Seafloor Spreading Theory

• What is seafloor spreading?


  It is a geological process in which tectonic plates split apart from each other.
• At what type of plate boundaries does seafloor spreading occur?

  At divergent plate boundaries.
• Who was Harry Hammond Hess?

  He was a scientist who used SONAR to study the ocean floor during World War II.
• What role does hot, less dense material play in seafloor spreading?

  It rises towards the mid-ocean ridge, carrying the seafloor away from the ridge.
• What happens to the magma that flows out of the cracks in the crust during seafloor spreading?

  It cools down and becomes the new seafloor.
• How does new oceanic crust affect old oceanic crust during seafloor spreading?

  The new oceanic crust pushes the old oceanic crust far from the ridge and subducts it.
• What are the evidences of seafloor spreading?

  • Youngest rocks are found near the ridge.
  • Oldest rocks are found far from the ridge.
  • Sediments are thinner near the ridge and progressively thickens as you move away.
  • The density of materials increases as you go far from the ridge.
  • Symmetrical stripes on both sides of a mid-ocean ridge.
  • Geomagnetic reversal.
• What does seafloor spreading create and how does it relate to subduction?

  Seafloor spreading creates new crust while subduction destroys old crust.
• How do seafloor spreading and subduction affect the shape of the Earth?

  The two forces roughly balance each other, so the shape and diameter of the Earth remain constant.
• What is the relationship between seafloor spreading and the shape of the Earth?

  Seafloor spreading and subduction keep the shape of the Earth constant.