Editing St. Lawrence River (section)

===Watershed===
With the draining of the [[Champlain Sea]], due to a rebounding continent from the [[Last Glacial Maximum]], the St. Lawrence River was formed. The Champlain Sea lasted from about 13,000 years ago to about 10,000 years ago and was continuously shrinking during that time, a process that continues today.<ref>[http://www.lcbp.org/Atlas/HTML/nat_geology.htm Lake Champlain Basin Atlas: Geology Page] {{webarchive |url=https://web.archive.org/web/20080720120640/http://www.lcbp.org/Atlas/HTML/nat_geology.htm |date=20 July 2008 }}</ref><ref name="Miller2015">{{cite book|first=William J.|last=Miller|title=Geology: The Science of the Earth's Crust (Illustrations)|url=https://books.google.com/books?id=XwWYBwAAQBAJ&pg=PT37|year=2015|publisher=P. F. Collier & Son Company|page=37|id=GGKEY:Y3TD08H3RAT}}</ref> The head of the St. Lawrence River, near [[Lake Ontario]], is home to the [[Thousand Islands]].<ref>{{Cite web |title=St. Lawrence River Ecosystem |url=https://www.savetheriver.org/river-info/ecosystem/ |access-date=2023-02-09 |website=Save The River! Thousand Islands - Clayton NY on the St. Lawrence River |language=en}}</ref>

Today, the St. Lawrence River begins at the outflow of Lake Ontario and flows adjacent to [[Cape Vincent (village), New York|Cape Vincent]], [[Gananoque, Ontario|Gananoque]], [[Clayton, New York|Clayton]], [[Alexandria Bay, New York|Alexandria Bay]], [[Brockville]], [[Morristown, New York|Morristown]], [[Ogdensburg, New York|Ogdensburg]], [[Massena (village), New York|Massena]], [[Cornwall, Ontario|Cornwall]], [[Montreal]], [[Trois-Rivières]], and [[Quebec City]] before draining into the [[Gulf of St. Lawrence]], often given as the largest [[estuary]] in the world.<ref>{{Cite web |title=Estuary - National Geographic Society |url=https://education.nationalgeographic.org/resource/estuary |access-date=2022-08-16 |website=nationalgeographic.org}}</ref> The estuary begins at the eastern tip of [[Île d'Orléans]], just downstream from Quebec City.<ref name="BenkeCushing2005">{{cite book|last1=Benke|first1=Arthur C.|last2=Cushing|first2=Colbert E.|title=Rivers of North America|url=https://books.google.com/books?id=faOU1wkiYFIC&pg=PA989|year=2005|publisher=Academic Press|isbn=978-0-12-088253-3|pages=989–990}}</ref> The river becomes [[tide|tidal]] around Quebec City.<ref name="Dawson2007">{{cite book|last=Dawson|first=Samuel Edward|title=The Saint Lawrence: Its Basin and Border-lands|url=https://books.google.com/books?id=r-LZjcqnPtEC&pg=PR36|access-date=21 March 2011|date=October 2007|publisher=Heritage Books|isbn=978-0-7884-2252-2|page=36}}</ref>

The St. Lawrence River runs {{convert|3058|km|mi|sigfig=4|lk=on}} from the farthest headwater to the mouth and {{convert|1197|km|mi|1|abbr=on}} from the outflow of Lake Ontario. These numbers include the estuary; without the estuary, the length from Lake Ontario is c. 500&nbsp;km (c. 300&nbsp;mi). The farthest headwater is the [[North River (Minnesota)|North River]] in the [[Mesabi Range]] at [[Hibbing]], Minnesota. Its drainage area, which includes the Great Lakes, the world's largest system of freshwater lakes, is {{convert|1344200|km2|sqmi|1|sigfig=5}}, of which {{convert|839200|km2|sqmi|1|abbr=on|sigfig=4}} is in Canada and {{convert|505000|km2|sqmi|1|abbr=on|sigfig=4}} is in the United States. The basin covers parts of [[Ontario]] and [[Quebec]] in Canada, parts of [[Minnesota]], [[Wisconsin]], [[Illinois]], [[Indiana]], [[Ohio]], [[Pennsylvania]], [[New York (state)|New York]], [[Vermont]], and nearly the entirety of the state of [[Michigan]] in the United States. The average discharge below the [[Saguenay River]] is {{convert|16800|m3/s|cuft/s}}. At Quebec City, it is {{convert|12101|m3/s|cuft/s|abbr=on}}. The average discharge at the river's source, the outflow of Lake Ontario, is {{convert|7410|m3/s|cuft/s|abbr=on}}.<ref name="BenkeCushing2005"/>

