Indian Geography — Earthquakes
1. Natural Hazards vs. Natural Disasters
Context: Both natural hazards and natural disasters are undesirable natural events with potential to harm life and property. However, natural disasters have relatively far greater impact.
- Natural Hazard: A natural event that has the potential to cause harm (e.g., earthquake, cyclone).
- Natural Disaster: When a natural hazard actually occurs and causes significant damage to life and property.
- Key Difference: Impact — disasters have far greater consequences.
📝 UPSC Previous Year Questions:
- UPSC Prelims 2019: Which states are most vulnerable to earthquakes in India? Answer: North-east states, Uttarakhand, Himachal Pradesh, Jammu and Kashmir, etc.
- UPSC Prelims 2017: The Pacific Ring of Fire is associated with which natural disaster? Answer: Tsunamis and Earthquakes.
2. Earthquakes
Context: Earthquakes are caused by tectonic movements, particularly the movement of the Indian Plate towards the Eurasian Plate. They are among the most devastating natural disasters.
- Cause: Tectonic Origin — Movement of the Indian Plate towards the Eurasian Plate.
- Most Devastating: Earthquakes are among the most destructive natural disasters.
- Most Vulnerable States:
- Jammu and Kashmir
- Himachal Pradesh
- Uttarakhand
- Sikkim
- Darjeeling subdivision of West Bengal
- All 7 states of Northeast India
📝 UPSC Key Points:
- Cause: Tectonic movement (Indian Plate → Eurasian Plate)
- Most Vulnerable: NE states, J&K, Himachal, Uttarakhand, Sikkim, Darjeeling
- Seismic Zones: Zone V (Very High) and Zone IV (High) are most vulnerable
3. Seismic Zones of India
Very High Damage Risk Zone (Zone V)
- North-east states (all 7 states)
- Areas to the north of Darbhanga and Araria along the Indo-Nepal border in Bihar
- Uttarakhand
- Western Himachal Pradesh
High Damage Risk Zone (Zone IV)
- Jammu and Kashmir
- Himachal Pradesh
- Northern parts of Punjab
- Eastern parts of Haryana
- Delhi
- Western Uttar Pradesh
- Northern Bihar
📝 UPSC Key Points — Seismic Zones:
- Zone V (Very High): NE states, Uttarakhand, Western Himachal, parts of Bihar
- Zone IV (High): J&K, Himachal, Punjab, Haryana, Delhi, Western UP, Northern Bihar
- Zone III (Moderate): Remaining parts of the country
- Zone II (Low): Least vulnerable areas
4. Tsunami / Shallow Water Waves
Context: Tsunamis are long-wavelength waves caused by earthquakes and volcanic eruptions. They have high speed in shallow waters and can cause devastating coastal impacts.
- Causes: Earthquakes and Volcanic Eruptions under the ocean.
- Characteristics:
- Long wavelengths over deep waters.
- Higher speed in shallow waters.
- Frequent Occurrence: Pacific Ring of Fire (coast of Alaska, Japan, Philippines), Islands of Southeast Asia, Indonesia, Malaysia, Myanmar, Sri Lanka, and India.
📝 UPSC Key Points:
- Cause: Earthquakes and volcanic eruptions
- Pacific Ring of Fire: Most tsunami-prone region
- India's Vulnerable Coast: East coast (Bay of Bengal), Andaman & Nicobar Islands
5. Summary: Natural Hazards at a Glance
| Hazard/Disaster | Cause | Vulnerable Areas | Key Feature |
|---|---|---|---|
| Earthquake | Tectonic movement (Indian Plate → Eurasian Plate) | NE states, J&K, Himachal, Uttarakhand, Sikkim, Darjeeling | Most devastating |
| Tsunami | Earthquakes and Volcanic eruptions | Pacific Ring of Fire, Southeast Asia, Bay of Bengal | High speed in shallow waters |
Key Takeaways for UPSC
- Natural Hazards vs Disasters: Disasters have far greater impact
- Earthquakes: Caused by tectonic movement (Indian Plate → Eurasian Plate)
- Most Vulnerable States: NE states, J&K, Himachal, Uttarakhand, Sikkim, Darjeeling
- Zone V (Very High Risk): NE states, Uttarakhand, Western Himachal, parts of Bihar
- Zone IV (High Risk): J&K, Himachal, Punjab, Haryana, Delhi, Western UP, Northern Bihar
- Tsunami: Caused by earthquakes and volcanic eruptions; Pacific Ring of Fire most prone
High-Yield Interactive UPSC Quiz (Natural Hazards and Disasters)
Q1. Earthquakes in India are primarily caused by the movement of which tectonic plates?
Correct Answer: B. Earthquakes in India are caused by the movement of the Indian Plate towards the Eurasian Plate, making India one of the most earthquake-prone regions in the world.
Q2. Which of the following states is NOT in the Very High Damage Risk Zone (Zone V)?
Correct Answer: C. Delhi is in Zone IV (High Damage Risk Zone), not Zone V. Zone V includes NE states, Uttarakhand, Western Himachal Pradesh, and parts of Bihar along the Indo-Nepal border.
Q3. Tsunamis are most frequently observed in which region?
Correct Answer: C. Tsunamis are most frequently observed in the Pacific Ring of Fire, including the coasts of Alaska, Japan, Philippines, and islands of Southeast Asia. (UPSC 2017)
Q4. Which of the following is in the Very High Damage Risk Zone (Zone V)?
Correct Answer: C. All 7 states of Northeast India are in the Very High Damage Risk Zone (Zone V). Jammu and Kashmir, Delhi, and Punjab are in Zone IV (High Damage Risk Zone).
Q5. The difference between a natural hazard and a natural disaster is primarily based on:
Correct Answer: B. Both are undesirable natural events with potential to harm, but natural disasters have relatively far greater impact and damage.
Q6. Which Indian states are most vulnerable to earthquakes?
Correct Answer: C. The most vulnerable states are Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, the Darjeeling subdivision of West Bengal, and all 7 states of Northeast India.
Q7. The Darjeeling subdivision of West Bengal falls under which seismic zone?
Correct Answer: D. The Darjeeling subdivision of West Bengal is in the Very High Damage Risk Zone (Zone V), along with Northeast states, Uttarakhand, and Western Himachal Pradesh.
Q8. Tsunamis have high speed in:
Correct Answer: B. Tsunamis have long wavelengths over deep waters but gain higher speed in shallow waters, causing devastating coastal impacts.
Q9. The Indo-Nepal border areas in Bihar (north of Darbhanga and Araria) fall under which seismic zone?
Correct Answer: D. Areas to the north of Darbhanga and Araria along the Indo-Nepal border in Bihar are in the Very High Damage Risk Zone (Zone V).
Q10. Which of the following is NOT a cause of tsunamis?
Correct Answer: C. Tsunamis are caused by earthquakes, volcanic eruptions, and underwater landslides. High tides are not a cause of tsunamis.