Volcanoes

• Layers of the Earth

  • Core-inner core and outer core
  • Mantle
  • Crust
• Inner core


  Solid and the hottest layer of the Earth, as temperature increases with depth
• Outer core


  Mostly made up of molten rock (semi-liquid rock) such as iron and nickel
• Mantle


  Largest layer, made up of molten rock called MAGMA (semi-liquid rock) - mainly silicate rocks
• Crust


  Thinnest layer, made up of solid rock
• Types of crust


  • Continental crust
  • Oceanic crust
• Continental crust


  • Up to 70 km thick
  • Less dense (light)
  • Cannot sink into the mantle
  • Difficult to destroy
  • Rocks are very old
• Oceanic crust


  • 5-10 km thick
  • More dense (heavy)
  • Can sink into the mantle
  • Easily destroyed
  • Rocks are very young
  • Made up of basalt
• The Earth's crust is divided up into segments called PLATES that float on the semi-liquid mantle below at an average speed of 70mm per year
• The edge of a plate where it meets another is called a PLATE MARGIN or BOUNDARY
• The consequences of plate movement are that the continents have changed positions and new oceans and seas have opened up
• Plate tectonics theory


  Demonstrates a knowledge and understanding of the processes and landforms associated with plate margins
• Types of plate margins

  • Constructive
  • Destructive
  • Collision
  • Conservative
• Constructive plate margin


  1. Plates are pulled apart (move away from one another)

  2. New crust is created
• Ascending convection currents in the mantle


  Causes the two oceanic plates to move apart
• Mid-ocean ridge


  Magma rises to plug the gap and new crust is created on the surface as it cools, creating a ridge of volcanoes under the ocean
• Constructive plate margin


  • Gentle earthquakes
  • Gentle volcanic activity
• Destructive plate margin


  1. Plates crash into one another (move towards one another)

  2. Oceanic crust is destroyed
• Descending convection currents in the mantle


  Drag plates towards each other, where an oceanic plate meets a continental plate the oceanic plate is subducted (forced downwards into the mantle because it is denser)
• Ocean trench


  Where convection currents pull the heavier oceanic crust down into the mantle, subducting it under the continental crust creating a deeper ocean floor
• Fold mountains


  A linear pattern forms parallel to the trench as the continental crust crumples upwards as it's not subducted
• Destructive plate margin


  • Violent earthquakes
  • Violent volcanoes
• Collision plate margin


  Two continental plates collide and push up to form mountain ranges
• Fold mountains


  Thick continental crust buckles and folds as both plates consist of continental rock, neither can sink, so the mountain continues to increase in height
• Collision plate margin


  • Violent earthquakes
  • No volcanic activity
• Conservative plate margin


  Plates slide past each other and crust is neither created nor destroyed
• Fault lines


  Visible in the crust at conservative plate margins
• Conservative plate margin


  • Violent earthquakes
  • No volcanic activity
• Types of rock


  • Igneous
  • Sedimentary
  • Metamorphic
• Igneous rock


  Forms when molten rock cools and hardens again
• Igneous rocks


  • Granite
  • Basalt
• Granite


  • Rough texture and speckled colour, often grey and pink, large crystals form as rock is cooled more slowly
• Basalt


  • Very hard, dark grey rock, often feels rough and heavy, small glittery speckles may be visible but less likely as rock cooled quickly above ground
• Sedimentary rock


  Forms when particles of rock get stuck together again after being eroded from their original place
• Sedimentary rocks


  • Limestone
  • Sandstone
• Limestone


  • Grey, white or yellow rock, may be hard and contain fossils and layers, porous
• Sandstone


  • Formed from grains of sand, no crystals, feels rough to touch, quite hard
• Metamorphic rock


  Rock which has been changed underground due to heat and pressure without melting
• Metamorphic rocks


  • Slate
  • Marble
• Slate


  • A dark grey rock with layers which are easily split apart, smooth, flat surface, impermeable