It produces a chemical transformation of the rock causing the loss of cohesion and alteration of the rock. The most important processes are atmospheric, water vapor, oxygen and carbon dioxide, which are involved in:

• - Oxidation. It is produced when some minerals react with atmospheric oxygen. New minerals are formed with elements in one or more oxidized states (higher positive charge).

• - Dissolution. It is very important in soluble minerals such as chlorides, nitrates, in calcareous rocks and in karst modeling.

• - Carbonation. It is produced when carbon dioxide combines with water forming carbonic acid, which combines with certain minerals such as calcium carbonate that transforms into bicarbonate: the first is insoluble in water but the second is not, so it is carried away by it. It is a very important and harmful process for soils, especially in drip irrigation.

• - Hydration. In this reaction, water is incorporated into the structure of some minerals, increasing in volume, as happens with gypsum or hydrated calcium sulfate. This process is easy to see, for example, by mixing anhydrite with water, which produces an exothermic reaction (releases heat) when it transforms into gypsum (hydrated calcium sulfate).

• - Hydrolysis. It is the breakdown in the structure of some minerals due to the action of H and OH ions of water, fundamentally in the weathering of feldspar, which is transformed into clays and granite, which can lead to kaolinization" (transformation into clays, especially kaolin).

• - Biochemistry. The action of organic acids from the decomposition of biological materials in the soil or from the physical-chemical action of living plants themselves.

• - Laterization. It is a widespread and deep chemical weathering process in which silica and bases are extracted by leaching (washing) of the parent rock, in which concretions of iron and aluminum are produced. They are residual red deposits associated with flat surface reliefs. In reality, the process is not limited only to the formation of soil (latosols) but is an authentic morphogenetic process. Soil formation regime (pedogenetic) that occurs in warm climates, with abundant rainfall, both in jungle and savanna regions, where great bacterial activity causes humus to be consumed quickly. Clay minerals dissolve, while iron and aluminum accumulate in the form of oxides and give rise to the formation of a hard crust, called laterite (from the Latin later, brick). They are not fertile soils.

Biological or organic weathering consists of the breakdown of rocks due to the activity of animals and plants. The construction of burrows and the action of tree roots can cause mechanical action, while the effects of the presence of water and various organic acids, as well as the increase in carbon dioxide, can complement weathering by altering the rock. Thus, the effects of biological weathering combine the processes of disintegration and alteration.

Vegetation plays a decisive role in chemical weathering processes, since they provide ions and dissolving acids to the water. Organic decomposition generates more or less acidic humus that causes podsolization phenomena.

Weathering disintegrates existing rocks and provides materials to form new ones. However, weathering also plays an important role in soil creation. A soil reflects, to some extent, the rock material from which it was derived, but the basal rock is not the only factor that determines the type of soil, since different soils develop on identical rocks in different areas when the climate varies from one area to another. Therefore, other factors exert important influences on soil development, such as relief, weather and type of vegetation. The composition of a soil varies with depth. The natural or artificial outcrop of a soil reveals a series of zones different from each other. Each of these zones constitutes a horizon, which represents, from the surface inward, the most weathered or decomposed layers and with different accumulations of minerals due to leaching or washing of the soil, until reaching the mother or fresh rock, from which the soil was derived. These soil horizons have developed from the underlying parent material. When this material is first exposed at the surface, the upper part is subject to intense weathering and decomposition occurs rapidly. As the decomposition of the material progresses, the water that percolates downward begins to leach some of the minerals and deposits them at lower levels, which, with the passage of time, become thicker and reach greater depths.[6]​.

Granitic rock, which is the most abundant crystalline rock exposed on the Earth's surface, begins to erode with the destruction of hornblende. The biotite then weathers to vermiculite, and finally oligoclase and microcline are destroyed. All are converted into a mixture of clay minerals and iron oxides.[7]​ The resulting soil is depleted in calcium, sodium and ferrous iron compared to bedrock, and magnesium is reduced by 40% and silicon by 15%. At the same time, the soil is enriched in aluminum and potassium, at least by 50%; for titanium, whose abundance triples; and by ferric iron, whose abundance increases by an order of magnitude compared to bedrock.[8]​.

