1. Igneous Rocks

2. Igneous rocks form from volcanoes
Igneous rocks form from volcanoes. They can either form from melted rock deep underground known as magma or melted rock on the surface of the earth known as lava.
Why does the magma rise to the surface?
It’s a liquid so it is less dense.

3. There are 2 main groups of igneous rocks.
Rocks that form from lava are known as extrusive. They form on the surface of the earth.
Rocks that form from magma are known as intrusive. They form deep underground. IN
trusive

4. Intrusive rocks cool underground. Do they cool quickly or slowly?
Extrusive rocks cool on the surface of the Earth. Do you think they cool quickly or slowly?
Quickly
Intrusive rocks cool underground. Do they cool quickly or slowly?
Slowly

5. Igneous Rocks are made up of crystals.
What do you think happens to the size of the crystals when they have a long time to grow?
They grow big.
Which type of igneous rock do you think has the bigger crystals, intrusive or extrusive?
Intrusive – it takes longer to cool.

6. A lava flow on the surface. Extrusive rocks are forming!!

7. I guess this road will be closed for awhile!

8. GRANITE SLOWLY An intrusive igneous rock.
Granite has big crystals because it cooled
SLOWLY

9. An extrusive igneous rock
BASALT
An extrusive igneous rock
Basalt has very small crystals because it cooled
QUICKLY

10. OBSIDIAN
Still an extrusive igneous rock
This rock cooled really fast!

11. Let’s Review

12. Igneous Rock Chart

13. Intrusive Igneous Rocks

14. Intrusive Igneous Rock with Large Crystals

15. Granite

17. Extrusive Igneous Rocks

18. Basalt

19. Compare Intrusive Rocks to Extrusive Rocks:
Small Crystals
Extrusive
Large Crystals
Intrusive

20. Obsidian – NO crystals!
Glassy
texture

22. Slow or fast cooling?
Large crystal, therefore slow cooling!

23. How to Identify Igneous Rocks…

24. 1. Color/Density Felsic – light colored, low density
Mafic – dark colored, high density

26. 2. Texture Large crystals Small crystals No crystals (obsidian)
Coarse-grained –
Fine-Grained –
Glassy –
Vesicular –
Small crystals
No crystals (obsidian)
Gas pockets

28. Vesicular Texture Example = Pumice
Gas Pockets

29. Pumice

32. Minerals found in Granite

33. Minerals found in granite.

34. Igneous Questions

35. Classify the following rocks as either:
volcanic or plutonic and mafic or felsic a b
Volcanic and mafic
Plutonic and mafic c d
Volcanic and felsic
Plutonic and felsic

36. Name the minerals found in Rhyolite

37. Name the minerals found in Basalt

38. Q: Name an extrusive igneous rock with a fine texture.

39. Q: Name an extrusive igneous rock with a fine texture and a felsic composition

40. Q: Name an intrusive igneous rock with a coarse texture and a mafic composition

41. Q: Name the minerals found in Granite.

42. Q: Name the minerals found in mafic rocks.

43. Q: Name the minerals found in Andesite.

44. Name the ELEMENTS found in Mafic rocks.
Fe = Iron
Mg =
Magnesium

45. Name the ELEMENTS found in Felsic Rocks
Al =
Aluminum

46. Why is it unlikely to find Fossils in Igneous Rocks?
Fossils cannot survive the heat from the lava and magma and are destroyed on contact.