Depending on the expansion and absorption coefficients "Absorption (optical)") of the minerals due to the action of the sun's rays, tension differences are produced in their structure when heated. For example, dark materials absorb more heat than light ones, especially in desert and high mountain regions, where high day/night temperature variations give rocks strong contractions and expansions, which will eventually culminate in the generation of fissures and their fragmentation. The smaller the fragments, the more easily they will be transported by agents such as the wind.

Water in a liquid state has an influence on the physical weathering of rocks, however transformed into ice inside the fissures it can greatly shorten this process. In the period of a few hours the ice can open cracks in the surface rocks and expose them to accelerated action of other agents.

When rocks appear at the most superficial layers of the Earth's crust, they present cracks or fissures (in blocks or plates) called joints, the result of the expansive action they manifest when the compression to which they are subjected inside the crust is reduced. When rainwater or water from melting ice penetrates inside these cracks, it is subjected to another expansive effect when the temperature drops below 0 °C.

As is known, when ice forms, the initial volume of water increases by up to 9%, which exerts pressures inside the crack that exceed 2,000 kilograms for every square centimeter. The result is the so-called gelivation or gelifraction, consisting of the flaking of the rock that after breaking culminates in fragmentation; If the rock is too porous so that water can soak it well, then its disintegration can reach a granular consistency.

As a result of gelivation, fragmentary deposits are created by gravity, which can be observed accumulated on slopes and walls called pedrizas or pedreras, or gleras or screes if they are angular fragments.

Biological activity also acts on the mechanical disintegration of rocks, although it always does so in a second phase. For example, when the rocks already have fissures, these can be occupied by the roots of trees, which exert pressure as they grow and increase in volume. The pressure exerted by the roots is not comparable to that of ice (it is not more than 15 kg per square centimeter), but it can be enough to generate breakage and detachment of rocks, which will then be at the mercy of other agents.

• - Weathering.

• - Rock.

• - Floor.

• - Wikimedia Commons hosts a multimedia gallery on Physical Weathering.

• - Educational nature.

Salts with high solubility common in deserts and accumulated in lake depressions or on rocks and sediments; They generally have fluorescent and white hues, and precipitate in the pore spaces of the rocks. Precipitation, accompanied by changes due to the activity of physical and chemical processes of the salts themselves, create volumetric expansions that lead to the disintegration of rocks.

Depending on the expansion and absorption coefficients "Absorption (optical)") of the minerals due to the action of the sun's rays, tension differences are produced in their structure when heated. For example, dark materials absorb more heat than light ones, especially in desert and high mountain regions, where high day/night temperature variations give rocks strong contractions and expansions, which will eventually culminate in the generation of fissures and their fragmentation. The smaller the fragments, the more easily they will be transported by agents such as the wind.

Water in a liquid state has an influence on the physical weathering of rocks, however transformed into ice inside the fissures it can greatly shorten this process. In the period of a few hours the ice can open cracks in the surface rocks and expose them to accelerated action of other agents.

When rocks appear at the most superficial layers of the Earth's crust, they present cracks or fissures (in blocks or plates) called joints, the result of the expansive action they manifest when the compression to which they are subjected inside the crust is reduced. When rainwater or water from melting ice penetrates inside these cracks, it is subjected to another expansive effect when the temperature drops below 0 °C.

As is known, when ice forms, the initial volume of water increases by up to 9%, which exerts pressures inside the crack that exceed 2,000 kilograms for every square centimeter. The result is the so-called gelivation or gelifraction, consisting of the flaking of the rock that after breaking culminates in fragmentation; If the rock is too porous so that water can soak it well, then its disintegration can reach a granular consistency.

As a result of gelivation, fragmentary deposits are created by gravity, which can be observed accumulated on slopes and walls called pedrizas or pedreras, or gleras or screes if they are angular fragments.

Biological activity also acts on the mechanical disintegration of rocks, although it always does so in a second phase. For example, when the rocks already have fissures, these can be occupied by the roots of trees, which exert pressure as they grow and increase in volume. The pressure exerted by the roots is not comparable to that of ice (it is not more than 15 kg per square centimeter), but it can be enough to generate breakage and detachment of rocks, which will then be at the mercy of other agents.

• - Weathering.

• - Rock.

• - Floor.

• - Wikimedia Commons hosts a multimedia gallery on Physical Weathering.

• - Educational nature.