BharatNotes What is Geophysical Phenomena (India)?
Geophysical phenomena are natural events produced by the Earth's internal energy and surface dynamics — earthquakes, volcanic eruptions, tsunamis and landslides. In India these are governed primarily by the ongoing collision of the Indian Plate with the Eurasian Plate (which raises the Himalaya) and by the Andaman-Nicobar-Sumatra subduction zone in the east. Together these tectonic settings make large parts of the country seismically active and expose its coasts to tsunamis.
Key Geophysical Hazards in India
| Phenomenon | Indian context | Key data (date-stamped) |
|---|---|---|
| Earthquakes | Himalayan belt, NE India, Kutch, Andaman | Four seismic zones II-V under IS 1893 (Part 1):2016, reinstated after IS 1893:2025 was withdrawn via gazette notification, 3 Mar 2026 |
| Volcanism | Barren Island, Andaman Sea | India's only confirmed active volcano; ~138 km NE of Port Blair; recent eruptive activity reported 2017-2019 and 2025 |
| Tsunamis | East coast, Andaman & Nicobar | 2004 Indian Ocean tsunami caused ~12,405 deaths in India (govt figures), Tamil Nadu worst hit (~8,009) |
| Landslides | Himalaya, Western Ghats, NE hills | ~0.42 million sq km, about 12.6% of India's land area, landslide-prone (Geological Survey of India) |
Seismic Zonation: Current Status
India's earthquake risk is mapped by the Bureau of Indian Standards in IS 1893. The applicable standard is IS 1893 (Part 1):2016, dividing the country into four zones — Zone II (low) to Zone V (highest, e.g. the NE, Kutch, parts of the Himalaya). A revised 2025 code introduced a fifth tier, Zone VI, placing the entire Himalayan arc in the highest-risk category, but it was withdrawn in early 2026 after the Ministry of Housing and Urban Affairs flagged sharp construction-cost increases and inadequate consultation. As a result the four-zone framework remains in force (as of June 2026).
Institutional Response
The 2004 disaster reshaped India's hazard governance. The Indian Tsunami Early Warning Centre was set up at INCOIS, Hyderabad (under the Ministry of Earth Sciences) and became operational in 2007, providing alerts for the Indian Ocean rim. The National Disaster Management Authority (NDMA) coordinates preparedness across earthquake and landslide hazards, while the Geological Survey of India leads landslide susceptibility mapping and is developing a regional landslide early-warning capability.
UPSC Angle
For Prelims, anchor the high-frequency facts: India has four seismic zones (II-V); Barren Island is the only active volcano; INCOIS runs the tsunami warning system under the Ministry of Earth Sciences. For Mains, link cause (Indo-Eurasian collision, subduction) to consequence (Himalayan seismicity, tsunami risk, landslide-prone slopes) and to mitigation (zonation codes, early-warning systems, building bye-laws). This is a foundational concept that underpins questions across physical geography and disaster management.
