4 WEATHERINGI. Weathering - The breakdown of rock due to exposure to the atmosphere, weather, plants, and animals.A. Mechanical Weathering (Physical Weathering) - Rock is split or broken into smaller material without changing its composition.B. Chemical Weathering – Process by which rocks break down as a result of chemical reactions.
5 Mechanical (Physical)Weathering 1. Ice wedging (Porus, rocks with cracks (ice heaving/Frost Action)2. Wetting and drying (for clay containing rocks)3. Plants (lichens, mosses, shrubs, trees)4. Exfoliation (the peeling away of surface layers) due to the relief of pressure from rocks above it.5, Expansion / Contraction (Temperature)6. Abrasion- process of breaking down by means of friction
21 WEATHERINGB. Chemical Weathering - Break down of rocks when the rock minerals are changed to different substances.
22 Chemical Weathering1. Hydrolysis - chemical reaction with water and other substances (feldspar, hornblende, augite) these combine to form clay.2. Oxidation - chemical reaction with oxygen and other substances. (Iron bearing substances) , (red soil in Carolina & Virgina)3. Carbonic acid/Carbonation - Carbon dioxide dissolves in H2O to form carbonic acid. (found in soda), P,Na,Mg and Ca (forms caves)4. Acid Rain - sulfur from cars and coal/oil plants5. Plants/Animals (Lichens) - produce rock dissolving acids
34 RATES OF WEATHERING II. Rates of Weathering 1. The rocks themselves - Igneous and metamorphic most resistant, sedimentary least resistant because of pores.2. Surface Area – More surface area = faster weathering3. Climate - Warm and wet = chemical weatheringCold and Dry = mechanical weathering4. Topography
45 EROSIONIV. EROSION - The breakup and removal of rock by moving natural agents (gravity, glaciers, wind, water)A. Water Erosion1. Raina. Sheet wash - thin sheets of soil removed prevent by - grass, continued plowing, crop rotation, strip crop, terracesb.Gullying - valleys in sloped land - farms2. Running water - most effective agent of erosiona. stream, river, creekb. Stream abrasion - grinding away of rock from bed or bank.c. The faster the river moves = more “stuff” it can carry
46 EROSION B. Wind Erosion - just as water; only less powerful 1. Abrasion - wearing down of particles2.Deflation - removal of loose particles by wind - the most important effect by wind3. Dunes - sand piled up, moved by windC. Glaciers – most powerful agent of erosion
53 EROSIONIV. EROSION - The breakup and removal of rock by moving natural agents (rivers, glaciers, wind, water)A. Mass movements - Earth material down a slope caused by gravity.1. Creep - Very, Very slow down slope movement of soil. (water in soil adds to it)a. Talus - Loose rock fragments at base of cliffs2. Landslides - sudden movement of bedrock or loose rocks down a cliff.3. Slumps - small landslides on hills4. Mudflow - fast movement of water saturated clay and silt.5. Avalanche