Unit 1 Lesson 4
Unit 1 Lesson 4 Erosion and Deposition by Wind,
Ice, and Gravity
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Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
Gone with the Wind
How can wind shape Earth?
• After rock is weathered by wind abrasion, it then can move soil, sand, and rock particles, acting as an agent of erosion.
• The removal of fine sediment by wind is called deflation.
• Desert pavement results when wind carries soil and fine sediment away from an area, leaving only pebbles and small rocks behind.
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Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
How can wind shape Earth?
• Dunes are mounds of wind-deposited sand, common in deserts and along the shores of lakes and oceans that usually move in the same direction the wind is blowing.
• A dune’s gently sloped side usually faces the wind, which moves material up this slope. Sand moves over the crest and slides down the steep face.
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Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
How can wind shape Earth?
• Loess consists of thick deposits of windblown, fine-grained sediment.
• Loess deposits can be found far from their original source and can build up over thousands or millions of years.
• Loess forms good soils for growing crops.
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Loess
Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
Groovy Glaciers
What kinds of ice shape Earth?
• A glacier is a large mass of moving ice that forms by the compacting of snow by natural forces.
• Glaciers move downhill by gravity and cause erosion. As a glacier melts, it deposits the materials it carries.
• Glacial drift is the general term for all materials carried and deposited by a glacier.
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Glacier Movement
Land being displaced
Glacier Movement
Land being displaced
Glacier Movement
Land being displaced
New Landform
Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
What kinds of ice shape Earth?
• An alpine glacier is a glacier that forms in a mountainous area.
• As a glacier flows down a mountain, it can erode a
V-shaped valley caused by a stream into a Ushaped glacial valley.
U-shaped
Glacial Valley
V-shaped
Stream Valley
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Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
What kinds of ice shape Earth?
• An alpine glacier can carve out bowl-shaped depressions called cirques, at the head of a valley.
• A sharp ridge called an arête forms between two cirques that are next to each other.
• When three or more arêtes join, they form a sharp peak called a horn.
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Arête
Horn
Cirques
Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
What kinds of ice shape Earth?
• Continental glaciers are thick sheets of ice that may spread over large areas, including across entire continents.
• Continental glaciers flatten and smooth the landscape.
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Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
Slippery Slopes
How can gravity shape Earth?
• Gravity influences the movement of water and ice.
Gravity also moves rocks and soil downslope.
• Mass movement is this shifting of materials due to gravity.
• Creep is the extremely slow movement of material downslope.
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Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
How can gravity shape Earth?
• Rapid mass movements usually happen on steep slopes and are the most destructive.
• A rockfall happens when loose rocks fall down a steep slope.
• A landslide is the sudden and rapid movement of a large amount of material downslope.
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Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
How can gravity shape Earth?
• A mudflow is a rapid movement of a large mass of mud.
• Mudflows happen when a large amount of water mixes with soil and rock.
• Deforestation, volcanic eruptions, and heavy rains can all create mudflows.
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Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
Melting the Ice
• During the last Ice Age, an ice dam held back the water of Glacial Lake Missoula.
• The dam broke and emptied the entire lake within
48 hours, forming huge waterfalls, deep canyons, and tall ripple marks in the land.
• Lake Missoula reformed and flooded about 40 more times.
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