ENGEO 2

• Petrology


  The branch of geology concerned with the compositions, structures, and origins of rocks
• Petrography


  A subdiscipline of petrology that deals specifically with the description and classification of rocks
• Rocks


  Solid collections of minerals mixed up through geological processes
• Minerals


  Naturally occurring substances with distinctive chemical and physical properties, composition, and atomic structure
• Common physical properties of minerals

  • Tenacity
  • Hardness
  • Fracture
  • Cleavage
  • Streak
  • Luster
  • Density
• Structures of minerals

  • Kidney
  • Chordal
  • Chordal radial
  • Concussion
  • Lump
  • Concentric
• Rock cycle

  1. Magmatic rocks formed from cooled or crystallized magma

  2. Plutonic rocks formed from magma intruding between other rocks and cooling below the surface

  3. Volcanic rocks formed from erupted magma (lava) cooling on or near the surface

  
• Metamorphic rocks


  Rocks that form when a pre-existing rock (protolith) changes due to temperature or pressure, and/or as a result of squashing or shearing

  
• Parent rocks (protolith) for metamorphic rocks

  • Igneous
  • Sedimentary
  • Other metamorphic rocks

  
• Metamorphic rocks


  • Heat and pressure is required for them to form
  • Pressure is proportional to the depth of the rock's location
• Different kinds of metamorphism

  • Contact or thermal metamorphism
  • Regional metamorphism
  • Burial metamorphism
  • Hydrothermal metamorphism
• Textures of metamorphic rocks

  • Foliated (shale, slate, phyllite, schist, gneiss)
  • Non-foliated (marble, quartzite)

  
• Sedimentary rocks


  Recycled rocks formed by the deposition of fragments of material (sediment) that have been eroded and weathered from other parent rocks
• Classification of sedimentary rocks

  • Originally Formed or Organic Sedimentary Rocks
  • Chemically Formed or Chemical Sedimentary Rocks
  • Mechanically Formed or Clastic Sedimentary Rocks

  
• Formation of sedimentary rocks

  1. Deposition of sediment in layers (strata)

  2. Compression of strata into solid rock

  
• Types of sedimentary rocks

  • Organic sedimentary rocks
  • Chemical sedimentary rocks
  • Clastic sedimentary rocks
• Clastic sedimentary rocks are broken fragments of other rocks due to weathering or erosion and created through compaction and cementation

  
• Chemical sedimentary rocks are made of the dissolved minerals that come out of solution
• Organic sedimentary rocks are made of the remains of once living things