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Download 2. Chemical Weathering
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Weathering Erosion and Deposition DO NOW: • What is a PHYSICAL change? • What is a CHEMICAL change? Weathering- the process that breaks down rocks into smaller fragments- resulting in soil. Rates of weathering are affected by: 1. Surface area-when more is exposed, more weathering occurs. 2. Rock composition- less resistant rocks weather faster. 3.Rocks weather (chemically) faster in hot humid climates Sinkholes in Guatamala TYPES OF WEATHERING 1.Mechanical Weathering- (disintegration) breaks rocks without changing the chemical composition. a. Abrasion- breaking up of rocks as they rub against each other b. Biologic activity Root wedging- roots from plants grow and break rock (ex) sidewalk Animals burrow creating more surface area available for weathering to happen on. c. Frost wedging- water seeps into cracks in rock and expands breaking it (ex) pot hole. Exfoliation or upward expansionigneous intrusions are exposed and expand from lack of pressure. <- Agents of Erosion (wind, running water riVers, wave action, glaciers, mass wasting) weather and move layers of sedimentary rock 2. Chemical Weathering (decomposition)- changes molecular structure of rock, making entirely different products. a. Oxidation- when oxygen unites chemically with minerals in rock (ex) rust b. Hydration- water unites chemically with minerals in rocks – sometimes makes clay. c. Carbonation- carbon dioxide unites chemically with minerals in rocks. Carbon dioxide + water = carbonic acid which dissolves rocks! CO2 Oh no! Slightly Acidic Rain! d. Biologic Activity: Hey, I’m a fun guy! Lichens, mosses, fungi, and enzymes on tree roots can decompose rock CaCO3 + 2 CH3COOH => Ca(CH3COO)2 + CO2 + H2O Calcium Carbonate (chalk) + Acetic Acid (vinegar) => Calcium acetate (That white stuff on the blue) + Carbon Dioxide (The bubbles you saw in the beginning of the experiment) + Water (The reason the chalk looks wet) The Great Chalk Experiment of 2015!!! *N TICE* YOU CAN’T GET SOMETHIN’ FROM NUTTIN’! http://www.yteach.co.uk/page.php/resources/view_all?id=limestone_chalk_marble_rock_water_dissolution_carbonate_mortar_cement_concrete_page_1&from=search Remember this? "Cleopatra's Needle”: Obelisk built in 1443 BCE. It was erected first at Heliopolis, Egypt, and moved to Alexandria in 12 BCE by the Romans. Later, presented to the City of New York by the Khedive of Egypt in 1879, and erected in Central Park early in 1881. Pink granite; 69 ft. x 8 ft. 21 meters high and weighs about 180 tons.) Hmmmm…. Why are they different? Chemical weathering of chalk bedrock in England. Sinkholes: http://youtu.be/tQvv8YFCGsY Infiltration happens http://www.teachersdomain.org/asset/ket09_vid_karst/ What is Erosion? http://youtu.be/XAYhNHhxN0A The MOVEMENT of (weathered) sediment by wind, water, ice or gravity which wears away or lowers Earth’s land surfaces. *Erosion is NOT weathering! What is the result of weathering and erosion? A mature soil profile Sediment Transported soil- was brought by an agent of erosion. Residual soil- weathered native bedrock The End! How are your notes?
