Question:
What is meant by a sedimentary rock? Describe the mode of formation of sedimentary rock.
Answer:
The literal meaning of sedimentary rock is settling; because it is formed due to settling and cementing of fragments of rocks.
The following are three steps to the formation of sedimentary rock:
Fragmentation of rocks:
- Rocks such as Igneous, sedimentary, and metamorphic rocks are broken down into various sizes fragments by denudational agents such as air, water, ice, wave, etc; this process is called fragmentation.
Transportation and deposition of fragments:
- Fragmentation is transported by different geomorphic agents such as water, air, glacial, wave, etc, and deposited.
Lithification:
- These deposited fragments turned into rocks through compaction, this process is called lithification.
Mode of formation of sedimentary rock:
There are three modes of formation:
- Mechanically formed
- Organically formed
- Chemically formed
Mechanically formed sedimentary rock:
It is formed due to the compaction of minerals of fragments at great depth due and fragments are formed due to mechanically weathering or act of physical factors. The followings are an example of mechanically formed sedimentary rocks:
- Sandstone
- Conglomerate
- Limestone
- Shale
- Loess
Organically formed sedimentary rock:
It has organic fragments in the composition. The following are an example of organically formed sedimentary rock:
- Geyserite,
- Chalk
- Limestone
- Coal
Chemically formed sedimentary rocks:
The sedimentary rocks formed due to chemical weathering of rocks :
- Chert
- Limestone
- Halite
- Potash
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