Earth sci 2

• Plate Tectonics


  The theory that the Earth's surface is made up of a number of plates that move and interact with each other
• Pioneers of Plate Tectonics

  • Alfred Lothar Wegener
  • Harry Hammond Hess
  • Frederick Vine and Drummond Matthews
  • John Tuzo-Wilson
  • Dan McKenzie
• Plate


  A large, rigid section of the Earth's surface
• Plate tectonics of the UK
• Harry Hammond Hess


  • Professor of geology at Princeton University (USA)
  • Interested in the geology of the oceans while serving in the US Navy in World War II
  • Used sonar (also called echo sounding) to map the ocean floor across the North Pacific
  • Published 'The History of Ocean Basins' in 1962, outlining a theory that could explain how the continents could actually drift, later known as 'Sea Floor Spreading'
  • Discovered that the oceans were shallower in the middle and identified the presence of Mid Ocean Ridges
  • Envisaged that oceans grew from their centres, with molten material (basalt) oozing up from the Earth's mantle along the mid ocean ridges, creating new seafloor which then spread away from the ridge in both directions
  • Believed that ocean trenches were the locations where ocean floor was destroyed and recycled
• Although his theory made sense, Hess knew, like Wegener, that he still needed convincing geophysical evidence to support it