Bring out the causes for more frequent occurrence of landslides in the Himalayas than in the Western Ghats.

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Ghissu Editorial · Accepted Answer

The Himalaya slides more often than the Western Ghats because its young, seismic, fragile fold belt meets cloudbursts, snowmelt and construction, while the Ghats are an old, stable block. The ISRO Landslide Atlas (2023) attributes about 85% of mapped landslides to the Himalaya against 14.7% to the Western Ghats.

**Introduction**

A landslide occurs when gravity overcomes the strength of slope material. The ISRO-NRSC Landslide Atlas of India (2023) attributes about 66.5% of mapped landslides to the North-western Himalaya and 18.8% to the North-eastern Himalaya, against only 14.7% to the Western Ghats.

**Geological Causes: Young Himalaya, Old Ghats**

SKETCH: comparison | Why the Himalaya slides more
a: Himalaya
b: Western Ghats
- Young, still rising :: Ancient, stable block
- Sheared, weak rock :: Compact basalt, gneiss
- High seismic hazard :: Low to moderate hazard
- Snow, glaciers, cloudbursts :: Monsoon rain only

1. **Active tectonics**: The Indian plate still pushes into Eurasia, so the Himalaya is a rising fold belt cut by the Main Central and Main Boundary Thrusts, while the Ghats are the edge of the stable Peninsular block.
2. **Fragile rock**: Shales, schists and loose glacial debris dominate Himalayan slopes, whereas the Ghats are compact Deccan basalt and gneiss.
3. **Seismic triggering**: Lying in India's highest seismic hazard belt, Himalayan slopes are shaken loose often; the 2005 Kashmir and 2015 Nepal earthquakes each set off thousands of landslides, while the Ghats rarely face such shocks.

**Climatic and Human Triggers in the Himalaya**

1. **Extreme precipitation**: Monsoon-western disturbance cloudbursts, as at Kedarnath in 2013, plus snowmelt and glacial lake outbursts like South Lhonak (2023), are triggers the snow-free Ghats lack.
2. **River undercutting**: Perennial, snow-fed rivers like the Alaknanda and Teesta erode the toe of slopes all year in deep gorges, unlike the seasonal Ghat streams.
3. **Development load**: Roads, tunnels and unplanned towns on weak slopes worsened the Joshimath subsidence (2023), though Wayanad (2024) shows the Ghats are not immune.

**Conclusion**

A young, seismic and fragile terrain meeting extreme rain and dense construction explains the Himalaya's higher landslide frequency. Hazard zoning based on GSI's susceptibility maps is the durable remedy for both ranges.

Bring out the causes for more frequent occurrence of landslides in the Himalayas than in the Western Ghats.

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