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?
• When wind moves soil, sand, and rock particles, it
acts as an agent of erosion.
• The grinding and wearing down of rock surfaces
by other rock or sand particles is abrasion.
• Rocks can become smooth and polished from
abrasion.
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Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity
How can wind shape Earth?
• 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
How can wind shape Earth?
• How does desert pavement form?
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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.
• Dunes 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
How can wind shape Earth?
• Why is the slip face of a dune steeper than the
windward slope?
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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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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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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.
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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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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.
• Erratics and kettle lakes are landforms produced
by continental glaciers.
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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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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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