The Process of Weathering
||edHelper's suggested reading level:
||grades 9 to 10
||Flesch-Kincaid grade level:
||carbonic, exfoliate, hydrolysis, hydronium, hydroxide, iron-bearing, kaolin, refreezes, scrubbers, wind-blown, feldspar, nitric, calcite, exfoliation, oxidation, abrasion
||Yosemite National Park, United States, Acid Rain Control Program, Clean Air Act
Print The Process of Weathering
The Process of Weathering
By Trista L. Pollard
1 The rocks that you step on in your backyard and in front of your house today were formed deep inside our planet. That's right; these unimportant pebbles traveled a long way through extreme temperature and pressure before they reached your backyard. Now that they are on the Earth's surface, these uplifted rocks will be exposed to the gases and water in the atmosphere. These environmental agents change their appearance and composition. Weathering is the process where rocks are changed physically or chemically. Mechanical weathering changes only the physical structure of rocks. Chemical weathering, however, changes only the mineral composition of rock.
2 Plants, animals, ice, gravity, running water, and wind are responsible for the mechanical weathering of rocks. As rocks are changed physically, this may also affect the process of mechanical weathering on underlying rock. When rocks are weathered mechanically, their overlying layer is slowly removed, decreasing the pressure on the underlying rock that forms deep beneath the surface. Once example of this process occurs with granite. As the pressure decreases on granite, it expands forming long curved cracks called joints. After these joints have developed on the surface of the granite, the rock breaks into curved sheets. These curved sheets exfoliate or peel away from the underlying rock. One area where you can see granite exfoliation at work is Yosemite National Park.
3 Mechanical weathering occurs in three major forms. Ice wedging usually occurs in cold climates where water that seeps into rocks freezes. The freezing water increases in volume, by about 10% causing an increase in pressure on the surrounding rock. When the ice thaws and refreezes, the cracks within the rock become wider and deeper. Over time, ice wedging causes the rock to split or break apart. Rocks that are found in higher elevations also experience ice wedging. These are the areas, along with colder climates, where the temperature regularly rises above and falls below freezing. If you visit the northeastern United States, try to look for evidence of ice wedging.
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