Transcript Igneous Rocks - Noadswood Science

IGNEOUS ROCKS
IGNEOUS ROCKS

To know how igneous rocks are formed
Volcanos
What do you think the rocks surrounding this
volcano will look like?
IGNEOUS ROCKS
Gabbro
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Look at the samples of igneous rocks
 What similarities do they have?
 What differences do they have?

Do they have crystals / layers / fossils / grains etc…
Basalt
Granite
IGNEOUS ROCKS
Basalt
Granite
Rhyolite
Pumice
Obsidian
Andesite
All the rocks are formed
from magma, so why do
they have different sized
crystals?
What may affect how big
the crystals form?
MAGMA & LAVA

We live on the Earth’s crust, and underneath this is a layer called the
mantle
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The mantle and the crust can melt as the Earth is extremely hot - the
molten rock is called magma
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When magma cools it can form igneous
rocks

Magma which reaches the Earth’s
surface is called lava
INTRUSIVE & EXTRUSIVE
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Igneous rocks are formed when magma cools and solidifies
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When magma cools above the surface, extrusive igneous rocks are
formed
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When magma cools below
the surface, intrusive
igneous rocks are formed
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Their crystals vary in size
depending upon how
quickly the magma cools…
MODEL VOLCANO
CRYSTAL COOLING
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Igneous rock crystals vary in size, depending on how quickly the molten
rock cools
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Carry out the salol experiment – place the salol on a hot slide / cold slide
and observe the difference in crystal size…
If salol cools slowly, the particles have longer to arrange
themselves in a pattern. Big crystals form.
The same happens in intrusive rocks as its inside the
earth and is still quite hot
Quick cooling makes small crystals – the
particles have less time to make a pattern.
The same happens to magma when it cools
quickly – normally outside of the volcano (lava)
Some magma cools under
the Earth’s surface.
magma cooling
slowly
area where cooled
magma has
formed rock
The surrounding rocks insulate the
magma. So it takes a long time to cool
down.
The crystals have time to grow big.
Granite is an example of a rock that was
formed under the surface.
When magma leaves a volcano,
we call it lava.
Lava cools quickly in cool air or
under water.
Elaborate
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Rocks from quickly cooled lava have small
crystals, just basalt.
Sometimes the lava cools so quickly that crystals
don’t have time to form at all.
That explains bubbly pumice and glassy obsidian.
CHANGING EARTH

Complete the changing Earth
worksheet
CHANGING EARTH

Complete the changing Earth
worksheet
quickly
Lava
igneous
small
Volcano
Magma
slowly
Mantle
igneous
large