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Do Now 11/3/2009

Do Now 11/3/2009. How are lakes and streams similar? How are they different? How do people use lakes? What are some ways lakes are formed?. Lakes. How does water enter into lakes?. Rainfall (Precipitation) Runoff- The water that does not sink into the ground, yet flows along the surface.

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Do Now 11/3/2009

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  1. Do Now11/3/2009 How are lakes and streams similar? How are they different? How do people use lakes? What are some ways lakes are formed?

  2. Lakes

  3. How does water enter into lakes? • Rainfall (Precipitation) • Runoff- The water that does not sink into the ground, yet flows along the surface.

  4. How do lakes form? • Glaciers: Glaciers scoured out depressions that over time fill in with runoff water. • Natural Lakes: • Ex. Great Lakes- They hold 18 percent of Earth’s freshwater. • http://upload.wikimedia.org/wikipedia/commons/c/c3/Great_Lakes_from_space.jpg • Crustal Movement: The Earth’s crust can move and create depressions that fill in with water. • Volcanic Eruption: After a volcanic eruption the top of the volcano can fill with water. • Caldera: http://www.gvb-csic.es/CCDB/iamgenes/KatmaiCaldera.jpg • Formation of a dam: • Human-made lake • Ex. Hoover dam • http://philip.greenspun.com/images/pcd2882/hoover-dam-aerial-91.4.jpg

  5. What is found in lakes? • Plant Life: Plant life near a lake is usually found near the shallow parts. Why? • Because, plants need sunlight to live and produce. • Amphibians: Organisms that use both the land and the water. • Ex. Frogs, Ducks, Turtles, etc. • Fish • Plankton: small organisms found near the surface of the water. • Sediment and Nutrients: • Nutrients: Compounds such as nitrates and phosphates that are used by plants and algae to grow. • Sediment: Can a lake be the same depth forever? • No, sediment will build and over time the lake will decrease in depth. Eventually becoming dry. • http://techalive.mtu.edu/meec/module08/FoodWeb.htm

  6. Lake Math Bay depth: A small bay in a large lake is filling at a rate of 0.01 cm per year. If the water in the bay averages 100 cm deep, how long will it take for the bay to become land. Solution: • This is what you know: • Infill rate- r= 0.01 cm/y • Average depth- d= 100 com • What you need to find: • Time: t • This is the procedure you need to use: • time= depth / infill rate • Solve: • Time= 100cm / 0.01cm/y = 1000 years Practice: A different bay in the same lake is filling at a rate of 0.3 cm/y. This bay averages 150 cm deep. How long will it take to fill in?

  7. How does a lake turnover? • Turnover- The mixing of lake water, which causes nutrients from deep in the lake to move to the surface. • Summer Lake: • Nutrients are concentrated on the bottom with the more dense colder water. • Low nutrient count on top with the less dense water . • There is a separation of nutrients due to water density. • Autumn Lake: • The top layer of water becomes colder and more dense. • The top layer sinks and mixes with the nutrient rich water from the bottom. * Turnover causes nutrients from deep in the lake to move upward toward the surface.

  8. Vocabulary • Nutrient • Eutrophication • Turnover

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