Geography

The concept

Nobody has drilled through the crust, so the interior is known mainly from seismic waves. P-waves (primary, longitudinal) are the fastest and travel through solids, liquids and gases. S-waves (secondary, transverse) are slower and cannot pass through liquids. Surface waves arrive last and do the most damage. Because S-waves vanish on the far side of the Earth, the outer core must be liquid; P-waves bend (refract) at the core and leave a shadow zone, which NCERT gives as roughly 105° to 145° from the epicentre (some books give about 103° to 142°; use the NCERT figure). Seismographs beyond 105° get no S-waves at all. This is how the layers were mapped.

The layers: the crust (oceanic about 5 km thick, continental about 30 km on average and up to 70 km under big mountains); the mantle down to about 2,900 km, whose upper weak part, the asthenosphere, is the source of magma; and the core, a liquid outer core and a solid inner core made mostly of nickel and iron (the old name NIFE). The boundaries have names MPSC loves: Conrad (upper and lower crust), Mohorovičić or Moho (crust and mantle), Gutenberg (mantle and core, about 2,900 km) and Lehmann (outer and inner core, about 5,150 km).

Wegener proposed continental drift in 1912 (the supercontinent Pangaea and the ocean Panthalassa) but could not explain the force. Arthur Holmes suggested mantle convection in the 1930s; Harry Hess showed sea-floor spreading in the 1960s; and plate tectonics (1967 onwards) joined them. The Indian plate broke from Gondwana, drifted north and collided with Eurasia; that collision of two continental plates crumpled the sediments of the Tethys Sea into the Himalaya, which is why the Himalaya is young, still rising and earthquake-prone. Ocean–continent convergence gives trenches and volcanic mountains (Andes); ocean–ocean convergence gives island arcs (Japan). The Pacific Ring of Fire follows these subduction zones.

Maharashtra itself sits on the Indian plate interior, yet it has three famous geology facts. The Deccan Traps are layer upon layer of basalt from fissure eruptions (lava pouring out of long cracks, not a cone) around the end of the Cretaceous, about 66 million years ago. The Koyna earthquake (1967) is the classic Indian example of reservoir-induced seismicity. The Killari (Latur) earthquake of 30 September 1993 showed that even the "stable" plateau can shake. India's only active volcano is Barren Island in the Andaman Sea; Lonar (Buldhana) is a meteorite-impact crater lake in basalt, a Ramsar site since 2020.

The concept

Latitude is the angular distance of a place north or south of the Equator (0° to 90°); lines of equal latitude are parallels, and they are all parallel circles that shrink towards the poles. One degree of latitude is about 111 km everywhere. Longitude is the angular distance east or west of the Prime Meridian (0°, through Greenwich, adopted in 1884), from 0° to 180°. Meridians are half-circles that meet at the poles, so the ground distance covered by one degree of longitude is about 111 km at the Equator and shrinks to zero at the poles.

Time comes from longitude. The Earth turns 360° in 24 hours, so 15° = 1 hour and 1° = 4 minutes (1′ of longitude = 4 seconds). The Earth rotates from west to east, so the sun appears earlier at eastern places: going east, add time; going west, subtract time. Every time-zone question reduces to: find the difference in longitude, multiply by 4 minutes, then add or subtract. When the two places are on opposite sides of Greenwich (one E, one W), add the longitudes to get the difference.

India stretches from about 68°7′E to 97°25′E, roughly 29°, so local time in the far east of Arunachal Pradesh is almost two hours ahead of western Gujarat. Rather than use several zones, India uses one: IST, based on 82°30′E, which is 82.5 × 4 = 330 minutes, that is 5 h 30 min ahead of GMT. The standard meridian passes through five states: Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Odisha and Andhra Pradesh. The north–south extent is about 8°4′N to 37°6′N on the mainland, and the Tropic of Cancer (23°30′N) cuts across eight states: Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand, West Bengal, Tripura and Mizoram (not Maharashtra).

The International Date Line follows roughly the 180° meridian, zig-zagging to avoid land. A traveller crossing it westward (America to Asia) moves the calendar forward one day; crossing eastward (Asia to America) moves it back one day. Maharashtra lies entirely west of 82°30′E, so local time everywhere in the state is behind IST; Mumbai (about 72°50′E) is nearly 39 minutes behind.

