Rocks and rock cycle\

• Rock


  A naturally occurring solid mixture of one or more minerals, or organic matter
• Rocks


  • Classified by how they are formed, their composition, and texture
  • Change over time through the rock cycle
• Processes responsible for rock formation

  1. Crystallization

  2. Weathering/Erosion

  3. Sedimentation

  4. Metamorphism
• Igneous rock


  Begins as magma, which can form when rock is heated, when pressure is released, or when rock changes composition. Magma freezes between 700 °C and 1,250 °C and is a mixture of many minerals.
• Types of igneous rocks

  • Felsic (light colored, rich in aluminum, potassium, silicon, sodium)
  • Mafic (dark colored, rich in calcium, iron, magnesium, poor in silicon)
  • Coarse grained (takes longer to cool, giving mineral crystals more time to grow)
  • Fine grained (cools quickly with little to no crystals)

  
• Igneous rock examples

  • Granite
  • Gabbro
  • Basalt
  • Rhyolite
• Intrusive igneous rocks


  Magma pushes into surrounding rock below the Earth's surface
• Extrusive igneous rocks


  Forms when magma erupts onto the Earth's surface (lava), cools quickly with very small or no crystals formed

  
• Obsidian


  • A dark-colored volcanic glass that forms from the very rapid cooling of molten rock material, so it cools so rapidly that crystals do not form

  
• Sedimentary rock


  Formed by erosion, with sediments moved from one place to another and deposited in layers, which become compacted and cemented together. Formed at or near the Earth's surface with no heat and pressure involved.

  
• Sedimentary rock

  • Strata - layers of rock
  • Stratification - the process in which sedimentary rocks are arranged in layers
• Types of sedimentary rocks

  • Clastic (made of fragments of rock cemented together)
  • Chemical (minerals crystallize out of solution)
  • Organic (remains of plants and animals)

  
• Sedimentary rock examples

  • Breccia (clastic sedimentary rock with large angular fragments)
  • Limestone (chemical sedimentary rock composed primarily of calcium carbonate)
  • Coal (organic sedimentary rock formed from plant materials)
• Metamorphic rock


  Changes with temperature and pressure, but remains solid. Usually takes place deep in the Earth.

  
• Types of metamorphic rocks

  • Foliated (contain aligned grains of flat minerals)
  • Non foliated (mineral grains are not arranged in plains or bands)

  
• Metamorphic rock examples

  • Hornfels (fine-grained non-foliated metamorphic rock produced by contact metamorphism)
  • Gneiss (foliated metamorphic rock with a banded appearance)
  • Marble (non-foliated metamorphic rock produced from the metamorphism of limestone)
• Amphibolite, Quartzite, and Phyllite are foliated metamorphic rocks
• Rock cycle


  A web of processes that outlines how each of the three major rock types - igneous, metamorphic, and sedimentary - form and break down based on the different applications of heat and pressure over time.

  
• Transitions in the rock cycle

  1. Transition to igneous: Rocks melt into magma, which then solidifies into igneous rock

  2. Transition to metamorphic: Rocks exposed to high temperatures and pressures are changed physically or chemically to form metamorphic rock

  3. Transition to sedimentary: Rocks exposed to weathering and erosion break down into smaller fragments that accumulate on the Earth's surface to form sedimentary rock