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Soil - The product of weathering Soil- rocks, minerals (mainly sand and clay), and organic material (regolith and organic matter) Soil forms layers of different characteristics called horizons. Weathering Weathering is the process that produces change in the surface of rocks exposed to the atmosphere and/or hydrosphere. The breakdown of the materials of the Earth’s crust into smaller pieces Two Types OF Weathering: Physical weathering is breaking rock by force. ex: hitting, scratching, cracking Chemical weathering is where the rock material is changed into another substance by reacting with a chemical. Frost action (ice wedging)- 1. Water seeps into small cracks in rocks. 2. When the water freezes it expands creating great pressure. 3. The crack widens and allows water to seep deeper into the rock. Frost Wedging Plant action- 1. Tiny root hairs seek out small cracks and pits in rock. 2. Once the root hairs find a place they grow and expand. 3. The expansion causes great pressure and cracks the rock. Plant Roots Exfoliation 1. 2. 3. Rocks formed deep in the Earth are made under high pressure. When the pressure is released the rocks expand & crack. May also be caused by alternate heating and cooling of rocks by weather conditions. Abrasion- rubbing by other rocks. Friction and Repeated Impact OxidationOxygen in the atmosphere chemically reacts with minerals. ex.: rusting of a nail Water (hydrolysis) Minerals are dissolved in water. ex.: Halite, calcite Acid- Carbonic acid: C02 dissolves in rain water forming a weak acid. Acid Rain: Sulfur Dioxide in the atmosphere dissolves in rain water forming a strong acid (sulfuric acid). Wanna hear how acid rain was discovered? Rates of weathering will be influenced by: Surface area exposed - weathering occurs on the surface. More surface exposed, the faster the weathering will occur. A full, solid block has the least surface area. The interior is safe from exposure. A smashed piece has greatest surface area exposed. The interior can now be attacked. Rates of Weathering will depend on: Mineral composition- some minerals are more resistant than others. – ex.:Quartz is resistant to chemical and physical weathering. Where is the rock more resistant to weathering? Where is the rock least resistant to weathering? You might also see it like this… You might also see it like this… Rates of Weathering will depend on: Climatic Conditions: Cold and/or dry climates favor physical weathering. Warm and wet climates favor chemical weathering. Frost action works best in areas where the temperature fluctuates wildly. Chemical Weathering The process that breaks down rock through chemical changes. The agents of chemical weathering Water Oxygen Carbon dioxide Living organisms Acid rain Oxygen Iron combines with oxygen in the presence of water in a processes called oxidation The product of oxidation is rust Carbon Dioxide CO2 dissolves in rain water and creates carbonic acid Carbonic acid easily weathers limestone and marble Living Organisms Lichens that grow on rocks produce weak acids that chemically weather rock Acid Rain Compounds from burning coal, oil and gas react chemically with water forming acids. Acid rain causes very rapid chemical weathering Karst Topography A type of landscape in rainy regions where there is limestone near the surface, characterized by caves, sinkholes, and disappearing streams. Created by chemical weathering of limestone Features of Karst: Sinkholes Features of Karst: Caves Features of Karst: Disappearing Streams Erosion The process by which water, ice, wind or gravity moves fragments of rock and soil. Water Erosion Rivers, streams, and runoff Ice Erosion Glaciers Wind Erosion Mass Movements Landslides, mudslides, slump and creep landslide clip.mpeg