28 January 2015

CBSE-NCERT Solution: Inside Our Earth

CBSE NCERT Class VII (7th) | Social Studies | Geography

Chapter  :  Inside Our Earth 

CBSE NCERT Solved Question Answer

1. What are the three layers of the interior of the earth?• Ans. Crust – It's the outermost layer of the earth’s crust.
• Mantle – It is the second layer of the earth.
• Core – It is the innermost layer of the earth.
2. Name three types of rocks. Give examples of each type of rock.• Igneous rocks- Granite, basalt
• Sedimentary – Sandstone
• Metamorphic – Slate, marble

Must Read: Inside Our Earth Chapter Summary

3. Define, ‘rock’.It is a natural mass of mineral matter that makes up the earth’s crust.
4. What are the main mineral constituents of continental and oceanic mass?
Continental mass – Silica and alumina.
Oceanic mass – Silica and magnesia.
5. Distinguish between extrusive and intrusive igneous rocks.Extrusive – when the molten lava comes on the earth’s surface, it rapidly cools down and becomes,
solid. Rocks formed in such a way, are called extrusive igneous rocks. They have a very fine, grained
Intrusive – Sometimes, the molten lava cools deep inside the earth’s crust. Solid rocks so formed are
called intrusive igneous rocks. Since they cool down slowly, they form large grains.
CBSE NCERT Class VII (7th) | Social Studies | Inside Our Earth,  CBSE NCERT Solved Environment, CBSE NCERT Solution.6. Describe the process of formation of sedimentary rocks.Rocks roll down, crack, & hit each other and are broken down into smaller fragments. These smaller particles are called ‘sediments’. These sediments are transported and deposited by wind, water, etc.
These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks.
7. How are metamorphic rocks formed?Igneous and sedimentary rocks are transformed to metamorphic rocks under great heat and

8. How are rocks useful to us?Rocks are useful to us in the following ways –
• Hard rocks are used to make roads, houses and buildings.
• Stones are used for playing several games.
• Sculptures are also made out of rocks.
9. Describe the rock cycle.One type of rock changes to another under specific conditions in a cyclical manner. This process of
transformation of rocks from one to another is known as the rock cycle. We know that, when molten
magma cools, it solidifies to become igneous rocks. This I.R. are broken down into smaller particles
that are transported and deposited to form sedimentary rocks. When igneous and sedimentary
rocks are subjected to heat and pressure, they change into metamorphic rocks. The M.R. which are
still under heat and pressure melt down to form molten magma. This molten magma cools down to
form igneous rocks, and so the cycle repeats.
10. Explain the 3 layers of rock.• Crust- It is the uppermost layer of the earth’s surface. It is the thinnest of all the layers. It's about 35 km on the continental masses and only 5 km on the ocean floor.
• Mantle- Just beneath the crust is the mantle which extends to a depth of 2900 km into the earth.
• Core- It is the innermost layer of the earth. It is mainly made up of nickel and iron called ‘nife’. The core has very high temperature and pressure.
11. What are lithospheric plates?Our lithosphere is broken into a number of plates called lithospheric plates. The plates move because of molten magma inside the earth.