EARTH SCIENCE CHAPTER 7 WEATHERING EROSION SOIL FORMATION

EARTH SCIENCE CHAPTER 7 WEATHERING EROSION SOIL FORMATION

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7. 1 Weathering • What is it? • 2 types 5

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• Mechanical (physical)—rocks are broken down into smaller pieces – Gravity— – Temperature— Ex: frost wedging – Pressure-- Ex: exfoliation 7

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• Review Definitions: – Weathering—rocks at Earth’s surface are broken down and changed – Erosion— – Deposition— – SO? All of these processes have been going on since Earth began! 15

Green? 16

• Chemical weathering— – Hydrolysis— • EX: decomposition of silicates – Oxidation— • EX: rust – Carbonic acid— 17

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– Acid rain—p. H of rain < 5. 6 acidic neutral basic 20

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What can affect rates of weathering? • Climate— – Chemical— – Mechanical— • Type of rock— • Surface area— • Topography—erosion in areas of high relief (steep) w/ deposition in areas of low relief (flat) 24

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7. 2 Erosion and Deposition 28

Agents of erosion • Gravity— • Running water— – Rivers, streams, water falls • Glaciers— • Wind— • Plants and animals (biological)— 29

GRAVITY EROSION 30

RUNNING WATER EROSION 31

GLACIAL EROSION WIND EROSION PLANT EROSION 32

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1930’S DUST BOWL CAUSED BY EROSION OF TOPSOIL DUE TO EXTENSIVE OVERFARMING AND DROUGHT 36

• A word about beaches…. – Ocean waves are constantly rebuilding and shaping coastlines – Sandbars can become barrier islands but they are not permanent! – Barrier islands threatened by hurricanes and beach erosion and rising sea levels 37

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Soil formation • What is soil? – Loose – Formed by chemical, mechanical and biological activity over very long periods of time – Humus— 40

• Soil Texture: – Sand— – Silt— – Clay— SO? The texture of a soil affects its capacity to 41

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Soil profile • A vertical sequence of soil layers • Residual soil— • Transported soil— 45

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