About 8200 years before present Glacial lake Agassiz was the largest lake in the world. It covered over 840'000 km2 in Canada (Manitoba, Saskatchewan, Ontario) and the US (North and South Dakota and Minnesota).
In this time of Climate warming it is particularly interesting to study some of the past changes in climate. Google Earth provides a unique tool to explore the maximum extent of this lake and its ultimate recession and drainage. This folder contains a series of land form features which can be used as reference and "legend" for mapping - exploring the maximum extent of this unique glacial lake.
The map below was completed in 1895 by Upham (USGS) one
of those remarkable early explorers. The map is already quite amazing
if you take into consideration the limited access and the tools
available. Just imagine what he could have done if you had access to GE at that time! Try to find other
signs of the maximum extent of the lake and retreat of the massive
The place marks in the Google Earth folder provide examples of interpretation of some of the glacial lake features which can be used as a "mapping and exploration legend"
The "Google Earth" Image below gives an interesting perspective of the challenge of finding the boundaries of Lake Agassiz at its various stages
Glacial lake Beach lines are some of the easiest features which can be found and traced with GE. Glacial Lake Agassiz receded from the top of the Duck Mountains Plateau (a ground moraine) on the left to the present day Lake Winnipegosis on the right. Numerous beach lines can be seen showing the many stages of this retreat. Many of the early roads were constructed on the former beaches.
With Google Earth you can follow these beach lines along the southern and western shorelines former shorelines of lake Agassiz. The northern and western shorelines are a bit more complex to map.
Undraped DEM, 8.0x VE, Orthogonal View of the Beach lines in the satellite image above. The Upper and Lower Campbell beaches are shown. Source: Manitoba Geological Survey
Glacial lake bottom ice scour features in the Red River valley
The Red River Valley forms the glacial lake bottom with heavy clay deposits. The scars in the landscape are thought to be the result of floating ice bergs and ice flows scouring in the soft glacial lake bottom. Here they are enhanced by the light snowfall in the right side of the image. These features occur in many parts of the former lake bottom, on agricultural and forested areas.
Assiniboine River Glacial Lake Delta
A large delta was formed when the then much larger Assiniboine River drained into the glacial lake. Extensive sandy deposits can be seen on the west side as moving (A) or stabilized sand dunes (B) and bare range land . D shows the former lake bottom with clay deposits and C&E indicates former beach lines.
Interlake Drumlinized Plain with Ice Scour Features
This area shows the intersecting lineaments, thought to be the scars of ice bergs and ice flows in Glacial Lake Agassiz, super imposed of a extensive plain showing clear signs of glaciation. The darker forest covered, parallel ridges in the top of the image, are drumlins, shaped by the flow of the massive ice sheet and showing the direction of the flow.
End Moraine with a Series of Glacial Lake Beach lines
The Pas Moraine shows a stagnant stage in the retreat of the large ice sheet. The fluted stripes in the landscape (E) show the direction of the ice flow. The dark ridge in the middle is the end of the ice sheet where glacial tills and end moraine formed a significant elevation in the landscape. About 10 different former glacial beach lines can be seen (B). The are essentially wave washed sand and gravel beaches. Typically roads follow beach lines, as road construction is easier and sources of gravel are close by.
This is an example of the delta of an esker kame complex formed by a major "river" under the ice sheet. The wave washed beach lines can clearly be seen on this dominant landscape feature formed from gravel and sand with a forest cover of Jack Pine. Even in the surrounding peat lands parallel beach lines can be seen where Black Spruce cover is denser. In these areas a thin layer of lacustrine clays can be found on top of the sand. With GE you can follow the esker in a north eastern direction. This delta coincides with another end moraine stage of the retreat of the ice sheet. In this area the crest of the end moraine is hidden under clay and organic deposits, but drainage pattern in the extensive wetlands here show its highest points. Permafrost occurs in peat plateaus and palsas in these wetlands [+].
The east side of the Red River Plain is marked by a series of beach lines. Part of the eastern shoreline? it is clear that the area to the right formed at one time an island, since the beach lines can be traced around it. Of course beach lines can be found as far south as Fargo. Try to find them.
