Weathering, also known as erosion, is the gradual disintegration of rocks and minerals near Earth’s surface due to physical and chemical processes occurring simultaneously on its surface. This continuous process is driven by water, ice, plants and living animals interacting together on this planet.
Rocks with natural weaknesses such as bedding planes, cracks and joints are more prone to mechanical weathering than rocks without these natural weaknesses. Mechanical weathering affects rocks which contain these natural vulnerabilities by wearing away at them through mechanical means such as weathering.
Water
Water is a key factor in weathering. It carries chemicals that carry away rock and soil while rain falls as mildly acidic raindrops, slowly dissolving limestone shorelines. Symbiotic fungi associated with tree roots may also impact mineral stability and cause chemical weathering reactions; for instance iron in rocks may break down and oxidize to form reddish-orange rust that colors the rock itself; silicate minerals in igneous rock convert to clays or disintegrate.
Mechanical weathering of rocks also works to break them apart, through both abrasion and erosion. Abrasion occurs when one rock bumps against another; erosion happens when rock fragments are carried away by water or ice flow, with liquid water seeping into cracks in rocks and freezing over, eventually cracking it further than before.
Ice
Weathering is the process of breaking rocks down into smaller pieces by mechanical or chemical means, with greater surface area rocks being easier to weather than others.
Ice is an invaluable mechanical weathering agent. Water seeps into cracks in rocks, then freezes when temperatures drop, creating cracks. As this freeze-thaw cycle repeats itself, wedged rocks may separate or larger ones be broken up into smaller fragments by mechanical weathering.
Minerals weather at different rates; some dissolve into water while others resist its effects more efficiently. Rocks that contain less resistant minerals tend to weather faster, leading to smooth sandstone cliffs in desert environments or rough, pitted rock spires like Devil’s Tower with quicker crumbling than harder and thicker rocks.
Weathering Agents
Earth’s rocks and minerals are gradually dismantled through physical and chemical weathering processes such as water, ice, acids, salts, plants, animals and changes in temperature that contribute to weathering.
Mechanical weathering occurs through forces such as rock fracture, freezing and thawing cycles or breaking during transport by rivers and glaciers. Plants and animals may also act as agents of mechanical weathering – for instance when roots grow into cracks in rocks which, with time, widen to weakening of said rock over time.
Chemical weathering occurs as the result of chemical interactions between minerals in rocks and external agents, such as oxygen reacting with iron to form compounds like rust that break apart rocks and weaken their foundations. This form of alteration is also known as weathering.
Chemical Weathering
Chemical weathering occurs when rocks break apart through various chemical reactions such as hydration, oxidation, reduction, hydrolysis and dissolution. Chemical weathering tends to occur more commonly in areas with large bodies of water.
Carbon dioxide gas found in the atmosphere reacts with rainwater to form weak acids like carbonic acid that seep through cracks in rock surfaces and dissolve them, eventually breaking them down and leading to further environmental degradation.
Minerals formed under high pressures and temperatures deep within the Earth can undergo chemical weathering processes that lead to their transformation into new minerals on Earth’s surface, known as chemical weathering. Chemical weathering contributes to landscape denudation in cold climates. Chemical weathering also has effects on hydrology, biota and stability of hillslopes; its processes could accelerate erosion while rapidly creating karst topographies.