🌍 Geography — India & World

🌌 1. Universe & Solar System (7 min read)

1.1 Universe — basic concept

• Big Bang Theory: The universe is believed to have originated from the expansion of a very small, hot, dense point. The universe is still expanding today (expanding universe — Edwin Hubble).
• Milky Way (Aakashganga / Mandakini): Our galaxy. Our Sun is an ordinary star in it. The nearest large galaxy — Andromeda.
• Light Year: it is a unit of distance, not of time! The distance light travels in one year ≈ 9.46 × 10¹² km.
• The star nearest to the Earth after the Sun — Proxima Centauri (~4.2 light years). Pole Star (Dhruv Tara / Polaris) — shows the north direction.

1.2 Sun — our star

• The Sun is a star — it has its own light. About 99.8% of the total mass of the Solar System is in the Sun.
• Main gases: Hydrogen, then Helium. Source of energy — Nuclear Fusion: Hydrogen → Helium.
• Average distance of the Earth from the Sun ≈ 15 crore km (149.6 million km = 1 AU). Sunlight reaches the Earth in ≈ 8 minutes 20 seconds.
• The visible surface of the Sun — Photosphere; the outer layer, the Corona, is seen only during a total solar eclipse. Sunspots — cooler, dark patches.

1.3 8 Planets — order from the Sun: "Bu-Shu-Pri-Man-Bri-Shani-Aru-Varun"

• Inner / Terrestrial planets (rocky): Mercury, Venus, Earth, Mars. Outer / Jovian planets (gas giants): Jupiter, Saturn, Uranus, Neptune — all of them have rings.
• Pluto (Yam): In 2006 the International Astronomical Union (IAU, Prague) declared it a Dwarf Planet. Other dwarf planets: Ceres, Eris, Haumea, Makemake.
• Asteroids: The belt between Mars and Jupiter (Asteroid Belt). The largest — Ceres (now a dwarf planet).
• Comet: Ice + dust; when it comes near the Sun it forms a tail, which always points away from the Sun (opposite direction). Halley's Comet — seen about every 76 years (last in 1986; next in 2061).
• Meteor ("shooting star"): Burns up as soon as it enters the atmosphere (in the Mesosphere). If it reaches the ground, it is a Meteorite. Example: Lonar crater lake (Maharashtra) — a lake formed by a meteorite.

1.4 Moon

• The Earth's only natural satellite; average distance from the Earth ≈ 3,84,400 km. Moonlight (reflected sunlight) reaches the Earth in ~1.3 seconds.
• Rotation on its axis and revolution around the Earth — both take almost the same time (~27.3 days) → so we always see the same side of the Moon.
• New Moon to New Moon (one lunar month) ≈ 29.5 days. There is no atmosphere on the Moon → no sound, and the sky looks black.
• India: Chandrayaan-1 (2008) helped confirm water molecules on the Moon; Chandrayaan-3's Vikram lander landed near the Moon's south pole on 23 Aug 2023 (23 Aug = National Space Day).

🌐 2. Earth: Latitude-Longitude, Time, Motions, Seasons, Eclipses (8 min read)

2.1 Shape of the Earth

• The Earth is not perfectly round — slightly flattened at the poles and slightly bulging at the equator: Geoid / Oblate spheroid.
• Equatorial diameter ≈ 12,756 km > polar diameter ≈ 12,714 km. Average distance to the centre (radius) ≈ 6,371 km.

2.2 Latitude and Longitude

• Torrid Zone: between the two tropics — here, at some time in the year, the midday sun is exactly overhead (direct rays) → hottest.
• Temperate: 23½° to 66½° (both hemispheres). Frigid: 66½° to the pole.

2.3 Time — from Longitude

• The Earth rotates 360° in 24 hours → 15° = 1 hour, 1° = 4 minutes.
• The Earth rotates from west to east (West → East) → time is ahead in the east (sunrise comes earlier).
• Greenwich Mean Time (GMT) — the time at 0° longitude.
• Indian Standard Time (IST): the time of the 82°30′ E longitude (passing near Mirzapur, UP) = GMT + 5:30 hours (82.5 × 4 = 330 min). This longitude passes through 5 states: UP, MP, Chhattisgarh, Odisha, Andhra Pradesh.
• India's east-west extent ≈ 30° of longitude → a difference of ≈ 2 hours between the local times of Arunachal and Gujarat.
• International Date Line: ~180° longitude; zig-zag in the Bering Strait/Pacific. When crossing towards the west, 1 day is added; when crossing towards the east, 1 day is subtracted.

2.4 Motions of the Earth

• Tilt of the axis: The Earth's axis makes an angle of 66½° with its orbital plane (i.e. it is tilted 23½° from the perpendicular).
• Perihelion: least distance from the Sun (~3 January). Aphelion: greatest distance (~4 July). Trap: in January the Earth is nearest to the Sun, yet it is winter in India — because seasons are caused by the tilt, not by the distance.

2.5 Eclipse

• Why is there no eclipse on every New Moon/Full Moon? — The Moon's orbit is tilted about 5° to the Earth's orbit; all three come in one straight line only sometimes.

🌋 3. Interior of the Earth, Rocks, Earthquakes-Volcanoes, Landforms (9 min read)

3.1 Interior of the Earth

It is not possible to look directly inside the Earth — information comes mainly from the behaviour of seismic waves.

