Natural Hazards for CSIR NET Earth Science: Earthquakes, Tsunami, Landslides and PYQ Strategy

Natural hazards link geology, atmosphere and ocean science, and they appear in CSIR NET Earth Science as both concept and data questions. The topics are familiar from the news (earthquakes, tsunamis, cyclones, floods, landslides), so the key is to learn the correct scientific terms and the measurement scales.

What the syllabus covers

• Earthquakes: focus and epicentre, seismic waves (P, S, Love, Rayleigh), magnitude scales (Richter, moment magnitude) versus intensity scales (Mercalli), seismic zonation and seismic gaps.
• Volcanic hazards: eruption styles, pyroclastic flows, lahars, ash fall, volcanic gases and the Volcanic Explosivity Index (VEI).
• Tsunami: generation by subduction earthquakes, landslides and eruptions; wave speed in deep water; run-up and warning systems.
• Cyclones and storm surges: formation conditions, structure, classification, and coastal impacts.
• Floods and droughts: causes, flood frequency and return period, and indices for drought monitoring.
• Landslides and subsidence: triggering factors, slope stability, factor of safety, mass movement types and mitigation.
• Risk framework: hazard, vulnerability, exposure and risk; prediction versus forecasting; early warning and mitigation.
• Impact events and climate-linked hazards: glacial lake outburst floods, sea-level rise and coastal erosion.

High-yield topics to prioritise

1. Magnitude versus intensity, and the main seismic wave types.
2. Tsunami generation and why wave speed falls in shallow water.
3. Landslide causes and the factor of safety concept.
4. Flood return period and probability of occurrence.
5. Hazard, vulnerability and risk definitions.
6. Cyclone formation requirements and the role of sea-surface temperature.

How to study this unit

• Keep a one-page sheet of scales: Richter and moment magnitude, Mercalli intensity, VEI, and the cyclone categories.
• Remember that return period T equals one divided by the annual exceedance probability. A 50-year flood has a 2% chance in any year.
• Link each hazard to its plate tectonic or climatic setting, so the answer follows from the cause.
• Practise short numerical questions on wave travel time and tsunami speed.

PYQ strategy

Natural hazards questions tend to be direct. Use our solved PYQ bank to practise by topic and note which scales and definitions come up repeatedly. Then revise with a timed mock test.

Common mistakes

• Using magnitude and intensity as if they meant the same thing.
• Assuming that a larger magnitude always means higher intensity at every location.
• Confusing prediction with probabilistic forecasting.
• Forgetting that risk depends on vulnerability and exposure, not just on the hazard.

Related guides

See our complete CSIR NET Earth Science syllabus guide for all units and our eligibility guide.