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Weathering & Erosion Name: __________________ What is Weathering? Weathering: breaking up rock into small sediment such as sand and silt. There are three types of weathering: 1. Mechanical 2. Biological 3. Chemical Examples of Mechanical Weathering 1) Water - Can occur suddenly or slowly -Examples: - Storm surges on shorelines - Spring flooding on river banks - Heavy rainstorms on soil - Waves breaking rocks of all sizes into smaller rocks and eventually sand 2) Wind - Light, dry soil particles are picked up and carried many kilometers. - Windblown particles of soil or sand can wear away rock (like sandpaper wears away wood). - Rate of weathering depends on hardness of rock. - Uluru (Ayers Rock), Australia has formed due to slow erosion of a mountain range; Brilliant red glow at sunset; Surface sediment flakes away like snake shedding its skin creating caves, hollows, and ridges 3) Ice & Glaciers - When glaciers move, the force exerted by these large ice masses, cause rock and soil to scrape, leaving behind a U-shaped valley. - Once a glacier melts, the sediment it has collected and eroded is deposited forming a moraine. - Can be as high as 100m. - Sediment that has been transported and deposited by glaciers is called till. - When rainwater seeps into cracks and pores of rocks it freezes and expands. - As it expands it puts pressure onto walls of the crack, causing it to widen. - Eventually, rock may split down crack or pieces may break off. Examples of Biological Weathering - Cracks in rocks can host soil and seeds. Roots of plant widens crack. - Lichen – fungi/plant grows on rocks -Uses the minerals in rocks for nutrients -Produces an acid which dissolves rock -Leaves a thin layer of soil for other plants to grow on Examples of Chemical Weathering 1) Water - When water passes over a rock, it dissolves certain minerals and carries them away, changing the make up of the rock. 2) Acid Precipitation -Snow or rain caused by pollutants & natural acid in air can cause a rock to break down -This monument once had a lion on the top of it but due to acid rain on limestone, it has deteriorated. Sea Caves - Form from a combination of mechanical weathering (wave erosion) and chemical weathering (water breaking down minerals of rock). Stalactites and Stalagmites -Form when water rich in calcium carbonate drips from a cave roof. Rates of Weathering - Can occur quickly or slowly depending on: - Size of rock —Smaller erodes quicker (more surface exposed) - Minerals making up rock —Granite is much more resistant than marble or limestone - Climate —Cold climates are faced with freezing and ice, warm climates have heavy storms Erosion - Erosion – wearing away and moving rock and soil from one place to another - Caused by: - Water - Wind - Chemical - Living Things Follow-Up Three types of weathering (breaking up land surfaces) 1.Mechanical – changes in landscape where large particles are broken down into smaller particles 2.Biological – changes in the landscape due to the action of living things 3.Chemical – changes in rock or soil due to chemicals in air or water Four causes of erosion (wearing away & moving rock and soil) 1.Water 2.Wind 3.Chemicals 4.Living Things
