Points to Remember:
- Plate Tectonics: Understanding the theory of plate tectonics is crucial.
- Plate Boundaries: Different types of plate boundaries (divergent, convergent, conservative) and their associated geological features.
- Benioff Zone Definition: A clear understanding of what a Benioff zone is and where it’s located.
Introduction:
The question asks about the relationship between a Benioff zone and different types of plate movements. Plate tectonics is the scientific theory that explains the large-scale motion of Earth’s lithosphere. This lithosphere is broken into several plates that move relative to each other, resulting in various geological phenomena. These movements are categorized into three main types: divergent (plates moving apart), convergent (plates moving together), and conservative (plates sliding past each other). A Benioff zone, also known as a Wadati-Benioff zone, is a planar zone of seismicity corresponding to the down-going slab in a subduction zone. Understanding the formation and characteristics of a Benioff zone will help us answer the question.
Body:
1. Understanding Plate Boundaries:
- Divergent Boundaries: Plates move apart, creating new crust (e.g., mid-ocean ridges). Seismic activity is generally less intense than at other boundaries.
- Convergent Boundaries: Plates collide. This can lead to subduction (one plate going under another) or continental collision (forming mountain ranges). Subduction zones are characterized by intense seismic and volcanic activity.
- Conservative Boundaries: Plates slide past each other horizontally (e.g., San Andreas Fault). Seismic activity is significant, but volcanic activity is generally absent.
2. The Benioff Zone and Subduction:
A Benioff zone is a defining characteristic of convergent plate boundaries, specifically those involving subduction. When an oceanic plate subducts beneath a continental plate (or another oceanic plate), it doesn’t sink smoothly. Instead, it descends at an angle, creating friction and causing earthquakes at increasing depths. These earthquakes define the inclined plane of the Benioff zone. The depth of earthquakes increases with distance from the trench, indicating the angle of the subducting plate. The deepest earthquakes occur at the bottom of the subducting slab. Volcanic activity is often associated with Benioff zones, as the subducting plate melts, generating magma that rises to the surface.
3. Why other options are incorrect:
- (A) Divergent movement: Divergent boundaries are associated with shallow earthquakes and are not characterized by a Benioff zone.
- (C) Conservative movement: Conservative boundaries produce earthquakes along the fault line, but these earthquakes are generally shallow and don’t form a dipping plane like a Benioff zone.
Conclusion:
The key characteristic of a Benioff zone is its association with the subduction process at convergent plate boundaries. The inclined plane of seismicity, defined by the earthquakes along the subducting slab, is the defining feature. Therefore, the correct answer is (B) Convergent movement. Understanding plate tectonics and the specific features of different plate boundaries is crucial for comprehending geological processes and mitigating associated hazards like earthquakes and volcanic eruptions. Further research into the specifics of subduction zones and their associated hazards can lead to better preparedness and disaster management strategies, promoting community safety and resilience.
JPSC Notes brings Prelims and Mains programs for JPSC Prelims and JPSC Mains Exam preparation. Various Programs initiated by JPSC Notes are as follows:-- JPSC Mains Tests and Notes Program 2025
- JPSC Prelims Exam 2020- Test Series and Notes Program 2025
- JPSC Prelims and Mains Tests Series and Notes Program 2025
- JPSC Detailed Complete Prelims Notes 2025