Convection Current Theory

It was proposed by Arthur Holmes (1928). He expressed the possibility of convection current operating in mantle portion.

Objective

  • To find scientific explanation of origin of the continents and oceans.

Basis

Convection current

  • Formed due to residual energy of earth: These currents are generated due to radioactive elements causing thermal differences in the mantle.
  • Molten rocks move like cells. 

 

    

The Theory

  • The extreme heat generated by radioactive chemicals in the mantle seeks a way to escape. Hence, it causes convection currents to emerge in the mantle.
  • When oceanic plates diverge, tensional stress causes fractures to occur in the lithosphere.
  • Basaltic magma rises from the fractures and cools on the ocean floor to form new seafloor.

Divergent limbs (rising limbs):

  • Pressurize the crust, formation of crust (eruption of Basaltic Magma).
  • Wherever rising limbs of these currents meet, oceanic ridges are formed on the seafloor due to the divergence of the lithospheric plates.

Converging limbs (descending limbs):

  • Destruction of crust at trenches.
  • Wherever the failing limbs meet, trenches are formed due to the convergence of the lithospheric plates.

Evaluation

  • Convection Current Theory explained the driving force for the Convection Current Theory, which led to its acceptance.
  • It is the soul of the Seafloor Spreading Theory. Later, Sea floor and continental drift became the basis of Plate Tectonics.

Thinkers on Convection Current Theory

Alfred Wegener:

  • Proposed the theory of continental drift in the early 20th century.
  • Suggested that continents were once joined in a supercontinent called Pangaea and drifted apart over time.
  • Believed that convection currents in the Earth's mantle could be a driving force for continental movement.
  • Wegener's views on convection currents supported the idea of continents moving due to heat and movement within the Earth.

Arthur Holmes:

  • Contributed to the understanding of convection currents in the Earth's mantle.
  • Proposed the concept of mantle convection as a mechanism for plate tectonics.
  • Holmes suggested that heat generated from radioactive decay in the mantle creates convection currents, causing the movement of tectonic plates.
  • His work supported the idea that convection currents play a crucial role in the dynamic processes shaping Earth's surface.

Harry Hammond Hess:

  • Developed the theory of seafloor spreading in the 1960s.
  • Proposed that new oceanic crust is formed at mid-ocean ridges through volcanic activity and then spreads outward.
  • Hess's model of seafloor spreading was based on convection currents in the mantle pushing plates apart at divergent boundaries.
  • His views emphasized the role of convection currents in the formation and movement of Earth's crust.
  1. Tuzo Wilson:
  • Introduced the concept of transform faults and plate boundaries in the 1960s.
  • Described how plates slide past each other horizontally along transform faults.
  • Wilson's model integrated the ideas of seafloor spreading and continental drift, emphasizing the role of convection currents in driving plate movements.
  • His views highlighted the dynamic nature of Earth's lithosphere influenced by convection currents beneath it.