1. Purchase lab manual in lab this weekHomework 1 due in lab this week Homework 2 due in lab next week Read Mt. Saint Helens disaster paper

2. Igneous Rocks

3. Earth Materials continued Mineral -Naturally formed -Solid -Formed by inorganic processes -Specific chemical composition -Characteristic crystal structure Rock – a coherent, naturally occurring solid, consisting of an aggregate of one or more minerals, or a mass of natural glass or organic matter.

4. Basic Rock Classifications • Igneous • Sedimentary • Metamorphic

5. Rock Cycle And Pressure Cementation Erosion SedimentaryRocks Sediment Erosion Heat Erosion Pressure Heat and Pressure Igneous Rocks MetamorphicRocks Cooling Heat Magma

6. ? Define - Freeze ?

7. Igneous Rocks -a rock that forms when hot molten rock (magma or lava) cools and freezes solid • Two types of igneous rocks • Plutonic – cools underground • Volcanic – cools above ground

8. Factors controlling Melting 1. Temperature: Melt at [800oC and 1200oC] Source of heat [radioactive decay]

9. Geothermal Gradient – the rate at which temperature increases with depth in the Earth 30OC/km

10. Bowen’s Reaction Series

11. Factors controlling Melting 2. Pressure: • as pressure increases, melting temperature increases • as pressure decreases, melting temperature decreases Lowering pressure causes melting in divergent margins.

12. Divergent Plate Boundary

13. Relationship between P, T, and Melt

15. Factors controlling Melting 3. Water content: as water content increases, melting temperature decreases Water in rocks causes melting in convergent margins.

17. Water increases melting at convergent plate boundaries

18. Where do igneous rocks occur?

19. Types of Molten Material 1. Magma – molten material below the Earth's surface 2. Lava – molten material above the Earth's surface

20. Magma Composition Changes • Partial melting • Assimilation • Magma Mixing • Fractional Crystallization

21. Partial Melting some minerals melt at a lower temperature than others.

23. Magma Viscosity Viscosity – resistance to flow honey – high viscosity water – low viscosity Viscosity increases as silica content increases.

24. Magma Chemistry Molten material can consist of liquid rock, mineral grains and gases (H2O, CO2, SO2). Silicon and oxygen (SiO2) make up the majority of magma 45% SiO2 - "low" silica content 75% SiO2 - "high" silica content

25. Endmember Magma Chemistry Mafic – low SiO2, iron, magnesium Felsic/Silicic – high SiO2, aluminum, calcium, sodium

26. Igneous Rock Types Intrusive (plutonic) rock – cools and solidifies below the Earth's surface. Extrusive (volcanic) rock – cools and solidifies above the Earth's surface.

27. Textures of Igneous Rocks Texture – overall appearance, related to size, shape, and arrangement of minerals. Texture is related to cooling history of an igneous rock, not its chemistry.

28. Textures of Igneous Rocks 1. Phaneritic (course grained) Magma 2. Aphanitic (fine grained) Lava Glassy Vesicular 3. 4.

29. Increasing Fe and Mg Increasing silica content

30. Aphanitic Texture – Rapid Cooling Small Crystals

31. Phaneritic Texture – Slow Cooling Large Crystals

32. Silicic Chemical Composition Aphanitic Texture – Rapid Cooling Small Crystals Phaneritic Texture – Slow Cooling Large Crystals Granite Rhyolite

33. Intermediate Chemical Composition Aphanitic Texture – Rapid Cooling Small Crystals Phaneritic Texture – Slow Cooling Large Crystals Diorite Andesite

34. Mafic Chemical Composition Aphanitic Texture – Rapid Cooling Small Crystals Phaneritic Texture – Slow Cooling Large Crystals Gabbro Basalt

35. Phaneritic Porphyritic-Phaneritic Phenocrysts in Groundmass

36. Aphanitic Porphyritic-Aphanitic Phenocrysts in Groundmass

37. Pegmatites

38. Ingersoll Mine Ingersoll mine, Pennington Co., South Dakota, United States One of the many adits at the old Ingersoll pegmatite. Private and Very dangerous. No Trespass.

39. Glassy Texture - Very Rapid Cooling - No Crystal Structure

40. Pyroclastic Texture Ash Fall Ash Flow

41. Plutonic Structures

42. Plutonic Structures