The St. Lawrence River includes [[Lake Saint Francis (Canada)|Lake Saint Francis]] at [[Salaberry-de-Valleyfield]], [[Lake Saint-Louis]] south of Montreal and [[Lake Saint Pierre]] east of Montreal. It encompasses four [[archipelago]]es: the [[Thousand Islands]] chain near [[Alexandria Bay, New York]] and [[Kingston, Ontario]]; the [[Hochelaga Archipelago]], including the [[Island of Montreal]] and [[Île Jésus]] ([[Laval, Quebec|Laval]]); the Lake St.&nbsp;Pierre Archipelago (classified a biosphere world reserve by the UNESCO in 2000)<ref>[http://www.pleinairalacarte.com/qc/monteregie/lac-saint-pierre-et-son-archipel.html Lac Saint-Pierre et son archipel] {{Webarchive|url=https://web.archive.org/web/20150402102145/http://www.pleinairalacarte.com/qc/monteregie/lac-saint-pierre-et-son-archipel.html |date=2 April 2015 }}. Pleinairalacarte.com (2008-11-07). Retrieved 2013-07-12.</ref> and the smaller [[Mingan Archipelago]]. Other islands include Île d'Orléans near Quebec City and [[Anticosti Island]] north of the [[Gaspé Peninsula|Gaspé]]. It is the second longest river in Canada.

[[Lake Champlain]] and the [[Ottawa River|Ottawa]], [[Richelieu River|Richelieu]], [[Saint-Maurice River|Saint-Maurice]], [[Saint-Francois River|Saint-François]], [[Chaudière River|Chaudière]] and Saguenay rivers drain into the St. Lawrence.

The St. Lawrence River is in a seismically active zone where [[fault (geology)|fault]] reactivation is believed to occur along late [[Proterozoic]] to early [[Paleozoic]] normal faults related to the opening of the [[Iapetus Ocean]]. The faults in the area are [[rift]]-related and comprise the [[Saint Lawrence rift system]].

According to the United States Geological Survey, the St. Lawrence Valley is a [[Physiographic regions of the world|physiographic province]] of the larger [[Appalachian Mountains|Appalachian]] division, containing the [[Champlain Valley|Champlain]] section.<ref name="USGS-Water">{{cite web | title = Physiographic divisions of the conterminous U.S. | publisher = U.S. Geological Survey | url = http://water.usgs.gov/GIS/metadata/usgswrd/XML/physio.xml | access-date = 2007-12-06 }}</ref> However, in Canada, where most of the valley is, it is instead considered part of a distinct [[St. Lawrence Lowlands]] physiographic division, and not part of the Appalachian division.<ref>{{cite web|title=Physiographic Regions of Canada|url=http://ftp.geogratis.gc.ca/pub/nrcan_rncan/raster/atlas_6_ed/reference/eng/physiographic_eng.pdf |archive-url=https://web.archive.org/web/20171021222228/http://ftp.geogratis.gc.ca/pub/nrcan_rncan/raster/atlas_6_ed/reference/eng/physiographic_eng.pdf |archive-date=2017-10-21 |url-status=live|website=Natural Resources Canada|publisher=Natural Resources Canada|access-date=18 February 2017}}</ref>