tectonic theory

• How many layers does the earth have?

  4
• • There are two types of crust:
  • The oceanic crust is thinner (5-10km) but heavier and denser
  • The continental crust is thicker (25-90km) but is older and lighter
• • Oceanic crust is continually being created and destroyed as a result of plate movement, where it is denser and so subducts under the continental crust
  • This is why continental crust is much older than oceanic crust, as it isn't destroyed
• what is a plate boundary/margin?

  where two plates meet
• where do most earthquakes occur?

  along the Pacific 'Ring of Fire'
• what are the 3 main types of plate boundaries?

  constructive, destructive and conservative
• at a constructive boundary, the plates are moving _____

  apart
• 1. at a destructive plate boundary, the plates are moving _____

  towards each other
• at a destructive plate boundary, the denser, heavier oceanic plate subducts under the lighter, less dense continental plate
• at a conservative boundary, the plates move passed each other in the same or opposite direction at different speeds.
• constructive plate boundary:

  A) plates moving apart

  B) ocean ridge

  C) lava

  D) lithosphere

  
• destructive plate boundary:

  A) oceanic

  B) continental

  C) towards each other

  D) magma

  E) friction

  
• conservative plate boundary:

  A) plates move passed each other