A23a Iceberg Drifting in South Atlantic: Antarctic Iceberg Lifecycle for UPSC Geography

Context

The giant Antarctic iceberg A23a, once the world’s largest, is drifting northwards into warmer waters of the South Atlantic near South Georgia Island, entering the final stage of its life cycle.

About A23a

• One of the largest icebergs ever recorded (~3,900 sq km).
• Broke off from Antarctica’s Filchner–Ronne Ice Shelf in 1986.
• Remained grounded in the Weddell Sea for decades before drifting since the 2020s.
• Now moving into warmer waters → expected to fragment and melt.

Earthquake Zoning in India: Draft IS 1893 Changes and Government Withdrawal Explained

Context:
The Centre withdrew the revised earthquake zoning under draft IS 1893:2025 after objections over its scientific basis and cost implications for infrastructure.

1. Earlier Zoning (IS 1893:2016)

Zone II (Low)
• Central & Peninsular interiors — e.g., Madhya Pradesh, Chhattisgarh, parts of Karnataka, Telangana.

Zone III (Moderate)
• e.g., Kerala, Tamil Nadu, Andhra Pradesh, Odisha, Maharashtra (parts).

Zone IV (High)
• e.g., Delhi, Haryana, Punjab, Bihar, West Bengal (parts).

Zone V (Very High)
• e.g., Jammu & Kashmir/Ladakh, Himachal Pradesh, Uttarakhand, Northeast, Rann of Kutch.

2. Proposed Change (IS 1893:2025 draft — exact shift)

• Based on probabilistic seismic hazard assessment (PSHA), new ground-motion data, tectonic mapping and historical earthquake records.

• Proposed six-zone gradation (II–VI):

Zone II: Low — peninsular interiors.
Zone III: Moderate — southern & central belts.
Zone IV: High — Indo-Gangetic plains (Delhi–Bihar belt).
Zone V: Very high — Himalayan belt & Northeast.
Zone VI (new): Extremely high — parts of Kashmir, Northeast and Kutch.

3. Basis for Introducing Zone VI

• Areas with highest peak ground acceleration (PGA) levels.
• Active faults and plate-boundary interactions (Himalayan collision zone).
• Past major earthquakes (Kashmir, Assam, Bhuj region).
• Required stricter building norms, deeper foundations and higher safety margins.

4. Why Questioned

• Agencies (MoHUA, NDMA/NDSA, Metro Rail bodies) flagged methodology concerns.
• Reclassification → higher construction costs for large infrastructure.
• Risks of delays and stranded projects cited.

5. Agency Responsible

• Bureau of Indian Standards (BIS) prepares seismic zoning and building codes.
• BIS is a statutory body under the BIS Act, 2016.
• Works under Ministry of Consumer Affairs, Food & Public Distribution.