Rocks and Minerals | Inside Our Earth – Class 7 Social Science(Geography)
In the previous article, we have discussed the Inside Our Earth. Here, we will discuss the Rocks and Minerals , Rock Cycle and Types of Rocks from chapter- 2 Class 7 Social science.
Rock is the natural mineral mass that makes the earth crust. Mineral has some physical properties and chemical composition. Rocks are of different types based on the texture color and size.
Different types of rocks
- Igneous Rock
These rocks are formed from the volcanic magma. When the molten magma cools, it becomes igneous rocks. These rocks are also known as volcanic rocks.
Igneous rocks are of two types
- a) Intrusive rock- when molten magma cools down, intrusive rocks are formed from magma flows and solidify underground. They are coarse-grained as it is formed from the slow cooling form of magma. Example- Granite, Diorite etc.
- b) Extrusive Rock- when molten magma comes out from the earth’s surface, it forms extrusive rocks. IT is smooth, crystalline and fine-grained. Example- Rhyolite, Andesite, Basalt etc. The Deccan plateau is made of basalt rock.
- Sedimentary Rocks
These rocks are formed by deposition of sediments. When the rocks break down, the small fragment is transported by wind and get compressed and hardened to form sedimentary rocks. They are deposited on the earth surface with water bodies. These rocks are also known as secondary rocks. These rocks also contain fossils of the plant, animal and microorganism that once lived on them. Example- shale, Limestone, Conglomerate etc.
- Metamorphic Rocks
These rocks are formed by heat, pressure and other chemical reactions. They are formed from igneous or sedimentary rocks. In a process called metamorphism.
Example- clag changing to slate, limestone changing to marble etc
Use of Rocks
- Rocks are used for construction activities like for making building, roads etc.
- Rocks are also a source of the mineral used for different purpose in daily life.
- Are used as precious stones as gold and silver.
- Used for chemicals used in fertilizers and medicine industries.
- Used as fuel like crude oil and coal.
Under heat, pressure and chemical process rock are converted into other forms of rock. This process is called the rock cycle. It refers to the transformation of one rock in another form. This process takes hundreds and thousands of years.
1- Rocks come from lava and go back to lava through a process called the rock cycle.
2- When molten magma cools, it solidifies and forms igneous rock.
3- These igneous rocks are broken down into small piece. It is transported and deposited to form sedimentary rock.
4- When sedimentary and igneous rocks are subjected to heat and pressure, they form metamorphic rocks.
5- The metamorphic rocks which are still under great heat and pressure meltdown to form molten magma.
6- This molten magma again cools down and form igneous rock.
A naturally occurring substance with some physical properties and chemical composition is known as minerals.
In the previous article, we have discussed the Inside Our Earth.
For more detail explanation click Online Class 7 Social Science .
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