2. Igneous Rocks Igneous – from the Latin “ignis” for Fire
Igneous Rocks are formed when molten rock cools and hardens.

3. Igneous Rocks
Two kinds of Igneous Rock
Intrusive
Extrusive

4. Intrusive Igneous Rock
Forms when magma cools beneath the Earth’s surface.
Rock cools slowly which gives crystals the chance to grow large.
granite
gabbro

5. Extrusive Igneous Rock
Formed when lava cools on or above the Earth’s surface.
Crystals are small because the rock cools so quickly there is not much time for crystals to develop.
Some rock cools SO quickly that there are no crystals : Obsidian

6. Extrusive Igneous Rock
Scoria cools quickly above Earth’s surface.
Obsidian cools so quickly that no crystals can form and has a glass-like appearance.

7. Granite Basalt Intrusive – coarse grained – WHY?
Extrusive – fine grained – WHY?

8. Mafic and Felsic
Mafic – darker colored rocks – more iron and magnesium (denser) Ex. Basalt
Felsic - lighter colored rocks- less iron and magnesium and more silica and aluminum
Ex. granite

9. Mafic and Felsic