Download ROCKS

THE ROCK CYCLE
How Rocks are Formed
Rocks are made of two or more different minerals
produced in a variety of ways and cycled many
times. This is called the rock cycle.
How are igneous rocks formed?
• Igneous rocks are
called fire rocks.
• Intrusive igneous
rock is formed within
the earth when
magma becomes
trapped in pockets
and then cools
slowly. Ex. Talkeetna
Mtns.
• Extrusive igneous
rock is formed when
volcanoes erupt and
lava rapidly cools
above ground.
•
Granite rocks are intrusive igneous rocks which
were formed by slowly cooling pockets of magma
that were trapped beneath the earth's surface.
Granite is used for long lasting monuments and
for trim and decoration on buildings.
•
Pumice rocks are extrusive igneous rocks which
were formed when lava cooled quickly above
ground. You can see where little pockets of air had
been. This rock is so light, that many pumice rocks
will actually float in water. Pumice is actually a
kind of glass and not a mixture of minerals.
Because this rock is so light, it is used quite often
as a decorative landscape stone. Ground to a
powder, it is used as an abrasive in polish
compounds and in Lava© soap.
•
Obsidian rocks are igneous rocks that form when
lava cools quickly above ground. Obsidian is
actually glass and not a mixture of minerals. The
edges of this rock are very sharp.
How are sedimentary rocks
formed?
• Over long periods of time
little pieces of rock are
eroded by wind and
water. These little pieces
are washed downstream
where they settle to the
bottom of the rivers,
lakes, and oceans.
• Layer after layer is
deposited on top of each
other. These layers are
pressed down over time,
until the bottom layers
slowly turn into
sedimentary rock.
• Sandstone rocks are sedimentary rocks
made from small grains of the minerals
quartz and feldspar. They often form in
layers as seen in this picture. They are
often used as building stones.
• Limestone rocks are sedimentary rocks
that are made from the mineral calcite
which came from the beds of evaporated
seas and lakes and from sea animal
shells. This rock is used in concrete and
is an excellent building stone for humid
regions.
• Shale rock is a type of sedimentary rock
formed from clay that is compacted
together by pressure. They are used to
make bricks and other material that is fired
in a kiln.
How are metamorphic rocks
formed?
• Metamorphic rocks
are rocks that have
"morphed" or
changed into
another kind of
rock.
• were once igneous
or sedimentary
rocks.
• formed under tons
of pressure which
causes heat to
build up, causing
them to change
form.
• Schist rocks are metamorphic.
These rocks can be formed from
basalt, an igneous rock; shale, a
sedimentary rock; or slate, a
metamorphic rock. Through
tremendous heat and pressure,
these rocks were transformed
into this new kind of rock.
• Gneiss rocks are metamorphic.
These rocks may have been
granite, which is an igneous
rock, but heat and pressure
changed it. You can see how the
mineral grains in the rock were
flattened through tremendous
heat and pressure and are
arranged in alternating patterns.
Internet Activity
Layers of the Earth
Have you ever wondered what it is made of?
Cantalope Analogy
Layers
•
•
•
•
•
Crust
Lithosphere
Mantle
Outer Core
Inner Core
Crust
• The outermost layer of the earth consisting of
moving plates floating on top of the liquid hot
upper mantle (molten rock).
• It is composed mainly of basalt and granite and
is part of the lithosphere.
Lithosphere
• Greek for "rocky" sphere. It is the solid outermost shell
of the Earth. It includes the crust and the uppermost
layer of the mantle which is joined to the crust. The
lithosphere is broken up into different plates.
Lithospheric Plates
• Hard plates that float and move on top of the
liquid molten magma of the mantle.
Mantle
• Hot liquid layer below the crust, has currents
that are driven by convection (hotter magma
rises cooler magma sinks).
Outer Core
• The liquid outer core
surrounds the inner
core and is believed
to be composed of
iron mixed with nickel
and trace amounts of
lighter elements.
Inner Core
• The deepest innermost
layer composed mainly of
a nickel is very hot. It is
under so much pressure
that it is solid.
• It has a radius of about
1,220 km and is located
from 5,100 to 6,300 km
below earth's surface and
can be as hot as 6000 C.
Internet Resources
• Science Monster
• Layers of Earth
Video Clip – 9 min.