Google Images= "Issue Atlas"
If you need some more clues to interpret the maximum extent of the lake there is of course always Google to help you find relevant information. One of the most effective and direct search approaches for environmental issues is Google Images. It is almost as if Google Images presents you with a real time issue atlas of "maps " which you can overlay on Google Earth.
As example for this exploration game I used "lake Agassiz" for an image search and I took the following screen shot of the search. This is the first page. It is amazing that all except one are maps rather than photos or other illustrations. They all lead information and web sites pertinent to this quest.
David Leverington has provided interesting digital reconstructions of the Lake Agassiz situation using GIS and paleotopographic techniques. (Leverington, D.W., Mann, J.D., Teller, J.T., 2000. Changes in the bathymetry and volume of glacial Lake Agassiz between 11,000 and 9300 14C yr BP. Quaternary Research 54, 174-181.) The image below represents the Upper Cambell stage around 9300 years before present (see above map by Thorleifson). KMZ overlay on Google Earth depicting Lake Agassiz around 9300 years BP.
Leverington also developed an interesting visualization of the Upper Campbell Stage below. This image reflect a computer visualization from a hight of 100 km above Winnipeg looking towards the North West. The Riding, Duck and Porcupine Mountains in Manitoba and the Pasquia Hills in Saskatchewan control the shapes of the western shoreline. See also the DEM image above (orange - yellow) of Duck Mountains, where the Upper and Lower Campbell beach lines are identified
The Manitoba Geological Survey has prepared a short video visualization of the retreat of the Wisconsin Ice Sheet and the various stages of Glacial Lake Agassiz: Link to video : Paleaogropahic Reconstruction during deglaciation between 11700 YBP to 7600 YBP
This image give a good visualization of the Lake Agassiz situation, dammed by the waning Laurentide Ice Sheet. The final drainage of this lake produced a flood that released 150,000 km3 northward to Hudson Bay. Ultimately the freshwater released from the flood was routed to the Atlantic Ocean. The ocean response to this huge influx of freshwater is thought to be the trigger for the cold event that occurred around 8,200 years ago.Authors:
A NASA Goddard Institute for Space Studies (GISS) computer model simulated the 8,200-year climate response to freshwater entering the Hudson Bay. The left and right panels show simulated changes in surface air temperature and precipitation, respectively (Image credit: NASA GISS). The model confirms and visualizes the impact of massive flood of fresh water into the North Atlantic and displays the abrupt change.
Lake Agassiz outburst sparked 'Big Freeze' in Europe 12,800 years ago
Lake Agassiz outburst sparked 'Big Freeze' in Europe 12,800 years ago. When an ice wall collapsed somewhere along Lake Agassiz's northeastern rim about 12,800 years ago, its freshwater contents gushed rapidly into the North Atlantic, wreaking havoc with ocean circulation patterns and plunging Europe into an unprecedented and prolonged winter that lasted centuries. In a study that highlights just how quickly a mini ice age took hold of Europe after the dramatic collapse of a glacial ice dam in ancient Canada, Saskatoon scientist Bill Patterson has gathered evidence suggesting the "Big Freeze" - a sudden and severe global cooling known to experts as the Younger Dryas - happened within three months of the Canadian cataclysm. But rather than unfolding over a decade as widely believed, the extreme chill set in so swiftly that ecosystems in the northern hemisphere were radically transformed within a single season, a research project led by Patterson has discovered. "If (Canada's earliest aboriginals) lived near Agassiz, they may simply have seen the lake level drop as the lake shrunk in size," Patterson said. "If they were in the East near the outlet, they would have seen what would look like a large, fast flowing river."
