Types of Disasters — Set 6

Correct Answer: B. Temperature departure of more than +6.4°C from normal

IMD classifies a severe heatwave when the temperature departure from the normal maximum exceeds +6.4°C, compared to +4.5°C to +6.4°C for a regular heatwave. Both classifications require the absolute maximum temperature to reach at least 40°C on plains (30°C for hill stations). Severe heatwaves pose greater public health risks and trigger higher-level alerts and mortality reduction action plans.

Correct Answer: B. Pyroclastic flow

A pyroclastic flow is a fast-moving current of hot gas, ash, and volcanic matter that flows down the side of a volcano at speeds exceeding 700 km/h and temperatures up to 1,000°C. Pyroclastic flows are among the most lethal volcanic phenomena and were responsible for the destruction of Pompeii during the 79 CE eruption of Mount Vesuvius. Barren Island's eruptions have so far been primarily effusive (lava flows) rather than producing pyroclastic flows.

Correct Answer: B. Bhopal Gas Tragedy

The Bhopal Gas Tragedy of 1984 is the classic example of an industrial disaster, caused by the release of toxic chemicals from a manufacturing plant due to negligence and safety failures. Industrial disasters include explosions, chemical releases, oil spills, and mine collapses at industrial facilities. They are categorised as man-made disasters distinguishable from natural hazards by their preventable nature.

Correct Answer: B. Hydro-meteorological / Geological

Glacial Lake Outburst Floods (GLOFs) are a hybrid hydro-geological hazard where a lake formed by glacial meltwater suddenly releases its waters due to dam failure, causing catastrophic downstream floods. GLOFs are increasingly common in India's Himalayan states of Uttarakhand, Himachal Pradesh, and Sikkim as glaciers retreat due to climate change. The February 2021 Chamoli disaster in Uttarakhand was partly attributed to a GLOF event.

Correct Answer: D. Landslide

Landslide is a geological disaster caused by the mass movement of rock, soil, and debris under gravity, though it can be triggered by hydro-meteorological events like heavy rainfall. Floods, cyclones, and hailstorms are purely hydro-meteorological hazards driven by atmospheric and hydrological processes. The distinction matters because landslide risk management requires geological surveys in addition to meteorological monitoring.

Correct Answer: D. Volcanic eruption (major)

India has minimal exposure to major volcanic eruptions as it has only one active volcano — Barren Island in the Andaman Sea — which is uninhabited and produces relatively small eruptions. In contrast, India is significantly exposed to earthquakes (59% of land vulnerable), cyclones (7,516 km of coastline), droughts (68% of area drought-prone), and floods (40 million hectares flood-prone). Major volcanic eruptions affect countries along active tectonic subduction zones such as Indonesia, Japan, and the Philippines.

Correct Answer: B. Man-made/technological disaster

Dam failure is classified as a man-made or technological disaster caused by structural failure, poor maintenance, design flaws, or extreme loading beyond design capacity. Though dam failures can be triggered by natural events like earthquakes or extreme floods, the disaster itself results from human engineering. The Vajont Dam disaster of 1963 in Italy and the Banqiao Dam failure of 1975 in China are classic examples of dam-failure disasters.

Correct Answer: B. Rapidly moving snow and ice

An avalanche consists of a rapidly moving mass of snow and ice that descends a mountainside at high speed, often carrying rocks, trees, and other debris. Avalanches are triggered by factors including fresh snowfall, rising temperatures, seismic activity, or human disturbances on steep snow-covered slopes. The Siachen Glacier area and Zoji La pass in Jammu & Kashmir are among the most avalanche-prone locations in India.

Correct Answer: B. Agricultural failure and water scarcity

Drought most commonly leads to agricultural failure, water scarcity, livestock mortality, and reduced economic activity in affected regions. India's agriculture is heavily dependent on monsoon rainfall, making it highly vulnerable to drought when the monsoon is deficient. The National Drought Management Policy (2016) distinguishes meteorological, hydrological, agricultural, and socio-economic drought as sub-categories.

Correct Answer: C. India Meteorological Department (IMD)

The India Meteorological Department (IMD) is responsible for issuing heatwave warnings and alerts through its network of meteorological stations across India. IMD uses a colour-coded warning system — Green (no warning), Yellow (watch), Orange (alert), and Red (warning) — to communicate heatwave risk to the public and authorities. IMD heatwave forecasts are integrated into district-level Heat Action Plans coordinated by state governments.