The concept

The atmosphere is about 78% nitrogen, 21% oxygen, 0.93% argon and roughly 0.04% carbon dioxide, plus variable water vapour and dust. Its layers by temperature: the troposphere (about 8 km at the poles to 18 km at the equator; all weather happens here; temperature falls about 6.5 °C per km), the stratosphere (to about 50 km; contains the ozone layer, temperature rises with height), the mesosphere (to about 80 km; the coldest layer, where meteors burn up), the thermosphere with the ionosphere (reflects radio waves) and the exosphere.

Uneven heating creates pressure differences, and air moves from high to low pressure. There are seven belts: the equatorial low (heated air rises, calm "doldrums"), two subtropical highs near 30° (air descending from the Hadley cell, calm "horse latitudes"), two subpolar lows near 60° (warm westerlies meet cold polar air and are pushed up), and two polar highs (cold, dense air). The equatorial and polar belts are thermal in origin; the subtropical and subpolar belts are dynamic, created by the movement of air and the Earth's rotation. All the belts shift north and south with the apparent movement of the sun, which is the key to the monsoon.

Winds do not flow straight from high to low because of the Coriolis force, an apparent force caused by the Earth's rotation. It deflects winds to the right in the Northern Hemisphere and to the left in the Southern (Ferrel's law). It is proportional to the sine of latitude: zero at the equator, maximum at the poles. That is why tropical cyclones do not form right at the equator. In the Northern Hemisphere air spirals into a low anticlockwise (cyclone) and out of a high clockwise (anticyclone); the directions reverse in the south. Buys Ballot's law: in the Northern Hemisphere, stand with your back to the wind and the low pressure is on your left.

The resulting planetary winds: the trade winds blow from the subtropical highs towards the equator (north-east trades in the north, south-east trades in the south); the westerlies blow from the subtropical highs towards the subpolar lows (south-westerly in the north, north-westerly in the south, very strong over the open southern oceans: the Roaring Forties, Furious Fifties and Shrieking Sixties); and the polar easterlies blow from the polar highs. Winds are named after the direction they come from.

The concept

The simple "land heats faster than sea" idea explains the reversal of winds but not the timing and suddenness of the monsoon. The modern explanation uses the ITCZ (Inter-Tropical Convergence Zone), the low-pressure belt where trade winds of both hemispheres meet. In the northern summer it shifts north, and in July it lies over the Ganga plain at about 20°–25°N, where it is called the monsoon trough. The south-east trades of the Southern Hemisphere are pulled across the equator towards it; once north of the equator the Coriolis force deflects them to the right, and they arrive as the south-west monsoon.

Upper-air jet streams control the timing. In winter the subtropical westerly jet blows south of the Himalaya and keeps the monsoon away (it also steers the western disturbances that give north-west India its winter rain, good for rabi wheat). In early summer this jet shifts north of the Himalaya, and a tropical easterly jet develops at about 15°N over the peninsula, helped by the heating of the Tibetan plateau. This switch sets off the sudden burst of the monsoon. The monsoon normally reaches Kerala around 1 June, covers the whole country by about 8 July, starts withdrawing from west Rajasthan around 17 September and leaves by about mid-October.

It arrives in two branches. The Arabian Sea branch strikes the Western Ghats head-on; forced to rise, the air cools and drops heavy orographic rain on the Konkan and the Ghats, then descends dry on the leeward side, creating the rain-shadow of Madhya Maharashtra and Marathwada. The Bay of Bengal branch is funnelled into the north-east (Mawsynram and Cherrapunji in Meghalaya get the world's heaviest rains) and up the Ganga plain. Within the season there are breaks when the trough moves to the Himalayan foothills. In October–December the retreating north-east monsoon picks up moisture over the Bay of Bengal and gives Tamil Nadu its main rain.

Year-to-year variation comes from distant oceans. El Niño is an abnormal warming of the central and eastern Pacific; linked with the Southern Oscillation (a pressure see-saw between Tahiti and Darwin) it is called ENSO, and it often but not always weakens the Indian monsoon; La Niña (cooling) usually helps it. The Indian Ocean Dipole (IOD) compares sea temperatures in the western and eastern Indian Ocean: a positive IOD (west warmer) usually favours good rain and can offset an El Niño. IMD calls seasonal rain "normal" when it is 96–104% of the Long Period Average (LPA, 87 cm for 1971–2020).

The concept

Ocean currents are driven mainly by the planetary winds (the trades push water westward, the westerlies push it eastward), deflected by the Coriolis force, and shaped by the coastlines. Differences in temperature and salinity (density) drive slower, deeper thermohaline circulation. The result in each major ocean basin is a gyre: clockwise in the Northern Hemisphere and anticlockwise in the Southern. In low and middle latitudes, warm currents run along the east coasts of continents (the western margins of oceans) and cold currents along the west coasts of continents.

