250
The Earth’s crust is made
up of different rocks. Some
of these are hard but others
are soft and crumbly. They
are formed in different ways.
Rocks and
minerals
Planet Earth
What is a rock?
A rock is formed from minerals.
Most rocks are made up of different
minerals, but some contain just one.
There are three main types of rock:
igneous, sedimentary, and metamorphic.
Metamorphic rock
Sometimes rocks
are crushed
underground, or
scorched by hot
magma. Then they
may be transformed
into new rocks such as
marble, slate, and gneiss.
Igneous rock
Igneous rocks are made
when hot molten magma
from the Earth’s interior
cools and solidifies. Some
harden underground like
granite. Some erupt first
as lava in a volcano.
Sedimentary rock
Wind and water
wear rocks away.
Small pieces, called
sediments, wash into
the sea. These settle
into layers, which
pack together to form
sedimentary rocks, such as
limestone and sandstone.
The rock cycle
Over millions of years, the
rocks in the Earth’s crust
can gradually change from
one type into another. They
are transformed by wind,
water, pressure, and heat.
Fossils in stones
Fossils are the remains
or imprints of plants
and animals that died
millions of years ago,
preserved in stone.
Which type of rock floats on water?
White mica
is a mineral
that you can find in some
kinds of toothpaste.
Gabbro
is a
rock that is used
to make kitchen
surfaces and
floors.
Serpentine
is
a mineral that
stone carvers
use to create
works of art.
