Download - Erosion and Deposition
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Erosion and Deposition
Pages D58-D64
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Mass Wasting
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• The downhill movement of Earth’s material caused by gravity.
• Depends on how steep a slope is
• It can happen slowly, particle by particle, over the years.
• It can happen suddenly when a buildup of loosened particles can no longer be supported by material beneath.
• It can happen after a heavy rain, earthquake, or anytime
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Deposition
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• The dropping off of particles
• These particles are called sediments.
• Changing the shape of the land.
• As materials are picked up and dropped off the land changes shape.
• Mountains wear down from steep pinnacles to low hills.
• Valleys widen, fill up with rock and soil, and become plains.
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Wind
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• Easily picks up fine particles, like clay and sand
• The faster the wind is, the larger the size of the particles it can carry.
• As the wind slows down, it drops the sediment off
• The biggest, densest particles are dropped first.
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• Wind can blow sediment against rocks
• These rocks act like tiny sandblasters.
• They can dig into hillsides and polish stones.
• As the sand is dropped off, it can build into a dune.
• The dunes continue to change shape over time
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Flowing Water
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• Can toss loose particles of rock around and carry them along as it flows downhill.
• The faster the water is moving, the bigger and denser the particles it carries can be
• Large particles are carried along by rolling, sliding, or bouncing along the bottom
• Smaller particles swirl along in the water or get dissolved in the water
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• The rocks being carried by the water slam into and chip away at rocks along the sides, the river bank.
• The particles are dropped off whenever the water slows down
• These dropped off particles form a mound or layer
• The flatter the stream or river is, the curvier it is
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*Turn to the back of your notes to copy the following:
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What Causes Moving Water to Slow Down
• An obstacle could block the flow of water.
• A steep river could flow onto a flat plain.
• The water could flow into a big standing body of water, like a lake or ocean.
• In each of the above cases sediments are deposited when the water slows down and forms a mound or layer.
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In which part of the river would deposition take place?
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*Turn to the back of your notes to copy the following:
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Glaciers
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• Huge moving sheets of ice.
• Glaciers form when more snow falls in the winter than melts in the summer
• Over time the snow gets deeper and deeper
• As snow piles up, the weight of the snow on top squeezes the snow at the bottom into a solid mass of ice.
• The weight above makes the ice at the bottom like a super-thick syrup and the whole sheet of ice moves downhill
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• They move like huge, slow bulldozers and push loose rocks and soil out of their path
• Loose rocks and soil get pushed up in piles along the front and sides of the glacier
• Rocks get frozen back into the ice as it is moving• These rocks can scrape against the land as it is
moving• Polishes rocks smooth• They act like blades on a huge plow.
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• When glaciers melt
• The reach areas that are warm and begin to melt.
• The rocks that were frozen into it fall to the ground in a jumble known as a till.
• Some piles of till get smoothed out if a glacier flows over them called drumlines.
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• A deposit of many sizes of sediment from a glacier that collects in front or along the sides of a glacier is a moraine.
• Left behind in mounds or long ridges.
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• Forms ponds or lakes
• Chunks of ice get buried in the till
• When the ice chunks melt, the till above collapses forming a hole in the ground
• The holes fill up with water.
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Or
• They scrape huge bowl shapes in the ground
• The bowls fill up with meltwater when the glacier melts
• The moraines act like dams, trapping the meltwater into lakes