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Erosion & Deposition Erosion • the process by which natural forces move weathered rock and soil from one place to another Causes of Erosion • Gravity • Running water • Wind • Glaciers Causes of Erosion • Gravity = force that moves rock and other materials downhill – Mass movement—process of moving sediment downhill – May be fast or slow Causes of Erosion • Gravity – Force that moves rock and other materials downhill – Mass movement—process of moving sediment downhill – May be fast or slow – Types of mass movement: • Landslides—rock & soil slide quickly down a steep slope Causes of Erosion • Gravity – Force that moves rock and other materials downhill – Mass movement—process of moving sediment downhill – May be fast or slow – Types of mass movement: • Mudflows—rapid downhill movement of a mixture of water, rock, and soil Causes of Erosion • Gravity – Force that moves rock and other materials downhill – Mass movement—process of moving sediment downhill – May be fast or slow – Types of mass movement: • Slump—one large mass of rock and soil suddenly slips down a slope Causes of Erosion • Gravity – Force that moves rock and other materials downhill – Mass movement—process of moving sediment downhill – May be fast or slow – Types of mass movement: • Creep—very slow downhill movement of rock and soil Causes of Erosion • Running Water = #1 agent of erosion Causes of Erosion • Running Water – #1 agent of erosion – Types of running water: • Streams – Small streams = creeks – Large streams = rivers Colorado River Grand Canyon Causes of Erosion • Running Water – #1 agent of erosion – Types of running water: • Streams • Waves Causes of Erosion • Wind = Blows sediment Sand dunes Dust Bowl Causes of Erosion • Glaciers = Large masses of moving ice – Movement changes the land beneath them Alaska Deposition • the natural process of laying down sediments in a new location – creates new landforms Deposition • the natural process of laying down sediments in a new location – creates new landforms: • Oxbow lake— deposition blocks off part of a river Deposition • the natural process of laying down sediments in a new location – creates new landforms: • Delta— sediment is deposited at the end of a river Deposition • deposited sediments are laid down in layers • layers of sediment are compacted under pressure and eventually form sedimentary rock Deposition • deposited sediments are laid down in layers • Layers of sediment are compacted under pressure and eventually form sedimentary rock Sedimentary rocks are like ogres and onions…they have layers. Deposition • deposited sediments are laid down in layers • Layers of sediment are compacted under pressure and eventually form sedimentary rock Most fossils are found in sedimentary rocks because organisms get covered and preserved by the layers then mineral replacement occurs over time. Weathering, erosion and deposition are all part of a never-ending cycle that constantly shapes and reshapes the land. Weathering, erosion and deposition are all part of a never-ending cycle that constantly shapes and reshapes the land. Destructive forces—break down Constructive forces—build up Weathering, erosion and deposition are all part of a never-ending cycle that constantly shapes and reshapes the land. Destructive Forces Destructive Forces Weathering Erosion Breaks down rock Carries sediment away Constructive Forces Deposition Takes sediment to a new location to build new rock layers
