Formation and Weathering of Rocks

Words: 553
Topic: Sciences

In the process of lithification, sedimentary rocks are traditionally formed, according to Lutgens and Tarbuck (58). As a rule, the process of lithification presupposes that sediments should remain under pressure; the sediments expel the so-called connate fluids in the process and finally turn into sediment rock.

The difference between a glassy and a porphyric texture in igneous rocks is rather basic. The glassy texture presupposes that the rock is very smooth and has a homogenous surface. A porphyric structure, in its turn, means that the surface of the rock in question has sponge-like qualities in terms of its texture.

Known for its volcanic origin, pumice is formed in the process of rock being thrown out of the crater of a volcano under a very high pressure and temperature (Lutgens and Tarbuck 62). As a result, the specific texture of pumice is created.

A coarse grained igneous rock of basaltic composition is intrusive. A fine grained igneous rock of felsic composition is extrusive.

As Lutgens and Tarbuck explain, mafic rock, in contrast to granitic rock, is extremely dense. As a rule, the former tend to sink underneath the latter due to the aforementioned difference in density (Lutgens. and Tarbuck 71).

Though both mechanical and chemical weathering contribute both to the process of erosion and to the process of rock formation (Lutgens and Tarbuck 65), there is a tangible difference between the two.

While chemical weathering is traditionally portrayed as the key force in the rock formation process, mechanical weathering is usually viewed as a supplementary one. However, without the mechanical weathering, which helps disintegrate rock into smaller particles, the process of chemical weathering, which requires that minor elements should be removed from the rock.

Life forms, in their turn, also affect the process of weathering to an impressive extent. The organic processes that occur in the soil lead to the creation of humus. The latter, in its turn, contributes to the faster decomposition of the elements of soil and rock into smaller particles, which will be later on split into even tinier pieces by chemical weathering.

The first and the most important difference between detrital and chemical sedimentary rocks concerns their origin. Unlike chemical sedimentary rocks, the material for which is traditionally transported in a river, detrital sedimentary rocks are formed from the material that has been transformed in solid particles.

A coarse crystalline chemical sedimentary rock that does not contain calcite can be identified as claystone or rock salt.

There is a major difference between brecca and siltstone. Unlike siltstone, which is composed of silt-sized sediment grains, brecca is made out of the components of a larger size. As a rule, these components include boulders, pebbles, gravel and cobbles.

When magma touches a cool country rock, temperature around the rock rises. If there is an intrusive igneous rock in the vicinity, contact metamorphism occurs. As a result, rocks are formed.

Two examples of coarse grained nonfoliated metamorphic rocks are marble and quartzite (Lutgens and Tarbuck 61).

Though schist and marble share a range of similarities, they still cannot be considered entirely the same. Indeed, taking a closer look at the two, one will notice that schist is metamorphic; marble, in its turn, is not. In addition, unlike schist, which is traditionally metamorphosed with the help of heat, marble is metamorphosed by considerable pressure.

Works Cited

Lutgens, Frederick K. and Edward J.Tarbuck. “Minerals: Building Blocks of Rocks.” Foundations of Earth Science (7th Edition). Prentice Hall. 2014. Print.