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UPSC Prelims 2004 · World Geography · Rocks, Quakes and Landforms
Consider the following geological phenomena: Which of the above causes earthquakes?
- Development of a fault
- Movement along a fault
- Impact produced by a volcanic eruption
- Folding of rocks
- (a) 1, 2 and 3
- (b) 2 and 4
- (c) 1, 3 and 4
- (d) 1, 2, 3 and 4
Show the answer and explanation
Answer: (d) 1, 2, 3 and 4
All four can cause earthquakes.
Statement by statement
1. ✓ YES Fault formation releases stress.
2. ✓ YES Slip along faults is the main cause.
3. ✓ YES Volcanic eruptions trigger quakes.
4. ✓ YES Folding builds stress that can release as quakes.
The idea
An earthquake occurs when stored strain is released suddenly and sends vibrations through rock. Tectonic deformation can load the crust, while fault slip releases much of that strain. Volcanic movement can also disturb the surrounding rock; slow bending alone need not produce a quake.
Tectonic forces deform rock → Stress accumulates → Rock fractures or an existing fault slips → Stored strain is suddenly released → Seismic waves spread → The ground shakes
Why the others are wrong
(a) Drops folding.
(b) Drops fault formation and volcanoes.
(c) Drops fault movement — the main cause.
Also know
Most damaging earthquakes are tectonic. Other kinds include volcanic, collapse and human-induced earthquakes, such as those linked to fluid injection or reservoirs. A fault is a fracture with displacement; a fold is bent rock. Folding and faulting can occur together, so a quake in a folded belt does not mean all folding is sudden.
🔒 Most quakes = tectonic (faults); others: volcanic, collapse, induced (dams, mining).
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