Geography Chapter 5 - rocks

• What is a rock


  The hard material that forms Earth's crust
• features of rocks:

  • Are solid
  • Occur naturally
  • Are made up of one or more minerals that have been compressed and cemented together
• Rocks differ from each other in

  • Mineral content
  • Colour
  • Hardness
  • Texture (how they feel to the touch)
• Groups of rocks


  • Igneous rocks
  • Sedimentary rocks
  • Metamorphic rocks
• How are igneous rocks formed?

  Formed as a result of volcanic activity, when volcanic material cools down and solidifies, either within the crust or on the surface
• How are Intrusive igneous rocks

  • Formed from material that cooled inside the crust
• how are Extrusive igneous rocks

  • Formed from material that cooled on the surface
• Examples of Igneous rocks:

  • Granite
  • Basalt
• How is Granite formed

  An intrusive igneous rock that formed when molten magma forced its way into the crust and cooled slowly over millions of years, allowing large crystals to form
• How is basalt formed

  An extrusive igneous rock that formed when lava spread out across Earth's surface and cooled and solidified very quickly because it was exposed to the air
• Formation of sedimentary rocks

  1. Weathering

  2. Erosion

  3. Transportation

  4. Deposition

  5. Compression and cementation
• Examples of Sedimentary rocks

  • Limestone
  • Sandstone
• how is Limestone formed

  Formed on the beds of shallow, warm seas from the skeletons of tiny sea creatures, fish and shells that piled up over millions of years and were compressed and cemented together
• How is Sandstone formed

  Formed when large amounts of sand were worn away from Earth's surface and transported by wind and rivers, then deposited on the beds of lakes and seas, as well as in deserts, and compressed and cemented to form sandstone
• How are Metamorphic rocks formed

  Formed when existing igneous or sedimentary rocks come into contact with great heat and pressure, causing them to change in both shape and form
• Examples of Metamorphic rocks

  • Marble
  • Quartzite
• How is Marble formed

  Formed when molten magma forces its way into a body of limestone, putting it under great heat and pressure and changing its make-up
• How is Quartzite formed

  Formed when sandstone came into contact with magma deep in Earth's crust, usually during periods of folding. Quartzite consists mainly of grains of quartz that are packed tightly together