Weathering refers to the gradual disintegration of rocks, soils and minerals when exposed to elements such as water, air, acids, salts and biological organisms such as plants or animals. Weathering differs from erosion in that disintegrated materials are transported away rather than disintegrating naturally over time.
Physical weathering is the process by which rocks become weaker and disintegrate through actions such as abrasion, frost chattering, temperature fluctuations and salt crystal growth. Animals also play a significant role in physical weathering by digging or trampling them to expose more exposed rock layers for weathering processes to take place.
Physical weathering alters the shape and size of rocks without altering their chemical composition, such as through abrasion, temperature variations, frost wedging or root action caused by burrowing animals.
Abrasion, which involves grinding away at rocks by glacial movement, is one of the primary forms of weathering; this phenomenon has resulted in many of Earth’s deep valleys being created as well as creating their characteristic features such as ravines.
Plants also play a part in mechanical weathering. When their roots grow into cracks in rocks, their roots widen them further until eventually breaking apart the rock itself. Burrowing animals such as moles and rabbits also initiate this form of weathering when digging for food or to create living spaces underground. Aeolian abrasion and pressure release are other types of mechanical weathering processes which take place.
Chemical weathering occurs when minerals in rock change in response to exposure to conditions on Earth that differ from when they formed. This process tends to take longer and should be seen over a longer time span than mechanical weathering.
Water that is slightly acidic can erode limestone and chalk over time, eventually creating large cracks in rocks or caves, as well as dissolving rock material to form what’s known as karst topography.
Chemical weathering involves processes like oxidation, hydrolysis and carbonation that usually take place in hot and humid environments. Plants and animals often accelerate these processes through roots penetrating rocks or the loosening of rocks by growing ivy up buildings.
Plant, animal and other living organisms often form biodeterioration through physical weathering by inhabiting cracks or fissures in rocks. This process can often co-exist with physical weathering as evidenced by tree roots entering rock layers through cracks or fissures or by ants digging away at stones with their nests. Furthermore, humans in agriculture, mining and construction work also ‘break down’ rocks through their activities – thus further contributing to this form of weathering.
Chemical weathering does not physically break down a rock’s structure but changes its chemical composition through processes such as carbonation, hydration, oxidation or hydrolysis; these processes can have an effect on surface minerals within it as well as help dismantle soft sedimentary rocks into smaller pieces through erosion.
Rocks, minerals and soils undergo constant change due to environmental forces such as erosion, chemical changes and mechanical weathering.
Erosion refers to the process by which rocks and other materials deteriorate due to exposure to wind, water or ice. Erosion breaks down materials, loosening them enough for transportation by wind, water or ice agents.
Material produced during this process is then transported and deposited at various places, creating different landforms and natural phenomena such as mountains, canyons, rivers and beaches – such as when waves batter rocks into beaches to form sand deposits.
Weathering susceptibility of rocks depends on their mineralogy and texture; for instance, coarse-grained rocks tend to be more vulnerable than finer-grained ones when exposed to chemicals for chemical weathering processes. Furthermore, climate has an impactful role in shaping both types and rates of weathering processes.
Weathering wears away rock surfaces and forms sandy beaches. In addition, it creates soils rich with various minerals which often make excellent farmland.
Weathering can be a slow or rapid process; for instance, when ivy creeps slowly up a brick wall. Different minerals in rocks weather at different rates; for example, calcite weathers faster than feldspar.
Weathering differs from erosion by not requiring moving agents for transporting weathered particles; however, these weathered particles can still be carried elsewhere by wind or water (see Erosion), eventually being deposited as sediment in valleys, riverbeds or washing into the sea in forms like pebbles, sand and mud.