unit 1 lesson 4 erosion and deposition by wind, ice, and gravity copyright © houghton mifflin...

Unit 1 Lesson 4 Erosion and Deposition by Wind,Ice, and Gravity

Copyright © Houghton Mifflin Harcourt Publishing Company

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.

Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity


• 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.




• How does desert pavement form?




• 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.




• Why is the slip face of a dune steeper than the windward slope?




• 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.



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.



• 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 U-shaped glacial valley.




• 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.




• 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.




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.

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.



• 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.




• 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.



unit 1 lesson 4 erosion and deposition by wind, ice, and gravity copyright © houghton mifflin...

Documents

mounds of wind

gravity slide

kinds of ice shape earth

cause erosion

agent of erosion

alpine glacier

large mass of moving

glacier flows