1. Igneous Rocks

2. How are Igneous Rocks Made
Most rock melts around 750 C – 1250 C
Temperatures in the mantle are at least this high
When molten rock hardens it forms Igneous Rock

3. Intrusive Igneous Rock
Made from Magma
Inside the Earth’s crust
Due to high temperatures
Cools slowly
Large Crystal size

4. Examples of Intrusive Igneous Rock
Granite
Most common
Continental
Used in countertops, paving stones, floor tiles, ext
Found at the surface – Mt. Rushmore, Stone Mt.
Made up mostly of Feldspar (pink), Quartz or Muscovite (clear or smoky gray), Biotite or Hornblende (Black)

5. Examples of Intrusive Igneous Rock
Diorite
Coarse-grained
Usually continental
Contains Feldspar, pyroxene, hornblende and sometimes quartz

6. Examples of Intrusive Igneous Rock
Gabbro
Usually black or dark green
Most abundant rock deep in oceanic crust
Usually contains
Feldspar
Clinopyroxene
Very little quartz (unlike most other igneous rocks)

7. Extrusive Igneous Rock
Formed on the surface
Formed when lava cools
Due to cooler temperatures
Cools quickly so small crystal structure

8. Examples of Extrusive Igneous Rock
Basalt
Dark-colored
Fine-grained
Made mostly of plagioclase and pyroxene minerals
Makes up most of the ocean floor

9. Examples of Extrusive Igneous Rock
Pumice
Usally Light-colored
Vesicular
Gas trapped in

10. Examples of Extrusive Igneous Rock
Rhyolite
Light-colored
Fine-grained
Usually continental
Typically made of
Quartz
Feldspar

11. Examples of Extrusive Igneous Rock
Obsidian
Has no crystals – Cools to quickly
Usually black in color
Forms
Along the edges of a lava flow
Where lava contacts water
When lava cools while airborn