Currents shape climate. The Gulf Stream and its extension the North Atlantic Drift keep north-western Europe mild and the Norwegian ports ice-free in winter. Cold currents cool and dry the air over the land beside them, which is why the great west-coast deserts sit next to cold currents: the Atacama (Humboldt or Peru current), the Namib (Benguela), parts of the Sahara (Canary) and the Sonoran (California). Where warm and cold currents meet — the Gulf Stream and the cold Labrador current off Newfoundland (the Grand Banks), the warm Kuroshio and cold Oyashio off Japan — the mixing produces fog and abundant plankton, so these are major fishing grounds. The northern Indian Ocean is special: its currents reverse with the monsoon, flowing clockwise in summer and anticlockwise in winter.

Tides are the periodic rise and fall of sea level caused by the gravitational pull of the Moon and, to a lesser extent, the Sun (the Moon's tidal effect is roughly twice the Sun's, because it is so much closer), together with the Earth's rotation. When Sun, Earth and Moon are in a line, at new moon and full moon (amavasya and pournima), the pulls add up and we get spring tides with the largest range. When the Sun and Moon are at right angles, at the first and last quarter (ashtami), they partly cancel and we get neap tides. Most coasts have two high and two low tides in a tidal day of about 24 h 50 min, so high tides come about 12 h 25 min apart and roughly 50 minutes later each day, because the Moon moves on in its orbit.

Tides matter for ports and power. Kolkata on the Hooghly and Kandla in the Gulf of Kutch rely on tidal water for ships. The Gulf of Khambhat and Gulf of Kutch have India's highest tidal ranges and hence the best tidal-energy potential; the world's greatest range is in the Bay of Fundy (Canada). Mumbai's fishermen and its coastal road planners alike work with tide tables.

The concept

NCERT divides India into six physiographic divisions: the Himalayan mountains, the Northern plains, the Peninsular plateau, the Indian desert, the Coastal plains and the Islands. The Himalaya is young fold mountain country with three parallel ranges: the Himadri (Greater Himalaya, the highest, average about 6,000 m), the Himachal (Lesser Himalaya) and the Shiwaliks (outer foothills of unconsolidated sediments); flat valleys between the Lesser Himalaya and the Shiwaliks are called duns (Dehra Dun). Its eastern hills (Patkai, Naga, Mizo) are the Purvanchal.

The Northern plains are built of alluvium. Near the foothills is the bhabar, a narrow belt of pebbles where streams disappear underground; then the marshy terai where they re-emerge; then the plains proper, made of older alluvium on raised ground (bhangar, with calcareous kankar) and new flood-plain alluvium (khadar, renewed every year and very fertile). The Peninsular plateau, the oldest and most stable part of India, has the Central Highlands (Malwa, Bundelkhand, Chhotanagpur) north of the Narmada and the Deccan plateau south of it, flanked by the continuous, higher Western Ghats (Sahyadri) and the broken, lower Eastern Ghats. The highest peak of the peninsula is Anamudi (2,695 m) in the Anaimalai hills. The western coastal plain is narrow and has estuaries and lagoons; the eastern coastal plain is broad with large deltas.

Himalayan rivers are perennial (snow-melt plus rain), long, with large basins; they erode deep gorges, meander in the plains and build huge deltas. Several, like the Indus and the Brahmaputra, are older than the Himalaya itself (antecedent). Peninsular rivers are mostly rain-fed and seasonal, shorter, flow in shallow mature valleys, and are much older. The Western Ghats are the main water divide, so the big peninsular rivers flow east. The two exceptions, the Narmada (from Amarkantak) and the Tapi, flow west through rift valleys (faulted troughs) and end in estuaries, not deltas. The Ganga is India's longest river (about 2,525 km); the Godavari (about 1,465 km) is the longest peninsular river and has the largest peninsular basin, earning it the name Dakshin Ganga.

The concept

India's census is conducted by the Office of the Registrar General and Census Commissioner under the Ministry of Home Affairs, under the Census Act, 1948. The first census was attempted in 1872 (non-synchronous) and the first synchronous census was in 1881. The 2011 Census was the 15th census and the 7th after independence, and it is still the last completed census. The next one was due in 2021 but was postponed (the COVID-19 pandemic). Status as of November 2026: Census 2027, the 16th census and the first digital one, with caste enumeration, is under way in two phases. The houselisting and housing census ran from April to September 2026. Population enumeration in Ladakh and the snow-bound areas of Jammu and Kashmir, Himachal Pradesh and Uttarakhand was done in September 2026 (reference date 1 October 2026). For most of the country it is notified for 25 January to 28 February 2027, with the reference date 1 March 2027 (a few states, such as Uttar Pradesh, Punjab and Goa, have separate schedules). Until its results are published, Census 2011 figures are the ones to quote.

