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Glossary Terms
| Term (EN) | Definition | Exam Relevance |
|---|---|---|
| Earthquake | Sudden energy release in Earth's crust along a fault; generates seismic waves | Core topic |
| Focus/Hypocenter | Underground point of energy release in an earthquake | Basic earthquake terminology |
| Epicentre | Surface point directly above the earthquake focus | Basic earthquake terminology |
| Richter Scale | Logarithmic scale (1935) measuring earthquake magnitude; 1 unit = 10× ground motion | Measurement 5-mark |
| Moment Magnitude (Mw) | Current scientific standard for measuring large earthquake energy | Measurement 5-mark |
| P-wave | Primary/compressional seismic wave; travels through solids, liquids, gases | Seismology |
| S-wave | Secondary/shear seismic wave; travels only through solids | Seismology |
| Ring of Fire | Circum-Pacific Belt; 40,000 km horseshoe; 80% earthquakes, 75% volcanoes | PYQ 2021 — 5 marks |
| Alpide Belt | Mediterranean-Himalayan seismic belt; 15% world earthquakes | Seismic belt Q |
| Tsunami | Ocean waves (wavelength 100–500 km) from seafloor disturbance; travel at 700–900 km/h | 2004 Tsunami Q |
| Volcano | Vent in Earth's surface through which magma, gases, and ash erupt | Core topic |
| Magma | Molten rock below Earth's surface | Basic terminology |
| Lava | Magma that has reached the surface; 700–1,200°C | Volcanic products |
| Shield Volcano | Broad, gently sloping basaltic volcano; effusive eruption | Volcano type — Mauna Loa |
| Composite/Strato Volcano | Steep, explosive andesitic/rhyolitic volcano; most dangerous | Volcano type — Fuji, Pinatubo |
| Pyroclastic Flow | Superheated (800°C) ash-gas-rock mixture moving at 700 km/h; deadliest volcanic hazard | Impact Q |
| Lahar | Volcanic mudflow; volcanic material + water | Volcano impact |
| Caldera | Large depression from volcanic summit collapse | Yellowstone, Crater Lake |
| VEI | Volcanic Explosivity Index (0–8 scale); Pinatubo = VEI 6; Tambora = VEI 7 | Volcano measurement |
| Liquefaction | Water-saturated soil behaves like liquid during shaking; causes building collapse | Earthquake impact |
| Megathrust | Largest type of fault at subduction zones; source of Mw 9+ earthquakes | 2004 Tsunami source |
| Barren Island | India's only active volcano — Andaman Sea | India geography |
| Geothermal Energy | Energy from Earth's internal heat; Iceland gets 66% electricity from this | Positive volcano impact |
| Volcanic Winter | Global cooling from SO₂ aerosols in stratosphere after large eruptions | Pinatubo 1991, Tambora 1815 |
| Hotspot | Stationary mantle plume creating volcanic chains as plate moves over it | Hawaii; not Ring of Fire |
Sources: USGS Earthquake Hazards Programme; Smithsonian Global Volcanism Program; NCERT Physical Geography Class XI; H.J. de Blij Physical Geography; INCOIS Tsunami Warning Centre; BIS IS-1893 Seismic Zone Map; RPSC Mains PYQ 2013–2023.