Answer the following questions.
(i) What are the three layers of the
(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?
(i)The three layers of the Earth are
the crust, the mantle and the core.
(ii)A rock refers to any natural mass
of mineral matter that makes up the
(iii)Igneous, sedimentary and
metamorphic rocks are the three types of rocks.
(iv)Extrusive rocks are formed when the
molten magma present inside the
interior comes out onto the
surface, cools down and becomes solid. When molten magma cools
down and solidifies deep within the
crust, intrusive rocks are formed.
(v)The transformation of one type of
rock into another, under certain conditions and in a cyclical
manner is referred to as the rock cycle. For example, igneous
rocks, formed as a result of the solidification of molten magma,
may break down into small particles, which may then be
transported and deposited to form sedimentary rocks. Sedimentary
and igneous rocks transform into metamorphic rocks when subjected
to heat and pressure. These metamorphic rocks may themselves get
broken down to form sedimentary rocks, or they may melt under
great heat and pressure to form molten magma, which would then
once again solidify to form igneous rocks.
(vi) Some of the uses of rocks are
(a) For building roads, houses and buildings
(b) For making jewellery
(c) For cutting and drilling purposes
(d) The fossilised remains of plants and animals present in rocks
help in scientific research.
(e) The different minerals that make up different rocks are used
as fuels, medicines, fertilisers, and in various industries.
(vii)Metamorphic rocks are the rocks
that get formed under great heat and pressure. Igneous and
sedimentary rocks, when subjected to heat and pressure, get
transformed into metamorphic rocks.
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