expansion of rock upon the release of pressure as erosion wears down the

Expansion of rock upon the release of pressure as

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expansion of rock upon the release of pressure as erosion wears down the surface or rocks are excavated -As rocks expand, fractures or joints develop -Almost all rock outcrops contain joints; some planar, some curving, some irregular -Exfoliation:large plutons often split into onion-like sheets along joints that lie parallel to a mountain face/top -Joints not only physically break up a solid mass of rock but are important rock structures since they allow water to penetrate into the rock and start the process of weathering long before the rock reaches the surface -Frost & salt wedging pushes rocks apart -Thermal shock fracture of rocks:because rock is such a poor heat conductor, the outer shell of rock will spall off or explode if exposed to intense heat -Organic activity:burrowing animals, seed germination, roots, organic decay -Grinding by moving glaciers: as the glacier flows over bedrock, both the glacier’s load and the bedrock get ground to a fine powder—rock flour -When the glacier eventually melts, the pebbles, boulders, and fine particles carried are left behind, creating a layer of sediment: glacial till Decaying of plants and organisms, with the help of bacteria, produce inorganic acids which contribute to chemical weathering Physical + chemical weathering help each other: -Physical weathering increases surface area available for chemical weathering -Chemical weathering dissolves grains that hold a rock together, transforms hard minerals into soft minerals, making physical weathering easier -As rocks are fragmented into smaller pieces they can be more easily transported by water and wind Rounding effects of weathering: spheroidal weathering
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-Weathering attacks an exposed rock from all sides at once -Decomposition is faster along the corners and edges Factors that control weathering rates: -Solubility/reactivity/structure:silica tends to be more resistant to chemical weathering because it is linked in long chains -Climate:chemical reaction rates increase with increasing temperature and availability of liquid water -Presence of soil/vegetation:microbial degradation of organic matter in soils produces inorganic and organic acids that accelerate weathering -Slope steepness -Time Chemical weathering:breakdown of rocks by chemical alteration of the constituent minerals and the formation of other minerals that are more stable -Dissolution:mineral constituents pass into solution -Hydrolysis:H+ or OH-, the constituents of water, replace other ions of a mineral -Oxidation:reaction with oxygen; combination of atmospheric oxygen with mineral constituent toproduce an oxide, especially important in the weathering of minerals rich in reduced iron -Hydration:addition of water into the crystal structure of minerals Podsolization: the process of soil formation -A soil consists of rock or sediment that has been modified by physical and chemical interaction with organic material and rainwater, over time, to produce a substrate that can support the growth of plants Regolith:
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