• Discontinuities: between Crust–Mantle, Mohorovičić (Moho); between Mantle–Core, Gutenberg (~2,900 km); between the outer and inner core, Lehmann.
• Seismic waves: P-waves (Primary) — fastest, longitudinal, travel through solids + liquids + gases. S-waves (Secondary) — transverse, only through solids → S-waves do not reach through the outer core → this is how we learnt that the outer core is liquid (S-wave shadow zone). Surface/L-waves — slowest but most destructive.

3.2 Rocks

• Rock cycle: one type of rock keeps changing into another type — no rock is permanent.

3.3 Plate Tectonics

• Continental Drift — Alfred Wegener (1912): all continents were once one — Pangaea; the ocean around it — Panthalassa. Pangaea broke into two parts: Laurasia in the north and Gondwanaland in the south (India was a part of it).
• The lithosphere is made of big and small plates which slowly move over the asthenosphere. 7 major plates: Pacific, North American, South American, Eurasian, African, Indo-Australian, Antarctic.

3.4 Earthquake

• Focus / Hypocentre: the point inside where energy is released. Epicentre: the point on the surface directly above the focus — maximum damage here.
• Measurement: Seismograph (instrument); Richter scale = magnitude (energy), logarithmic (an increase of 1 point means ~10 times the amplitude); Mercalli scale = intensity (damage), I–XII.
• Tsunami (Japanese word — "harbour wave"): huge waves raised by an earthquake/volcano on the sea floor (e.g. the 26 Dec 2004 Indian Ocean tsunami).
• Seismic zones of India: as per BIS map IS 1893 (Part 1): 2016, 4 zones — II, III, IV, V (Zone V most dangerous: the whole North-East, parts of J&K, Kutch, Andaman-Nicobar etc.). Trap: In Nov 2025 BIS had notified a new map (with Zone VI), but it was withdrawn on 3 March 2026; the 2016 4-zone system is still in force (as of Sep 2026).

3.5 Volcano

• When magma comes to the surface it is called lava. The mouth = crater; a large collapsed crater = caldera.
• Pacific "Ring of Fire": most of the world's active volcanoes and earthquakes are along the edges of the Pacific Ocean.
• Types (by activity): Active — such as Etna (Sicily), Stromboli — "Lighthouse of the Mediterranean", Mauna Loa (Hawaii — a huge shield volcano); Dormant; Extinct.
• India's only active volcano — Barren Island (Andaman Sea). Narcondam (Andaman) — considered dormant.
• Deccan Trap: ~6.5 crore years ago basalt lava spread through fissure eruption → this formed the black soil (MP's Malwa is also part of it).
• Mountains formed by volcanoes: Kilimanjaro (the highest in Africa), Fujiyama (Japan).

3.6 Main Landforms — which agent forms what

• Types of mountains: Fold — Himalaya, Alps, Andes, Rockies (young); Aravalli, Appalachian, Ural (old). Block — the part raised between two faults (Europe: Vosges, Black Forest); the part sunk down = Rift valley — the Narmada and Tapi flow in rift valleys. Volcanic — Kilimanjaro, Fujiyama. Residual — old mountains left after wearing down (Aravalli).
• Plateau: Tibet — the highest plateau ("Roof of the World"); Deccan plateau (India); Chhota Nagpur (store of minerals).

☁️ 4. Atmosphere, Insolation & Heat Transfer (9 min read) — 10 PYQs!

4.1 Composition of the Atmosphere

• Water vapour and dust particles are mostly in the lowest layer (troposphere) — that is why clouds, rain and weather occur there.

4.2 Layers of the Atmosphere — 5 layers based on temperature (NCERT)

4.3 Insolation, Terrestrial Radiation and Heat Budget

• Insolation: the energy received by the Earth from the Sun (in the form of short waves).
• Terrestrial radiation: the warm Earth gives out energy in long waves → this is how the atmosphere is heated from below (not directly by sunlight). CO₂ and greenhouse gases absorb it.
• Albedo (reflection coefficient): the proportion of light reflected by a surface. Snow has the highest albedo. The Earth's average albedo is ~35 units (out of 100) — NCERT heat budget.
• Heat budget: the Earth gives back as much energy as it receives — so the Earth neither keeps getting warmer nor colder.

4.4 4 Ways of Heat Transfer — a PYQ favourite

• Temperature Inversion: the reverse of normal — temperature rises with height; in valleys on long, clear winter nights (fog/smog).
• Greenhouse gases: CO₂, Methane (CH₄), Nitrous oxide, CFCs, water vapour. Main cause of ozone depletion — CFCs; Montreal Protocol (1987).

🌀 5. Pressure Belts, Winds & Cyclones (9 min read) — 6 PYQs

5.1 Basics of Air Pressure

• Air always flows from high pressure (High) to low pressure (Low). Measuring instrument — Barometer; wind speed — Anemometer; direction — Wind vane; humidity — Hygrometer.
• Isobar: a line on a map joining places of equal air pressure. Isobars close together = steep pressure gradient = strong wind; far apart = slow wind.
• Coriolis force: the rotation of the Earth deflects the wind — to the right in the northern hemisphere, to the left in the southern hemisphere (Ferrel's law). Coriolis force is zero at the equator and maximum at the poles.
• Geostrophic wind: in the upper atmosphere (away from surface friction), when the pressure gradient force and the Coriolis force balance each other, the wind blows parallel to the isobars.

