Weathering refers to the breaking down and dissolution of rocks and minerals at Earth’s surface through physical, chemical, and biological processes.
Water, ice, acids, salts, plants and animals all play an integral part in weathering rock. Physical weathering includes rocks tumbling downstream or sand eroding an entire mesa and grinding away at it into other rocks.
Water
Water is an integral element in weathering processes. It can freeze and crack rocks, dissolve minerals and alter their chemical makeup, as well as cause erosion by washing away chunks of rock or earth from their original locations.
Erosion is another natural force that shapes our planet, as small pieces of Earth that have been washed away through erosion are eventually deposited elsewhere through deposition.
Carbon dioxide in the atmosphere combines with water to form acid rain, which accelerates chemical weathering. Although this process occurs naturally, humans also contribute by burning fossil fuels.
Ice
Weathering is one of nature’s most potent means of changing landscapes. Its power to carve away at rocks into works of art ranges from desert hoodoos to polished cliffs braced against violent seas is immeasurable.
Mechanical weathering is caused by water in its liquid state. Water seeps into cracks and crevices of rock during the daytime hours before temperatures drop at night and it turns to ice, acting like a wedge to widen them over time.
Repeated freeze-thaw weathering breaks apart rocks very rapidly in areas that experience climates that often fluctuate between above-freezing temperatures and subfreezing temperatures, also known as “ice wedging or frost weathering”.
Acids
Acids are molecules or ions which can give away hydrogen ions to other substances known as bases, providing them with hydrogen for use as a building block in synthesising. Acids have a sour taste and conduct electricity; additionally they turn blue litmus red.
Rock and soil molecules influence their susceptibility to weathering. Carbon dioxide in air reacts with water to form carbonic acid that dissolves limestone, producing spectacular caves such as Carlsbad Caverns in New Mexico.
Weathering rates of rocks depend on their mineralogy and composition as well as local climate. Any remaining material from weathering becomes soil, potentially including iron oxides, clay minerals and organic matter.
Salts
Salts are ionic compounds formed through the reaction between an acid and base, with large cations and anions present, making them excellent electrolytes that conduct electricity. Salts can also dissolve easily in water and have distinctive smells such as the common table salt aroma.
Road crews and plows that apply salt on roads during winter help clear them of snow and ice by lowering its freezing point, making it harder for water molecules to form ice crystals and more safe for plants, animals, and vehicles alike.
Plants
Weathering is an unavoidable natural process that reshapes our landscapes and produces soil. Water, ice, acid rain, salts and plants all act as weathering agents; weathering forces such as erosion are ultimately responsible for shaping landmarks such as the Grand Canyon.
Chemical weathering alters rock structures by altering their chemical makeup; for instance, carbonic acid in rainwater erodes limestone.
Mechanical weathering occurs when rocks crumble as a result of thermal expansion and contraction, changes in pressure or the action of living things such as tree roots enlarging cracks in rocks or lichens etching designs on them.
Animals
There’s a popular perception that animals can detect changes in weather. Although this may not be entirely accurate, animals certainly react to certain environmental signals which indicate when weather patterns shift.
Mechanical weathering occurs when plant roots invade a rock crack and widen it; burrowing animals such as rodents or moles also contribute to mechanical weathering by digging away at it and dislodging stones.
Animals can also contribute to chemical weathering by secreting acids that break down rock minerals. Abrasion is another form of physical weathering which smooths out sharp, jagged rocks into round ones reminiscent of beach glass – this process often creates landforms like hoodoos and mushroom rocks as a result.