Lecture8 rocks
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Lecture8 rocks Lecture8 rocks Presentation Transcript

  • Rocks
  • 3 types of rocks
    • igneous
    • sedimentary
    • metamorphic
  • 1. Igneous rocks ( fire-formed )
    • = rock that solidified from a molten state
    • majority of crustal rock (although it is often covered with sedimentary rocks)
    • consists of silicate minerals w/ metallic elements
    • “ interlocking grains”
    • e.g. granite, basalt, obsidian, pumice
    • Magma : molten rock beneath Earth’s surface
  • Granite Basalt Obsidian Pumice
  • Composition of igneous rocks Felsic Mafic Elements Si & Al Fe & Mg Melting pt low temp. high temp. Density low (light) high (heavy) Color light dark e.g. granite, diorite basalt, gabbro
  • Global Composition Distribution Continents- Felsic Oceans- Mafic Digital Elevation Model (DEM)
  • Cooling and crystals
    • Slow cooling = bigger crystals
    • Fast cooling = smaller crystals
    • So, the cooling history of an igneous rock determines how big its crystals will be
  • Intrusive “Plutonic”
    • cools slowly under the surface
    • large crystals
    • e.g. granite
    Extrusive “ Volcanic”
    • cools quickly above the surface
    • small crystals
    • e.g. basalt
  • Felsic Intermediate Mafic Intrusive Extrusive Rhyolite Classifying igneous rocks Andesite Basalt Granite Diorite Gabbro
  • Yellowstone Sierra Nevada Andes Ocean basement Hawaii New Zealand Rhyolite Andesite Basalt Granite Diorite Gabbro
  • Intrusive features batholith dike (vertical) sill (horizontal) Pluton : body of intrusive rock
  • Famous extrusive rocks
  • Famous intrusive rocks
  • 2. Sedimentary rocks
    • = formed through erosion, transportation, deposition, compaction, cementation, and hardening of sediment
    • Sediment = fine-grained mineral matter transported by air, water or ice
    • accumulates at low elevations to form strata (rock layers)
  • Sedimentary rocks
    • majority of surface rock
    • often fossiliferous
    • e.g. sandstone, shale, limestone, coal
  • Classifying sedimentary rocks
    • Clastic
    • 2. Chemical
    • Organic
  • Classifying sedimentary rocks
    • Clastic
      • derived from weathered & fragmented rock
      • boulder  microscopic grain sizes
      • e.g. mudstone, shale, sandstone
    Sandstone Shale
  • Classifying sedimentary rocks
    • 2. Chemical
      • dissolved minerals
      • transported in solution & precipitated
      • e.g. limestone, evaporites
    Limestone Halite
  •  
  • Classifying sedimentary rocks
    • Organic
      • remains of dead organisms
      • e.g. coal
    Coquina Coal
  • Famous sedimentary rocks
  • 3. Metamorphic rocks (change form)
    • rocks changed by heat &/or pressure
    • changes structure, appearance , composition, & texture of parent rock WITHOUT MELTING IT
    • commonly at roots of mountains
    • e.g. slate, schist, gneiss
  • Metamorphic processes
  • 3. Metamorphic rocks
    • limestone  marble
    • sandstone  quartzite
    • granite  gneiss
    • shale  slate  schist
  • Somewhat famous metamorphic rocks
  • Rock Identification
    • Break into groups of 4, 5, or 6
    • Have one person come up and get a set of 3 rocks.
    • Use the flow chart on the following slide to identify your rocks.
    • Determine the type of each rock (igneous, sedimentary, or metamorphic).
    • Write your names, rock ID #’s, rock names, and rock types on a sheet of paper to hand in.
  • Granite Basalt Sandstone Shale Limestone Gneiss Schist Can you see the mineral grains? Are the grains interlocking, or cemented together? Are there layers or stripes (foliation) to the grains? yes no interlocking cemented yes no Is the rock “scaly” or “glittery”? yes no Is it very dark colored (mafic)? yes no Definitive test: Does it react to a weak acid by “fizzing”? Ok substitute test for today: is it layered in flat sheets? no yes yes no Double check: is it layered in flat sheets? no yes Include Rock # Rock Name Rock Type
  • Answer key Granite Basalt Sandstone Shale Limestone Gneiss Schist 2 1 3 5 4 6 7