1. Section 6.2 Igneous rocks

2. The Magma Process to form Minerals (Unit 4)
Molten (liquid) rock in a magma chamber
At, near or under earth’s surface, RISES
The magma begins to COOL.
The atoms, ions and molecules combine
to form various mineral compounds.
The molecules arrange into an orderly repeating pattern to form CRYSTALS.
quartz

3. Igneous Rocks form from molten (melted) rock
Magma located
Lava located
Cooling rate is:
Crystals are:
Cooling rate:
Crystals are:
Intrusive igneous rocks
Where:
Extrusive igneous rocks
Where:
Very coarse grains
10 mm or larger
Coarse grains
1 mm -10 mm
Fine-grained
Less than 1 mm
Glassy or gassy
(no crystals grains)
Example rocks:
Example rocks:
Example rocks:
Example rocks:

4. The RATE at which the molten magma cools determines the crystal size.
If the magma cools s-l-o-w-l-y
(under the surface taking hundreds of years)
then the crystals will be…
granite
well-formed

5. Crystallization of Salol Lab
Slow cooling made large, well-formed crystals
Quick cooling made small crystals
Slow cooling allowed for larger, well-defined crystals

6. Group/Sort
Sort the igneous rocks into 3 groups by their crystal size: large small None: glassy or gas holes

7. Intrusive igneous Rocks

8. Igneous rock terms to know
Magma - Lava
Intrusive – Extrusive
Plutonic – Volcanic
Mafic - Felsic
Course texture - Fine texture
High viscosity – Low viscosity
Porphrytic - Pyroclastic

9. Igneous Plutons (pg 125) Laccolith Volcanic neck Volcano Sill Dike
Batholith

10. Violent pyroclastic
eruption
Ocean floor
LAVA
Fissure eruption

11. If the magma reaches the surface, erupts from a volcano as LAVA flows on the surface or erupts underwater, it cools quickly, and the crystals will be small / microscopic / not well-formed
basalt
If the magma erupts explosively from a volcano and cools at a very fast rate, quickly, then the crystals will…. None
obsidian a volcanic rock, cools instantly.
so it has no crystal structure, but a
glass-like structure
EXTRUSIVE

12. Felsic magma Mafec* magma
Page 121
Felsic magma Mafec* magma
Feldspar, silica magnesium and iron

13. Mafic (dark) Dark colored minerals: Magnesium and iron Fe
Olivine, pyroxene,
Hornblende, augite,
biotite
Less than 50% silica

14. Felsic (light) Light colored minerals: Quartz, orthoclase Feldspar
More than 60% silica

15. Which has a HIGH viscosity?
Resistance to flow
honey
water

16. Is this igneous rock intrusive or extrusive
Is this igneous rock intrusive or extrusive? Is it mafic or felsic in composition?
Name this rock – page 124
Felsic:
light-colored
High silica
content
fine crystals
extrusive,

17. Classification of Igneous rocks

18. Large, well-formed crystals AND small, fine crystals

19. Is this igneous rock intrusive or extrusive
Is this igneous rock intrusive or extrusive? Is it mafic or felsic in composition?
Name this rock – page 124
course crystals,
intrusive
Felsic:
light-colored
High silica
and feldspar
content

20. Is this igneous rock intrusive or extrusive
Is this igneous rock intrusive or extrusive? Is it mafic or felsic in composition?
Name this rock – page 124
NO crystals,
extrusive
Felsic:
(High silica
Content)

21. Is this igneous rock intrusive or extrusive
Is this igneous rock intrusive or extrusive? Is it mafic or felsic in composition?
Name this rock – page 124
Course AND
Fine crystals,
Intrusive AND
extrusive
Course Mafic crystals
AND
Fine Felsic crystals

22. Porphrytic Texture
Then it erupted out of a volcano to the surface and the rest of the magma cooled quickly forming small, fine crystals
The magma started to cool deep in the magma chamber and form large crystals

23. FELSIC INTERMEDIATE MAFIC
FELSIC
INTERMEDIATE
MAFIC
Color
Minerals (pr. 703)
Silica percent %
Thick or Thin
High or Low
VISCOSITY
Fast or Slow moving
Hotter or colder temp.?
Examples:
Names of the rocks

25. After reading page 121-126 in your notebook….
Select an igneous rock (2,3,5,6,7,9,11,14)
Rock _______#
Intrusive or Extrusive? ______________
Mafic or Felsic? ______________
Which Family? ______________

26. Bell work Match the following terms to their definitions
Igneous rock that cools beneath the surface.
Igneous rock that contains both large and fine crystals.
A batholith and sill are examples.
Ash, cinders, and lava that erupt from a volcano.
An igneous rock that is both intrusive and extrusive.
Plutonic
Pyroclastics
Porphyrytic

27. Edible Igneous Textures
Food/candy
name
Texture
Fine, coarse-grained, glassy, gassy,
porphyritic
Which igneous rock could this represent?

28. Match the food with the igneous rock texture
Next. Use to chart on page 124 to match and igneous rock to the food.
1.Course grained
2. Fine grained
3.Glassy
4.Gassy/porous
5.porphrytic

29. Edible Igneous Textures
Food/candy
name
Texture
Fine, coarse-grained, glassy, gassy,
porphyritic
Color:
Mafic, felsic.
intermediate
Which igneous rock could this represent?
Chocolate
Fine-grained
mafic
Basalt
Granola bar
Course-grained
Granite
Root beer barrel
glassy
looks mafic
(but it’s really just clear candy with brown food color, so it’s FELSIC)
obsidian
Marshmallow
gassy
felsic
pumice
Chocolate chip cookie
Porphyritic:
(fine-gained, with big crystals)
Felsic (background)
Porphyritic
(rhyolite)

30. Rock Poems I am fine-grained And so light stained.
My color ranges from light gray to pink, which probably makes you think…
rhyolite

31. This rock is rough and oh so tough.
This rock is not light, but dark as the night.
It’s mafic but not fantastic.
It’s found in the ocean and happens to be extrusive.
basalt

32. gabbro It may be coarse, it may be grainy.
It’s so dark, it makes you zany.
It contains feldspar, augite and olivine.
The sweet look of it is so divine.
What rock is this?
You don’t know?
Take a GUESS, it’s….
gabbro

33. Smooth as glass - didn’t have much time. Got no crystals
I am so fine
Yes, I even shine.
Smooth as glass - didn’t have much time.
Got no crystals
Shot out of a volcano like a pistol
I’m felsic, but I don’t look it
Started to cool as soon as I reached the top
Here’s a hint, I’m an extrusive rock
obsidian

34. A B C
D E F