THEORY OF THE SEA FLOOR SPREADING
The seafloor spreading is a process in which the creation of the oceanic crust is formed continuously in the seafloor. The seafloor spreading occurs in the mid Atlantic ocean when two tectonic plates move in opposite directions. Most of the volcanic activities occur along the mid Atlantic ridge.
The concept of the seafloor spreading was propounded by Hary Hess in 1960 and first coined by Robert Dietz. His concept was based on Euler's theorem to calculate the plates movements. He discovered the variation of temperature on the sea floor.the temperature near oceanic ridge is higher than away from the ridge.
MAIN CONCEPT
According to Hess, the oceanic crust moves away from each other due to thermal convection current. The continuous upwelling of magma along the mid oceanic . These lava gets cooled and solidified ,thus the new crust formed. There is created a numerous new crust and old crust moves away. In this way seafloor spreads.
THE PROCESS OF SEAFLOOR SPREADING
There are two processes to spread the dense basaltic crust .
- The dense oceanic crust subducted into ocean trench. The subduction is downward movement of oceanic crust , while the old rocks moves away from the ridge, these old rocks moves until meet oceanic trenches.
- On the other side,the crust moves and reaches to the coast .
The downward crust melts into asthenosphere for another convection current. On the other side,The oceanic crust burst into Continental crust and create volcanism.
For instance, the Atlantic ocean is spreading because of few trenches,it is spreading at the rate of 1.0 to 1.5cm per year.
Pacific ocean has more trenches and the spreading of the Pacific ocean is at the rate of 6.0 cm per year.
