The layers of Earth are a medium for the geophysicists and geologists to dwell deeper on the concepts of how the formation of rocks took place, the layers that comprise other planets, the medium of incurring the Earth’s resources etc. The earth’s zones are interrelated to each other thus giving sustainability and a distinguishing feature from other planets.

BRIEFING – BIOSPHERE, LITHOSPHERE, HYDROSPHERE 

The limited segment of the planet earth that is a support for the living elements consists of one of the systems referred to as the biosphere. The rocky outermost segment of the earth/terrestrial type planet/natural satellite. It is referred to as the Lithosphere. The word lithosphere is a derivation from the Greek word called ‘lithos’ inferring rocky.  It comprises the topmost portion of the mantle layer and frangible crust. Thirdly, the sites present at the earth’s surface are distributed with huge stretches of water bodies called the hydrosphere. 

SEDIMENTARY ROCKS

The sedimentary rocks are the result of fragmentation of the existing organic substance or rock. The three classifications of the sedimentary rocks are as follows:

  • Clastic sedimentary rocks: For example, sandstone. It is formed by clasts or other fragments of rocks.
  • Organic/biogenic sedimentary rocks: For example, coal. It is obtained from biological substances including plants, bones, shells, etc. that undergo compression and result in rocks.
  • Chemical sedimentary rocks: For example, halite, limestone, flint etc. The chemical sedimentary rocks are a result of chemical precipitation. 

The initiating key to the making up of the organic and clastic sedimentary rocks is the event of weathering down, withering off of the exposed piece of rock into little fragments. The phenomena of erosion, transport these small segments of rocks away from their source via water, ice, wind or biological processes to an all-new site. After the settlement of these sediments at some other site, and getting over a time of collection at the same place, the lowermost layers become compactly packed with almost no space so they form a solid rock. 

A chemical compound called a chemical precipitate —for example, salt, silica and calcium carbonate (CaCO3) is produced. The compound is dissolved in the solvent (generally water), and the resultant solution evaporates, leaving the compound behind in the form of a residue. This phenomenon takes place when the water flows through the crust layer of the earth. This is accompanied by weathering off of the rocks, including dissolution of minerals along with them and gets deposited elsewhere. The dissolved mineral elements are then precipitated post evaporation of water.

METAMORPHIC ROCKS

  • The process of ‘metamorphism’ refers to the transformation of prevailing rock materials to their new changed varieties.
  • Metamorphic rocks contribute to a huge fraction of the Earth’s crust forming 12% of the land surface. They are described based on their protolith, the mineral and chemical makeup, and the properties of texture. 
  • The formation of metamorphic rocks can be viewed as two aspects. Simply, could be a result of deep burial under the surface of the earth. The deep burial subjects them to high pressure of the rock layers above and high temperatures. 
  • Secondly, it could be a result of tectonic processes. For example, continental collisions, (leading to horizontal pressure conditions. Additionally, the process of distortion and friction also assist the formation of metamorphic rocks. 
  • The study of metamorphic rocks can be useful to extract information about the ranges of temperature and pressure prevailing deep down the interiors or at the crust of Earth. 
  • Examples of metamorphic rocks: marble, schist, gneiss, slate, quartzite etc.

IGNEOUS ROCKS

They can be classified into two forms:

  • Intrusive igneous rocks: They contribute largely to the majority composition of igneous rocks. They are produced after the solidification of magma within the crust.  
  • Extrusive igneous rocks: Extrusive igneous rock, colloquially called volcanic rock, is made by the cooling of molten rock (in the form of magma) on the surface of the earth. Through the events such as fissures or volcanic eruptions, magma is brought up to the earth’s surface where it undergoes rapid solidification. 

The characteristics of such rocks are that they have a fine-grained/aphanitic or sometimes glassy appearance. The commonest extrusive igneous rock example is Basalt.

CONCLUSION

The dissection of the earth into various layers is based on the chemical and mechanical properties of every layer. The earth’s zones are interrelated to each other thus giving sustainability and a distinguishing feature from other planets. The process of the rock cycle involves a variety of rocks: sedimentary, igneous, and metamorphic rocks. The initiation of igneous and sedimentary rocks begin in some other form but not rock. The igneous rocks form after the eventual cooling and solidification of rock in its molten form (for example, magma and lava). Sedimentary rocks are originally sediments in their raw form. The metamorphic rock initiates as a rock—sedimentary, igneous, or a different sort of rock formation.