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Lake-making.

There are more ways for lakes to form than you can shake a canoe-paddle at.

Most of Canada's lakes were formed by glaciers. Huge fields of ice, several kilometres thick, pushed out across the land during the last Ice Age. This started about 125,000 years ago and ended about 10,000 years ago.

The glaciers completely altered the landscape by smoothing out hills and gouging out basins. As the glaciers melted, the basins filled with water--glacial lakes. Examples include: Lake Superior and Lake Winnipeg.

Other lee Age remnants, called moraines, formed lakes. As the glaciers scraped the surface, they picked up rocks, gravel, and dirt, which became locked in the ice. As the ice melted, the debris settled downwards forming huge piles--moraines. A moraine at the end of an old river valley would plug the drainage and back up the water--morainal lakes. Examples include: Swan Lake near Dawson Creek, B.C., and the appropriately named Moraine Lake (pictured below) in Banff National Park, Alberta.

When ice scours mountain ranges some particularly spectacular lakes are formed. Deeply cut, bowl shaped depressions are formed by mountain glaciers. When these fill with water they are called cirque lakes and one of the world's most beautiful examples is Lake Louise in the Banff National Park, Alberta. Sometimes a series of cirque lakes forms at successively lower levels. If seen from above they look like a string of beads, similar to the paternoster beads used by Roman Catholics during prayer--hence the name, paternoster lakes.

Moraines are involved in one more type of lake-making, and that's kettle lakes. As the last glaciers melted away, sometimes blocks of ice were stranded and became buried as melt water covered them with sand and gravel. Later, as the ice block melted (a process that could take thou sands of years), the overlying sediment collapsed and left a depression in the ground surface that filled with water--kettle lakes. Examples include: Puslinch Lake in southwestern Ontario and Alleyne, and Kentucky Lakes in southern British Columbia.

Three kilometres of ice sitting on top of the land is a lot of weight: so much weight that it squashes the ground surface down. When the ice retreats, the ground lifts back upwards in what the experts call isostatic rebound. This creates fiord lakes that are usually long, twisty valley-floor lakes that run to bedrock valley walls on either side. The delightfully named Turn-Turn Lake in the Shuswap district of British Columbia is an example.

With the ice gone from the last glaciation, the rivers began to flow. Water erodes the landscape in much the same way as ice, but without the drama. Rivers rarely flow in straight lines, they twist and turn and the bends become more and more pronounced over time. Gradually, the curves form a U-shape and erosion narrows the gap between the open ends. Eventually, most likely during a spring flood, the river cuts a channel through the last remaining bit of land, isolating the bend. What's left behind looks like the wooden frame that goes around the neck of an ox and is attached to the yoke. This frame is called an oxbow, so is the name given to this type of lake--oxbow lakes.

Over time, the oxbow lake dries up and just becomes a depression left in the land around the river. There's evidence of old oxbow lakes in many places including central Winnipeg. Look at a street map of the St. Boniface district and there are two curving roads that defy the grid pattern--Enfield Crescent and St. Mary's Road. These two streets follow the bank of an ancient oxbow lake, left behind by the meanderings of the Red River.

Most areas of the country have examples of this kind of lake and many of them have been named, through a great burst of creativity, Oxbow Lake.

Rivers crashing over a cliff can also form small lakes below. They are called plunge-pool lakes, but are usually too small to get names of their own. Photos of these features are very popular for putting in tourist brochures and as a backdrop for selling shampoo.

The Ancient Greek god of the winds was called Aeolus, and his name is given to lakes formed by wind action. At the southern end of Lake Athabasca in Saskatchewan is a huge field of sand dunes. The wind moves these dunes around leaving depressions among them. These depressions fill with water, forming aeolian lakes.

From the heavens let's come down to earth, where plants and animals sometimes create lakes.

In Nova Scotia, dense growth of sphagnum moss and other bog plants have been known to form a dam across streams that drain valleys. The water that is thus held back floods the valley to form a lake.

Then, there is the nation's industrious population of beavers. These busy animals fell trees to dam up streams in order to create their own habitats. The valleys they flood are seldom grand enough to qualify as lakes and are mostly referred to as beaver ponds.

However, there is animal that creates huge lakes--humans. We dam up rivers for flood control, to provide a source of drinking and irrigation water, and for the production of hydro electricity. Lake Diefenbaker was created in southern Saskatchewan to provide a more reliable water supply in that semi-arid region. The Lake of the Prairies, which straddles the Manitoba-Saskatchewan border was formed to control flooding on the Assiniboine River. The experts call these Anthropogenic lakes.

Nature also dams up rivers in other ways. Lava flows from volcanic eruptions can plug the river drainage of a valley and create a lake. There are several of these lava-dammed lakes (e.g. Murtle and Clearwater) in the Wells Gray Provincial Park in British Columbia.

Landslides do the same job as lava flows. Foley Lake in the Chilliwack area of B.C. is an example.

Lakes form in the bowls of extinct volcanoes or in the crater produced when a meteorite crashes into our planet. Solution lakes are created when limestone, gypsum, or salt are dissolved by vain to form basins.

Finally, the naming of lakes is a matter that falls within the responsibilities of Natural Resources Canada. Many carry First Nations names: Ashuanipi Lake (Newfoundland and Labrador), Sipiwesk Lake (Manitoba), Kamilukuak Lake (Nunavut). Some are named in honour of historical figures: Lake Simcoe (Ontario), Peter Pond Lake (Saskatchewan), Princess Mary Lake (Nunavut). A lake's shape or some unusual feature can lead to a name: Round Lake (there are 107 of them--2139 if you include all the Lac Ronds), Mud Lake (182 in number), Little Lake (101).

Then, there are the bizarre ones: Flyingshot Lake (Alberta), Muncho Lake (British Columbia). But, nothing beats the small body of water tucked away in the backwoods of eastern Ontario. Did they drink the water in it before or after they named it Pisspot Lake?

FACT FILE

According to the Canadian Dam Association, there were 933 large dams in the county in 2003; there are many thousands of smaller dams.

FACT FILE

The highest waterfall in Canada is Della Falls in B.C. at 440 metres.
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Title Annotation:Formation
Publication:Canada and the World Backgrounder
Geographic Code:1CANA
Date:Jan 1, 2005
Words:1185
Previous Article:Land of lakes.
Next Article:Bulk-water exports.
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