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Quick Revision Table
| Item | Key Fact | Exam Relevance |
|---|---|---|
| Earth's radius | 6,371 km | Basic reference |
| Crust thickness (continental) | 30–70 km (avg 35 km) | Interior structure Q |
| Crust thickness (oceanic) | 5–10 km | Interior structure Q |
| Sial composition | Silica + Aluminium, density 2.7 g/cm³ | PYQ 2021 (2 marks) |
| Sima composition | Silica + Magnesium, density 3.0 g/cm³ | PYQ 2021 |
| Mohorovičić discontinuity | ~35 km, crust-mantle boundary | 5-mark question |
| Gutenberg discontinuity | 2,900 km, mantle-outer core boundary | 5-mark question |
| Lehmann discontinuity | 5,100 km, outer core-inner core | 5-mark question |
| Outer core | Liquid Fe-Ni; generates magnetic field | 10-mark question |
| Inner core | Solid Fe-Ni; density ~13 g/cm³; ~5,500°C | 10-mark question |
| Asthenosphere | 100–350 km; partially molten; enables plate movement | Plate tectonics Q |
| Mesozoic Era time range | 252–66 Ma | PYQ 2021 (2 marks) |
| Carboniferous period | 359–299 Ma; coal forests; first reptiles; O₂ 35% | PYQ 2023 (5 marks) |
| P-T extinction | 252 Ma; 96% marine species extinct | 5/10-mark question |
| K-Pg extinction | 66 Ma; Chicxulub asteroid; 75% species; ends Mesozoic | 5/10-mark question |