Q1. Which of the following best explains the primary cause of volcanism on Earth?
- Radioactive heat in Earth’s interior
- Tidal forces due to Moon and Sun
- Plate tectonic movements
- Friction between atmosphere and lithosphere
Select the correct answer:
A. 1 and 3 only
B. 2 and 4 only
C. 1, 2 and 3 only
D. 1, 3 and 4 only
Q1. (A)
Explanation:
- Volcanism driven by internal heat (radioactive decay) and plate tectonics.
- Tidal forces have negligible role.
- Atmosphere–lithosphere friction irrelevant.
Q2. Consider the following features of Shield Volcanoes:
- Broad base with gentle slopes
- Highly viscous lava
- Predominantly basaltic lava
- Explosive eruptions are common
A. 1 and 3 only
B. 1, 2 and 4 only
C. 2 and 4 only
D. 1, 3 and 4 only
Q2. (A)
Explanation:
- Shield volcanoes: low-viscosity basaltic lava, gentle slopes.
- Eruptions generally effusive, not explosive.
- Viscous lava is characteristic of composite volcanoes.
Q3. “Ring of Fire” is associated with:
A. Transform boundaries
B. Divergent boundaries only
C. Convergent plate boundaries
D. Hotspot volcanism only
Q3. (C)
Explanation:
- Pacific Ring of Fire linked to subduction zones.
- ~75% of world’s active volcanoes located here.
Q4. Which gases are most commonly emitted during volcanic eruptions?
- Water vapour
- Carbon dioxide
- Sulphur dioxide
- Nitrogen
A. 1, 2 and 3 only
B. 2, 3 and 4 only
C. 1 and 4 only
D. All four
Q4. (A)
Explanation:
- Major volcanic gases: H₂O vapour (largest share), CO₂, SO₂.
- Nitrogen: Incorrect as a major/common gas. Nitrogen (N₂) is present only in trace amounts in volcanic emissions (far less than 1% in most cases). It is not considered one of the primary or most commonly emitted gases;
Q5. Which of the following volcanoes is/are located in India?
- Barren Island
- Narcondam
- Dhinodhar Hills
A. 1 only
B. 1 and 2 only
C. 2 and 3 only
D. 1, 2 and 3
Q5. (D)
Explanation:
- Barren Island – India’s only active volcano.
- Narcondam – dormant volcano.
- Dhinodhar (Gujarat) – extinct volcanic plug.
