Tectonic plates are massive, slowly moving slabs of Earth’s lithosphere that interact at boundaries, causing most earthquakes when built-up stress from friction is suddenly released. These, roughly 15, major plates, including the Pacific and North American plates, move a few centimeters annually, creating seismic activity primarily at convergent, divergent, and transform boundaries.
NDA & CDS 1 2026 Exam GK – Plate Tectonics & Earthquake
1. Consider the following statements regarding the theory of Plate Tectonics:
- Lithospheric plates move over the semi-molten asthenosphere.
- Plate boundaries are the only regions where earthquakes occur.
- New crust is created at divergent boundaries.
Which of the statements given above are correct?
(a) 1 and 2 only
(b) 1 and 3 only
(c) 2 and 3 only
(d) 1, 2 and 3
✅ Answer: (b) 1 and 3 only
Explanation:
- The lithosphere floats and moves over the ductile asthenosphere.
- Earthquakes mainly occur at plate boundaries but can also occur within plates (intraplate earthquakes).
- Divergent boundaries such as mid-ocean ridges create new crust.
2. Which of the following is NOT correctly matched?
| Plate Boundary | Associated Feature |
|---|---|
| (a) Divergent | Mid-ocean ridge |
| (b) Convergent | Ocean trench |
| (c) Transform | Subduction |
| (d) Convergent | Mountain building |
✅ Answer: (c) Transform – Subduction
Explanation:
- Transform boundaries involve horizontal sliding of plates, not subduction.
- Subduction occurs at convergent boundaries.
3. The Ring of Fire around the Pacific Ocean is primarily associated with:
(a) Divergent plate boundaries
(b) Convergent plate boundaries
(c) Transform plate boundaries
(d) Intraplate volcanic activity
✅ Answer: (b) Convergent plate boundaries
Explanation:
The Pacific Ring of Fire has intense subduction zones, producing frequent earthquakes and volcanoes.
4. Which of the following correctly explains Benioff Zones?
(a) Zones of intense volcanic activity
(b) Deep earthquake zones in subduction regions
(c) Regions of continental rifting
(d) Areas with maximum crustal thickness
✅ Answer: (b) Deep earthquake zones in subduction regions
Explanation:
Wadati–Benioff zones are inclined zones of deep earthquakes that occur where one tectonic plate subducts beneath another.
5. Consider the following pairs:
| Region | Plate Interaction |
|---|---|
| 1. Andes Mountains | Oceanic–Continental Convergence |
| 2. Himalayas | Continental–Continental Convergence |
| 3. Mid-Atlantic Ridge | Transform Boundary |
Which of the pairs given above are correctly matched?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
✅ Answer: (a) 1 and 2 only
Explanation:
- Andes: Nazca plate subducts under South American plate.
- Himalayas: Indian plate collided with Eurasian plate.
- Mid-Atlantic Ridge is divergent, not transform.
6. Which of the following waves are the fastest seismic waves?
(a) Surface waves
(b) S-waves
(c) P-waves
(d) Love waves
✅ Answer: (c) P-waves
Explanation:
- Primary (P) waves are compressional waves and travel fastest through solids, liquids, and gases.
7. Which seismic waves cannot travel through liquid?
(a) P waves
(b) S waves
(c) Surface waves
(d) Rayleigh waves
✅ Answer: (b) S waves
Explanation:
Secondary waves require rigid material, so they cannot move through liquids, which helped scientists confirm the liquid outer core.
8. The focus (hypocenter) of an earthquake refers to:
(a) Point on the Earth’s surface where shaking is maximum
(b) Point inside Earth where earthquake originates
(c) Area where seismic waves stop
(d) Area of volcanic eruption
✅ Answer: (b) Point inside Earth where earthquake originates
Explanation:
- Focus (Hypocenter) → origin point inside Earth.
- Epicenter → point directly above it on the surface.
9. Which scale measures energy released by earthquakes?
(a) Mercalli scale
(b) Richter scale
(c) Beaufort scale
(d) Fujita scale
✅ Answer: (b) Richter scale
Explanation:
- Richter scale measures magnitude (energy).
- Mercalli scale measures damage/intensity.
10. Consider the following statements regarding intraplate earthquakes:
- They occur away from plate boundaries.
- They are usually caused by reactivation of ancient faults.
- They are more common than boundary earthquakes.
Which of the statements given above are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
✅ Answer: (a) 1 and 2 only
Explanation:
Examples include Bhuj Earthquake (2001).
They occur due to stress accumulation in old fault zones.
11. The San Andreas Fault in California is an example of:
(a) Convergent boundary
(b) Divergent boundary
(c) Transform boundary
(d) Subduction zone
✅ Answer: (c) Transform boundary
Explanation:
It marks the boundary between the Pacific Plate and North American Plate, where they slide past each other.
12. Which of the following processes forms mid-ocean ridges?
(a) Subduction
(b) Seafloor spreading
(c) Continental collision
(d) Mantle plume volcanism
✅ Answer: (b) Seafloor spreading
Explanation:
At divergent boundaries, magma rises and solidifies, creating new oceanic crust.
13. Consider the following statements:
- Oceanic crust is denser than continental crust.
- Oceanic crust is generally older than continental crust.
Which of the statements given above is/are correct?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
✅ Answer: (a) 1 only
Explanation:
- Oceanic crust is denser but younger because it is constantly recycled by subduction.
14. The Himalayan earthquakes are mainly caused by:
(a) Transform plate movement
(b) Divergent plate movement
(c) Collision of Indian and Eurasian plates
(d) Subduction of Indian plate beneath Pacific plate
✅ Answer: (c) Collision of Indian and Eurasian plates
Explanation:
The Indian Plate continues to push northward, causing frequent earthquakes in the Himalayan region.
15. Which of the following conditions is most likely to produce a tsunami?
(a) Deep focus earthquake under continents
(b) Submarine earthquake causing vertical displacement of seabed
(c) Transform fault movement on land
(d) Earthquake with magnitude below 5
✅ Answer: (b) Submarine earthquake causing vertical displacement of seabed
Explanation:
Tsunamis occur when large volumes of seawater are displaced, usually due to subduction zone earthquakes.
