earth forces

• Layers of the Earth's structure


  • Crust (lightest layer)
  • Mantle (thickest layer)
  • Outer core (mostly iron and nickel)
  • Inner core (hottest layer)
• Main plates that make up the Earth's crust


  • Pacific plate
  • North American plate
  • Eurasian plate
  • Antarctic plate
  • African plate
  • Indo-Australian plate
  • South American plate
• Why the Earth's plates move


  Heat from radioactive processes within the planet's interior cause the plates to move, sometimes toward and sometimes away from each other
• Scientific evidence that the Earth's continents are drifting
• What happens at each plate boundary

  • Destructive (convergent) plate boundary: Oceanic crust is dragged into the mantle at a subduction zone, continental crust is pushed upwards to form mountain ranges
  • Constructive plate boundary: Tectonic plates move away from each other, creating a new pathway for rising hot magma to flow on the surface, volcanoes sometimes form
  • Conservative boundary: Two crustal plates slide past each other in a horizontal movement
  • Collision plate boundary: Two continental plates collide, causing the land to buckle upwards to form mountains
• Main features of a volcano


  • Magma chamber at the bottom
  • Main vent from magma chamber to crater
  • Layers of ash and lava on top
  • Secondary cone formed on the side due to a blockage of the main vent
• Effects of volcanic activity


  • Spews out hot, dangerous gases, ash, lava and rock
  • Can result in additional threats like floods, mudslides, power outages, drinking water contamination and wildfires
  • Can cause death
• Why people choose to live in areas with dangerous tectonic activity

  The nutrients in the soils are really good for farming, it is their source of income, they could have an emotional attachment and refuse to leave the area no matter the danger
• Main features of an earthquake


  • Focus (point inside the earth's crust where the earthquake originates)
  • Epicenter (point on the earth's surface directly above the focus)
  • Fault line (fracture between two blocks of rock)
  • Seismic waves (vibrations generated by sudden movements of rock)
• Cause of the Sichuan earthquake
• How to prepare for an earthquake


  • Secure furniture so it can't fall over or down
  • Confirm the strength of your house and walls
  • Be ready to extinguish fires
  • Prepare emergency supplies in advance