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Published byKristina Poppy Harmon Modified over 8 years ago
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Forces that Shape the Earth Chapter 5, lesson 4
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Weathering: the breaking down of rock into smaller pieces by natural process Ice Moving Water Vegetation
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1. PHYSICAL Breaking down of rock by physical movements Water Plants Animals Frost wedges into cracks and expands Moving water carries pieces of rock Plants root under rocks and grow Animals burrow and bring pieces underground
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2. CHEMICAL Breaking down of rock by changes in its chemical composition Oxygen VS iron Acids Rocks contain iron which reacts with oxygen in the air Oxygen and iron make rust, which makes the rock less strong than it was before Carbonic acid, or acid rain, can wear away at natural limestone
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Erosion is the picking up and removing of rock pieces Deposition is the dropping off of particles in another location Wind contributes to erosion Carries small particles in the wind Shapes sand dunes Water contributes to erosion Freezing and thawing changes landscape Melting snow affects soft rocks
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Flowing water is a major cause of erosion When the river slows down, some of the particles are deposited as sediment, or loose pieces of rock This can cause the river to meander, or curve
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Gravity and glaciers are other agents that cause erosion Glaciers form when more snow falls than it can melt When ice sheets are about 100 meters thick, it begins to fall downhill When it falls, it takes loose pieces of land with it This mixture of land pulled loose by glaciers is called till These deposits take the form of a ridge or mound, called a moraine
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Weathering results in loose rock pieces which become a part of soil Soil: a mixture of weathered rock, air, water, living things, and humus Humus: material made of decayed plant and animal remains Bacteria, fungi, worms, and insects all contribute to the formation When plants or animals die, their remains enrich the soil and develop layers called soil horizons
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Minerals in soil cannot be replaced, it must be conserved Soil can be ruined by….. Growing too many plants Or the same plants many years in a row Dumping waste in soil Paving over land Building dams
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