SEAFLOOR SPREADING

• Seafloor Spreading - process by which new ocean floor is formed near the mid-ocean ridge and moves outward.
• Mid-ocean ridges - system of ridges or mountains in the seafloor.
• Ridge - offset by fracture zones or rift valleys.
• The idea of Wegener about continental drift theory was not accepted by the scientific society in 1960.
• In early 1960's, scientists Harry Hess and Robert Dietz suggested seafloor spreading theory.
• According to the Seafloor Spreading theory; hot, less dense materials from below the Earth's crust rises towards the surface at the mid-ocean ridge. These materials flow sideways, and create cracks in the crust.
• As magma flows into these cracks, it cools down and solidifies as basaltic rock, which becomes the new seafloor.
• Rocks are younger at mid-ocean ridge
• Rocks far from the mid-ocean ridge are older.
• Sediments are thinner at the ridge
• Rocks at ocean floor are younger than those at the continents.
• East Pacific Rise - most active sites of seafloor spreading of 14cm per year.
• The similarities between the theory of Wegener, Hess and Dietz is to prove that the plates are moving.