evidence of plate movements

• continents fit together like puzzle pieces (geological fit)
• same fossils are found on different continents
• same rock structures on different continents
• glacial scars
• climate evidence - coal have been found in polar regions but col is formed in tropical regions
• in 1960s, harry hess proposed hypothesis of seafloor spreading and discovered mid atlantic ridge
• sonar (sound navigation and ranging) - use sound waves to 'see' in the water
• why people didnt believe in continental drift


  people couldnt imagine how earth could be millions of years old

  people couldnt imagine a force great enough to move continents
• seafloor spreading is the strongest and most accepted evidence of continental drift
• evidence supporting seafloor spreading

  from molten material - rock pillows show molten material erupting repeatedly from cracks and cool quickly

  from drilling samples - older rocks far from mid ocean ridge, young rocks are found in the center of ridge

  from magnetic stripes - pattern of regular and reversed magnetic stripes at ridges which causes magnetic reversal
• magnetic reversal is also called

  magnetic flip
• magnetic reversal happens when


  north transforms to south and vice versa
• why magnetic reversal happens

  change in direction of material flow in earth's outer core (has a strong magnetic field)
• the ocean floor is like a conveyor belt that carries the continents with it
• new ocean floor forms by

  cracks in ocean crust as molten material from mantle spreads out and pushes older rocks away
• the earth does NOT get wider and larger due to seafloor spreading because of

  subduction
• subduction is a process where ocean floor sinks beneath deep ocean trench and back into mantle