The whole earth is made out of some or other kinds of rocks, and it is very easy to identify them anywhere and everywhere. Earth has many layers, and all these layers have different compositions. The surface or the outermost layer of the earth is formed so that most of its portion is sedimentary rocks. If one observes, then they will get to know that sedimentary rocks are the major part of the outermost layer. 

Still, as one goes deeper into it, most portions are formed out of igneous and metamorphic rocks. These are the three major kinds of rocks that form the earth, and every other rock is a kind of one of these. In this article, the focus will be given to sedimentary rocks.

Sedimentary Rocks

There are various rocks, but the one formed throughout millions of years by sediments is known as sedimentary rocks. Sediments are the particles formed after the breakdown of various organic materials formed on earth. These are primarily of two types, one is known as geological detritus, which is the kind of sediment formed from existing rocks on the surface of the earth, and the other one is known as biological detritus, which is formed by the remains of organic matter such as dead bodies of animals in the ocean. 

These sediments further erode and move either by wind or water and settle down at different places depending upon the direction of their carriers and form sedimentary rocks. The process of the formation of sedimentary rocks is called sedimentation. Sedimentation occurs in various ways depending upon the type of sediments. In the case of mi earls, it happens through erosion with the help of water and wind, and in the case of biological matter such as dead bodies of animals, it piles up and forms the rocks. The compositions of all these rocks formed are different from each other and will be further classified into different types. The studies on sedimentary rocks are very important for people because it is the surface of the earth, and all the things made by humans artificially are made on this surface which consists of these rocks.

Types of sedimentary rocks based on origin

There are various ways of formation of sedimentary rocks, and they are classified based on the same. 

• Clastic sedimentary rocks- Clastic rocks are the kind which is formed by various fragments of different types of materials that vary at different places. These are combined and cemented together by the natural process of sedimentation and are further given different names based on the size of fragments formed out of. It is further named mud and clay, and sand and these materials are also different in texture. 
• Biochemical sedimentary rocks- It is a kind of sedimentary rock that is not as common as the clastic one and is formed through a completely different process that involves the formation of tissues in animals via materials found in the environment. Major examples of biochemical sedimentary rocks are limestones which are formed by the skeleton of dead animals, and coal which the plants form.
• Chemical sedimentary rocks- Rocks such as gypsum and rock salt are formed through a process of supersaturation in minerals and are known as chemical sedimentary rocks.
• Other Sedimentary Rocks- This category includes the rocks which are formed by either lava or breccias or any other major disruptive event.

Types of sedimentary rocks on the basis of materials information

Rocks are formed by the mixture of various substances available in nature, and there are various types of sedimentary rocks that consist of more than one substance. The most common and significant among these are discussed below.

• Siliciclastic sedimentary rocks- The most prominent category of sedimentary rocks which are formed by the sedimentation process of weathering and erosion and form a major chunk of variety in rocks on the surface of the earth are these Major examples can be mudrocks and sandstone.
• Carbonate sedimentary rocks- Rocks such as limestone fall under the category of sedimentary carbonate rocks composed of calcite, aragonite, and dolomite, all of which are present in different proportions in different proportions of rocks.
• Organic sedimentary rocks- Rocks such as coal formed out of organic material are known as organic-rich sedimentary rocks.
• Iron-rich sedimentary rocks- Any rock with more than ten per cent of iron in its composition is known as iron-rich sedimentary rock.
• Siliceous sedimentary rocks- Rocks mostly composed of silica, such as chalcedony, fall under this category.
• Phosphatic sedimentary rocks- Sedimentary rocks such as phosphatic mudrocks, which are composed in a way that consists of at least 6% phosphate, is known as phosphatic sedimentary rock.

Conclusion

Sedimentary rocks form a major chunk of the earth’s surface and are very crucial for human beings as all the work is done on the surface because they reside where. Besides, it comes in various shapes, sizes and colours and differentiating it from the other two rocks is a matter of expertise.