2 Objective: Explain the agents of mechanical and chemical weathering and analyze the factorsthat affect the rate of weathering.Weathering: The process that breaks down rocks andother substances at Earth’s surface.Erosion: Is the movement of rock particles by wind,water, ice, or gravity.Uniformitarianism: This principle states that the sameprocesses that operate today operated in the past.
3 Mechanical Weathering: Breaks rock into smaller pieces. Freezing and ThawingIce Wedging: Wedges of ice in rocks widen and deepencracks. With repeated freezing & thawing, cracks expanduntil pieces of rock break off.Release of PressurePlant GrowthAnimal ActionsAbrasion: The grinding away of rock particles carried byWater, ice, wind, or gravity.
4 Chemical Weathering: A process that breaks down rock through chemical changes. It produces rock particlesthat have a different mineral make-up from the rock theycame from.Causes of Chemical Weathering:Action of water:OxygenOxidation: When iron combines with oxygen in thePresence of water. The product of this is RUST.Carbon DioxideLiving OrganismsAcid Rain
5 The most important factors that determine the rate at which weathering occurs are the type of rock and theclimate.Permeable: A material that is full of tiny, connected airspaces that allow water to seep through it.Both chemical and mechanical weathering occur fasterIn wet climates.Chemical reactions occur faster at higher temperatures.That’s why chemical weathering occurs more quickly inHot and wet climates.