Earth Rocks Science
& Minerals
How are rocks
classified?
How are rocks classified
There are 3 types of rocks!
Igneous
Sedimentary
Metamorphic
Rocks are classified & identified
by …
how they
are formed.
Igneous
Igneous: from the Greek word “fire”
Granite
Igneous rock is formed when hot,
molten rock (melted rock) cools and
becomes hardens, becoming solid.
The melting of
the rock
happens
deep within
the Earth.
Volcano Eruptions
Lava
is
magma
that has
erupted
from a
volcano
Lava
Magma – hot, molten rock
Igneous rocks formed from magma
Some igneous rocks are formed inside the
volcano from cooled magma. Trapped
magma cools and hardens very slowly
over thousands or
millions of years.
Granite is an example.
Do you remember the
3 minerals of granite?
Igneous rocks formed from magma
Gabbro is a coarse-grained, dark
colored, igneous rock that forms inside
the volcano. It has time to form large
crystals just like granite.
Gabbro also contains
a white version
of feldspar.
Igneous rocks formed from lava
Magma that erupts from the
volcano is called lava.
Lava cools and hardened almost
instantly when it is
exposed to the
much cooler
temperatures
outside the volcano.
Example of lava (volcanic) rocks
How would
you describe the
luster of this
Quartz
volcanic rock?
What is this rock
called?
Obsidian is often called
what?
“volcanic glass.”
Indians used
this rock to
make tools.
Example of lava (volcanic) rocks
Quartz
Basalt is one of the most
common igneous rocks. It
can be found on the upper
layer of the ocean floor –
and is often call …
“pillow basalt.”
Example of lava (volcanic) rock
Pumice cools
rapidly. Gases
are trapped
inside the rock
as it cools …
leaving a rough, holey texture.
What do you predict will happen
when we put pumice in water?
Why do you think this?
Let’s Review …
There are 3 types of rocks!
Igneous
Sedimentary
Metamorphic
Let’s Review …
Rocks are identified by …
how they
are formed
Let’s Review …
Igneous rocks are formed when…
Molten magma or lava
cools and hardens.
Molten means …
melted
Let’s Review …
Igneous means what in Greek?
Fire
Yep!
Let’s Review …
Does magma hardens inside or
outside the volcano?
Inside the volcano
Slowly or rapidly?
You’re right … very slowly.
Let’s Review …
Does lava rock hardens inside or
outside the volcano?
Outside the volcano
Slowly or rapidly?
You’re right!
Very rapidly.
Let’s Review …
Some rocks that form inside the
volcano from magma are:
Granite
Gabbro
Well done!
Let’s Review …
Some rocks that form outside of
the volcano from cooled lava
are:
Obsidian
Basalt
Pumice
Very good!
1. What thinking map could
we use to record what we
know about igneous rocks?
2. What thinking map could
we use to record how rocks
are classified?
Your Assignment Today
This is our assignment today. Two thinking
maps in your science journal!
1. How Rocks are Classified and Formed
2. All About Igneous Rocks
Use your textbook to help you.
Chapter 6, Lesson 3.
Be neat, draw, label, describe, give
examples, & color.
Next week we’ll learn
more about sedimentary and
metamorphic rocks.
Good Web Links
Geology for Kids
All about volcanos
Go to our class website
for this powerpoint
and these web links.