Ncert 7th geography solution :Chapter 2 Inside our earth

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a. Fill in the blanks.
1. The rock which is made up of molten magma is Igneous rock.
2. The innermost layer of the earth is core.
3. Gold,petroleum and coal are examples of fossils.
4. Rocks which contain fossils are sedimentary  rocks.
5. The thinnest layer of the earth is crust.

b. Match the following.
1. Core- Innermost layer.
2. Minerals- Has definite chemical composition.
3. Rocks- Used for roads and buildings.
4. Clay- Changes into slate.
5. Sial- Made of silicon and alumina.

C. Answer the following questions.
1.what are the three layers of the earth?
The three layers of the earth are
  1. Crust 
  2. Mantle
  3. Core
2. What is a rock?
Any natural mass of mineral matter that makes up the earth's crust is called a rock. Rocks can be of different colours, sizes, and texture.

3. Name three types of rocks.
The three types of rocks are:
  • Igneous rocks. 
  • Sedimentary rocks.
  • Metamorphic rocks.

4. What are the uses of rocks?
Rocks are very useful to us. The hard rocks are used for making roads,houses and buildings. They are even used for games like seven stones,five stones. etc.

d. Answer in detail 
1.Give a brief description of three layers of the earth.
Crust
  • The upper most layer of the earth surface is called crust.
  • It is the thinnest of all the layers.
  • It is almost 35 km on the continental masses and 5 km on the ocean floor. 
  • The main mineral constituents of the continental masses are silica and aluminium soil.
Mantle 

Just beneath the crust is the mantle which extends up to 2900 km below the crust.
Core
  • The innermost layer is the core with a radius of 3500 km.
  • It is made of nickel and iron, i.e nife.
2.What do you understand by 'Rock cycle?
  • One type of rocks changes into another type under certain conditions in a cyclic manner.
  • This process of transformation of the rock from one to another is known as rock cycle.
  • When the molten magma cools down, it solidifies to become igenous rock.
  • The igneous rocks break down into small particles that are transported and deposited to form sedimentary rocks.
  • When the igneous and sedimentary rocks are subjected to great heat and pressure, they change into metamorphic rocks.

3. How extrusive and intrusive rocks are formed?Give an example. 
Extrusive igenous rocks 

When the molten lava comes on the earth's surface, it rapidly cools down and becomes solid . Rocks formed in such a way on the crust are called extrusive igneous rocks e.g. basalt 
Intrusive igneous rocks

Sometimes the molten magma cools down deep inside the earth's crust,leading to the formation of solid rocks. These are called intrusive igneous rocks. E.g. granite.

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