Shaping Earth’s Surface
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Transcript of Shaping Earth’s Surface
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Shaping Earth’s Surface
Chapter 3, Lesson 5
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What is weathering?
• Weathering is the process through which rocks or other materials are broken down.
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Physical weathering
• Physical weathering: weathering caused by temperature changes, pushing, pulling, or rubbing.
• Plants and trees growing up between cracks in the street, or sidewalk. The pressure from their roots pushing against the rock will cause particles to break off.
• The breaking of material is a physical change.
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Physical weathering
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Physical weathering
• Gravity pulling rocks down a slope. The rocks bump into other rocks, causing chips, and cracks to form.
• Wind and water will pick up small particles of sand and dirt and rub it against exposed rock. Causing the surfaces of exposed rock to wear away.
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Physical weathering
Rock slide
Water erosion
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Chemical weathering
• Chemical weathering occurs when chemicals break down rocks.
• Chemical weathering in ground water break up underground rock, caves.
• Above ground, acid rain causes statues to tarnish, or metals to rust.
• Chemical weathering can also kill vegetation.
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Chemical weathering
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Erosion
• Erosion is the process through which weathered rock is moved from one place to another place.
• Land can be eroded in five different ways.–1. gravity–2. glaciers–3. running water–4. waves–5. wind
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What is deposition
• Deposition: Particles of dirt and rock that are dropped off in another place.
• Deposition by water forms deltas at the mouth of a river.
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Delta
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What is Deposition by Waves
• Eventually, rivers flow into larger bodies of water, such as lakes or oceans. As a river enters a lake or an ocean, its speed slows. The river then deposits the rest of its sediment. This sediment builds up over time to form a delta.
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What is Deposition by Waves
• http://images.google.com/imgres?imgurl=http://www.greatdreams.com/weather/hurricane-ike11-gilchrist-tx.jpg&imgrefurl=http://www.greatdreams.com/weather/hurricanes-2008c.htm&usg=__Hy_2EL74SW9R9QH0iqHpEukDIQE=&h=1040&w=990&sz=396&hl=en&start=15&um=1&itbs=1&tbnid=dWa02EhClDAczM:&tbnh=150&tbnw=143&prev=/images%3Fq%3DHurricane%2Bin%2BBarrier%2BIslands%2BTexas%26um%3D1%26hl%3Den%26safe%3Dactive%26sa%3DN%26rls%3Dcom.microsoft:*%26tbs%3Disch:1
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What is Deposition by Waves
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What is Deposition by Wind
• Wind can wear away at rocks, smoothing them out.
• Wind also can move sand or sediment from one place to another.
• When the winds slow down, the sand and soil are deposited.
• (Snow drifts in the plains during winter!)• (Sand dunes in the desert actually move!)
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What is Deposition by Wind
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What is Deposition by Wind
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How are rivers changed?
• A river is changed by the erosion and deposition of sediment.
• Water can erode sediment as it flows through a river channel.
• As the water in the river or stream slows, the sediments are deposited along the shoreline.
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How are rivers changed?
• When water enters a river or steam faster than it is carried away, it is called a flood.
• Floods occur when water from a river or stream overflows its banks.
• Natural wetlands can soak up water and reduce the changes of a flood.
• A floodplain is an area that easily floods.
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How are rivers changed?
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Flood control
• Floods are dangerous to people.• The force of moving water can wash away
trees, animals, cars, people, and even buildings.
• Floods leave mud, trash, and other debris in homes and on the streets.
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Flood control
• Atlanta Flood – $250 Million
September 23, 2009ByJennifer Brett
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Flood control
• A dam is a structure built across a river.• Water builds up behind the dam and is stored.• The water is released slowly over time to
prevent flooding.• Levees are walls built along the sides of a river.
• A levee raises the banks of a river so that
more water can flow through without flooding the surrounding area.
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Flood control
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Flood control
• In rural areas, plants help control floodwaters.• The roots of plants, along side a river or
stream, helps to hold soil in place, and can soak up floodwaters.
• Canals or channels can also be dug to carry away water that would cause floods.
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Flood control
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How are shorelines changed and protected?
• A shoreline or the edge of a body of water is changed by the erosion and deposition of sediment.
• Sediment is eroded and deposited along a shoreline by waves and wind.
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How are shorelines changed and protected?
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How are shorelines changed and protected?
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How are shorelines changed and protected?
• Waves: As waves wash sand off beaches, they deposit it in the water.
• Sandbar: a strip of sandy land that stretches for hundreds of kilometers along a coastline. (If above the water, Barrier Island.)
• Barrier Islands protect beaches from erosion.• http://
science.howstuffworks.com/barrier-island.htm
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How are shorelines changed and protected?
• Wind: Some coastal areas have one or more sets of dunes along the shoreline.
• Dunes protect areas farther inland from the large waves that can occur during storms.
• Dunes also shelter inland areas from the wind.
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How are shorelines changed and protected?
• Barricades, a breakwater is a long wall built out in the ocean parallel to the shore.
• Waves hit the breakwater and are slowed.• Slower waves cannot carry as much sand away
from the beach.
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How are shorelines changed and protected?
• Reclamation: Some beaches have been badly damaged and are in danger of being lost.
• Beach reclamation is a process where sand is brought from another place. The new wand “reclaims” the old shoreline.