Weathering refers to the process by which rocks and minerals break down when exposed to air, water and living organisms for long enough. Exposed minerals degrade faster than those buried underground.
Chemical weathering includes processes like carbonation (where rainwater with slightly acidic conditions dissolves limestone), hydrolysis (where water wears away at rocks), and other activities accelerated by humans such as burning fossil fuels that emit sulfuric and nitric acids into the air.
Physical
Weathering is a natural process that gradually wears away bits of rock and mineral over time, driven by various forces such as water, ice, acids, salts, plants and animals, temperature variations, as well as changes in atmospheric pressure. Over time this wear and tear creates stunning landforms like canyons and mountains.
Unloading and pressure release are the two primary forms of physical weathering. Unloading occurs when overlying material is removed through erosion, relieving confining pressure from underlying rock structures that is then released, allowing expansion and fracture formation leading to further weathering processes and ultimately more decay processes.
Weathering occurs due to interactions among water, oxygen and minerals found in soil. Human activities like air pollution can accelerate this natural process of weathering; for instance burning fossil fuels such as coal and oil releases chemicals that turn into nitrogen oxide and sulfur dioxide that then fall back down as raindrops – potentially eroding and dissolving limestone, marble and other soft stones from our landscapes.
Chemical
Chemical weathering occurs when rock is dissolving due to environmental chemicals. Rainwater is naturally slightly acidic, and raindrop acidity has the power to dissolve rocks like limestone and chalk. Carbonic acid from decomposing organic matter by plants and animals also plays a part in this process, while Lichens produce weak acidity that weathers rocks as well as changes the chemistry of rocks they come into contact with through plant roots penetration and transformation by changing mineral chemistry – according to Bowen’s Reaction Series silicate minerals such as quartz as well as K- and Na-rich Feldspars weather more easily than their counterparts olivine or pyroxene counterparts do in chemical weathering processes.
People can speed up chemical weathering by emitting sulfur dioxide into the atmosphere through burning coal, smoke and oil, which combines with oxygen to form sulphuric acid that attacks stone surfaces – known as acid rain – which has damaged many historic buildings and monuments. Another type of weathering called thermal stress weathering happens when temperature variations cause rocks to expand and contract over time, eventually weakening them enough that fragmentation occurs over time and layers break apart into fragments or separate into layers.
Biological
Mineral precipitates are small particles of rock formed when minerals interact with water and play an integral part in creating soils and landscapes.
Living things also play an essential part in weathering rocks. Ants and termites for instance contribute by drilling holes into them and digging tunnels through them, leading to physical and chemical weathering processes.
Roots pierce cracks to slowly mechanically break apart rocks. Meanwhile, plants secrete chemicals to extract minerals from them, contributing to chemical weathering. Animals that den or nest in rocks as well as trees widening gaps are biological agents of weathering that also aid the process.
Recent advances in modeling such as PROFILE and ForSAFE have taken steps to incorporate biological processes that contribute to mineral weathering, such as mycorrhizal fungi, litter fall and root uptake into their estimates of the rate at which elements are released from minerals.
Human
Biological weathering is the process by which living organisms such as plants, lichens, bacteria and fungi break down rocks and soil to a greater degree than physical factors alone can. By creating cracks in rock surfaces that lead to more cracking and cleavage of those same surfaces; cracks that in turn increase susceptibility to other physical factors of weathering; burrowing animals such as ants, shrews or earthworms also play a part in biological weathering by excavating holes into which rocks that then become subject to chemical and mechanical weathering as they come closer to surface weathering factors that influence further weathering processes.
Weathering plays an integral role in soil formation. It provides essential materials that make up soil such as clay, silt and sand; additionally it contributes minerals that form sedimentary rock such as limestone and sandstone.
Weathering processes not only serve an environmental function; they are also essential life-support mechanisms for humans. According to studies, those experiencing chronic stress, such as those in low-income societies, experience allostatic load. This condition causes wear-and-tear damage over time in their bodies.