What is Sea Floor Spreading Theory? What is its mechanism? What are the pieces of evidence supporting the theory? What is the remaining criticism? Read to know more about it.
Henry Hess propounded it in 1961- 62 by taking the attributes from the earlier theory of Continental displacement and thermal Convection currents.
According to this theory oceanic lithosphere is as mobile as Continental land mass and its mobility depends on the impulsive action and direction of thermal Convection currents.
In this way, the theory rejects the whole contention of Alfred Wegener that only the Continental Sial is floating over oceanic Sima.
According to this theory Convection currents, originating from the boundary of the mantle and core became more impulsive after reaching the zone of the asthenosphere and further carry the magma of the asthenosphere with them towards the surface of Earth.
At the boundary of mantle and crust when they divert away from each other and run parallel to the surface of Earth, the ever-diverging Convection impulses instigate the prominence of tensional thrust over the Earth’s surface to develop some cracks or fractures in the lithosphere.
Along the fault line with the increase in the intensity of convection impulses the magma of the asthenosphere up well and erupts over the earth’s surface as a silent type of volcanic eruption. This further creates several relief features over and adjacent to the fault line.
Low-magnitude earthquakes are also identified along the fault line where the Rock columns diverged away from each other with the ever-diverging convection impulses.
Pieces of evidence
According to Henry Hess, this particular phenomenon of seafloor spreading and the creation of several relief features over and adjacent to the fault line is very well acknowledged in the ocean basin of the Atlantic and the Indian Ocean.
In the center of the respective Ocean, a long fault line has developed in the north-south direction along with horizontal divergence of oceanic lithosphere taking place continuously.
Relief features like ridges, archipelagos, islands, and seamounts are very well-identified, and low-magnitude earthquakes are also frequent along the same fault line.
The theory also provides substantial evidences concerning the process of divergence and several relief features.
According to the theory, the composition and configuration of the rock above and lateral to the fault line show structural dissimilarities. The rock above the fault line is more recent in configuration while the adjacent rock system shows a high level of metamorphism.
Apart from this it also clarifies the magnetic properties and polarity of the rock system that evolved during different geological time scales.
The Rock above the fault line are having distinct magnetic properties and adjacent Rock systems show a magnetic reversal in their composition.
The reversal is mainly due to the change in the magnetic polarity regulated by the ferrous component of accumulated igneous rock.
The theory provides substantial evidence of the origin and evolution of several second-order relief features but doesn’t able to explain two geological and geomorphological phenomena taking place over the Earth’s surface.
The theory only explains the process of formation of new crust but not its dismemberment or disintegration.
The theory provides substantial evidence about the same resultant phenomena in the Ocean basin but not over the continental land mass.
Article written by Chetna Yadav.
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