5.2 World Pressure Belts and Planetary Winds

• ITCZ (Inter Tropical Convergence Zone): the low-pressure zone near the equator where the trade winds meet (converge); air rises → clouds and rain. In summer it shifts north over North India (monsoon trough) — linked to the Indian monsoon.
• Jet streams: fast, narrow air currents in the upper troposphere. In winter the Subtropical Westerly Jet south of the Himalaya brings Western Disturbances (winter rain in North-West India — useful for rabi). In summer the Tropical Easterly Jet — linked to the monsoon.

5.3 Local Winds

5.4 Cyclones

• Cyclone = low pressure at the centre; air spirals inward from outside — anticlockwise in the northern hemisphere, clockwise in the southern. Anticyclone = high pressure at the centre, clear weather.
• Conditions for tropical cyclone formation: warm sea surface (above ~27°C), Coriolis force (so they do not form very close to the equator), low vertical wind shear, a pre-existing weak low-pressure area.
• The calm, cloud-free part at the centre — the Eye; around it the strongest winds and rain — the eye wall.
• Why does it weaken as soon as it reaches land? — the supply of moisture (energy) from the sea stops + friction of the land.
• In India, the Bay of Bengal has more cyclones than the Arabian Sea; main seasons: pre-monsoon (Apr–May) and post-monsoon (Oct–Dec).
• Warning: IMD (India Meteorological Department) — tracking and warning of cyclones; RSMC New Delhi maintains the naming list for North Indian Ocean cyclones. Rescue — NDRF (Card 20).

🌊 6. Oceans, Ocean Currents & Tides (Hydrosphere) (6 min read)

6.1 Oceans — big facts

• ~71% of the Earth's surface is covered by water; ~97% of the Earth's total water is in the oceans (salty). Fresh water is very little — and most of that is in ice (ice caps, glaciers).
• Order of size: Pacific > Atlantic > Indian > Southern > Arctic.
• Pacific — the largest and the deepest; Mariana Trench (Challenger Deep, ~11 km deep) — the deepest point in the world. Atlantic — "S" shaped; the busiest sea route. Indian Ocean — the only ocean named after a country (India).
• Ocean floor: Continental shelf (shallow; the best fishing grounds, petroleum; Mumbai High is on it) → Continental slope → Deep sea plain (Abyssal plain) → Trench.
• Salinity: normally 33–37 ‰ (parts per thousand) in the open ocean, average ~35 ‰. Up to ~41 ‰ in the Red Sea. The saltiest water bodies: Lake Van (Turkey), Dead Sea, Great Salt Lake (USA).

6.2 Ocean Currents

• Rule: In the tropics, cold currents flow along the western coasts of continents → less moisture in the air → coastal deserts there (Atacama, Namib, western coast of the Sahara).

6.3 Tides

• Main cause — the Moon's gravitational pull (the Sun's too, but less — the Sun is very far away).
• Spring tide: Sun, Earth and Moon in one line — on New Moon and Full Moon → the highest tide.
• Neap tide: the Sun and the Moon at right angles (90°) to the Earth — on the eighth day (ashtami) of the bright/dark fortnight → a lower tide.
• At any place there are about two high tides and two low tides every day; ~12 hours 25 minutes between two high tides.
• The highest tide in the world — Bay of Fundy (Canada). Potential for tidal energy in India — Gulf of Khambhat, Gulf of Kutch (Gujarat), Sundarbans.
• El Nino / La Nina — in Card 11 (Monsoon).

🗺️ 7. World Geography (Continents, Mountains, Rivers, Deserts, Grasslands, Straits, Lakes) (10 min read)

7.1 Continents — order of size

Asia > Africa > North America > South America > Antarctica > Europe > Australia

7.2 Major Mountain Ranges

• Andes — the longest (S. America). Himalaya — the highest and a young fold mountain. Rockies (N. America), Alps (Europe; Mont Blanc), Atlas (NW Africa), Ural (Europe-Asia boundary; old), Appalachian (USA; old), Great Dividing Range (Australia), Drakensberg (South Africa), Pamir Knot — "Roof of the World" (the Hindukush, Karakoram, Kunlun and Tien Shan radiate from here).

7.3 Major Rivers

7.4 Deserts

7.5 Grasslands

7.6 Straits: a narrow strip of water joining two large water bodies

• Canals: Suez (Egypt) — joins the Mediterranean with the Red Sea (the shortest sea route between Asia and Europe). Panama — joins the Atlantic with the Pacific.

7.7 Lakes & other "superlatives"

• Caspian Sea — the largest lake in the world (salty). Lake Superior (USA–Canada, Great Lakes) — the largest freshwater lake (by area). Lake Baikal (Russia, Siberia) — the deepest lake. Lake Victoria — the largest in Africa (source region of the Nile). Titicaca — the highest navigable lake (Peru-Bolivia). Dead Sea (Israel-Jordan) — the lowest place on the Earth's surface, very salty.
• Angel Falls (Venezuela) — the highest waterfall. Niagara — USA–Canada border. Victoria Falls — Zambezi river (Zambia-Zimbabwe).
• The largest island — Greenland (Denmark). The largest country — Russia; the smallest — Vatican City. The most populous — India (UN estimate, ahead of China in 2023).

7.8 Nicknames — they come in MCQs

7.9 Capitals of Neighbouring Countries

Nepal — Kathmandu · Bhutan — Thimphu · Bangladesh — Dhaka · Myanmar — Naypyidaw · China — Beijing · Pakistan — Islamabad · Afghanistan — Kabul · Sri Lanka — Sri Jayawardenepura Kotte (administrative/legislative; Colombo is the commercial capital) · Maldives — Malé.

