Context: 

Recently, an earthquake of 4.3 magnitude hit Andaman and Nicobar Islands.

Reason for earthquake in Andaman and Nicobar:

• Andaman and Nicobar Islands region is an earthquake hotspot, caused by ‘subduction’ of the Indian plate beneath the Burmese plate.
• Indo-Australian plate subducts beneath the Burmese microplate resulting in the formation of a major island arc-trench system.
• Andaman-Nicobar-Sumatra subduction zone is an active oblique subduction zone in the northeast Indian Ocean. 
• Previous Earthquake in Region:
  • Tsunami 2004: Great Nicobar is not far from Banda Aceh in Indonesia, which was the epicentre of the December 2004 earthquake and tsunami that caused unprecedented damage. 
  • The coastline of Great Nicobar saw permanent subsidence of nearly four metres as evidenced by the fact that the lighthouse at Indira Point now stands surrounded by water. 

About Tectonic Plate:

• Tectonic plates are gigantic pieces of the Earth’s crust and uppermost mantle. 
  • They are made up of oceanic crust and continental crust. 
  • Earthquakes occur around mid-ocean ridges and the large faults which mark the edges of the plates.
• According to theory of plate tectonics, Earth’s outermost layer, or lithosphere—made up of the crust and upper mantle—is broken into large rocky plates. 
  • These plates lie on top of a partially molten layer of rock called the asthenosphere. 
  • Due to the convection of the asthenosphere and lithosphere, the plates move relative to each other at different rates, from two to 15 centimeters (one to six inches) per year. 
  • This interaction of tectonic plates is responsible for many different geological formations such as the Himalaya mountain range in Asia, the East African Rift, and the San Andreas Fault in California, United States.

News Source: The Hindu

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