For example, when carbonic acid reacts with limestone, it produces calcium bicarbonate, which is partially soluble in water. Carbonic acid has the ability to attack many kinds of rocks, changing them into other forms. One of the most common such reactions occurs when carbon dioxide in the air reacts with water to form a weak acid, carbonic acid. Three chemical reactions in particular are effective in bringing about the weathering of a rock: acid reactions, hydrolysis, and oxidation. Chemical weathering represents a second stage of rock disintegration in which small pieces of rock produced by physical weathering are then further decomposed by chemical processes. Chemical weatheringĬhemical weathering is the process by which changes take place in the chemical composition of rocks. If water fills the cracks in a rock during the day and the temperature falls below freezing at night, the water will freeze, expand, and crack the rock. This effect is likely to be more pronounced if water is present. The constant expansion and contraction of the rocks may result in breakage and mechanical weathering. In some regions, rocks are heated to relatively high temperatures during the day and then cooled to much lower temperatures during the night. ![]() When rock is warmed, it expands when it cools, it contracts. In many locations, changes in temperature and moisture content of the environment cause significant physical weathering. The wind-sandpaper scours off pieces of grit and sand from these rocks, contributing to their physical weathering. Tiny particles of sand are carried along by the wind, a current of air that acts like sandpaper on rocks that stand in its pathway. Imagine a windstorm blowing across a broad expanse of sandy desert. As pressure on these rocks is relieved, they may begin to expand outward, often breaking into thin sheets by a process known as exfoliation.Ībrasion can also cause physical weathering. As overlying rocks and soils are removed by natural or human-caused forces, underlying rocks may work their way to Earth ’s surface. Ground movements can also result in physical weathering. When the boulder strikes solid ground, it may break apart into many smaller pieces. Large boulder to break loose from the top of a mountain and fall. This process can come about as the result of a number of natural processes. Physical (mechanical) weatheringĭuring physical weathering, a large piece of rock is broken down into smaller and smaller pieces. But rocks beneath a humid rainforest are more likely to be weathered by chemical reactions made possible by abundant water. ![]() ![]() For example, rocky formations along a seacoast are likely to be exposed to the mechanical action of waves and tides. The exact way in which weathering occurs in any particular situation depends primarily on two factors: the type of rock and the environmental conditions to which the rock is exposed. Weathering is an important phenomenon for the human species because it is the mechanism by which one of the planet ’s most important natural resources -soil -is formed. Weathering is the process by which rocks and minerals are decomposed into simpler materials by means of physical (mechanical), chemical, and biological processes.
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