cirque lakes in the rockies glaciers in headwater valleys tend to scour out a bowl shaped basin and...
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![Page 1: Cirque lakes in the rockies Glaciers in headwater valleys tend to scour out a bowl shaped basin and the excavated material forms a moraine at the lake](https://reader030.vdocuments.net/reader030/viewer/2022032800/56649d385503460f94a1173c/html5/thumbnails/1.jpg)
Cirque lakes in the rockies
•Glaciers in headwater valleys tend to scour out a bowl shaped basin and the excavated material forms a moraine at the lake outflow that maintains the lake level after the glacier has receded.
•Drainage in Moraine lake was further impeded by a large landslide across the outflow
•Most cirque lakes are fishless unless stocked
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•Large blocks of ice left behind in moraines and till mounds as glaciers melt and grow “stagnant”. •As they gradually melt, they leave behind a depression in the till that fills by seepage •Many of the small pothole lakes in Alberta are kettle lakes.
Pothole or kettle lake formed in glacial --usually small < 30 ha, but can be quite deep--10-40 m. Watersheds are very small.
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Polygon ponds form along the Arctic coastal lowlands.
Form in the summer as wedges of ice melt within the permafrost to form smallpolygonal basins (around 50 m across) that fill up with surface water.
See Fig. 6.2 in your text
Polygonal ponds near the Lena River, Russia
Another type of basin associated with ice melting.
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Most of the large and old lakes in the world are Tectonic lakes
Many occupy ancient basins called grabens—formed by large geological faults
Rocks before faulting
Lake in a symmetrical graben
Lake in a tilted graben
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Lake Baikal—one of the most famous tectonic lakes in the world, has existed for over 20 million years
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Crater Lake, Oregon -589 m deep and possibly the clearest lake in the world, Transparency up to 90 m.Thermocline very deep for its size No rooted plants. Mud doesn’t accumulate on the bottom till > 90 m depth
Some of the most spectacular tectonic lakes are formed in volcanic craters.
Why is this lake so different from most lakes?
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Physical features of lakes that determine habitat characteristics
•inflow from the watershed/Catchment
•Water residence time
•Morphometry, Mean depth and volume
•Thermal stratification and physical mixing
•wind./currents/wave action
•Sediment deposition
•Light extinction