Weathering

The rocks were formed inside the Earth, under conditions different from those on the surface. The environmental conditions of the surface cause physical and chemical transformations in the rocks.

The weathering is the breakdown rocks of the earth 's surface being in contact with the atmosphere, hydrosphere and biosphere. The transport of these materials does not take place, because if there were, we would speak of erosion.

As a result of weathering, fragments of rocks of different sizes called clasts are obtained. These materials are deposited at the foot of the rocks from which they come, forming a debris.

There are three types of weathering:

• Physical or mechanical weathering.
  
• Chemical weathering.
• Biological weathering.

Physical or mechanical weathering

The physical weathering causes disintegration or breaking rock, without changing their chemical or mineralogical composition. The rock is fracturing and the small fragments that are generated can be eroded and transported later.

Some types of physical weathering are:

• Decompression. Rocks expand and crack because they have been formed with great pressure at great depth, and if they reach the surface, as there is less pressure, they expand, forming cracks or joints that form horizontal slabs.
• Thermoclasty. If the temperature differences between day and night are very great, the rock continuously expands and contracts. As not all the minerals that form them expand in the same way, the rock ends up disintegrating. For example, in the desert.
• Gelifraction. The water in the small crevices of the rock freezes, increases in size and, after repeating it many times, ends up fracturing the rock. For example, the fields.

Stone River in Orihuela del Tremedal (Teruel)

Chemical weathering

The chemical weathering produces a chemical transformation, transforming minerals other substances, causing them to lose cohesion and rock is altered.

Some types of chemical weathering are oxidation, dissolution, carbonation, hydration, hydrolysis.

There is also a type of biochemical weathering, produced by the action of organic acids from the decomposition of remains of living beings or by the physical-chemical action of living plants.

Biological weathering

The action of living beings can weather rocks both physically and chemically.

Activity: Crossword about weathering.