1. 3.2 – Igneous Rocks

2. Videos/Websites http://www.youtube.com/watch?v=7FLlccELWUo

3. Do Now
What are the two ways igneous rocks are formed?

4. Do Now What are the two ways igneous rocks are formed?
Intrusive (beneath Earth’s surface)
Extrusive (above Earth’s surface)

5. Texture
Classified
Key Words

6. Vocab Words Intrusive Igneous Rock Extrusive Igneous Rock
Porphyritic Texture
Vocab Words

7. Igneous Rocks Commonly known as “fire” or “volcano” rocks.
Igneous rocks are formed when magma under the surface cools, and when lava cools at the surface.
Intrusive vs. Extrusive

8. Intrusive Igneous Rocks
Igneous rocks that form when magma hardens beneath Earth’s surface.
Large crystals form.
Only reason we see these rocks is because of erosion. The erosion breaks away layers above the intrusive igneous rocks.
Diorite
Gabbro
Granite
Pegmatite
Peridotite

9. Extrusive Igneous Rocks
Igneous rocks that form when lava hardens on Earth’s surface.
Andesite
Basalt
Obsidian
Pumice
Rhyolite
Scoria
Komatiite (rare)
Tuff (Ejected fragments from a volcanic eruption)

10. Classification of Igneous Rocks
Texture and composition are two characteristics used to classify igneous rocks.
Texture describes the appearance of an igneous rocks based on its size, shape, and the arrangement of its interlocking crystals.
The composition classes of igneous rocks are based on the proportions of light and dark minerals in the rock.

11. Texture Coarse-Grained Fine-Grained
Slow cooling results in the formation of large crystals.
Fine-Grained
Rapid cooling results in small, interconnected mineral grains.

12. Texture Glassy Porphyritic
When there is not enough time for the ions in the lave to arrange themselves into a network of crystals.
Porphyritic
Rocks with different rates of cooling, with large crystals surrounded by fine grains.

13. Composition Granitic Basaltic
Made almost entirely of the light-colored silicate minerals quartz and feldspar.
Basaltic
Made almost mostly of dark silicate minerals and plagioclase feldspar. Rich in magnesium and iron. Darker and denser than granitic compositional rocks.

14. Composition Andesitic Ultramafic
Rocks with a composition in between granitic and basaltic. 25% dark silicate minerals.
Ultramafic
Composed almost entirely of dark silicate minerals. These are rare.

15. Classification Chart

16. Group Activity
On page 74, use that table to fill in the blanks on your group paper and place it in your folder when complete.