1. Igneous Rocks Born of fire (or at least melted rock)

2. Igneous Rocks Form from melted rock –Magma or Lava When they cool (freeze), they form interlocking crystals –See petrographic slides

3. Batholith (magma trapped underground)

4. Batholiths cool Bathos = deep lith = rock Form Plutonic (also called intrusive) rocks Pluto = god of the underworld These can be uplifted to make huge mountain ranges (Sierra Nevada in CA)

5. Sierra Nevada

8. Intrusive Igneous Rocks When magma cools underground (intrusive or plutonic), it will cool slowly Slow cooling = large crystals Some also call these rocks “coarse grained”

9. Granite, Diorite, Gabbro

10. Igneous Rock Classification Chart Pyroxene

11. What happens if magma makes it to the surface? Magma on the surface is called lava When lava freezes, it forms volcanic (or extrusive) igneous rocks Vulcan = god of fire

12. Volcanoes Crater Lake Oregon

16. Extrusive (volcanic) igneous rocks When lava cools on the surface of the Earth, it freezes very quickly Fast cooling = small (or no) crystals Some also call these rocks “fine grained”

17. Rhyolite, Andesite, Basalt

18. Igneous Rock Classification Chart Pyroxene

19. Classifying Igneous rocks Use texture Coarse grained = intrusive (plutonic) –Granite –Diorite –Gabbro Fine grained = extrusive (volcanic) –Rhyolite –Andesite –Basalt

20. Classifying Igneous rocks Color Light –Granite –Rhyolite These rocks are the same chemically (SAME MINERALS) – only the texture is different

21. Classifying Igneous rocks Color Grey –Diorite –Andesite These rocks are the same chemically (SAME MINERALS) – only the texture is different

22. Classifying Igneous rocks Color Dark –Gabbro –Basalt These rocks are the same chemically (SAME MINERALS) – only the texture is different

23. Igneous Rock Classification Chart Pyroxene

24. Chemical Igneous names Felsic –More SiO 2 –Lesser amounts of Fe and Mg What minerals are associated with these rocks? Mafic –Less SiO 2 –More Fe and Mg What minerals are associated with these rocks? What does Ultramafic mean?

25. Igneous Rock Classification Chart Pyroxene

26. Bowen’s Reaction Series Amphibole Biotite

27. Special Igneous Textures and Associated Rocks

28. Special Igneous Textures Usually Volcanic –Breccia –Tuff

29. Special Igneous Textures Pumice

30. Special Igneous Textures Scoria

31. Special Igneous Textures Vesicular basalt

32. Special Igneous Textures Obsidian

33. Special Igneous Textures Porphyritic Andesite –Could be Porphyritic Rhyolite or Porphyritic Basalt also!