View source for Glacial Lake Iroquois

{{Short description|Prehistoric lake that became Lake Ontario}}
{{Infobox body of water
| name               = Lake Iroquois
| image              = 19th century estimate of the boundaries of Lake Iroquois.jpg
| caption            = This map shows the valley of the [[Mohawk River]], through which Glacial Lake Iroquois crossed the mountains to the [[Hudson Valley|Hudson River Valley]].
| coords = {{coord|43.7|N|77.9|W|type:waterbody_scale:3000000|display=inline,title}}
| location           = [[North America]]
| group              = [[Great Lakes]]
|pushpin_map=North America
| lake_type          = [[:Category:Former lakes|former lake]]
| etymology       = Iroquois or Haudenosaunee (/ˈhoʊdənoʊˈʃoʊni/; "People of the Longhouse")<ref>Beauchamp, William Martin (1905). A History of the New York Iroquois. New York State Education Department. p. 165. Retrieved May 7, 2016.</ref>
| inflow             = [[Niagara River]]
| outflow            = [[Mohawk River]] to the [[Hudson River]]
| catchment          =
| basin_countries    = Canada<br />United States
| length             = {{convert|196|mi|km|abbr=on}}
| width              = {{convert|57|mi|km|abbr=on}}
| area               = 
| depth              = 
| max-depth          = 
| volume             = 
| residence_time     = 
| shore              = 
| elevation          = {{convert|345|ft|m|0|abbr=on}}
| islands            = 
| islands_category   = 
| cities             = 
| reference      = United States Geological Survey, George Otis Smith, Director; The Pleistocene of Indiana and Michigan and the History of the Great Lakes; Frank Leverett and Frank B. Taylor; Department of the Interior, Monographs of the United States Geological Survey; Volume LIII; Washington; Government Printing Office; 1915
}}

'''Glacial Lake Iroquois''' was a prehistoric [[proglacial lake]] that existed at the end of the last [[ice age]] approximately 13,000 years ago.<ref>
{{cite book
| isbn=978-1-4437-2173-8
| url=https://books.google.com/books?id=m6zLfVSAOJcC&q=%22Lake%20Frontenac%22%20%22Lake%20Ontario%22%20glacier%20OR%20glacial&pg=RA2-PA261
| title=Glacial Geology and the Pleistocene Epoch
| date=2008
| author=Richard Foster Flint
| publisher=Read Books }}</ref>

== Description ==
[[File:Glacial lakes.jpg|thumb|300px|left|Stages of great lake development.]]

The lake was essentially an enlargement of the present [[Lake Ontario]] that formed because the [[St. Lawrence River]] downstream from the lake was blocked by the ice sheet near the present [[Thousand Islands]]. The level of the lake was approximately 30 m  (~100&nbsp;ft) above the present level of Lake Ontario.<ref name=Larson>{{cite journal |title=Review: Origin and Evolution of the Great Lakes |last1=Larson |first1=Grahame |last2=Schaetzl |first2=Randall<!--authorlinks [[Grahame Larson]], [[Randall Schaetzl]]--> |journal=J. Great Lakes Res. |volume=27 |issue=4 |year=2001 |pages=518–546 |doi=10.1016/S0380-1330(01)70665-X |url=http://www.geo.msu.edu/schaetzl/PDFs/Larson-Great_lakes.pdf |url-status=dead |archive-url=https://web.archive.org/web/20081031073825/http://www.geo.msu.edu/schaetzl/PDFs/Larson-Great_lakes.pdf |archive-date=2008-10-31 }}  The work of Anderson and Lewis (1985) is the basis for these authors' views on the history of the postglacial water levels.</ref>

The lake drained to the southeast, through a channel passing near present day [[Rome, New York]]. The [[Rome Sand Plains]] has several sand ridges that geologists think were formed at this time. The channel then followed the valley of the [[Mohawk River]] to the [[Hudson River]].<ref name=Larson />

The lake was fed by [[Early Lake Erie]], as well as [[Glacial Lake Algonquin]], an early partial manifestation of [[Lake Huron]], that drained directly to Lake Iroquois across southern [[Ontario]], along the southern edge of the ice sheet, bypassing Early Lake Erie.

