PHYSICAL WEATHERING
Physical Weathering is the physical breakdown of rocks and minerals. Physical weathering can also be referred to as mechanical weathering. This interactive lesson gives digital example of different
forms of physical weathering allowing students to observe different forms and
outcomes of physical weathering.
fROST wedging
Ice wedging occurs when water repeatedly thaws and freezes in a crack of a rock. As the water freezes it expands and breaks the rocks. The linked artifact is a hands-on lab activity that shows how water expands when it is frozen.
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ROOT WEDGINGDuring root wedging plants move their roots into small cracks and fractures in rocks and minerals to expand their hold in the earth. As the root grows it creates an outward pressure on the rocks and minerals causing them to fracture or break more then they originally were. The attached pictures capture the strength of a root as it weathers a rock.
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abrasionRock abrasion is the breaking down and weathering of rocks by natural forces. When wind, gravity, or water cause rocks, sand, and other particles to scratch and hit against each other. This causes the surface of the rock to wears away at slow or quick speed depending on the rate in which they rub against each other. The attached hands-on activity allows one to complete an investigation to observe how abrasion occurs.
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water
Water is a physical weathering agent. Rocks break when moving water moves them against each other. Running water alone also wears away rock, like at the bottom of waterfalls. Attached is a lesson plan to show how water causes weathering in rocks.
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CHEMICAL WEATHERING
Chemical weathering involves the change in the chemical composition of rocks; often leading to breaking or wearing away of the rock. This type of weathering happens over a period of time and can change a rocks color. The attached website shows a number of images that exemplifies chemical weathering.
oxidationOxidation is a chemical reaction that is the combining of oxygen with various elements and compounds. An example of oxidation is the rusting of iron nails. The attached interactive website shows examples of oxidation weathering when the iron mineral in sandstone changes the color of the rock.
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Dissolution
Dissolution is when acid dissolves a rock leaving nothing solid behind. For example, the slow action of carbonic acid on limestone over a very long time causes limestone caves. The attached animation shows how caves are formed in limestone by dissolution weathering.
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