Weathering & Erosion Chapter 14

Weathering Natural process by which atmospheric and environmental agents change, disintegrate, and decompose rocks Wind, rain, temperature changes

Mechanical Weathering Weathering by physical means Does not change rock composition, only makes it smaller Ice, plants, animals, gravity, running water, and wind Exfoliation – peeling off of layers of rock

Exfoliation

Mechanical Weathering Ice wedging –Freeze-thaw cycles break off rock pieces Abrasion –Gravity, running water, and wind Organic activity –Root growth, burrowing animals

Chemical Weathering Rock breaks down by means of chemical reactions Oxidation –Rocks with iron will rust (Georgia red clay) Hydrolysis –Rock reacts with water

Chemical Weathering Carbonation –Carbonic acid reacts with rocks to form carbonates (Acid rain) Organic Acids –Acids produced by living organisms –Lichens, mosses

Chemical Weathering Acid precipitation –Burning fossil fuels –NO x + H 2 O  HNO x –SO x + H 2 O  H 2 SO x

Surface Area

Rates of Weathering Differential Weathering –Softer rock weathers faster than harder rock Rock composition –In general, sedimentary weathers fastest Exposure –Surface area, fractures, joints

Rates of Weathering Climate –Alternating hot and cold climates --- fastest weathering –Warm, humid climates --- fairly fast –Hot, dry climates --- slowest Topography / Elevation –Elevation and slope increases weathering

Rates of Weathering Human Activities –Mining, construction, rec activities can increase rates

Rates of Weathering Plant and Animal Activity –Roots and burrowing can weaken rock –Bigger animals bring smaller animals that can burrow into rock

Erosion Materials loosened, dissolved, or worn away and transported from one place to another by a natural agent Natural agents are wind, water, ice, or gravity

Sheet Erosion Layers of topsoil being stripped away

Soil Conservation Methods Contour Plowing Strip Cropping Terracing Crop Rotation

Gravity & Erosion Mass Movement –Rockfalls –Landslides –Mudflows –Slumps –Solifluction –Creep

Landslides

Landforms Mountains Plains – flat & at sea level Plateaus – flat & at high elevation

Mountains Tetons – uplift & erosion Appalachians – only erosion

Buttes & Mesas Buttes Mesas