Basalt rock weathers more easily than granitic rock, due to its formation at higher temperatures and drier conditions. The fine grain size and presence of volcanic glass also accelerate weathering. In tropical environments, it degrades rapidly to clay minerals, aluminum hydroxides, and titanium-enriched iron oxides. Because most basalt is relatively potassium-poor, basalt degrades directly to potassium-poor montmorillonite, then to kaolinite. When leaching is continuous and intense, as in tropical rainforests, the final weathering product is bauxite, the main aluminum mineral. When rainfall is intense but seasonal, as in monsoon climates, the end product of weathering is laterite rich in iron and titanium.[9]​ The conversion of kaolinite to bauxite occurs only with intense leaching, as running river water is in equilibrium with the kaolinite.[10]​.

Soil formation requires between 100 and 1000 years, a very short interval in geological time. As a result, some formations display numerous paleosol beds (fossil soil). For example, the Willwood Formation of Wyoming contains more than 1,000 layers of paleosols in a 770-meter section representing 3.5 million years of geologic time. Paleosols have been identified in formations as old as the Archean (more than 2.5 billion years old). However, paleosols are difficult to recognize in the geologic record. Indications that a sedimentary bed is a paleosol include a gradual lower boundary and a sharp upper boundary, the presence of much clay, poor sorting with few sedimentary structures, torn clasts in the overlying beds, and desiccation cracks containing material from the beds above.

The degree of weathering of a soil can be expressed as the "chemical alteration index", defined as . This varies from 47 for unweathered upper crustal rock to 100 for completely weathered material.[13]​.

Wood can be physically and chemically eroded by hydrolysis and other mineral-relevant processes, but in addition, wood is very susceptible to weathering induced by ultraviolet radiation from sunlight. This induces photochemical reactions that degrade the surface of the wood.[14]​ Photochemical reactions are also important in the wear of paint[15]​ and plastics.[16]​.

• - Erosion.

• - Weathering halo.

• - Reptation.

• - Wiktionary has definitions and other information about weathering.

• - Wikimedia Commons hosts a multimedia category on Weathering.

It produces a chemical transformation of the rock causing the loss of cohesion and alteration of the rock. The most important processes are atmospheric, water vapor, oxygen and carbon dioxide, which are involved in:

• - Oxidation. It is produced when some minerals react with atmospheric oxygen. New minerals are formed with elements in one or more oxidized states (higher positive charge).

• - Dissolution. It is very important in soluble minerals such as chlorides, nitrates, in calcareous rocks and in karst modeling.

• - Carbonation. It is produced when carbon dioxide combines with water forming carbonic acid, which combines with certain minerals such as calcium carbonate that transforms into bicarbonate: the first is insoluble in water but the second is not, so it is carried away by it. It is a very important and harmful process for soils, especially in drip irrigation.

• - Hydration. In this reaction, water is incorporated into the structure of some minerals, increasing in volume, as happens with gypsum or hydrated calcium sulfate. This process is easy to see, for example, by mixing anhydrite with water, which produces an exothermic reaction (releases heat) when it transforms into gypsum (hydrated calcium sulfate).

• - Hydrolysis. It is the breakdown in the structure of some minerals due to the action of H and OH ions of water, fundamentally in the weathering of feldspar, which is transformed into clays and granite, which can lead to kaolinization" (transformation into clays, especially kaolin).

• - Biochemistry. The action of organic acids from the decomposition of biological materials in the soil or from the physical-chemical action of living plants themselves.

• - Laterization. It is a widespread and deep chemical weathering process in which silica and bases are extracted by leaching (washing) of the parent rock, in which concretions of iron and aluminum are produced. They are residual red deposits associated with flat surface reliefs. In reality, the process is not limited only to the formation of soil (latosols) but is an authentic morphogenetic process. Soil formation regime (pedogenetic) that occurs in warm climates, with abundant rainfall, both in jungle and savanna regions, where great bacterial activity causes humus to be consumed quickly. Clay minerals dissolve, while iron and aluminum accumulate in the form of oxides and give rise to the formation of a hard crust, called laterite (from the Latin later, brick). They are not fertile soils.

