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Shaping the Earth: External Forces

Shaping the Earth: External Forces. Weathering, Erosion and Building Soil World Geo, pgs 42-45. Weathering. External force that refers to the physical and chemical processes that change the characteristics of rock on or near the Earth’s surface Occurs slowly (over years)

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Shaping the Earth: External Forces

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  1. Shaping the Earth: External Forces Weathering, Erosion and Building Soil World Geo, pgs 42-45

  2. Weathering • External force that refers to the physical and chemical processes that change the characteristics of rock on or near the Earth’s surface • Occurs slowly (over years) • Breaks down rock into smaller pieces called sediment- very fine particles of rock ( mud, sand and silt) • 2 types: Mechanical vs Chemical weathering

  3. Mechanical Weathering • Processes that help break rock into smaller sediment pieces • Does not change the composition (the make-up of) the rock, but changes the size. • Effects such as frost or plant roots can break apart rocks, even human activity such as construction, drilling/blasting and mining. • Example: Crystals growing in cracks/crevices can break apart rocks

  4. Chemical Weathering • Occurs when the composition changes into a new substance • Interaction between elements in the air or water and the minerals in the rock • Decomposition- to break down or break up; to break apart • Location and climate also plays apart in how a rock decomposes. Example: Warm/moist climates will produce more chemical weathering than cool dry.

  5. Erosion • Occurs when weathered material is moved by wind, water, ice or gravity. For erosion to occur, a transporting agent like water, needs to be present. • Erosion helps to forms or reshapes landforms and coastal regions, waterbeds and riverbanks. • There is also water, glacial and wind erosion (pages 43-44)

  6. Building Soil • Weathering and erosion are part of a process that produces soil • Soil- the loose mixture of organic matter, air, rock and water. • The variety of soils and the climates in which they are found are determined by the types of vegetation.

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