Global Geological And Climatic Events

Subduction Zone discovered beneath Gibraltar Strait


From UPSC perspective, the following things are important :

Prelims level: Gibraltar Strait, Tectonic Plate Boundaries, Subduction Zones

Mains level: Read the attached story

What is the news?

  • Scientists in Portugal have uncovered a concerning revelation about the fate of the Atlantic Ocean, highlighting a potential ‘Ring of Fire’ (a Subduction Zone).
  • Researchers caution that the Atlantic may be on the brink of closure due to subduction activity.

Why discuss this?


  • Closure of Gibraltar Strait: Computer simulations project the subduction zone’s expansion over the next 20 million years, forming the ‘Ring of Fire’ in the Atlantic leading to the closure of Gibraltar Strait.
  • Geological Parallel: This process mirrors the Pacific Ocean’s Ring of Fire, reshaping the ocean basin through gradual subduction of the ocean floor beneath continents.


About Gibraltar Strait

  • Connects the Atlantic Ocean to the Mediterranean Sea;
  • Separating the southern tip of the Iberian Peninsula of Europe from the northern coast of Africa.
Width Approximately 13 km (8.1 miles) at its narrowest point.
Depth Varies, with the deepest point reaching around 300 meters (984 feet).
  • Convergence point for the Eurasian Plate and the African Plate.
  • Formed around 5.33 million years ago during the Messinian salinity crisis when the Atlantic Ocean breached the barrier separating it from the Mediterranean Sea, resulting in a catastrophic flood known as the Zanclean flood.
  • The strait’s current shape and depth were further influenced by tectonic movements and erosional processes over geological time.
Historical Significance Serves as a key maritime passage for trade and military purposes.
  • Subject of contention between Spain and the United Kingdom;
  • Gibraltar Overseas Territory under British control.


What are Subduction Zones?

  • Subduction zones occur at convergent plate boundaries, where two tectonic plates move toward each other.
  • This convergence is often between an oceanic plate and a continental plate or between two oceanic plates.
  • Subduction Process:
  1. Collision of Tectonic Plates: When two tectonic plates collide, the denser oceanic plate is forced beneath the less dense continental plate or another oceanic plate.
  2. Partial Melting: As the oceanic plate descends into the mantle, it generates intense heat and pressure, causing partial melting of the mantle material.
  3. Volcanic Activity: The molten material formed by the subduction process rises through the Earth’s crust, leading to volcanic eruptions at the surface.
  4. Formation of Volcanic Arcs: These eruptions often occur in chains known as volcanic arcs, which parallel the subduction zone. Ex. Andes in S. America; Cascade Range in North America.

Implications of this Activity

  • Earthquakes: Subduction zone earthquakes can be particularly destructive and may trigger tsunamis due to the displacement of large volumes of water.
  • Trench Formation: The surface expression of a subduction zone is often a deep oceanic trench, where the descending plate bends and plunges into the mantle.
  • Mountain Building: Over time, the continuous subduction of oceanic crust can lead to the uplift and deformation of the overriding plate, resulting in the formation of mountain ranges adjacent to the subduction zone. These mountains may exhibit complex geological structures, including folds and faults.
  • Recycling of Oceanic Crust: As oceanic plates are subducted, they are gradually consumed by the mantle, releasing minerals and elements that are eventually returned to the surface through volcanic activity.


2010: Which one of the following can one come across if one travels through the Strait of Malacca?

  1. Bali
  2. Brunei
  3. Java
  4. Singapore


2011: Between India and East Asia, the navigation time and distance can be greatly reduced by which of the following?

  1. Deepening the Malacca straits between Malaysia and Indonesia.
  2. Opening a new canal across the Kra Isthmus between the Gulf of Siam and Andaman sea.

Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2


Practice MCQ:

Which of the given statement about the Gibraltar Strait is NOT correct?

  1. It connects the Atlantic Ocean to the Mediterranean Sea.
  2. It is approximately 13 kilometers wide at its narrowest point.
  3. The deepest point of the Gibraltar Strait reaches around 300 meters.
  4. It was formed around 5.33 million years ago during the Holocene Epoch due to tectonic movements.

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