Presentation on theme: "WEATHERING Definition: The physical and chemical processes that break down rock on earth’s surface."— Presentation transcript:
1 WEATHERINGDefinition: The physical and chemical processes that break down rock on earth’s surface.
2 2 Types of WeatheringPHYSICAL/ MECHANICAL WEATHERING – rocks are fractured and broken apart increasing the surface area.Initial product = Final productCHEMICAL WEATHERING – Chemical reactions dissolve minerals that were stable when the rocks were formed below the surface to types that are now stable at surface temperatures and pressure. Products have different chemical composition than the original.Initial product ≠ Final product
3 EXAMPLES OF CHEMICAL WEATHERING OXIDATION OCCURS when free oxygen combines chemically with metallic elements (usually iron)AKA RUST
4 CARBONATIONWater containing carbonic acid dissolves minerals (all rain water is slightly acidic)Most strongly affected are calcite minerals:limestone and marble
31 SOIL – THE PRODUCT OF WEATHERING AFTER THOUSANDS OF YEARS…
32 SOIL HORIZONSLayers that develop as a result of the weathering processes, biologic activity, and leaching (flow of water through rocks)O = Organic. It consists of fragments of leaf litter, twigs, roots, and other organic material lying on the surface of the soil. This layer is not present in cultivated fields.A = Topsoil. It is usually darker than lower layers, loose, and crumbly with varying amounts of organic matter. This is generally the most productive layer of soil.B = Subsoil. It is usually light colored, dense, and low in organic matter.C = Parent Material. Partially decomposed parent material The unconsolidated organic and mineral material in which soil forms..R = Bedrock. The solid rock that underlies the soil and other unconsolidated material
33 Soil Development Size and thickness of each horizon depends on: ClimateVegetationSlope (gradient or incline)Time
34 2 TYPES OF SOILTRANSPORTED SOIL: SOIL CARRIED BY EROSION AND DEPOSITED ON THE BEDROCK (MOST SOIL IS TRANSPORTED)RESIDUAL SOIL: SOIL FORMED BY THE WEATHERING OF THE BEDROCK DIRECTLY BENEATH IT
37 FERTILE SOIL IS EXTREMELY VALUABLE FOR FOOD PRODUCTION
38 WEATHERING SUMMARY WEATHERING IS THE BREAKDOWN OF ROCK INTO SEDIMENTS PHYSICAL WEATHERING – INCREASES SURFACE AREA - COLD/HUMID CLIMATECHEMICAL WEATHERING – WARM/HUMID CLIMATEIN BOTH CASES, WATER IS THE PRIMARY INGREDIENT
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