Earthquakes, Tsunamis, Volcanoes and Cyclones · GPSC (Gujarat)

What the official syllabus says

General Studies-III (Main Examination, Paper VI), (C) Geography:
Important Geophysical phenomena such as earthquakes, tsunami, volcanic activity, cyclone, etc.

Gujarat gives examples for every phenomenon on this line: the Kachchh earthquakes, the risk of a tsunami from the Makran coast, the old volcanic rocks of Saurashtra and Pavagadh, and Arabian Sea cyclones.

Topics in detail

Interior of the Earth and plate tectonics

Crust, mantle and core; discontinuities; evidence from seismic waves
Continental drift (Wegener), sea-floor spreading, plate tectonics
Plate boundaries: divergent, convergent, transform; the Indian plate and its northward movement

Earthquakes

Focus and epicentre; P, S and surface waves; seismographs
Measuring earthquakes: magnitude (Richter, moment magnitude) and intensity (Modified Mercalli)
Causes: plate boundaries, faults, intraplate stresses, reservoir-induced seismicity
Seismic zoning of India (the BIS seismic zone map) and the Himalayan, North-East and Kachchh risk
Intraplate earthquakes in Peninsular India: Koyna (1967), Latur (1993), Kachchh (2001)
The Kachchh earthquakes: Allah Bund (1819) and Bhuj (2001); faults of Kachchh
Effects: ground shaking, liquefaction, landslides, tsunamis; earthquake-resistant design

Tsunamis

Causes: undersea earthquakes, landslides, volcanic eruptions
How a tsunami travels and grows near the coast
Indian Ocean tsunami of 26 December 2004
The Makran subduction zone and the threat to Gujarat's coast (the 1945 tsunami)
The Indian Tsunami Early Warning Centre (INCOIS, Hyderabad); coastal protection by mangroves

Volcanic activity

Types of volcanoes and eruptions; volcanic landforms (intrusive and extrusive)
Distribution: the Pacific Ring of Fire, mid-ocean ridges, hot spots
In India: Barren Island (active) and Narcondam in the Andaman Sea
The Deccan Traps: lava flows that built the plateau, including Saurashtra; Pavagadh and Girnar as remains of old volcanic activity
Effects of eruptions on climate and air travel

Cyclones

Tropical cyclones: formation conditions, structure (eye, eye wall), stages, storm surge
Arabian Sea and Bay of Bengal cyclones compared; seasons of cyclones
Classification by the India Meteorological Department; naming of cyclones in the north Indian Ocean
Temperate cyclones and western disturbances
Cyclones and Gujarat: Kandla (1998), Tauktae (2021), Biparjoy (2023)
Rising cyclone activity in the Arabian Sea with warming seas

Earthquake risk in Gujarat in more detail

Kachchh as a zone of active faults (the Kachchh mainland fault, the Allah Bund and Island Belt faults)
Saurashtra and the Narmada rift (Son-Narmada lineament) as zones of moderate risk
Ahmedabad and Surat as large cities on soft alluvium, where shaking can be amplified
Monitoring by the Institute of Seismological Research (Gandhinagar)

Other phenomena

Landslides and their causes; landslide zones of India
Lightning, cloudbursts, heat waves and cold waves
Floods and droughts as hydro-meteorological events

Overlaps

Disaster Management in India and Disaster Management in Gujarat on this paper.
Prelims General Studies: internal structure of the Earth, earthquakes, landslides, atmospheric disturbances and cyclones.