1. Igneous Rock Notes

2. Igneous rock forms when magma cools and solidifies.

3. Composition Texture Classification Felisc or Mafic
Intrusive or Extrusive

4. Classification Felsic – light colored, less dense
Granite
Felsic – light colored, less dense
Rich in aluminum, potassium, silicon, and sodium.
Rhyolite

5. Classification Mafic – dark colored, more dense
Gabbro
Mafic – dark colored, more dense
Rich in calcium, iron, and magnesium
Basalt

6. Texture
Intrusive Igenous Rock – inside Earth’s crust (corase-grained)

7. Texture Intrusive Igneous Rock Formations
Pluton: Large, irregular shaped intrusive bodies
Batholiths: The largest of all igneous intrusions
Stocks: Intrusive bodies that are exposed over smaller areas than batholiths
Dikes: Sheetlike intrusions that cut across previous rock units
Laccolith: Sheetlike intrusions that are oriented parallel to previous rock units
Volcanic neck: A column of igneous rock formed when magma hardens with in a vent

8. Texture
Extrusive Igenous Rock – on Earth’s surface (fine-grained)

9. Texture Extrusive Igneous Rock Formations
Lava Flow: Formed when lava erupts from a volcano
Fissure: Long cracks in Earth’s crust where lava can flow

10. Igneous Rock Flow Chart
rock melts
rock cools
igneous rock
Slow cooling (coarse-grained)
pressure
composition
temperature
Fast cooling (fine-grained)