Weathering refers to the gradual breakdown of rocks, soils and minerals – including wood and man-made materials – due to exposure to water, air and biological organisms. It differs from erosion, which involves movement of material.
Mechanical weathering breaks rocks down into smaller pieces through processes such as freeze-thaw, abrasion and thermal stress.
Physical
Physical weathering causes rocks to break apart through various means. These methods include abrasion, freeze-thaw cycles, wedging, and root expansion. Breaking apart rocks exposes more surface area for weathering to take place at once and therefore increases their rate of weathering.
Water is an effective agent in physical weathering. When temperatures fall, water seeps into cracks and pores in rocks where it collects as moisture, eventually freezing over and acting as a wedge to widen cracks – known as frost wedging.
Burrowing animals also contribute to physical weathering by breaking and stirring rocks and sediments, while plants that seek water and nutrients may push their roots through rock fractures to find water, thus widening cracks further and making chemical weathering easier to work on them. Furthermore, root growth itself creates organic acids which aid chemical weathering processes.
Chemical
Chemical weathering of rocks involves chemical reactions that alter the form or structure of rock mineral particles. This form of weathering takes much longer than physical or mechanical weathering; its speed depends on temperature, moisture levels and surface area of mineral particles as well as which minerals comprise it and their relative stability during weathering processes.
Weathering involves various chemical processes that lead to weakening and disintegration of rocks, most frequently caused by exposure to moist conditions over long periods. Weathering usually begins with exposure of rocks to oxygen for extended periods. This exposure leads to further chemical reactions such as oxidation, hydrolysis and carbonation that contributes to weathering processes.
Oxidation refers to the process by which minerals react with oxygen, decreasing their resistance to weathering and making them less resistant. Iron rusts. Hydrolysis involves water reacting with rock minerals; for instance feldspar may be altered into clay minerals by this method. Carbonation involves rainwater reacting with carbon dioxide in the air to form acidic water which dissolves silicate minerals like silicates into solution.
Biological
Biological weathering refers to the degradation of rocks and minerals by means of plants, animals and microorganisms – typically plants, animals and microorganisms – over time. Although this process takes more time than its physical equivalent does it help contribute to breaking down fragments of rock and mineral into their basic constituent parts.
Plant roots that penetrate rock surfaces exert pressure that widens cracks and makes them more vulnerable to further weathering. Furthermore, plants contribute chemical weathering by producing organic acids which corrode minerals of rocks while lichens – which form colonies of fungi and algae – contribute biological weathering by solubilizing minerals from rocks surfaces.
Animals play an essential role in biological weathering by disturbing the arrangement of rocks and soil, helping break apart large chunks of rock into smaller ones and expose them to greater physical, chemical, and biological weathering processes. Even humans indirectly contribute to biological weathering by walking over rock surfaces and crushing its particles.
Human
Weathering refers to more than just soil erosion near busy roads; it also refers to how socioeconomic hardship, political marginalization, racism and discrimination can gradually diminish people’s health over time; ultimately leading them to die early or be left with reduced lifespan due to these experiences.
Humans accelerate nature’s weathering process by burning fossil fuels such as coal, oil and gas – this releases harmful emissions such as nitrogen oxide and sulfur dioxide which combine with sunlight and atmospheric moisture to form acid raindrops which quickly degrade limestone, marble and other types of stone surfaces.
Recent discoveries reveal that certain trees’ symbiotic fungi can influence mineral stability and release inorganic nutrients, acting like biological weathering agents. Studies also revealed that Black women experience faster weathering due to shorter telomeres than White counterparts, suggesting faster weathering processes within their bodies.