rock types

• Igneous

  Formed by magma in molten centre of the earth. Magma erupts, cools, forms volcanic landforms. If magma cools inside the earth, it forms intrusive rock which may be later exposed by erosion and weathering e.g. GRANITE. If magma erupts on the surface as lava, it will form extrusive rock e.g. BASALT
• Igneous rocks


  • Formed when magma solidifies
  • Magma cools: mineral crystals grow
  • Crystals grow, interlock hard crystalline rock
  • BASALT lava solidifies on earth's surface or ocean floor, surface is much cooler than mantle, cools quickly, crystals are small
  • GRANITE hardens in Earth's crust-temp. is higher, cools more slowly larger crystals
• Sedimentary


  Formed by sediments that settle at the bottom of the sea, lakes or oceans. Sediment: eroded rocks (carried by rivers or ice), skeletons of sea creatures
• Sedimentary rocks


  • Limestone, sandstone, shale, mudstone
  • Sandstone: rough to touch, porous, sedimentary layering often visible
  • Limestone: composed of calcium carbonate from skeletons of sea creatures, visible layers often contain fossils that react with acids
• Sedimentary rocks


  • Formed due to build up of sediment over time
  • Weathered, eroded: built up in layers
  • More material added: push air and water out (compact together into hard rock)
  • Contain fossils
• Metamorphic


  Subjected to tremendous heat causes it to change into another rock type
• Metamorphic rocks


  • Slate (clay): dark grey/green, can be split into thin layers, roofing material
  • Marble (limestone): white, swirls of colour, crystallised structure
• Metamorphic rocks


  • Formed when igneous or sedimentary rock is changed
  • Heat and/or pressure cause elements in original rock to react and re-form
  • Metamorphic rocks are highly resistant to erosion
  • Used as building materials