Weathering involves the fragmentation or degradation of rocks and minerals.
Weathering is a process that occurs when minerals and rocks , when in contact with the biosphere, hydrosphere or atmosphere , degrade or fragment . This weathering can be physical or chemical and can be carried out totally or partially.
It should be noted that the consequences of weathering are numerous. The formation of soils and reliefs on Earth is closely associated with this phenomenon. The creation of new rocks is also linked to weathering.
Physical weathering
In the case of physical weathering , the rock breaks or disintegrates without experiencing changes in its chemical structure. Heat , salt and water , for example, are some of the environmental conditions that can cause these variations to develop.
We can add that there are several agents that can cause physical weathering. Among them the following stand out:
* decompression : when lithostatic pressure decreases, rocks found at depth begin to expand and crack. These changes that occur in their structure give rise to the emergence of subhorizontal joints , fractures that do not involve a displacement of the rock. In the case of homogeneous and compact rocks, this results in the appearance of large horizontal slabs;
* thermoclasty : is the name given to the fissure that is seen in the rocks that emerge, and is produced due to the clash between the lower and outer temperatures , particularly those of day and night. During the hours of sunshine, the rock heats up and, consequently, expands, but the cold of the night cools it and contracts it. After a while of going through these opposing processes, it breaks;
* gelifraction : this is the name given to the breakage caused by the pressure of the ice on the rock. When water freezes, its volume increases by 9 percent; If it is inside the rock, the pressure it exerts can fragment it. In climates where humidity reigns and thawing is very common, this type of weathering is very important;
* haloclasty : in this case, it is the salt that causes the breakage. It all begins when it becomes embedded in the fissures and pores of the rocks. Later, when it recrystallizes, since its volume increases, a phenomenon similar to gelifraction takes place.
With respect to thermoclasm , we can add that from this process a common type of mechanical weathering called ball exfoliation arises in granitic rocks. When the sun's radiation penetrates the rock superficially, it heats only a few centimeters of its outer layer, which begins to separate from the core after cooling. This phenomenon is often compared to that of an onion whose layers fall off one by one.
There are different types of weathering.
Chemical and biological processes
Chemical weathering , meanwhile, causes a transformation that alters the composition of the rock. Carbon dioxide , water vapor and oxygen , in different ways, promote these chemical modifications.
Some scientists also refer to organic weathering or biological weathering . This situation originates if there are plants or animals that cause the rock to break and trigger various changes. The growth of a tree's roots and burrowing species cause this type of weathering.
It is important to know that the different types of weathering are often combined. Thus, high temperatures can produce fissures in rocks (physical weathering), into which roots are introduced to exert pressure (biological weathering). The presence of fragments, on the other hand, favors hydrolysis and new breaks (chemical weathering).