Weathering transforms landforms by breaking down rocks and disintegrating into rivers. Furthermore, it creates soil formation as well as concentration of minerals for mining purposes.
Rock can be broken apart using physical, chemical or biological means. Biological weathering refers to plant and animal organisms causing it to weather like rabbits burrowing in cracks in rocks or tree roots enlarging these cracks until eventually breaking apart the rock mass itself.
Physical
Physical weathering breaks rocks and minerals down into smaller chunks through freeze-thaw cycles, abrasion, wet-dry cycles and frost wedging, in which water seeps into cracks then expands when frozen, widening them further and breaking apart rocks. Physical weathering also occurs through exfoliation; this process layers squared off sections on corners and sides like an onion skin resulting in exfoliated layers similar to what would occur under an onion skin.
Physical forces that cause physical weathering may accelerate chemical weathering by making it easier for chemical reactions to take place on larger rocks’ surfaces, similar to how granulated sugar dissolves more rapidly than its lump equivalent in water. Mineral weathering works similarly: The larger its exposed surface area is, the faster it disintegrates will occur; hence why physical weathering is more prevalent in warmer, humid climates than cold, dry ones.
Chemical
Chemical weathering occurs when rocks’ minerals combine with water to form new mineral compositions that become less resistant to erosion and become softer over time. Chemical weathering is most prominent in warmer climates where reaction rates are high.
There are three basic forms of chemical weathering: oxidation, hydrolysis and carbonation. Oxidation involves reacting with oxygen; hydrolysis involves reacting with water; while carbonation involves reacting with carbon dioxide.
As one example of weathering, granite’s feldspar crystals react with water to form clay minerals that corrode its strength. This type of weathering also causes hoodoos in deserts and caves as well as stalactites to grow over time. Chemical weathering also plays a large role in why oceans have such high salt concentrations – rain that has absorbed carbon dioxide from the air makes acidic water that dissolves rocks and sand more quickly, ultimately becoming salty over time until it evaporates leaving only salt deposits behind.
Biological
Biological weathering refers to wear-and-tear caused by plants, animals and microorganisms on rocks. While biological weathering does not alter their composition in any significant way, it can hasten physical or chemical weathering by creating cracks or openings in rock surfaces and speeding up physical or chemical weathering processes.
Plants such as trees and grasses can help weather rocks physically by growing into cracks in them, exerting pressure that fractures rocks while also degrading their minerals.
Fungi and other microorganisms can chemically weather rocks by producing acids which cause corrosion. Lichens, which consist of colonies of fungi and algae living together symbiotically, may also break down rock surfaces by eating away at them from within.
Burrowing animals such as shrews, moles, earthworms and ants can create holes in the ground which enable rock fragments to move to the surface for exposure to other forms of weathering processes. Birds pecking at rocks also accelerate weathering processes while humans contribute biological weathering by walking on rocks which then crush soil particles they carry and engaging in construction activities that widen gaps in them such as road building activities that create gaps between rocks.
Exfoliation
Weathering is an ongoing process that shapes landscapes, creates soil, and plays an essential part in the rock cycle. It occurs when rocks come in contact with water, atmospheric gases, plants and animals as well as temperature changes – this stands in stark contrast to erosion which refers to transport of weathered material by water, wind or ice.
Different types of rock weather at different rates. Intrusive igneous rocks such as granite weather slowly due to being dense and hard, while other rocks such as limestone with carbonate may erode more quickly as their structure allows water to seep through more easily than dense granite rocks.
Chemical weathering occurs when rainwater or sea water come in contact with rocks, dissolving them. This process includes carbonation weathering (where acidic rainwater reacts with calcium in sedimentary rocks to produce chalk or limestone), hydrolysis (where acids break down minerals) and oxidation (where oxygen reacts with water to break down rocks). Bacterial decay also plays a part by releasing inorganic nutrients into soil, leading to chemical weathering.