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? 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. Copyright © Houghton Mifflin Harcourt Publishing Company 2

How can wind shape Earth? 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. Copyright © Houghton Mifflin Harcourt Publishing Company 3

How can wind shape Earth? Unit 1 Lesson 4 Erosion and Deposition by Wind, Ice, and Gravity How can wind shape Earth? How does desert pavement form? Copyright © Houghton Mifflin Harcourt Publishing Company 4

How can wind shape Earth? 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. Copyright © Houghton Mifflin Harcourt Publishing Company 5

How can wind shape Earth? 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? Copyright © Houghton Mifflin Harcourt Publishing Company 6

How can wind shape Earth? 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. Copyright © Houghton Mifflin Harcourt Publishing Company 7

Groovy Glaciers What kinds of ice shape Earth? 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. Copyright © Houghton Mifflin Harcourt Publishing Company 8

What kinds of ice shape Earth? 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 U-shaped glacial valley. Copyright © Houghton Mifflin Harcourt Publishing Company 9

What kinds of ice shape Earth? 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. Copyright © Houghton Mifflin Harcourt Publishing Company 10

What kinds of ice shape Earth? 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. Copyright © Houghton Mifflin Harcourt Publishing Company 11

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. Copyright © Houghton Mifflin Harcourt Publishing Company 12

Slippery Slopes How can gravity shape Earth? 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. Copyright © Houghton Mifflin Harcourt Publishing Company 13

How can gravity shape Earth? 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. Copyright © Houghton Mifflin Harcourt Publishing Company 14

How can gravity shape Earth? 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. Copyright © Houghton Mifflin Harcourt Publishing Company 15