1. Igneous Rock Notes

2. Igneous rock forms when magma cools and solidifies. Formation

3. Igneous rocks are classified by texture and composition. Texture The sizes, shapes, and positions of the grains that a rock is made of Composition – The minerals or elements that make up a rock Classification

4. Composition Felsic or Mafic Texture – Fine-grained (extrusive) or coarse-grained (intrusive) Classification

5. General Composition – The types of minerals found in an igneous rock (the composition) impact the color and density of the rock.

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

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

8. Composition

9. Intrusive Texture Intrusive Igneous Rock – Form inside Earth’s crust Cool slowly – Coarse-grained (large particles)

10. Intrusive Igneous Rock Formations – Batholiths: The largest of all igneous intrusions – Stocks: Intrusive bodies that are exposed over smaller areas than batholiths – Dikes: Sheet-like intrusions that cut across previous rock units – Laccolith: Sheet-like intrusions that run parallel to previous rock units – Volcanic neck: A column of igneous rock formed when magma hardens with in a vent Intrusive Texture

11. Extrusive Texture Extrusive Igneous Rock – Form on Earth’s surface Cool quickly – Fine-grained (small particles)

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

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