1. Igneous Rocks

2. Igneous rocks are rocks formed when molten rock cools and solidifies.
What is an Igneous Rock?
Igneous rocks are rocks formed when molten rock cools and solidifies.
There are two terms used for molten rock.

3. MAGMA Molten rock inside the Earth is called magma.
Once formed, magma rises toward the surface because it is less dense than the surrounding rocks.

4. LAVA
Lava is the word for magma when it erupts onto the Earth's surface.

5. 2 Types of Igneous Rocks Intrusive Igneous Rocks:
Form beneath Earth’s surface
Cool slowly
Large crystals

6. 2 Types of Igneous Rocks Extrusive Igneous Rocks:
Form on Earth’s surface
Cool quickly
Small crystals
Sometimes no crystals

7. Classification is based on crystal size and composition.

8. Crystallization
The formation and growth of a crystalline solid from a liquid or gas.
Remember the crystal shapes we discussed for properties of minerals.

9. Types of Igneous Textures
Aphanitic
Phaneritic
Porphyritic
Glassy
Pyroclastic
Pegmatitic

10. Aphanitic/Phaneritic
Rapid cooling
Small crystals
Fine –grained texture
Extrusive rock
Phaneritic
Slow cooling
Large crystals
Coarse-grained texture
Intrusive rock

11. Porphyritic/Glassy Porphyritic Glassy
Contains large and small crystals in one rock.
Due to certain minerals crystallizing quicker than others.
Glassy
Rapid cooling
No crystals
Looks like glass
Extrusive rock

12. Pyroclastic/Pegmatitic
Clumps of rock fragments
Form from volcanic rock
Pegmatitic
Exceptionally coarse-grained texture
Formed from a fluid-rich environment
Crystals all larger than 1cm

13. Igneous Compositions:
Granitic composition
Basaltic composition
Composed of light colored silicates.
Ex. quartz and feldspar
-Make up the continental crust
Composed of dark colored silicates.
Ex. ferromagnesian minerals
-Make up the oceanic crust