(a) What are the causes of earthquakes and volcanic activities ? Discuss their mitigation possibilities. (20 marks) (b) What is…

(a) Causes of earthquakes and volcanic activity and their mitigation (20 marks)

Causes of earthquakes.

• Tectonic: the sudden release of elastic strain along faults, as in the elastic-rebound theory, mostly at plate boundaries (subduction zones, transform faults, collision zones such as the Himalaya) and, less often, within plates.
• Volcanic: movement of magma and gas under a volcano.
• Induced: reservoir loading (as at Koyna), mining, deep fluid injection and nuclear tests; and collapse of caves and mines.

Causes of volcanic activity.

• Subduction zones: water released from the descending plate lowers the melting point of the mantle wedge, giving andesitic magma and arcs.
• Divergent boundaries: decompression melting of rising mantle, giving basalt at ridges and rifts.
• Hotspots and mantle plumes: hot mantle upwelling, as at Hawaii and the Deccan (Réunion).
• Eruption is driven by the buoyancy of magma and by exsolution and expansion of dissolved gases. India's only active volcano is Barren Island in the Andaman Sea.

Mitigation of earthquakes. Earthquakes cannot yet be predicted, so the measures are:

• Seismic zoning and microzonation, and land-use control on fault lines, unstable slopes and liquefiable soil.
• Earthquake-resistant design and construction under codes (IS 1893 and IS 4326), and retrofitting of old buildings.
• Early warning from seismic networks, public awareness, drills, insurance, and disaster-management plans under the NDMA.

Mitigation of volcanic hazards. Eruptions can often be forecast.

• Monitoring of seismicity, ground deformation, gas emission and temperature.
• Hazard maps and exclusion zones, evacuation plans and warning.
• Diverting lava, protecting water supply and airline routes from ash.

(b) Status of legislative measures for environmental protection in India (15 marks)

Constitutional basis. Article 48A (a directive principle) and Article 51A(g) (a fundamental duty) were added by the 42nd Amendment in 1976. The Supreme Court has read a right to a healthy environment into Article 21, and Article 253 lets Parliament legislate to implement international treaties.

Statutes and rules.

• Wildlife (Protection) Act 1972, Water (Prevention and Control of Pollution) Act 1974, Forest (Conservation) Act 1980 (as amended in 2023) and Air (Prevention and Control of Pollution) Act 1981.
• Environment (Protection) Act 1986, the umbrella act after the Bhopal gas tragedy, with the rules under it: the EIA Notification 2006, the CRZ Notification 2019, and the rules on hazardous waste, solid waste and plastic waste.
• Public Liability Insurance Act 1991, Biological Diversity Act 2002, Forest Rights Act 2006 and National Green Tribunal Act 2010.

Judicial principles. Polluter pays, the precautionary principle (Vellore Citizens' Welfare Forum), absolute liability (M.C. Mehta), the public trust doctrine and sustainable development.

Institutions. The Ministry of Environment, Forest and Climate Change, the Central and State Pollution Control Boards, and the National Green Tribunal.

Assessment. The framework is comprehensive, yet implementation is weaker: SPCBs are short of staff and resources, enforcement and compliance with EIA conditions are poor, and agencies overlap. Recent reforms that decriminalise some offences and ease clearances are debated for their effect on deterrence. The need is strong enforcement, transparent and participatory clearance, and better monitoring.

(c) Use of primary thermodynamics in understanding geological processes (15 marks)

Thermodynamics tells us which minerals and assemblages are stable under given pressure, temperature and composition.

• Free-energy criterion: Gibbs free energy G = H − TS. A reaction proceeds if ΔG < 0, and equilibrium exists when ΔG = 0, so ΔG° = −RT ln K, with ΔG = ΔH − TΔS + ΔV(P − 1).
• Clapeyron equation: dP/dT = ΔS/ΔV = ΔH/TΔV gives the slope of a reaction line in P–T space. This is used for polymorphs such as graphite and diamond, and the Al₂SiO₅ polymorphs (kyanite, sillimanite and andalusite), and for the melting curve of a mineral.
• Phase rule: F = C − P + 2 gives the degrees of freedom, and Goldschmidt's mineralogical phase rule (P ≤ C) applies to rocks in equilibrium.
• Chemical potential and activity: it controls the distribution of components between phases, and so the composition of solid solutions.
• Applications: petrogenetic grids and pseudosections for metamorphic facies; geothermobarometry, such as Fe–Mg exchange between garnet and biotite (temperature) and the GASP assemblage (pressure); oxygen fugacity buffers such as QFM; and melting relations, including eutectics and the solidus.

Limitations. Thermodynamics gives equilibrium, not rates, so kinetic barriers lead to metastable phases such as diamond and aragonite at the surface, and disequilibrium textures.