🇮🇳 8. India: Location, Extent, Boundaries, Neighbouring Countries, States-Capitals (9 min read) — 2 PYQs

8.1 Location & Extent

• Entirely in the northern and eastern hemispheres. Mainland: 8°4′N – 37°6′N latitude, 68°7′E – 97°25′E longitude.
• Area: 32,87,263 sq km — ~2.4% of the world's total land area; the 7th largest country in the world (after Russia, Canada, USA, China, Brazil, Australia).
• North-south extent ~3,214 km; east-west ~2,933 km.
• The Tropic of Cancer divides the country into almost two equal parts (8 states — Card 2). IST meridian 82°30′E (Mirzapur).
• Extreme points: Southernmost — Indira Point (Great Nicobar; it was submerged in the 2004 tsunami); southernmost point of the mainland — Kanyakumari (Cape Comorin). Northernmost — Indira Col (Siachen/Ladakh). Easternmost — Kibithu (Arunachal Pradesh). Westernmost — Guhar Moti (Kutch, Gujarat).
• Coastline: 7,516.6 km (including islands; mainland ~6,100 km) — this is the old, textbook figure that was asked in the 2025 paper. New official figure: 11,098.81 km (MoPSW circular, 29 April 2025 — re-measured by a new GIS method). The longest coastline — Gujarat (in both figures; 2,340.62 km in the new measurement).
• Land border: ~15,200 km (NCERT) / 15,106.7 km (MHA).

8.2 Neighbouring Countries and Border Length (MHA)

• Boundary lines: Radcliffe Line — India–Pakistan & India–Bangladesh (1947). McMahon Line — India–China (eastern part, Arunachal; 1914 Shimla). Durand Line — Pakistan–Afghanistan (1893). LoC — India–Pakistan in J&K. LAC — India–China.
• Maritime neighbours: Sri Lanka (separated by the Palk Strait and the Gulf of Mannar), Maldives. 10° Channel — separates Andaman from Nicobar. 9° Channel — separates Minicoy from the main group of Lakshadweep. 8° Channel — separates Minicoy from the Maldives. Coco Channel — between North Andaman and Coco island (Myanmar). Duncan Pass — between South Andaman and Little Andaman.
• The state bordering the most countries — West Bengal (Bangladesh, Nepal, Bhutan — 3). Sikkim and Arunachal also border 3 countries each.

8.3 States and Capitals (28 States + 8 UTs — as of Sep 2026)

• The largest state by area — Rajasthan, then Madhya Pradesh, then Maharashtra. The smallest — Goa.
• The newest state — Telangana (2 June 2014). Chhattisgarh (from MP) was formed on 1 Nov 2000, Uttarakhand on 9 Nov 2000, Jharkhand on 15 Nov 2000.
• MP cross-ref: MP borders 5 states — UP, Chhattisgarh, Maharashtra, Gujarat, Rajasthan (details in 04_Madhya_Pradesh_GK).

⛰️ 9. Physical Features of India (Physiography) (10 min read) — 5 PYQs

6 physiographic divisions (NCERT): (1) The Himalayan mountains (2) The Northern Plains (3) The Peninsular Plateau (4) The Indian Desert (5) The Coastal Plains (6) The Islands.

9.1 Himalaya — young fold mountains

• Trans-Himalaya / Tibetan Himalaya: Karakoram (K2 / Godwin Austen — 8,611 m, in PoK; claimed as India's highest peak), Ladakh, Zaskar ranges.
• Purvachal (Eastern hills): Patkai Bum, Naga, Mizo (Lushai), Manipur hills; Garo-Khasi-Jaintia (the Meghalaya plateau — actually a part of the peninsular plateau).
• West-to-east division (on the basis of river valleys): Punjab Himalaya (Indus–Satluj), Kumaon Himalaya (Satluj–Kali), Nepal Himalaya (Kali–Teesta), Assam Himalaya (Teesta–Dihang).
• Passes: Zoji La (Srinagar–Leh), Khardung La (Ladakh), Shipki La (HP, Satluj), Lipulekh (Uttarakhand — Kailash Mansarovar yatra), Nathu La (Sikkim), Bom Di La (Arunachal), Banihal (Jawahar Tunnel), Rohtang (Atal Tunnel, HP).

9.2 Northern Plains

• Formed by the alluvial soil of the Indus, Ganga and Brahmaputra; ~7 lakh sq km; very fertile and densely populated.
• Bhabar — at the foot of the Shiwalik, an 8–16 km wide belt; pebbles and stones; rivers disappear. Terai — south of the bhabar, marshy, rivers re-emerge; dense forests (Dudhwa NP).
• Bangar — old alluvial soil, higher ground, kankar nodules (calcareous). Khadar — new alluvial soil, flood plains, renewed every year, more fertile.
• Doab — the land between two rivers. The Punjab plain has 5 doabs. Majuli in the Brahmaputra — one of the largest river islands in the world (Assam).

