Day 44 – Q 1.Explain the correlation between plate tectonics and earthquakes with the help of suitable examples. 

1. Explain the correlation between plate tectonics and earthquakes with the help of suitable examples. 

उपयुक्त उदाहरणों की मदद से प्लेट टेक्टोनिक्स और भूकंप के बीच संबंध को समझाएं।

Introduction:

According to the theory of plate tectonics, the earth’s lithosphere is broken into distinct plates which are floating on a ductile layer called asthenosphere (upper mantle). The tectonic plates) vary from minor plates to major plates, continental plates (Arabian plate) to oceanic plates (Pacific plate), sometime a combination of both continental and oceanic plates (Indo-Australian plate).

Body:

The movement of these crustal plates causes the formation of various landforms and is the principal cause of all earth movements. Earthquakes are a direct consequence of interaction between various lithospheric plates.       

Divergence forming divergent edge or the constructive edge:

• The plates diverge or move away from each other. Here, the basaltic magma erupts and moves apart giving rise to sea floor spreading. 
• Earthquakes (shallow focus) are common along divergent edges.
• Example: East African Rift Valley, Mid-Atlantic Ridge, minor earthquakes near Azores and Iceland etc. 

Convergence forming convergent edge or destructive edge:

• Plates move towards each other at a boundary. This type of is called a convergent boundary.
• There are mainly three ways in which convergence can occur: between an oceanic and continental plate; between two oceanic plates; and between two continental plates.
• These boundaries tend to produce most of the earthquakes that have magnitudes greater than 6.0, and subduction zones produce the deepest earthquakes. 
• Examples include deep ocean trenches like the Peru–Chile trench, Himalayan Boundary Fault, Andes etc.       

Conservative edge or transform fault:

• In this kind of interaction, two plates grind against each other and there is no creation or destruction of landform but only deformation of the existing landform. [Crust is neither produced nor destroyed as the plates slide horizontally past each other].
• Transform boundaries typically produce large, shallow-focus earthquakes. Although earthquakes do occur in the central regions of plates, these regions do not usually have large earthquakes. 
• Examples include the San Andreas Fault and the Anatolian fault, earthquakes close to and in California.

Conclusion:

Seismologists associate different kinds of seismic activity with what is happening at different types of plate boundaries. The theory of plate tectonics can be used to provide a simplified explanation of the global distribution of earthquakes, their evolution and provide a background research for sustaining loss and resistive measures.