Page 124 - SST Class 07

INTRUSIVE ROCKS
Cooled rock that has
risen close to the
DEEP-SEA FLOOR
The earth’s surface earth’s surface.
beneath the seas
and oceans.

SEDIMENTARY ROCKS
These rocks form over
long periods from broken
rocks, chemical sediment
and debris.

BASALTIC LAYER
Basalt rock forms
the deep-sea floor.
IGNEOUS ROCKS
This kind of rock is formed from
magma (liquid rock) that has cooled
and hardened inside the earth.
METAMORPHIC ROCKS
These rocks have been exposed to
lots of high pressure and very
hot temperatures.

The Earth’s Crust

Uses of Rocks and Minerals g These igneous rocks are exposed to different

g In ancient times, rocks were used to make agents of weathering and erosion on the
tools and weapons. earth’s surface.
g Rocks are widely used in the construction of g The broken rock fragments, when trans-
roads, houses and buildings. ported and deposited in basins, form
sedimentary rocks.
g Minerals like coal and petroleum provide
the sources of power. g The leftover igneous rocks and the newly
formed sedimentary rocks are subjected to
g Chemicals found in some sedimentary rocks
intense heat and pressure. They change into
are used to make fertilizers.
metamorphic rocks in due course of time.
g Soil is formed from rocks.
g The sedimentary and metamorphic rocks
Rock Cycle
are buried again and melt to form magma.
The change of one type of rock into another type
g This magma again cools down and forms
under certain conditions in a cyclic manner is
igneous rocks.
known as the rock cycle. The rock cycle has
neither a beginning nor an end. In this process, g Throughout the geological period of millions
the matter of the earth’s crust is not lost. of years, rocks and minerals have been
changing due to the working of the rock
The rocks cycle operates in the following ways :
cycle.
g The hot and molten magma forms igneous
rocks on cooling.

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