Lexikon
living organisms contribute to the weathering process in many ways.
Trees put down roots through joints or cracks in the rock in order to find moisture. As the tree grows, the roots gradually prize the rock apart.
Even the tiniest bacteria, algae and lichens produce chemicals that help break down the rock on which they live, so they can get the nutrients they need.
Many animals, such as these Piddock shells, bore into rocks for protection either by scraping away the grains or secreting acid to dissolve the rock.
Source: http://www.geolsoc.org.uk/gsl/education/resources/rockcycle/page3568.html
chemical weathering is caused by rain water reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts. These reactions occur particularly when the water is slightly acidic.
These chemical processes need water, and occur more rapidly at higher temperature, so warm, damp climates are best.It means that soil formation is faster under tropic klimate compared to moderate or cold climate.
Chemical weathering (especially hydrolysis and oxidation) is the first stage in the production of soils.
There are different types of chemical weathering, the most important are:
Solution - removal of rock in solution by acidic rainwater. In particular, limestone is weathered by rainwater containing dissolved CO2, (this process is sometimes called carbonation).
Hydrolysis - the breakdown of rock by acidic water to produce clay and soluble salts.
Oxidation - the breakdown of rock by oxygen and water, often giving iron-rich rocks a rusty-coloured weathered surface.
physical weathering is caused by the effects of changing temperature on rocks, causing the rock to break apart. The process is sometimes assisted by water.
There are two main types of physical weathering:
- Freeze-thaw occurs when water continually seeps into cracks, freezes and expands, eventually breaking the rock apart.
- Exfoliation occurs when minerals in the rocks are continuously heated and cooled in hot climates.
- On the effect of cristal-formation of salts or oxide formation of iron or other metals. Increased volume of these chemical componunds break the rock.
- Plnat root growth is able to break the rock too.
Physical weathering happens especially in places places where there is little soil and few plants grow, such as in mountain regions and hot deserts. Either through repeated melting and freezing of water (mountains and tundra) or through expansion and contraction of the surface layer of rocks that are baked by the sun (hot deserts).
weathering is the breakdown of rocks at the Earth’s surface, by the action of rainwater, extremes of temperature, and biological activity. It does not involve the removal of rock material.
There are three types of weathering, physical weathering, chemical weathering and biological weathering.
The result of weathering is soil formation.