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Earth Materials continued

Earth Materials continued. Mineral Naturally Occurring Inorganic Solid Chemical Composition Crystalline Shape. Rock. a coherent, naturally occurring solid, consisting of an aggregate of one or more minerals, or a mass of natural glass or organic matter. Basic Rock Classifications.

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Earth Materials continued

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  1. Earth Materials continued • Mineral • Naturally Occurring • Inorganic • Solid • Chemical Composition • Crystalline Shape

  2. Rock • a coherent, naturally occurring solid, consisting of an aggregate of one or more minerals, or a mass of natural glass or organic matter.

  3. Basic Rock Classifications • Igneous • Sedimentary • Metamorphic

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

  5. ? Define - Freeze ?

  6. Igneous Rocks

  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. Norman Bowen

  11. Bowen’s Reaction Series Illustrates the order in which minerals crystalize from a magma Liquid Solid

  12. Iron and Magnesium rich Dark colored minerals Al, Ca, and Sodium rich Light colored minerals

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

  14. Relationship between P, T, and Melt Less Pressure More Pressure

  15. Divergent Plate Boundary

  16. Factors controlling Melting 3. Water content: As water content increases, melting temperature decreases

  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.

  22. Magma Viscosity Viscosity – resistance to flow honey – high viscosity water – low viscosity Viscosityincreasesas silica content increases.

  23. 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

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

  25. 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.

  26. 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.

  27. Textures of Igneous Rocks Aphanitic (fine grained) 1. Lava Earth’s surface 2. Phaneritic (course grained) Magma

  28. Aphanitic Texture – Rapid Cooling Small Crystals

  29. Phaneritic Texture – Slow Cooling Large Crystals

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

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

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

  33. PHANERITIC texture It means that the size of all grains in the rock are large enough to be distinguished with the unaided eye

  34. APHANITIC texture It means that not all grains in the rock are large enough to be distinguished with the unaided eye. Most of the rock is background mass.

  35. Pegmatites

  36. 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.

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

  38. Pyroclastic Texture Ash Fall Ash Flow

  39. Plutonic Structures

  40. Plutonic Structures

  41. Image courtesy of geoinfo.nmt.edu

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