Lakes

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Lakes

• 11.6

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Definition

• A large, inland body of standing water that
  occupies a depression in the land surface.
• What could cause a depression in the land
  surface? (Think of past chapters)

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Lake formation

• Oxbow lakes
• Volcanoes (crater lakes)
• Rift valleys
• Shallow groundwater or springs
• Glaciers- several processes

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Oxbow lakes

• Typically long, narrow, and shallow

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Crater Lake, Oregon

• 1932 feet deep (9 in the world)

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Bathymetry image of Crater Lake by USGS.
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Lake Baikal (Russia)

• Deepest lake in the world- 5369 feet deep!
• Located in a
• RIFT VALLEY
• Sediments get deposited, but then the plates move
  apart again (1 per yr)

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Lake Baikal
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Lake Okeechobee, Florida

• Large, but shallow lake in Everglades
• Formed from high water table (springs)

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Minister Lake, WI (Seepage lake)
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Glacial Lakes

• Glaciers erode depressions.

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Glacial Lakes

• 2. Glaciers deposit sediments (moraines) as they
  recede, blocking stream valleys.

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Glacial Lakes

• 3. Glacier leaves a chunk behind and it
  melts to form a kettle lake.

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Life Cycle of a Lake

• Form
• Fill with sediment
• Become a swamp
• Become a meadow or forest w. stream.

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Lake nearing end of life cycle
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Nutrients in lakes

• Oligotrophic (nutrient poor)
• vs.
• Eutrophic lakes (nutrient-rich)
• (In your notebook make a t-chart of differences)

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Turbidity (Measured with secchi disk)
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• What causes eutrophication?
• Natural cause
• Human-induced
• See page 278

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Layers of a lake- Define termsEpilimnion
Thermocline - Hypolimnion
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Yearly Cycle of a Temperate Lake

• Layered or stratified in summer.
• Includes a spring and fall turnover or mixing.
• Ice covered in winter.
• CONSEQUENCES?

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• How does the turnover affect life in the lake?
• What would happen if ice sank rather than
  floating?