1. Proposed by Harry Hess2. Occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge3. Result of mantle convection4. Wherever rising limbs of these currents meet, oceanic ridges are formed due to divergence5. Wherever the failing limbs meet, trenches are formed due to the convergence6. When oceanic plates diverge, basaltic magma rises up the fractures and cools on the ocean floor to form new sea floor7. Older rocks away from spreading zone; newer rocks near spreading zone8. Occurs along mid-oceanic ridges

1. 1. Proposed by Harry Hess
2. Occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge
3. Result of mantle convection
4. Wherever rising limbs of these currents meet, oceanic ridges are formed due to divergence
5. Wherever the failing limbs meet, trenches are formed due to the convergence
6. When oceanic plates diverge, basaltic magma rises up the fractures and cools on the ocean floor to form new sea floor
7. Older rocks away from spreading zone; newer rocks near spreading zone
8. Occurs along mid-oceanic ridges


Trade Winds
Sea Floor Spreading
Abdul Kalam Island
Tropical cyclone in India