Formation of Rocks

• Heavier elements are pulled together to form the core of the earth, followed by the lighter elements to form the outer layers
• Layers of the Earth Diagram

  A) crust

  B) mantle

  C) outer core

  D) inner core

  
• Rock - a combination of one or more minerals
• Mineral - naturally occuring inorganic substance with specific chemical composition
• Igneous rocks - rock made during a volcanic process when molten rock from the crust and upper mantle cools

  • e.g. granite, basalt
• Magma - molten rock that is below the surface and is lava when it reaches the surface

  • found in the outer mantle
  • hot, liquid rock under pressure from rocks above it
• When magma cools, it turns into a solid rock

  • the process of cooling is faster when it comes to the surface and becomes lava
• Crystals in rocks are formed when solutions of minerals cannot absorb any more dissolved minerals
• Solutions - formed when a solid is dissolved into a liquid
• Formation of crystals in rocks:

  • a bit of each mineral type precipitates out of a solution to form the centre of the crystal
  • the centre then provides a surface for more mineral ions to precipitate onto
  • the crystal becomes larger until the solution disappears
• Ions - an atom where the number of positively charged protons is not equal to the number of negatively charged electrons
• If a rock cools quickly, only small crystals form before the rock becomes solid

  • rapid cooling occurs when magma is released from volcanoes onto the surface of the Earth’s crust
• If a rock cools slowly, larger crystals will be formed

  • magma that rises from the mantle into the crust without reaching the Earth’s surface will cool slower
  • many of these crystals contain valuable minerals that have a wide range of uses
• Heat and pressure causes minerals to become dissolved so a reduction in heat and pressure will form crystals
• Sedimentary Rocks - rock formed from material derived from the weathering of other rocks or the accumulation of dead plants and animals

  • e.g. limestone, sandstone, and shale
  • the precipitation of dissolved materials out of solution in water can also create sedimentary rocks
• Weathering process - releases small mineral particles that accumulate to form sediment, creating layers over time, forming sedimentary rock
• Sediments include many different-sized mineral particles (important for soil as well):

  • clays (smallest)
  • silt (middle)
  • sands (largest)
  • larger particles of gravels and small boulders can be found too
• Sediment particles are transported by streams and rivers, then deposited as sediment

  • each layer becomes more compact and harder because of pressure from new deposits
• Metamorphic rock - rock formed from existing rocks through heat and pressure

  • e.g. marble and slate
  • the heat and pressure causes changes in the rock crystals without melting the existing rock, changing the structure, creating metamorphic rocks
  • changes in structure can be chemical or physical or both
• • Characteristics of different rock types

  A) magma

  B) magma

  C) solid rock

  D) present

  E) size

  F) speed of coolinh

  G) fossils

  H) rock

  I) rock

  J) buried

  K) pressure

  L) absent

  M) fossils

  N) existing rock

  O) through heat and pressure

  P) present

  Q) fossils

  
• Sedimentary and igneous can become metamorphic rocks and a metamorphic rock can become another metamorphic rock

  • metamorphic rocks are harder than sedimentary rocks
• Rock cycle - a representation of the changes between the three rock types and the processes causing them

  • all rock types are constantly eroded and formed
• Rock cycle process:

  • when the earth’s crust was first formed, the rocks were igneous
  • igneous rocks were then eroded, releasing small particles that form sediment and these sediments start forming rocks
  • rocks that make up the Earth’s crust are always moving which creates heat and pressure needed to form metamorphic rock
• • Rock cycle diagram

  A) weathering and erosion

  B) surface rock

  C) transported

  D) deposited

  E) layers

  F) layers

  G) layers

  H) compacted

  I) sedimentary rock

  J) heat and pressure

  K) metamorphic rocks

  L) remperatures

  M) melt

  N) magma

  O) cools

  P) igneous rock

  Q) movements

  R) raise rocks

  S) uplift

  
• Intrusive igneous rock - igneous rocks form under the earth through magma
• Extrusive igneous rock - igneous rocks that form above the earth through lava
• Rock Cycle

  A) -

  B) weathering and erosion

  C) transportation

  D) sedimentation

  E) sedimentary rocks

  F) heat and pressure

  G) uplift

  H) metamorphic rocks

  I) melting

  J) magma

  K) melting

  L) cooling

  M) igneous rock

  N) heat and pressure

  O) uplift

  P) uplift

  Q) surface rock

  
• Uplift happens due to the tectonic plate shifts in the earth