Question 1

(i) What are the three layers of the earth?
(ii) What is a rock?
(iii) Name three types of rocks.
(iv) How are extrusive and intrusive rocks formed?
(v) What do you mean by a rock cycle?
(vi) What are the uses of rocks?
(vii) What are metamorphic rocks?

Answer

(i) Three layers of the earth are:

 Crust (outermost layer), Mantle (middle layer) and core (innermost layer)

(ii) Any natural mass of minerals matter which makes up the earth’s crust is known as rock. Rocks can be of different colour, size and texture.

(iii) There are three types of rocks:
- Igneous rock of primary rocks
- Sedimentary rock
- Metamorphic rock

(iv) formation of extrusive rocks and intrusive rocks is:
- Extrusive rock are formed when molten magma cools down deep down inside the earth’s surface.
- Intrusive rocks are formed when molten magma cools down inside the earth’s crust.



(v) The change of one type of rock into another type under certain conditions in a cyclic manner is called a rock cycle.

(vi) Following are some uses of rocks:
- They are used as fuels.
- They are used in industries.
- They are used in medicines.
- They are used in fertilizers.
- They are used in making roads, houses, building etc.

(vii) The types of rocks formed when igneous and sedimentary rocks undergo heat and pressure are known as metamorphic rocks.

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