9.3 Peninsular Plateau

• The oldest landmass (part of Gondwana); igneous-metamorphic rocks. Two parts: the Central Highlands — north of the Narmada (Malwa plateau, Bundelkhand, Baghelkhand, Chhota Nagpur plateau) and the Deccan Plateau — south of the Narmada, triangular.
• Deccan Trap — formed of volcanic basalt; the region of black soil (parts of Maharashtra, MP, Gujarat).
• Aravali — among the oldest fold mountain ranges in the world; highest peak Guru Shikhar (Mount Abu).
• Western Ghats (Sahyadri) — continuous, high (average 900–1,600 m); Anai Mudi (2,695 m, Kerala — the highest peak of the peninsula), Doda Betta (Nilgiri). Eastern Ghats — broken, low (average ~600 m); the highest is Mahendragiri (Odisha; Jindhagada in some sources). Both Ghats meet in the Nilgiri hills.
• MP cross-ref: the Narmada flows between the Vindhya and the Satpura; the highest peak of the Satpura is Dhupgarh (Pachmarhi, Mahadev hills); Amarkantak (Maikal) — source of the Narmada and the Son.

9.4 Indian Desert (Thar)

• West of the Aravali; rainfall less than 15 cm/year; the Luni is the only large river (salty water — into the Rann of Kutch). Barchans — crescent-shaped sand dunes; longitudinal dunes near the Indo-Pak border.

9.5 Coastal Plains

9.6 Islands

• Andaman & Nicobar (Bay of Bengal) — peaks of a submerged mountain range; Barren Island — India's only active volcano; Saddle Peak (the highest peak, North Andaman).
• Lakshadweep (Arabian Sea) — coral islands; old names Laccadive, Minicoy and Amindive (renamed Lakshadweep in 1973); capital Kavaratti; Pitti island — a bird sanctuary.

🌊 10. Drainage System: Rivers, Dams, Projects (Drainage) (12 min read) — 10 PYQs

10.1 Drainage patterns

10.2 Himalayan vs Peninsular Rivers

10.3 Himalayan River Systems

• Indus: rises in Tibet near Mansarovar (Bokhar Chu); flows through Ladakh (Leh) into Pakistan → Arabian Sea. Tributaries: Jhelum (Verinag; Wular lake), Chenab (the largest tributary), Ravi, Beas (Beas Kund near Rohtang), Satluj (Rakas Tal, Tibet; enters through Shipki La; Bhakra Nangal). Indus Waters Treaty 1960 — India could use 20% of the water of the Indus system (after the Pahalgam attack on 23 April 2025 India kept the treaty "in abeyance" (suspended); on 31 Aug 2026 the Court of Arbitration at The Hague said the treaty is in force, but India rejected the decision — as of Sep 2026).
• Ganga: Bhagirathi (Gangotri/Gaumukh) + Alaknanda (Satopanth) → meet at Devprayag to form the Ganga. Enters the plains at Haridwar. India's longest river (~2,525 km); National River (2008). Left-bank tributaries: Ramganga, Gomti, Ghaghara, Gandak, Kosi ("Sorrow of Bihar"). Right-bank: Yamuna (Yamunotri; Sangam at Prayagraj — the longest tributary), Son (from Amarkantak). In Bangladesh it is the Padma; together with the Brahmaputra it forms the Sundarban delta (the largest delta in the world).
• Tributaries of the Yamuna (from the Peninsula): Chambal (Janapav near Mhow, MP), Betwa, Ken, Sindh.
• Brahmaputra: rises from the Chemayungdung glacier near Mansarovar in Tibet; called Tsangpo in Tibet; it turns near Namcha Barwa and is called Dihang/Siang in Arunachal; in Assam the Dibang + Lohit join to form the Brahmaputra; in Bangladesh it is the Jamuna. Majuli (river island) and Umananda (near Guwahati, Peacock Island — Umananda Shiva temple) — both are in the Brahmaputra.

10.4 Peninsular Rivers

10.5 Major Dams / Projects

• Indira Gandhi Canal: old name Rajasthan Canal; foundation stone 31 March 1958; renamed in 1984. Water from the Harike Barrage (Punjab — confluence of the Satluj and Beas); irrigation in the Thar desert — one of the longest canal systems in the world.
• Ken–Betwa Link Project — India's first river-linking project (MP–UP; Daudhan dam, Panna). Foundation stone 25 Dec 2024.

10.6 Lakes (India)

• Wular (J&K) — the largest freshwater lake (Jhelum). Chilika (Odisha) — the largest lagoon/saltwater lake. Sambhar (Rajasthan) — the largest inland salt lake. Loktak (Manipur) — phumdi (floating islands), Keibul Lamjao — the world's only floating NP. Vembanad (Kerala) — the longest; Nehru Trophy boat race (Punnamada). Lonar (Maharashtra) — meteorite crater lake. Dal (Srinagar), Kolleru (AP), Pulicat.

🌧️ 11. Climate & Monsoon of India (9 min read) — 3 PYQs

11.1 Basics

• India's climate is "Tropical Monsoon". The word "Monsoon" comes from the Arabic "Mausim" (season) — the seasonal reversal of wind direction.
• Controlling factors: latitude (the Tropic of Cancer passes through the middle), altitude, pressure and winds, distance from the sea (continentality), the Himalaya (blocks the cold winds of Central Asia), jet streams, El Nino.
• Alpine climate in the higher Himalaya (very cold, snow) — temperature falls as height increases (~6.5°C / 1,000 m).

11.2 4 Seasons (IMD)

11.3 Rainfall Distribution

• Mawsynram (Meghalaya) — the highest average rainfall in the world; Cherrapunji (Sohra) is nearby. Leh and Jaisalmer — the lowest.
• Rain shadow: the Deccan east of the Western Ghats (beyond Pune), Shillong (behind the Khasi hills).

