Natural Disasters

Natural Disasters

• Geophysical

Main Event: Earthquake/Mass movement of earth materials

Secondary Disasters:

Landslides occurring after an earthquake

Urban fires initiated by earthquakes

Liquefaction: the process by which partially water- saturated soil loses its solidity and behaves like a liquid due to an earthquake

Movement of earth materials, typically down slopes

Surface displacement of earthen materials as a result of ground shaking from earthquakes

Examples: 2001 Gujarat Earthquake: Magnitude 7.7; triggered urban fires and ground fissures, 2005 Kashmir Earthquake: Magnitude 7.6; caused massive landslides in hilly regions, 2015 Nepal–India Border Earthquake (Uttarakhand & Bihar impact): Triggered landslides in Himalayan terrain.

Main Event: Volcano Secondary Disaster:

Displacement of surface materials due to ground shaking

caused by volcanic eruptions.

• A geological phenomenon occurring near an opening or vent on the Earth's surface, involving the eruption of lava, ash, hot vapor, gases, and pyroclastic material.

• Deposition of volcanic ash.

• Lahar – A flow of hot or cold earthen material down the slopes of a volcano, occurring either during or between eruptions.

• Lava flow.

• Pyroclastic flow – A high-speed surge of extremely hot gases, ash, and other volcanic materials, exceeding 1,000 degrees Celsius and traveling at speeds over 700 km/h down the volcano's slopes during an eruption.

Examples: Barren Island Volcano (Andaman Sea, Andaman & Nicobar Islands):

Only active volcano in India, Recent eruptions (2021, 2022) produced lava flows, ash clouds, and pyroclastic activity.

Narcondam Volcano (Andaman & Nicobar Islands):

Dormant; no recent eruptions.

Main Event: Tsunami Secondary Disaster:

• Tsunamis are challenging to classify, as they are

primarily an oceanic phenomenon that manifests as a coastal water-related hazard.

A sequence of waves with long wavelengths in deep ocean waters, generated by the displacement of large volumes of water due to underwater earthquakes, volcanic eruptions, or landslides.

Tsunami waves move rapidly across the ocean but slow down upon reaching shallow waters, causing the waves to increase in height and become steeper.

Example: The 2004 Indian Ocean tsunami struck India’s east coast (Tamil Nadu, Andhra Pradesh, Andaman & Nicobar), caused by an underwater earthquake, leading to massive loss of life and coastal damage.

• Hydrological

Main Event: Floods, Landslides, Wave Action Secondary Disaster:

An avalanche is a rapid descent of a large mass of loosened

snow, ice, or earth material down a mountainside due to gravitational force.

• Coastal erosion refers to the temporary or permanent loss of sediments or landmass along coastal areas due to wave action, wind forces, or human activities.

• Coastal flooding occurs when water levels along the coast rise above normal due to tidal variations or storms, leading to inundation that may persist for days or even weeks.

• Debris flow, mudflow, and rockfall are types of landslides triggered by heavy rainfall or the rapid melting of snow and ice, causing large volumes of vegetation, mud, or rocks to move downslope due to gravity.

• A flash flood is a hydrological event in which heavy or excessive rainfall within a short period generates immediate runoff, leading to flooding within minutes or a few hours after the rainfall.

• A flood is a general term for water overflowing onto normally dry land, including riverine flooding (when water spills over stream channels), coastal flooding (higher-than-normal water levels along coasts, lakes, or reservoirs), and flash floods (localized water accumulation at or near the site of rainfall).

• Wave action refers to wind-driven surface waves that form on bodies of water such as oceans, rivers, and lakes. The size and intensity of these waves depend on wind strength and the distance over which they travel (fetch).

Examples: Floods – Kerala (2018), Assam (2022); Landslides

– Malin, Maharashtra (2014), Kedarnath (2013); Coastal flooding – Cyclone Yaas (2021).

• Meteorological

Main event: Hazards are caused by short-lived, small- to medium-scale extreme weather and atmospheric conditions that can persist for minutes to several days.

Secondary Disaster:

• Cyclone, storm surge, tornado, convective storm, extratropical storm, and strong winds.

• Cold wave, derecho (a widespread, long-lasting windstorm with straight-line winds).

• Extreme temperature variations, fog, frost, freezing conditions, and hailstorms.

• Heatwave.

• Lightning and heavy rainfall.

• Sandstorm and dust storm.

• Winter storm and blizzard.

Examples: 2005 Mumbai Floods – >1,000 deaths from heavy rainfall; 2015 Andhra Pradesh & Telangana Heatwave –

~2,000 deaths; 2020 Cyclone Amphan – ~100 deaths and ₹1 lakh crore losses.

• Climatological Hazards

Main Event: Extreme or unusual weather patterns associated with long-term, meso- to macro-scale atmospheric processes, spanning from intra-seasonal to multi-decadal climate variability.

Secondary Disaster:

• Drought

• Extreme hot/cold conditions

• Forest/Wildfire

• Glacial Lake Outburst Flood (GLOF)

• Subsidence

• Biological

Examples: Drought – Maharashtra, Karnataka, Telangana, Andhra Pradesh (2015–16), affecting ~330 million people; GLOF – Chamoli, Uttarakhand (2021), >200 deaths and major infrastructure loss.

Main Event: Exposure to germs and toxic substances

Secondary Disaster:

• Epidemics: viral, bacterial, parasitic, fungal, or prion (or misfolded protein agent) infections

• Insect infestations

• Animal stampedes

Examples of biological disasters in India: COVID-19 Pandemic (2020–22) – 4 crore+ cases, 5 lakh+ deaths, economic and health crisis; Locust Attack (2020) – major crop destruction in Rajasthan, Gujarat, MP, UP.