Subduction Zone beneath The Gibraltar Strait

Context- Recently, a group of scientists has predicted the ‘Ring of Fire’ Subduction Zone beneath the Gibraltar Strait.

About Subduction Zones

• They are the areas wherein tectonic plates collide and one plate is thrust under every other, descending into the Earth’s mantle at rates of 2-8 centimetres per year.
• There are three approaches wherein convergence/collision can arise
  • Between an oceanic and continental plate;
  • Between  oceanic plates;
  • Between two continental plates.
• The system of subduction is driven by the temperature difference between the subducting slab and the encircling asthenosphere, because the colder oceanic lithosphere has, on average, a greater density.
• The subducting plate, or ‘slab’ sinks into the mantle in large part under its weight.
• These are responsible for the planet’s most powerful earthquakes, tsunamis, volcanic eruptions, and landslides.

Subduction Zones and the Plates

• • The Earth’s lithosphere is divided into  sorts of plates: continental and oceanic, and  is split into seven major and some minor plates.
  • The oceanic plates are comparatively heavier, so while those collide with the continental plates, they subduct downwards, forming a subduction zone.

• Major Plates

• • Antarctica and the surrounding oceanic plate;
  • North American (with western Atlantic floor separated from the South American plate along the Caribbean islands) plate;
  • South American (with western Atlantic floor separated from the North American plate along the Caribbean islands) plate;
  • Pacific plate;
  • India-Australia-New Zealand plate;
  • Africa with the eastern Atlantic floor plate;
  • Eurasia and the adjoining oceanic plate;
• Minor Plates:
  • Cocos Plate : Between Central America and Pacific plate;
  • Nazca Plate : Between South America and Pacific plate;
  • Arabian plate : Mostly the Saudi Arabian landmass;
  • Philippine plate : Between the Asiatic and Pacific plate

Subduction Zones and Seismic Activity

• At shallow depths the interface between the plates may become ‘locked’ and stresses build alongside those giant ‘megathrust’ faults.
• Eventually, stresses exceed the fault’s strength and it breaks free, releasing the stored energy as seismic (shaking) waves in an earthquake.
• The massive size of those faults produces the largest earthquakes on Earth.

Subduction Zones and Volcanic Activity

• As the subducting plate descends into the mantle, it undergoes changes in pressure and temperature that cause the release of water.
• This water can trigger the melting of the overlying mantle, leading to the formation of magma that may upward thrust to the floor, resulting in volcanic eruptions.

Future Implications

• Subduction zones are not static and can evolve over time.
  • For instance, the scientists, in a recent study, raised worries about the future of the Atlantic Ocean.
• They identified a subduction region, known as the ‘Ring of Fire’, that could doubtlessly swallow the Atlantic Ocean near to the Strait of Gibraltar.
• It is predicted to expand westwards over the next 20 million years.

Source: The ToI

UPSC Mains Practice Question

Q.What is a ‘subduction zone’? How does subduction lead to seismic activities? Also identify the major subduction zones of the world.

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