by Clara da Silva

Water, a powerful component of weathering, can seep into rock crevices. In regions with temperature changes ranging above and below freezing, water freeze-thaw cycling has the power to break rock. As ice water increases in volume swelling to crack rock. Running water, waves, and glacial ice tumble and stress rock, too. Water is one example of physical (or mechanical) weathering. Other forces include abrasion by rock particles carried by the wind, the widening of cracks by plant roots or fluctuations in temperature and pressure. Even the removal of surface soils can weather; removal of surface weight (unloading) results in cracking known as exfoliation or sheeting. 


Chemical and biological forces are also at play. Chemical weathering can alter the original compounds by dissolving material or changing minerals. Water, oxygen, and carbon dioxide are prime operators in chemical weathering. Some rock components dissolve in water allowing these components to combine with other water-borne substances changing the original rock. The combination of carbon dioxide with water yields a weak carbonic acid able to weaken rock.


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