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2.4 External Forces Shaping the Earth

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D
Dan Ewert

External forces shape the Earth through weathering, erosion, and deposition. Weathering breaks down rock through mechanical and chemical processes. Erosion then transports weathered material through water, wind, and glacial activity. The eroded material is deposited elsewhere, forming landforms like deltas at river mouths or dunes in windy regions, completing the cycle that builds soil in new areas.

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External Forces Shaping the Eath
Weathering Physical and chemical processes that change the characteristics of rock on or near the Earth’s surface Breaks rock down into smaller pieces called sediment (mud, sand, or silt) 2 types Mechanical Weathering The composition of the rock stays the same, it just gets broken down into smaller bits
Chemical Weathering Rock is changed into new substance Rust, acid rain, etc.
Erosion Weathered material moved by action of wind, water, ice, or gravity 3 types Water erosion Water strips away material This can happen in rivers and streams by the current eroding the banks and on coasts by waves eroding the shores Eroded material becomes sediment In rivers, sediment is carried downstream and deposited at its mouth and forms a delta
Nile Delta Mississippi Delta
Wind erosion Powerful winds erode soil and blow them hither and thither. May form new landforms, such as dunes May also just get in your nose and ears in Lubbock
Iraq
Glacial erosion Large masses of ice eroding the landscape – glaciation Building soil Weathering and erosion are part of the cycle of dirt (my term) Soil gets stripped away and deposited Soil Factors See p. 45 in textbook

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2.4 External Forces Shaping the Earth

  • 2. Weathering Physical and chemical processes that change the characteristics of rock on or near the Earth’s surface Breaks rock down into smaller pieces called sediment (mud, sand, or silt) 2 types Mechanical Weathering The composition of the rock stays the same, it just gets broken down into smaller bits
  • 3. Chemical Weathering Rock is changed into new substance Rust, acid rain, etc.
  • 4. Erosion Weathered material moved by action of wind, water, ice, or gravity 3 types Water erosion Water strips away material This can happen in rivers and streams by the current eroding the banks and on coasts by waves eroding the shores Eroded material becomes sediment In rivers, sediment is carried downstream and deposited at its mouth and forms a delta
  • 6. Wind erosion Powerful winds erode soil and blow them hither and thither. May form new landforms, such as dunes May also just get in your nose and ears in Lubbock
  • 8. Glacial erosion Large masses of ice eroding the landscape – glaciation Building soil Weathering and erosion are part of the cycle of dirt (my term) Soil gets stripped away and deposited Soil Factors See p. 45 in textbook