The subsequent melting of the [[Proglacial lake|ice dam]] resulted in a sudden lowering of the lake to its present level, a potential trigger for the [[Younger Dryas]] episode.<ref name= Donnelly2005>{{Cite journal  | last = Donnelly  | first = Jeffrey P. |author2=Neal W. Driscoll |author3=Elazar Uchupi |author4=Lloyd D. Keigwin |author5=William C. Schwab |author6=E. Robert Thieler |author7=Stephen A. Swift | title = Catastrophic meltwater discharge down the Hudson Valley: A potential trigger for the Intra-Allerød cold period  | journal = Geology  | volume = 33  | issue = 2  | pages = 89–92  | date = February 2005  | doi = 10.1130/G21043.1  | bibcode = 2005Geo....33...89D }}</ref>

==Remnant shorelines==
Two ancient shorelines in the [[Toronto]] area mark the existence of former glacial lakes. About 2&nbsp;km inland from the shore, a ridge known as the ''Iroquois Shoreline'' can be discerned. The old shoreline runs west-east, running roughly parallel to [[Davenport Road]] just south of [[St. Clair Avenue]] West.  Further east, the [[Scarborough Bluffs]] also formed part of the shoreline of the ancient lake.<ref>{{cite book |last=Eyles |first=Nick |title=Ontario Rocks: Three Billion Years of Environmental Change |date=2002 |publisher=Fitzhenry & Whiteside |location=Markham, Ontario |isbn=9781550416190 |oclc=48940760}} See chapter 17.</ref> In [[Mississauga]], the shoreline is found south of [[Dundas Street]] and most visible with hills found east and west of Mavis Road.<ref>{{Cite web |title=Natural Areas Survey (NAS) Site: ER6 |url=http://www6.mississauga.ca/onlinemaps/planbldg/nas/Site_maps/er6.pdf |access-date=2023-07-10 |website=mississauga.ca}}</ref>

Another ancient shoreline exists between 2–4&nbsp;km offshore of Toronto. It is known as the ''[[Toronto Scarp]]'' and formed the shore of [[Lake Warren|Glacial Lake Warren]] or [[Admiralty Lake]]. From Bluffer's Park in Scarborough to just west of Hanlan's Point is an underwater bluff.<ref>{{Cite web |title=Nearshore Geology |publisher=City of Toronto TRC |date=n.d. |url=http://www.aquatichabitat.ca/nearshore_geology.shtml |access-date=26 December 2009 |url-status=dead |archive-url=https://web.archive.org/web/20120226233631/http://www.aquatichabitat.ca/nearshore_geology.shtml |archive-date=26 February 2012 }}</ref>

In [[Hamilton, Ontario]] the [[Burlington_Heights_(Ontario)|Burlington Heights]] represents a sand and gravel bar formed across the mouth of [[Cootes Paradise]], at the western end of Glacial Lake Iroquois. 

In [[New York (state)|New York]], [[Ridge Road (Western New York)|Ridge Road]] and [[New York State Route 104]] run from west to east along a ridge of the old shoreline of Lake Iroquois.<ref>{{cite book |title=Colossal cataract: the geologic history of Niagara Falls |last=Tesmer |first=Irving H. |author2=Bastedo, Jered C. |year= 1981|isbn= 978-0-87395-522-5|page=48 |publisher=SUNY Press |url= https://books.google.com/books?id=_IFDxu0oGQMC&q=route%20104%20iroquois%20lake&pg=PA48 |access-date= 2 February 2010}}</ref>

==See also==
*[[Lake Agassiz]]
*[[List of prehistoric lakes]]
*[[Lake Coleman]]

==References==
{{reflist}}

==External links==
*[http://www.fof-clarington.com/lakehist.html History of Lake Iroquois]
*[http://www.lostrivers.ca/points/Lake_Iroquois.htm Lake Iroquois and its shore cliff], showing map of the lake
*[https://web.archive.org/web/20040620095513/http://hannover.park.org/Canada/Museum/champlain/EVENTS.HTM Deglaciation of the Central St. Lawrence Lowland]

{{Pleistocene Lakes and Seas}}
{{Greatlakes}}
{{Authority control}}

{{DEFAULTSORT:Iroquois, Lake}}
[[Category:Natural history of Ontario]]
[[Category:Proglacial lakes]]
[[Category:Geology of New York (state)]]
[[Category:Glacial lakes of Canada]]
[[Category:Glacial lake outburst floods]]