Glacial Lake Ojibway
Encyclopedia
Glacial Lake Ojibway was a prehistoric lake in what is now Northern Ontario
and Quebec
in Canada
. Ojibway was the last of the great proglacial lake
s of the last ice age
. Comparable in size to Lake Agassiz
(to which it was probably linked), and north of the Great Lakes
, it was at its greatest extent c. 8,500 years BP
.
Lake Ojibway was relatively short-lived. The lake drained in what must have been a catastrophic and dramatic manner around 8,200 years BP. One hypothesis is that a weakening ice dam
separating it from Hudson Bay
broke, as the lake was roughly 250 metres (820.2 ft) above sea level
. A comparable mechanism produced the Missoula floods
that created the Channeled scablands
of the Columbia River
basin.
A recent analysis states it has not been conclusively determined whether the lake drained by a breach of the ice dam, by water spilling over the glacier, or by a flood under the glacier. It is also not conclusively known whether there were one or more pulses, and the route the water took to reach Hudson's Bay has not been determined.
The draining of Lake Ojibway was the most likely cause of the 8.2 kiloyear event
, a major global cooling that occurred 8,200 years BP.
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
and Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. Ojibway was the last of the great proglacial lake
Proglacial lake
In geology, a proglacial lake is a lake formed either by the damming action of a moraine or ice dam during the retreat of a melting glacier, or by meltwater trapped against an ice sheet due to isostatic depression of the crust around the ice...
s of the last ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
. Comparable in size to Lake Agassiz
Lake Agassiz
Lake Agassiz was an immense glacial lake located in the center of North America. Fed by glacial runoff at the end of the last glacial period, its area was larger than all of the modern Great Lakes combined, and it held more water than contained by all lakes in the world today.-Conception:First...
(to which it was probably linked), and north of the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
, it was at its greatest extent c. 8,500 years BP
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...
.
Lake Ojibway was relatively short-lived. The lake drained in what must have been a catastrophic and dramatic manner around 8,200 years BP. One hypothesis is that a weakening ice dam
Ice dam
An ice dam occurs when water builds up behind a blockage of ice. Ice dams can occur in various ways.-Caused by a glacier:Sometimes a glacier flows down a valley to a confluence where the other branch carries an unfrozen river...
separating it from Hudson Bay
Hudson Bay
Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...
broke, as the lake was roughly 250 metres (820.2 ft) above sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
. A comparable mechanism produced the Missoula floods
Missoula Floods
The Missoula Floods refer to the cataclysmic floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age. The glacial flood events have been researched since the 1920s...
that created the Channeled scablands
Channeled scablands
The Channeled Scablands are a unique geological erosion feature in the U.S. state of Washington. They were created by the cataclysmic Missoula Floods that swept periodically across eastern Washington and down the Columbia River Plateau during the Pleistocene epoch. Geologist J Harlen Bretz coined...
of the Columbia River
Columbia River
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...
basin.
A recent analysis states it has not been conclusively determined whether the lake drained by a breach of the ice dam, by water spilling over the glacier, or by a flood under the glacier. It is also not conclusively known whether there were one or more pulses, and the route the water took to reach Hudson's Bay has not been determined.
The draining of Lake Ojibway was the most likely cause of the 8.2 kiloyear event
8.2 kiloyear event
The 8.2 kiloyear event is the term that climatologists have adopted for a sudden decrease in global temperatures that occurred approximately 8,200 years before the present, or c. 6,200 BCE, and which lasted for the next two to four centuries...
, a major global cooling that occurred 8,200 years BP.
See also
- Tyrrell SeaTyrrell SeaThe Tyrrell Sea, named for Canadian geologist Joseph Tyrrell, is another name for prehistoric Hudson Bay, namely as it existed during the retreat of the Laurentide Ice Sheet....
- Glacial lake outburst floodGlacial lake outburst floodA glacial lake outburst flood is a type of outburst flood that occurs when the dam containing a glacial lake fails. The dam can consist of glacier ice or a terminal moraine...
- Glacial Lake AgassizLake AgassizLake Agassiz was an immense glacial lake located in the center of North America. Fed by glacial runoff at the end of the last glacial period, its area was larger than all of the modern Great Lakes combined, and it held more water than contained by all lakes in the world today.-Conception:First...
- Glacial Lake MissoulaGlacial Lake MissoulaGlacial Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago...
- List of prehistoric lakes
- Deluge (prehistoric)Deluge (prehistoric)In geomorphology, an outburst flood, which is a type of megaflood, is a high magnitude, low frequency catastrophic flood involving the sudden release of water. During the last deglaciation, numerous glacial lake outburst floods were caused by the collapse of either ice sheets or glaciers that...
External links
- AFP Sun Feb 24, 3:42 PM , “How it happened: The catastrophic flood that cooled the Earth” retrieved Feb 25, 2008 from http://www.cosmosmagazine.com/news/1864/catastrophic-ancient-flood-cooled-earth