11.4 El Nino, La Nina, Jet stream

• El Nino — abnormal warming of the sea near the Peru coast (eastern Pacific); occurs every 3–7 years (NCERT Class 11); in India it often means a weak monsoon / drought. La Nina — the opposite (cold); in India it often means a good monsoon. ENSO = El Nino Southern Oscillation.
• Indian Ocean Dipole (IOD) — a positive IOD is good for India's monsoon.
• Jet stream: in winter the Subtropical Westerly Jet (south of the Himalaya); in summer the Tropical Easterly Jet — helps the onset of the monsoon. The ITCZ shifts towards the Ganga plain in summer (monsoon trough).

11.5 Koppen Classification (India — main types)

🟫 12. Soils of India & Soil Erosion (8 min read) — 5 PYQs

ICAR has divided the soils of India into 8 main types: Alluvial, Black, Red & Yellow, Laterite, Arid, Saline, Peaty/Marshy, Forest soil.

12.1 Soil Erosion and Conservation

• Gullies — running water cuts through clayey soils and makes deep channels; such land is unfit for farming = "Bad land"; "Ravines" (beehad) in the Chambal valley — MP-Rajasthan-UP.
• Sheet erosion — water washes away the top layer of soil over a large area. Wind erosion — in deserts.
• Conservation: contour ploughing, terrace farming — on hills, strip cropping, shelter belts (rows of trees — check wind erosion; Rajasthan), bunding.
• Soil Health Card scheme — 2015 (from Suratgarh, Rajasthan). World Soil Day — 5 December.

🌳 13. Natural Vegetation (9 min read) — 10 PYQs

13.1 Montane forests — by altitude (NCERT)

13.2 Forest Cover (ISFR 2023 — released in Dec 2024)

• Total forest + tree cover 25.17% (8,27,357 sq km); forest cover alone 21.76%. Target of the National Forest Policy 1988 — 33% of the area under forests.
• The largest forest area: Madhya Pradesh (77,073 sq km) > Arunachal > Chhattisgarh. By percentage: Lakshadweep (91.33%) > Mizoram (85.34%) > A&N.
• ISFR — by the Forest Survey of India, Dehradun, every 2 years.

🐅 14. Wildlife, National Parks, Biosphere Reserves (Wildlife & Protected Areas) (11 min read) — 10 PYQs

14.1 Numbers (as of Sep 2026)

14.2 UNESCO's 13 Biosphere Reserves (MAB)

Nilgiri (TN-Kerala-Karnataka) · Gulf of Mannar (TN) · Sundarban (WB) · Nanda Devi (Uttarakhand) · Nokrek (Meghalaya) · Pachmarhi (MP) · Simlipal (Odisha) · Achanakmar-Amarkantak (MP-CG) · Great Nicobar (A&N) · Agasthyamalai (Kerala-TN) · Khangchendzonga (Sikkim) · Panna (MP) · Cold Desert (HP).
The other 5 (national only): Manas (Assam), Dibru-Saikhowa (Assam), Dehang-Dibang (Arunachal), Kachchh (Gujarat), Seshachalam (AP).

14.3 Major National Parks — for which animal

14.4 Himalayan / High-altitude Animals (NCERT)

• In the snowy heights of Ladakh — yak (shaggy horned wild ox, weight ~1 tonne), Tibetan antelope (chiru), Bharal (blue sheep), wild sheep, Kiang (Tibetan wild ass), ibex, snow leopard, red panda.
• Hoolock gibbon — forests of the North-East. Golden langur — Assam-Bhutan. Red panda — state animal of Sikkim.

14.5 Important Laws / Projects

• Wildlife Protection Act 1972; Forest Conservation Act 1980; Biological Diversity Act 2002. Project Tiger 1973; Project Elephant 1992; Project Cheetah 2022; Project Crocodile 1975.
• India is among the world's 17 megadiverse countries; 4 biodiversity hotspots — Himalaya, Indo-Burma, Western Ghats–Sri Lanka, Sundaland (Nicobar).

🌾 15. Agriculture & Crops (8 min read) — 3 PYQs

15.1 Cropping Seasons

15.2 Major Crops — conditions and producers

15.3 Revolutions

• Types of farming: Jhoom (Slash & burn / shifting) — North-East (Assam, Meghalaya, Mizoram, Nagaland); called "Bewar/Dahiya" in MP, "Podu/Penda" in Andhra, "Deepa" in Chhattisgarh (Bastar) (NCERT). Plantation — tea, coffee, rubber, sugarcane, banana. Intensive subsistence — densely populated areas.

⛏️ 16. Mineral Resources (Minerals) (12 min read) — 16 PYQs

16.1 Basic rule of distribution

• Metallic minerals — in the old crystalline (igneous-metamorphic) rocks of the peninsular plateau. Coal — in Gondwana sedimentary rocks (Damodar, Son, Mahanadi, Godavari valleys). Petroleum — sedimentary basins (Assam, Gujarat, Mumbai High).
• 3 main mineral belts: (1) North-eastern plateau region — Chhota Nagpur (Jharkhand), Odisha plateau, WB, part of CG — the richest; (2) South-western plateau — Karnataka, Goa, TN-Kerala; (3) North-western — Aravali (Rajasthan), Gujarat.
• Jharkhand, Chhattisgarh, MP (+ Odisha) — rich in both minerals and coal; deforestation and land degradation due to mining are also the greatest here.