Easter outlets of glacial Lake Agassiz
David W. Leverington and James Teller provide an interesting overview of this topic in their paper "Paleotopographic reconstruction of the eastern outlets of glacial lake Agassiz (Canadian Journal of Earth Sciences 40: 1259-1278 (2003) doi:10.1139/e03-043 | © 2003 NRC Canada
Abstract: Paleotopographic reconstructions of the eastern outlets of glacial Lake Agassiz provide a foundation for understanding the complex manner in which terrain morphology controlled the routing of overflow through the eastern outlets during the lake's Nipigon Phase (ca. 9400–8000 14C years BP) and for understanding the causes of outlet-driven declines in lake level during that period. Although flow paths across the divide between the Agassiz and Nipigon basins were numerous, eastward releases from Lake Agassiz to glacial Lake Kelvin (modern Lake Nipigon) were channeled downslope into a relatively small number of major channels that included the valleys of modern Kopka River, Ottertooth Creek, Vale Creek, Whitesand River, Pikitigushi River, and Little Jackfish River. From Lake Kelvin, these waters overflowed into the Superior basin. The numerous lowerings in lake level between stages of the Nipigon Phase, controlled by topography and the position of the retreating southern margin of the Laurentide Ice Sheet, had magnitudes of between 8 and 58 m, although some of these drawdowns may have occurred as multiple individual events that could have been as small as several metres. The total volumes of water released in association with these drops were as great as 8100 km3, and for all Nipigon stages were probably between about 140 and 250 km3 per metre of lowering. The topographic reconstructions demonstrate that Lake Agassiz occupied the area of glacial Lake Nakina (located northeast of modern Lake Nipigon) by the The Pas stage (ca. 8000 14C years BP) and that Lake Agassiz drainage through the Nipigon basin to the Great Lakes ended before the succeeding Gimli stage.
Map showing the 1.5 million km2 total area that Lake Agassiz occupied over its 5000-year history. The lake gradually shifted from south to north, following the retreating southern margin of the LIS, with the earliest lake stages confined to the southernmost portion of the indicated area and the final stages occupying the lowlands south of modern Hudson Bay. Primary routes of overflow are labeled as follows: E, region of eastern outlet systems to the Superior basin via the Nipigon basin, shown in Fig. 3; HB, general outburst direction of the final release of Lake Agassiz waters into the Tyrrell Sea (modern Hudson Bay); K, Kaministikwia route to the Superior basin; KIN, Angliers and Kinojévis outlets to the St. Lawrence River valley via the Ottawa River; NW, northwestern outlet to the Arctic Ocean via the Clearwater and Mackenzie river valleys; S, southern outlet to the Gulf of Mexico via the Minnesota and Mississippi river valleys.
The reduction in the level of Lake Agassiz between the end of the Upper Campbell stage and the end of the subsequent Lower Campbell stage would have been about 20 m (Table 2).
The initial opening of eastern drainage at the end of the Upper Campbell stage probably occurred in the area of Kashishibog Lake (5, Fig. below), the main divide feature of the Kaiashk Outlet (Fig. 3) (see also Zoltai 1965a; Thorleifson 1983; Teller and Thorleifson 1983, 1987). Initial Lake Agassiz overflow to Lake Kelvin would have occurred through segments of the Roaring River (A) and Gull River (B) valleys to the area east of Kabitotikwia Lake (3). As the ice retreated north, flow would likely have followed parts of the Pantagruel Creek valley (C). Subsequent flow would have followed Ottertooth Creek (D) directly from the area of Kashishibog Lake (5), reaching Lake Kelvin southeast of modern Obonga Lake (8). After a drop in lake level of 10 m, the drainage route across the Kashishibog Lake (5) area would have closed, with drainage first occurring through the area of Siesse Lake (6) and subsequently through the Uneven Lake (7) area.
Upper Campbell Stage map overlaid 'semi-transparent' on Google Earth Image below
A detailed version of the map overlay above showing the drainage channel near D on the map above
Upper Campbell stage.
Glacial lake Agassiz: North Wester Drainage Outlet- Digital Elevation Model
Drainage of Glacial lake Agassiz is always a very interesting topics. This overlay shows the North Western Outlet of Glacial Lake Agassiz using a digital elevation model representing the landscape topography at the time of drainage.
The outlet is in the well known Fort McMurray area, home of the Tar Sands
Outlet Chronology and History of Glacial lake Agassiz
The figure below shows the large proglacial lakes along the retreating Laurentide Ice Sheet at between 12'650 and 12'750 years before present. Source is article in Nature 464, 740-743 (1 April 2010): Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Ocean by Julian B. Murton, Mark D. Bateman, Scott R. Dallimore, James T. Teller and Zhirong Yang
This page was started in 2007 as part of contributions to the Google Earth Community on the use of satellites for the monitoring of environmental change.
The GE discussion forum also includes a large number of KML files which highlight the location of many of the images used on this page.
Links to most of the KMZ files are included on this page embedded in the text near their respective images.