Weathering refers to the gradual break down and disintegration of rocks and minerals near Earth’s surface due to various influences including plant/animal activity, air/water interactions and tectonic movements.
Physical weathering includes fractured rock fragments, freezing and thawing minerals in cracks, as well as exfoliation – which is the peeling away of layers of rocks known as exfoliation.
Physical weathering occurs when rocks disintegrate under the influence of wind, water, ice and plants. These processes erode away at loosen rock fragments while producing chemical weathering products.
Water is an indispensable agent in physical weathering as it dissolves minerals while also altering their shape. With only two hydrogen and one oxygen atoms bonded together, its chemical formula is fairly straightforward. Glaciers also help shape terrain as they move; and, finally, water has also been shown to dissolve carbon dioxide from the air, altering its chemical structure significantly.
Acid rain is another example of physical weathering, with sulfur dioxide and nitrogen gases released into the atmosphere from burning coal, oil, natural gas or other fuels reacting with sunlight to form acids that then fall to Earth as rain, quickly wearing away at limestone, marble and other types of stone. Another form of physical weathering known as frost wedging or ice-fused cracking occurs when water seeps into cracks in rocks then freezes solid, widening and eventually splitting apart over time.
Chemical weathering refers to the process by which rocks change form and break down as a result of chemical interactions with water and other agents, most notably oxidation that turns iron-rich minerals into compounds such as rust. This weakens and crumbles away at rocks over time.
Hydrolysis, another form of chemical weathering, refers to the breakdown of mineral grains under wet conditions to create clays and soluble salts; this form of weathering is most prevalent in warmer and more humid climates.
Air pollution accelerates chemical weathering of rocks by producing acids which react with rainwater and return as acid rain to Earth as acid rain. Lichens, which form symbiotic relationships between fungi and algae, also release chemicals which break apart rocks and soil.
Biological weathering refers to the natural process of disintegrating rock through plant life, animals and microbes. It plays an integral part of landscape ecology and contributes to its diversity; sometimes leading to mineral or metal resources becoming accessible; yet at other times creating or dismantling habitats for wildlife.
Growing roots of trees or plants exert pressure on rocks that weather through biological weathering processes known as “biotic weathering”. Plants produce organic acids which dissolve mineral particles. Microbes contribute to chemical weathering by altering mineral composition; an example being lichen; where fungi release chemicals to break down rock minerals which then decay as algae consume them and leave holes and gaps in the rock which then subject further physical and chemical weathering processes to take place.
Burrowing animals are another force behind biotic weathering by burrowing into the ground and uncovering rock fragments to external factors that accelerate or enhance weathering processes. Humans too contribute to this form of weathering through altering landscapes.
Human activities have the power to alter weathering. For instance, burning fossil fuels such as coal and natural gas releases chemicals into the atmosphere which eventually turn into acid rain which returns back down as rain on Earth, possibly eroding some types of rock surfaces in its path.
Weathering can also be affected through construction activities like road building and mining. When we dig into rocks, this exposes deeper layers that are susceptible to physical (mechanical) and chemical weathering processes.
Stressful daily life experiences can wreak havoc on our bodies. Cortisol production increases in response to danger, but over time this constant stress wears down our heart, arteries, and neuroendocrine system so quickly that it leads to much earlier aging than those experiencing less stress. This phenomenon is especially evident among Black and Brown communities whose members frequently endure socioeconomic disadvantage, persistent prejudice, or discrimination that increases cortisol production and wear down these parts of their system faster than expected.