Sedimentary rocks

sedimentary rocks

Depending on the origin and formation, on our planet there are different types of rocks. Today we are going to talk about sedimentary rocks. Among all the various geological formations that can be known, there are these types of rocks that make up 75% of the earth's surface. Although this percentage seems quite high, they are a very small proportion and we compare them with the igneous rocks that make up most of the earth's crust. The entire mantle of the earth is also composed of igneous rocks.

In this article we are going to tell you about all the characteristics, origin and formation of sedimentary rocks.

Key features

stratification

They are called like this to those rocks that are formed as a result of the accumulation of various particles that have different sizes and that come from others with rocky formations. All the particles that make up the rock are called sediments. This is where its name comes from. These sediments are transported by external geological agents such as water, ice and wind. The sediments that form the sedimentary rocks are transported by the various geological agents to be deposited in what are known as sedimentary basins.

During the transport of sediments, the stone particles are subjected to various physical and chemical processes that are known by the name of diagenesis. With this name we refer to the process of rock formation. The most normal thing is that sedimentary rocks are formed on the banks of rivers, bottom of the seas, lakes, mouths of rivers and streams or ravines. As you might expect, the formation of sedimentary rocks takes place over billions of years. Therefore, in order to be able to analyze the origin and formation of sedimentary rocks, the scale of geological time.

Formation of sedimentary rocks

places of rock formation

In order to analyze the formation of these types of rocks, it is necessary to consider that there are different types of external geological processes. One of the processes that most affects the transport of rocks is the wind. Geological processes in their first stage are responsible for weathering and eroding pre-existing rocks. Weathering is nothing more than a process that consists of the original rocks breaking into other small pieces. On the other hand, erosion is nothing more than the wear of rocks and their subsequent fracture into smaller particles. The particles that they are eroded and weathered are known by the name of clasts or debris. Let's not forget that water is also a people I follow that manifests itself through rainfall just like the wind.

All the smaller stone fragments produced through weathering or erosion are transported by external agents. Once they have been transported along an important route, all the particles are lodged in sedimentary basins. Throughout these accounts, all the sedimentary particles accumulate little by little. The route from the clasts to the basin depends on their size. That is to say, those smaller sediments will have a much greater distance traveled until they are permanently lodged in the sedimentary basins. On the other hand, the type of dragging and transport that exists depending on the size of the sediments must also be taken into account.

Once they have settled in the sedimentary basins, they begin a process known as sedimentation. And it is that this process will be in charge of the environment and the participation of other organisms. Many living organisms, both animal and plant, can contribute to the formation of sedimentary rocks. In this case, we are referring to the presence of fossils. The rest of the sedimentary rocks are formed from the pressure exerted by the sediments on each other. This pressure, over billions of years, causes a cementing process to end up forming sedimentary rocks.

Sedimentary environment of continental type

sedimentary rock environments

We are going to see what are the different sedimentary environments that exist in the continental area and that give rise to the formation of sedimentary rocks. One of the most important aspects in the formation of these rocks is linked to the environment where they are produced. The sedimentation of the clasts and debris depend on the environment where they are found and on their physical-chemical characteristics. It is a fairly broad classification since there are numerous sedimentary environments, both continental and marine.

Let's see what the different continental sedimentary environments are:

  • Glacier: It is an environment where sedimentation takes place from deposits left by glaciers. Here, the debris comes from the mechanical weathering of the rocks by changes in temperature and the freezing and thawing process. The clasts present angular features and with little presence of organic matter. Sediments usually appear unstratified.
  • Deserts: These sedimentary environments cause the clasts that are formed by mechanical weathering to select the particles and formations such as dunes appear from sands that are approximately 4 mm thick.

Sedimentary rocks of continental sedimentary environment

We are going to see what are the continental environments that can be classified according to the degree of stratification that the rocks formed here present:

  • Fluvial fan: are the river currents and torrents where there are sudden changes in slopes. They are usually found at the foot of mountains and original fan-shaped debris deposits.
  • River: the rivers carry all the clasts that originate from mechanical weathering. Here, with the action of the water current, the clay generates sedimentary rocks:
  • Lacustrine and marshlands: occurs at the bottom of lakes and swamps. Here debris accumulates and is formed with abundant organic matter.
  • lagoon: it is a place where the sands and pretty that arrive through channels of the sea are deposited.
  • Deltaics: are those that are generated in combination of fluvial and swampy environments. The rock is generated from both thick and fine clasts.

I hope that with this information you can learn more about the types of sedimentary rocks that exist depending on their origin.


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