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9 Formation of Rocks

and Minerals

l Formation of rocksFormation of rocks
l Formation of rocks
l Different types of rocks
l Igeneous rocks, Sedimentary rocks, Metamorphic RocksIgeneous rocks, Sedimentary rocks, Metamorphic Rocks
Inside l Igeneous rocks, Sedimentary rocks, Metamorphic Rocks
Inside
the
the l Minerals Minerals
l Minerals
Chapter
Chapter
l Uses of rocks and minerals
l Uses of rocks and mineralsUses of rocks and minerals
l Coal, petroleum and natural gas
l Coal, petroleum and natural gasCoal, petroleum and natural gas
l Limitations of sources of energy
l Limitations of sources of energy Limitations of sources of energy
ROCKS

The earth is made up of rocks. What we see as soil
and as mountains is only the surface of the earth,
which is also called the crust . Underlying the crust is

the mantle and below is the core. All rocks are made
up of substances called minerals .
Rocks are formed in many ways. Some are formed
when layers of sand and seashells pile up and get

sandwiched together. Others are made when hot
melted rock from inside the earth erupts out as
volcano. It cools down and goes hard. Rocks can be

changed by heating or squashing. Fossils are often
found in layered rocks, such as limestone and shale .
What happens when a volcano erupts? happens when a volcano erupts?
What
What happens when a volcano erupts?
Volcanoes erupt when hot molten rock from deep
down the earth’s mantle rises through the earth’s
hard outer layers and reaches the surface. The
molten rock is called magma , but when it reaches the
surface it is called lava . Volcano

Magma reaches the surface through vents , the holes in the ground. When

volcanoes erupt, they may throw rocks and ash into the air and lava may
flow down the slopes.
Geologists trace the history of the Earth by studying rocks. They find oil
deposits by studying the age, structure and composition of rock layers.

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