Weathering is the slow process of breaking down rocks and minerals as well as wood and artificial materials when they come into contact with water, ice, acids, salts plants or animals. This differs from erosion which involves the transportation of rocks by waterways such as rivers or ocean waves; weathering cannot transport rocks directly; erosion does.
Physical
Physical weathering refers to the process of breaking apart rocks and minerals without changing their chemical makeup, leading to the creation of lithic clasts (rock fragments).
Physical weathering occurs for various reasons. Thermal stress weathering occurs when rocks warm or cool down with changes in temperature and expand/contract along natural fault zones, cracking along these weak points and eventually crumbling away altogether. A similar process called exfoliation peels away rocks away.
Biological and chemical weathering play an essential part in the disintegration of rocks. Plant roots may grow into and widen cracks in rocks, while microbial activity and decay make rainwater more acidic, leading to disintegration of silicate minerals comprising rocks.
Chemical
Chemical weathering transforms rocks into materials with different chemical and physical characteristics over time, when their minerals react with each other or with water and air. Water helps facilitate this process at warmer temperatures to accelerate chemical weathering further.
Iron-containing rocks may be chemically weathered through oxidation (reaction with oxygen), producing rust that weakens them and facilitates their disintegration. Minerals with greater stability such as quartz may withstand this form of weathering better.
Other chemical processes include hydrolysis (reacting with water), carbonation, and salt crystallization or haloclasty – in this last process evaporation of saltwater into cracks and pores of rock causes it to slowly disintegrate over time – such as seen in China’s Stone Forest. Such disintegrated landscapes are known as karst environments and can create stunning landscapes like China’s Stone Forest.
Biological
Biological weathering refers to the process by which organisms such as plants, bacteria, fungi and algae break down rock surfaces through the action of living organisms like plants, bacteria, fungi or algae. Animal burrowing into rock or wearing down its surfaces also play a part. Humans can contribute to this type of weathering by walking over rocks creating frictional forces which loosen particles from within it and break apart its components.
Lichens and mosses are examples of plant-like organisms that break down rocks through both physical and chemical means. Their acid secretions weaken rock layers, making it easier for erosion and ultimate breakdown into sediment. Furthermore, fungal hyphae penetrating the fabric of rock under lichen thallus may further facilitate physical weathering processes.
As stress hormones release when exposed to adversity and violence, Black and Brown people become at greater risk for health conditions like heart disease, diabetes, obesity and mental illness. Closing this gap between Black and Brown lives will require more than general stress management techniques or wellness practices; action must also be taken at local, state and national levels to address structural inequalities that impede good health.
Environmental
Weathering is a natural process that breaks down rocks at or near Earth’s surface through physical, chemical, and biological means.
Physical weathering includes rock fracturing and erosion caused by rain or wind. Plants and animals also play a part in physical weathering – for instance tree roots can enlarge cracks in rocks to break them apart, while digging animals digging or trampling upon rocks may also cause them to crumble over time.
Chemical weathering refers to any process which alters the mineral composition of rocks over time. Oxygen can oxidize certain minerals to alteration products while water can convert silicates to clays. Carbon dioxide in the atmosphere combines with water in precipitation forms acid rainstorms which accelerate this process further.
The Grand Canyon serves as an example of weathering and erosion. Over millions of years, water slowly worn away at its rocks in this deep chasm, leaving behind alluvial deposits, loess deposits and various sedimentary rocks resulting from weathering and erosion.