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How Weathering Impacts the Community
Lab 9 - Jessica Syrylo
Physical Weathering
Physical weathering is a form of weathering that occurs in one of four ways, either by near-surface fracturing, frost and mineral wedging, thermal expansion, or biological activity. Physical weathering breaks apart pieces of the earth using these processes (292). The form of weathering that is shown in this picture is freeze-thaw. This process works by water getting into the surface of the rock and then freezing, which causes the water to expand, making the rock break apart even more.
Chemical Weathering
Chemical weathering occurs when chemical reactions cause surfaces of the earth to be broken down. Chemical weathering can occur in four different ways: dissolution, oxidation, hydrolysis, and biological reactions. The form of weathering that occurred in this picture is oxidation. Oxidation happens when minerals are exposed to oxygen. Since this bridge most likely contains a lot of iron and it is constantly being exposed to oxygen, most of the surface of the bridge is covered in rust.
Biotic Weathering
Biotic weathering is when materials are broke down by any living thing. Common forms of this are root wedging, root acid secretion, and like in this picture, animal burrowing (390). When small animals burrow into rock or wood surfaces, it breaks down what was previously there. In this picture you can see a large hole created at the end of this fallen tree, but throughout the rest of the tree there were many other smaller ones and other signs of organism interaction.
River Erosion
Erosion is when material is moved to a different place than where it originally was broken down. The five types of erosion that occur are wind, river, waves, mass wasting, and glaciers (293). The type of erosion in this picture is river erosion, you can see how the water has carried new material to the bank of the river. You can also see how the water has altered the shape of the side of the river as well.