Explain the different process involved at convergent plate boundaries.
UPSC Mains
Syllabus topic
Important Geophysical Phenomena such as earthquakes, Tsunami, Volcanic activity
Why was this question asked?
Why are the world’s fold mountain systems located along the margins of continents? Bring out the association between the global distribution of fold mountains and the earthquakes and volcanoes.
Introduction
The Earth’s lithospheric plates interact at plate boundaries, where various processes shape the Earth’s surface. Among these boundaries, convergent plate boundaries involve the collision or subduction of plates.
Body
Types of Convergent Plate Boundaries:
Convergent plate boundaries are categorized based on the types of lithospheric plates involved.
1. Oceanic-Oceanic Convergence: When two oceanic plates collide, one plate subducts beneath the other, forming an oceanic trench and a subduction zone. This collision results in the formation of volcanic island arcs, characterized by active volcanoes and frequent seismic activities.
2. Oceanic-Continental Convergence: In this scenario, an oceanic plate collides with a continental plate. The denser oceanic plate subducts beneath the lighter continental plate, forming a continental volcanic arc. This convergence gives rise to volcanic activity, earthquakes, and the development of deep-sea trenches.
3. Continental-Continental Convergence: When two continental plates collide, neither subducts due to their low density. Instead, the collision leads to the compression and uplift of crustal materials, resulting in the formation of large fold-thrust mountain belts. The Himalayas and the Tibetan Plateau are prominent examples of such convergent boundaries.
Processes Involved in Convergent Plate Boundaries:
Convergent plate boundaries exhibit several geological processes due to the interaction of plates.
Subduction and Consuming of Plates: At convergent plate boundaries, the denser plate subducts beneath the less dense plate. The subducting plate descends into the mantle, eventually being consumed or destroyed. This process contributes to the recycling of Earth’s crustal materials.
Formation of Island Arcs and Volcanic Arcs: Oceanicoceanic convergence results in the formation of volcanic island arcs, characterized by active volcanoes and seismic activity. Oceanic-continental convergence gives rise to continental volcanic arcs, where the subduction of oceanic plates beneath continental plates leads to volcanic activity.
Fore-Arc and Trenches: The region between an oceanic trench and the associated volcanic arc is known as the forearc. Fore-arcs are found at convergent margins and often experience intense tectonic stresses, leading to thrust earthquakes. Trenches, on the subducting side of the island arc, are deep and narrow features that form due to the flexing of oceanic lithosphere. They are associated with subduction zones and are the deepest features of ocean basins.
Marginal Basins: Marginal basins develop between the continental margin and the island arc on the concave side of the arc. They are elongated and narrow basins formed by tensional tectonics resulting from the rifting of an existing island arc.
Conclusion
Convergent plate boundaries play a significant role in shaping the Earth’s surface. The collision or subduction of lithospheric plates at these boundaries leads to diverse geological processes such as subduction, formation of islandarcs, volcanic arcs, fore-arcs, trenches, and marginal basins. Understanding these processes helps us understand theformation of mountains, volcanic activity, and seismic events associated with convergent plate boundaries.
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