SUBDUCTION ZONE

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Context:

Subduction zone discovered beneath Gibraltar Strait.

Details:

Subduction Zone

• Subduction Zones (SZs) or Benioff Zones are locations of convergent plate boundaries where one tectonic plate is pushed below the other tectonic plate and sinks into the mantle (a process called subduction).

Subduction initiation

• This subduction process frequently occurs because of the two different types of lithosphere that make up tectonic plates: Continental and oceanic.
• Because oceanic material is denser than continental lithosphere, when the two collide or converge, the oceanic portion sinks into the mantle beneath the more buoyant continental lithosphere and subduction zone occur.
• Subduction zones can also occur when both colliding plate sections consist of oceanic material. In these cases, older, denser oceanic lithosphere sinks below younger, more buoyant oceanic lithosphere.

The process and result

• The impact of the colliding plates can cause the edges of one or both plates to buckle up into a mountain ranges or one of the plates may bend down into a deep seafloor trench.
• A chain of volcanoes often forms parallel to convergent plate boundaries and powerful earthquakes are common along these boundaries. The Pacific Ring of Fire is an example of a convergent plate boundary.
• At convergent plate boundaries, oceanic crust is often forced down into the mantle where it begins to melt.
• Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents.
• Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed.
• Subduction produces deep trenches, earthquakes, and volcanoes that often form arcs of islands along the convergent boundary

Not always resulted into subduction zone

• Tectonic plate smash-ups don’t always result in a subduction zone.
• When two sections of continental lithosphere converge, it creates a collision zone and the plates crumple together like crashing cars, pushing up material.
• Himalaya mountain chain was created this way, when the Indian tectonic plate slammed into the Asian plate.

Recent Developments

• A recent study from scientists in Portugal has raised concerns about the future of the Atlantic Ocean.
• They have identified a subduction zone, known as the 'Ring of Fire', that could potentially swallow the Atlantic Ocean.
• Currently located beneath the Gibraltar Strait, between Spain and Morocco, this subduction zone is predicted to expand westwards over the next 20 million years.

Eurasian Plate and the African Plate

• The Gibraltar Strait, a 10-mile gap separating Europe and Africa, marks the meeting point of the Eurasian Plate and the African Plate.
• The African Plate is currently subducting beneath the Eurasian Plate in this region, leading to seismic events and earthquake risks.
• Despite the slow movement of the subduction zone beneath the strait, experts believe it could grow and extend into other parts of the ocean, a phenomenon known as 'subduction invasion'.

New  Atlantic subduction system

• Although the current subduction zone below the Gibraltar Strait is relatively small, measuring about 125 miles in length, projections suggest it could expand to around 500 miles in the next 20 million years. Using computer simulations, researchers traced the evolution of this subduction zone from its formation millions of years ago to its potential future development.
• The model indicates that the subduction zone will progress westwards through the Gibraltar Strait, forming a new Atlantic subduction system referred to as the 'Ring of Fire'.
• This process, similar to the Pacific Ocean's Ring of Fire, involves the gradual pulling of the ocean floor beneath the continents, leading to the closure of the ocean basin.
• The study highlights the possibility of the Atlantic Ocean 'closing up' in the distant future. The researchers suggest that the extended subduction zone will propagate further into the Atlantic, eventually reshaping the ocean's geography.
• While the timeline for these changes spans millions of years, the implications could be significant for the planet's geological landscape.

Conclusion

The findings of the study shed light on the dynamic nature of Earth's tectonic processes and the long-term evolution of ocean basins. The concept of the Atlantic Ocean shrinking and potentially ceasing to exist over a vast timeframe offers a glimpse into the geological forces shaping our planet.

PRACTICE QUESTIONS What term is used to describe the potential expansion of the subduction zone into other parts of the ocean? Oceanic crust reduction Seismic Invasion Subduction invasion Seismic expansion Answer C