Biological or organic weathering consists of the breakdown of rocks due to the activity of animals and plants. The construction of burrows and the action of tree roots can cause mechanical action, while the effects of the presence of water and various organic acids, as well as the increase in carbon dioxide, can complement weathering by altering the rock. Thus, the effects of biological weathering combine the processes of disintegration and alteration.

Vegetation plays a decisive role in chemical weathering processes, since they provide ions and dissolving acids to the water. Organic decomposition generates more or less acidic humus that causes podsolization phenomena.

Weathering disintegrates existing rocks and provides materials to form new ones. However, weathering also plays an important role in soil creation. A soil reflects, to some extent, the rock material from which it was derived, but the basal rock is not the only factor that determines the type of soil, since different soils develop on identical rocks in different areas when the climate varies from one area to another. Therefore, other factors exert important influences on soil development, such as relief, weather and type of vegetation. The composition of a soil varies with depth. The natural or artificial outcrop of a soil reveals a series of zones different from each other. Each of these zones constitutes a horizon, which represents, from the surface inward, the most weathered or decomposed layers and with different accumulations of minerals due to leaching or washing of the soil, until reaching the mother or fresh rock, from which the soil was derived. These soil horizons have developed from the underlying parent material. When this material is first exposed at the surface, the upper part is subject to intense weathering and decomposition occurs rapidly. As the decomposition of the material progresses, the water that percolates downward begins to leach some of the minerals and deposits them at lower levels, which, with the passage of time, become thicker and reach greater depths.[6]​.

Granitic rock, which is the most abundant crystalline rock exposed on the Earth's surface, begins to erode with the destruction of hornblende. The biotite then weathers to vermiculite, and finally oligoclase and microcline are destroyed. All are converted into a mixture of clay minerals and iron oxides.[7]​ The resulting soil is depleted in calcium, sodium and ferrous iron compared to bedrock, and magnesium is reduced by 40% and silicon by 15%. At the same time, the soil is enriched in aluminum and potassium, at least by 50%; for titanium, whose abundance triples; and by ferric iron, whose abundance increases by an order of magnitude compared to bedrock.[8]​.

Basalt rock weathers more easily than granitic rock, due to its formation at higher temperatures and drier conditions. The fine grain size and presence of volcanic glass also accelerate weathering. In tropical environments, it degrades rapidly to clay minerals, aluminum hydroxides, and titanium-enriched iron oxides. Because most basalt is relatively potassium-poor, basalt degrades directly to potassium-poor montmorillonite, then to kaolinite. When leaching is continuous and intense, as in tropical rainforests, the final weathering product is bauxite, the main aluminum mineral. When rainfall is intense but seasonal, as in monsoon climates, the end product of weathering is laterite rich in iron and titanium.[9]​ The conversion of kaolinite to bauxite occurs only with intense leaching, as running river water is in equilibrium with the kaolinite.[10]​.

Soil formation requires between 100 and 1000 years, a very short interval in geological time. As a result, some formations display numerous paleosol beds (fossil soil). For example, the Willwood Formation of Wyoming contains more than 1,000 layers of paleosols in a 770-meter section representing 3.5 million years of geologic time. Paleosols have been identified in formations as old as the Archean (more than 2.5 billion years old). However, paleosols are difficult to recognize in the geologic record. Indications that a sedimentary bed is a paleosol include a gradual lower boundary and a sharp upper boundary, the presence of much clay, poor sorting with few sedimentary structures, torn clasts in the overlying beds, and desiccation cracks containing material from the beds above.

The degree of weathering of a soil can be expressed as the "chemical alteration index", defined as . This varies from 47 for unweathered upper crustal rock to 100 for completely weathered material.[13]​.

Wood can be physically and chemically eroded by hydrolysis and other mineral-relevant processes, but in addition, wood is very susceptible to weathering induced by ultraviolet radiation from sunlight. This induces photochemical reactions that degrade the surface of the wood.[14]​ Photochemical reactions are also important in the wear of paint[15]​ and plastics.[16]​.

• - Erosion.

• - Weathering halo.

• - Reptation.

• - Wiktionary has definitions and other information about weathering.

• - Wikimedia Commons hosts a multimedia category on Weathering.