smaller physiographic provinces: the [[Laurentian Upland]], [[Kazan Region]], Davis and James.<ref name=ca-atlas>{{Cite web| author-link =Atlas of Canada |title=Physiographic Regions Map|author=The Atlas of Canada |date=12 September 2016|publisher=Natural Resources Canada |url=https://atlas.gc.ca/phys/en/ |access-date=2019-11-15 }}</ref> The shield extends into the United States as the [[Adirondack Mountains]] (connected by the [[Frontenac Axis]]) and the [[Laurentian Upland#Superior Upland|Superior Upland]]. The Canadian Shield is a U-shaped subsection of the Laurentia [[craton]] signifying the area of greatest [[glacial]] impact (scraping down to bare rock) creating the thin soils. The age of the Canadian Shield is estimated to be 4.28 [[Gigaannus|Ga]] (4.28 billion years). The Canadian Shield once had jagged peaks, higher than any of today's mountains, but millions of years of erosion have changed these mountains to rolling hills.<ref name="Canadian Shield">{{cite web |author1=Alexander Murray |author2=Harrisson Panabaker |author3=Holy O'Rourke |author4=David Barrett |title=Canadian Shield |url=https://www.thecanadianencyclopedia.ca/en/article/shield |publisher=The Canadian Encyclopedia |access-date=29 May 2024 |date=7 February 2006 |quote=Formed over 3 billion years through processes such as plate tectonics, erosion and glaciation}}</ref>

The Canadian Shield is a collage of [[Archean]] plates and accreted juvenile arc [[terrane]]s and [[sedimentary basin]]s of the [[Proterozoic]] Eon that were progressively amalgamated during the interval 2.45–1.24 Ga, with the most substantial growth period occurring during the [[Trans-Hudson orogeny]], between c. 1.90–1.80 Ga.<ref name=Corrigan>{{cite web |author=Corrigan, D. |year=2008 |title=Metallogeny and Tectonic Evolution of the Trans-Hudson Orogen |url=http://www.pdac.ca/pdac/conv/2008/pdf-tech-session/ts-corrigan.pdf | access-date =2008-03-05 |archive-url = https://web.archive.org/web/20080409105436/http://www.pdac.ca/pdac/conv/2008/pdf-tech-session/ts-corrigan.pdf |archive-date = April 9, 2008}}</ref> The Canadian Shield was the first part of North America to be permanently elevated above sea level and has remained almost wholly untouched by successive encroachments of the sea upon the continent. It is the Earth's greatest area of exposed Archean rock. The metamorphic base rocks are mostly from the Precambrian (between 4.5 Ga and 540 Ma) and have been repeatedly uplifted and eroded. Today it consists largely of an area of low relief {{convert|300|–|610|m|ft|abbr=on}} above sea level with a few [[monadnock]]s and low mountain ranges (including the [[Laurentian Mountains]]) probably eroded from the plateau during the [[Cenozoic]] Era. During the [[Pleistocene]] Epoch, continental ice sheets depressed the land surface (creating [[Hudson Bay]]) but also tilted up its northeastern "rim" (the [[Torngat Mountains|Torngat]]), scooped out thousands of lake basins, and carried away much of the region's soil. The northeastern portion, however, became tilted up so that, in northern [[Labrador]] and [[Baffin Island]], the land rises to more than 1,500 metres (5,000 feet) above sea level.

When the [[Greenland]] section is included, the Canadian Shield is approximately circular, bounded on the northeast by the northeast edge of Greenland, with Hudson Bay in the middle. It covers much of Greenland, all of Labrador and the [[Great Northern Peninsula]] of [[Newfoundland (island)|Newfoundland]], most of [[Quebec]] north of the [[St. Lawrence River]], much of [[Ontario]] including northern sections of the [[Ontario Peninsula]], the Adirondack Mountains<ref>Peterson Field Guide to Geology of Eastern North America by Roberts, David & Roger Tory Peterson.</ref> of [[New York (state)|New York]], the northernmost part of [[Lower Peninsula of Michigan|Lower Michigan]] and all of [[Upper Peninsula of Michigan|Upper Michigan]], northern [[Wisconsin]], northeastern [[Minnesota]], the central and northern portions of [[Manitoba]], northern [[Saskatchewan]], a small portion of northeastern [[Alberta]],<ref>[http://www.abheritage.ca/abnature/shield/shield.htm Alberta Heritage - Alberta Online Encyclopedia] {{webarchive|url=https://wayback.archive-it.org/2217/20101208161019/http://www.abheritage.ca/abnature/shield/shield.htm |date=2010-12-08 }} - The Canadian Shield Region of Alberta</ref> mainland [[Northwest Territories]] to the east of a line extended north from the Saskatchewan-Alberta border, most of [[Nunavut|Nunavut's]] mainland and, of its [[Arctic Archipelago]], Baffin Island and significant bands through [[Somerset Island (Nunavut)|Somerset]], [[Southampton Island|Southampton]], [[Devon Island|Devon]] and [[Ellesmere Island|Ellesmere]] islands.<ref name=britannica>{{Cite encyclopedia|url=https://www.britannica.com/place/Canadian-Shield|encyclopedia=[[Encyclopædia Britannica]] |title=Canadian Shield|access-date=2009-02-10|url-status=live|archive-url=https://web.archive.org/web/20150624232123/https://www.britannica.com/place/Canadian-Shield|archive-date=2015-06-24}}</ref> In total, the exposed area of the shield covers approximately {{convert|8000000|km2|mi2|abbr=on}}. The true extent of the shield is greater still and stretches from the [[North American Cordillera|Western Cordillera]] in the west to the [[Appalachian Mountains|Appalachians]] in the east and as far south as [[Texas]], but these regions are overlaid with much younger rocks and sediment.{{wide image|Flin Flon Wilderness and Outcrop.jpg|1000px|Panorama of Canadian Shield geography in the [[Flin Flon]], [[Manitoba]], region. Big Island Lake is in the background.}}