16.2 Major Minerals — where (NCERT)

⚡ 17. Energy Resources (9 min read) — 8 PYQs

17.1 Conventional

• Petroleum: Assam — Digboi (the oldest oilfield), Naharkatiya, Moran. Gujarat — Ankleshwar, Kalol, Mehsana, Nawagam, Kosamba, Lunej. Mumbai High — an offshore field ~160 km away from Mumbai; discovered in 1973, production since 1976. Others: KG basin (Krishna-Godavari), Kaveri basin, Barmer (Rajasthan).
• Organisations: ONGC — 1956; Oil India Ltd (OIL) — incorporated in 1959 (Duliajan, Assam); OIL built the Naharkatiya–Barauni (1,157 km), Asia's first cross-country pipeline. Digboi refinery (1901) — the oldest; Jamnagar (Reliance) — the world's largest refinery complex.
• Natural gas: GAIL (1984); HVJ / HBJ pipeline (Hazira–Vijaipur–Jagdishpur).
• Thermal power — India's largest source of electricity (based on coal). NTPC — 1975. Vindhyachal (Singrauli, MP) — the largest thermal power station in the country.
• Hydro power: Arunachal Pradesh — the highest hydro-power potential (rich in water resources). The first — Darjeeling (1897), Shivasamudram (1902).

17.2 Nuclear Energy

• Atomic Energy Commission — 1948 (Homi J. Bhabha); DAE — 1954. Singrauli, Bhilai, Talcher, Neyveli = thermal/mining centres — not nuclear.

17.3 Non-conventional / Renewable

• Solar: two main methods — Photovoltaic (PV) and solar thermal. The highest potential — western India, especially Gujarat and Rajasthan (strong sunshine + open land). Bhadla Solar Park (Jodhpur, Rajasthan); MP — Rewa Ultra Mega Solar, Omkareshwar floating solar. International Solar Alliance (2015; headquarters Gurugram).
• Wind: Gujarat and Tamil Nadu lead; Muppandal (TN) — a major wind farm.
• Geothermal: according to NCERT, a plant has been commissioned at Manikaran (Himachal); potential also in the Puga valley (Ladakh).
• Tidal: Gulf of Khambhat, Gulf of Kachchh (Gujarat), Sundarban. Bio-energy: farm waste, gobar gas.
• Targets (as of Sep 2026): 500 GW non-fossil capacity by 2030; Net Zero — 2070 (COP26, Glasgow).

🏭 18. Industries (7 min read)

18.1 Iron & Steel

SAIL — 1973. India is the world's second largest producer of crude steel (after China).

18.2 Other Major Industries

• Cotton textile: the first successful mill in Mumbai (1854). Mumbai — "Cottonopolis"; Ahmedabad — "Manchester of India"; Kanpur — "Manchester of the North"; Coimbatore — "Manchester of the South". MP: Indore, Ujjain, Burhanpur.
• Jute: the first mill at Rishra (1855), near Kolkata; concentrated along the Hooghly river. India is the world's largest jute producer.
• Aluminium: NALCO (Angul-Damanjodi, Odisha), HINDALCO (Renukoot, UP), BALCO (Korba, CG).
• Fertilizer: Sindri (Jharkhand, 1951) — the first large government plant.
• Petrochemicals: Jamnagar, Vadodara (Koyali), Mumbai. IT / Software: Bengaluru — "Silicon Valley of India"; Hyderabad, Pune, Chennai, Noida-Gurugram.
• Paper: Nepanagar (MP) — newsprint. MP cross-ref: Pithampur — "Detroit of India"; BHEL Bhopal; Security Paper Mill Hoshangabad (Narmadapuram). Details in 04_Madhya_Pradesh_GK.
• NCERT's 8 major industrial regions: Mumbai-Pune, Hugli, Bengaluru-Tamil Nadu, Gujarat, Chhota Nagpur, Visakhapatnam-Guntur, Gurugram-Delhi-Meerut, Kollam-Thiruvananthapuram.

🚆 19. Transport & Communication (12 min read) — 22 PYQs

19.1 Roads

• Total road length: NCERT/paper figure 62.16 lakh km (MoRTH 2020-21); now more than 63 lakh km (31 Mar 2025) — the world's second largest road network (after the USA). National Highways (NH): ~1,46,204 km (official figure as of Sep 2026).
• Roads carry ~85% of passenger and ~70% of freight traffic (NCERT).
• NH — only ~2% of the total road length, but ~40% of road traffic. Construction and maintenance — Central Government (through MoRTH, NHAI). Rural roads ~80% of the length. PMGSY — 2000.
• The first 20-year road plan — 1961 (after Independence; before it the Nagpur Plan 1943). Sher Shah Suri built the Shahi (Badshahi) road — from the Indus valley to the Sonar valley (Bengal); in the British period the Grand Trunk (GT) Road (Kolkata–Peshawar).
• NHAI — Act in 1988, operationalised in 1995. Border Roads Organisation (BRO) — 1960; Chandigarh–Manali–Leh road, average altitude ~4,270 m.
• Golden Quadrilateral — 5,846 km, Delhi–Mumbai–Chennai–Kolkata. North-South corridor — Srinagar–Kanyakumari; East-West corridor — Silchar–Porbandar (3,640 km). The longest NH — NH-44 (Srinagar–Kanyakumari).

