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Aim: Weathering and Erosion Weathering • The breakdown of the materials of Earth’s crust into smaller pieces. 1. Physical Weathering • Process by which rocks are broken down into smaller pieces by external conditions. • Types of Physical weathering – Frost heaving and Frost wedging – Plant roots – Friction and impact – Burrowing of animals – Upward Expansion of Rock – Temperature changes Frost Wedging Frost Heaving Plant Roots Friction and Repeated Impact (Stream ABRASION) Burrowing of Animals Upward Expansion of Rock due to the releasing of pressure of overlying rock unloading off the surface. (notice the peeling of the rock) Ex. Granite (Exfoliation…peeling) Temperature Changes Part II Chemical Weathering • The process that breaks down rock through chemical internal changes. • The agents of chemical weathering – Water – Oxygen – Carbon dioxide – Living organisms – Acid rain KEY IDEA: Water plus humid and warm environments • Water weathers rock by dissolving it Oxygen • Iron (Fe) combines with oxygen (O2) in the presence of water in a process called oxidation • The product of oxidation is rust Carbon Dioxide • CO2 dissolves in rain water and makes carbonic acid • Carbonic acid easily weathers Limestone and marble …key mineral is CALCITE 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. • Made 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. A BIG KEY is Water Erosion • Rivers, streams, and runoff Ice Erosion • Glaciers-Ice moves and picks up rock Wind Erosion- mostly in dry climates Mass Movements • Landslides, mudslides, slump and creep landslide clip.mpeg SOME MOVIES (Brain Pop) PHOTOS http://glencoe.mcgrawhill.com/sites/dl/free/0078600499/164213/00 050754.html http://science.nationalgeographic.com/sc ience/photos/weathering-erosiongallery.html ANIMATION: http://ees.as.uky.edu/sites/default/files/el earning/module07swf.swf