19.2 Railways

• The first train — 16 April 1853, from Bombay (Bori Bunder) to Thane, 34 km. Indian Railways is the second largest network in Asia and the fourth largest in the world (traditional fact).
• Length: NCERT/paper — 67,956 km (2019-20); now the route length is more than 68,000 km.
• Gauge: Broad — 1.676 m; Metre — 1.000 m; Narrow — 0.762 m and 0.610 m. Project Unigauge — converting all to broad gauge.
• Konkan Railway (1998) — from Roha (Maharashtra) to Mangaluru (Karnataka), ~760 km; a joint project of Maharashtra, Goa, Karnataka; ~146 rivers, 2,000 bridges, 91 tunnels (NCERT).
• Metro Rail — a revolution in urban transport; the first metro Kolkata (1984); Delhi Metro (2002). The first bullet train — Mumbai–Ahmedabad (under construction).

19.3 Water Transport

• The cheapest mode of transport; most suitable for heavy & bulky goods; fuel-efficient, eco-friendly.
• Inland waterways ~14,500 km navigable (only ~1% of the country's transport). Inland Waterways Authority of India (IWAI) — 1986 (headquarters Noida). National Waterways Act 2016 — 111 National Waterways.
• NW-1: Ganga — Prayagraj to Haldia (1,620 km, the longest). NW-2: Brahmaputra — Sadiya to Dhubri (891 km). NW-3: West Coast Canal — Kottapuram–Kollam (Kerala).
• Backwaters (Kayal) of Kerala — cheap transport + tourist attraction; Nehru Trophy boat race (Vallamkali) — Punnamada lake, Alappuzha.

19.4 Ports — 12 major operational ports (as of Sep 2026)

Under construction: Vadhavan (Maharashtra) and Galathea Bay (Great Nicobar).

19.5 Air Transport, Pipelines, Communication

• Airports Authority of India (AAI) — 1995. GAGAN (GPS Aided GEO Augmented Navigation) — satellite-based navigation system of AAI + ISRO. UDAN scheme — 2016.
• Pawan Hans — helicopter service: connectivity and tourism in hilly regions, the North-East, and petroleum fields (ONGC offshore).
• Pipelines: Asia's first cross-country pipeline — Naharkatiya (Assam) to Barauni (Bihar), 1,157 km — built by Oil India Ltd (OIL); later extended up to Kanpur. HVJ gas pipeline — GAIL.
• Satellite communication: satellites give a continuous and synoptic view of large areas — weather, disaster warning. INSAT (communication) and IRS (remote sensing).

👥 20. Population, Census, Regional Planning & Disaster Management (10 min read) — 7 PYQs

20.1 Census — history

• The first census — 1872 (Lord Mayo; non-synchronous). The first regular/synchronous census — 1881 (Lord Ripon). Every 10 years since then. The first of independent India — 1951. 2011 — the 15th census (7th after Independence).
• 1921 — "Year of the Great Divide" — after it the population grew continuously; 1951–1981 — the period of "population explosion".
• Conducted by — Registrar General & Census Commissioner, Ministry of Home Affairs (MHA); Census Act 1948.

20.2 Census 2027 (status as of Sep 2026)

• The 2021 census was postponed because of COVID; now Census 2027 — the country's 16th and first digital census; along with it, caste enumeration too.
• Phase 1 — Houselisting: April–September 2026. Phase 2 — Population enumeration: February 2027.
• Reference date: 1 March 2027. In snow-bound areas (parts of Ladakh, J&K, HP, Uttarakhand) enumeration is in September 2026, with reference date 1 October 2026.

20.3 Census 2011 — main figures

• SC — 16.6%, ST — 8.6% of the population. Definition of literacy — a person aged 7 years+ who can read and write with understanding in any language.
• According to UN estimates, India overtook China in 2023 to become the most populous country in the world.
• MP cross-ref (2011): population ~7.27 crore, sex ratio 931, literacy 69.3% — details in 04_Madhya_Pradesh_GK.

20.4 Regional Planning — NCERT Class 12

• Target area planning: Command Area Development, Drought Prone Area Programme (DPAP) — 4th Plan, Hill Area Development Programme (HADP) — 5th Plan, covering 15 districts — all the hilly districts of UP (now Uttarakhand), the Mikir Hill and North Cachar hills of Assam, Darjeeling of WB, Nilgiri of TN.
• Bharmaur tribal region (Chamba, HP): region of the Gaddi tribe; declared a notified tribal area on 21 November 1975; developed under the Tribal Sub-Plan (1974) in the 5th Plan.
• Indira Gandhi Canal command area — expansion of farming in the Thar through irrigation (Card 10).
• In place of the Planning Commission (1950) — NITI Aayog — 1 January 2015.

20.5 Disaster Management

• Disaster Management Act 2005 → NDMA (chairperson — Prime Minister), SDMA (Chief Minister), DDMA (Collector). NDRF (2006) — rescue & evacuation during natural disasters. NIDM — training.
• Cyclone warning and monitoring — IMD (India Meteorological Department, 1875).
• Landslide: the Himalaya, the Western Ghats and the North-East are the most vulnerable. Human causes — deforestation and unplanned construction, road building, mining.
• Forest fire: frequent in Uttarakhand, Himachal, MP, Chhattisgarh (and Odisha, NE); FSI gives "fire alerts" through satellites.
• Mining-led deforestation and land degradation: Jharkhand, Chhattisgarh, MP, Odisha — the mineral-rich states.
• Understanding climate change — helps communities in disaster preparedness, resilience and adaptation. Sendai Framework (2015–2030) — disaster risk reduction.