Census 2011, India: population about 121.09 crore; decadal growth (2001–11) about 17.7%; density 382 per km²; sex ratio 943; literacy 74.04% in the provisional figures, revised to 72.98% in the final data (MPSC questions usually quote 74.04%, so read the options); urban share about 31%. Uttar Pradesh is the most populous state and Maharashtra the second. Bihar has the highest density (1,106) and Arunachal Pradesh the lowest (17). Kerala has the highest sex ratio (1,084) and literacy (about 94%); Haryana has the lowest sex ratio (879) and Bihar the lowest literacy (about 61.8%).

Census 2011, Maharashtra: population 11,23,74,333 (about 9.3% of India); decadal growth about 16.0%; density 365 per km² (below the national 382); sex ratio 929 (below the national 943); literacy 82.34% (above the national average); urban share about 45.2%, among the most urbanised large states. Within the state, Ratnagiri has the highest sex ratio and Mumbai City the lowest, because of male migration out of Konkan to Mumbai; Mumbai Suburban has the highest literacy and the tribal district of Nandurbar the lowest.

Definitions matter in statement questions. A literate person is one aged 7 years or above who can read and write with understanding in any language. An urban area is either a statutory town (with a municipal body or cantonment) or a census town, which meets three tests: population at least 5,000, density at least 400 per km², and at least 75% of male main workers outside agriculture. Density = population ÷ area; sex ratio = (females ÷ males) × 1,000; decadal growth = (new − old) ÷ old × 100.

The concept

Maharashtra covers 3,07,713 km², the third largest state by area after Rajasthan and Madhya Pradesh, and has a coastline of about 720 km. As of November 2026 it has 36 districts (Palghar, carved out of Thane in 2014, is the newest; proposals for more districts have not been implemented) in six revenue divisions: Konkan, Pune, Nashik, Chhatrapati Sambhajinagar, Amravati and Nagpur. Remember the renamings: Aurangabad is now Chhatrapati Sambhajinagar, Osmanabad is Dharashiv and Ahmednagar is Ahilyanagar. Physically it has three parallel belts from west to east: the Konkan, the Sahyadri and the Deccan plateau, with the Satpura hills along the northern edge.

The Konkan is a narrow coastal plain, roughly 30–60 km wide, between the Arabian Sea and the Sahyadri, cut by short west-flowing rivers with creeks and estuaries, and dotted with lateritic plateaus. The Sahyadri rises abruptly from it as a steep west-facing escarpment, generally around 1,000 m high, and is the main water divide of the state. Its highest peak, and Maharashtra's highest, is Kalsubai (1,646 m) in Ahilyanagar district; Salher (1,567 m, Nashik) is second, and Mahabaleshwar (Satara; the town is at about 1,350 m and its highest point, Wilson Point, about 1,439 m) is the best-known hill station. Roads and railways cross at passes: Thal (Kasara) ghat on the Mumbai–Nashik route, Bor ghat on the Mumbai–Pune route, Kumbharli (Karad–Chiplun), Amba (Kolhapur–Ratnagiri) and Amboli near Sawantwadi.

The Deccan plateau makes up most of the state. It is built of near-horizontal flows of basalt (the Deccan Traps), which weather into step-like, flat-topped hills (mesas and buttes) and into black soil. It tilts gently to the east and south-east. Spurs of the Sahyadri run east across it and divide the river basins: the Satmala–Ajanta hills (between the Tapi and Godavari), the Harishchandra–Balaghat range (between the Godavari and Bhima) and the Shambhu Mahadev range (between the Bhima and Krishna). In the north the Satpura forms the boundary with Madhya Pradesh, with Toranmal (Nandurbar) and, in its Gawilgarh hills, Chikhaldara (Amravati), the only hill station of Vidarbha. In far-eastern Vidarbha (the Wainganga basin) the basalt gives way to much older rocks and to Gondwana coal-bearing rocks around Chandrapur.

The concept

The Godavari rises at Trimbakeshwar in the Brahmagiri hills of Nashik district and is the longest river of peninsular India (about 1,465 km). It flows south-east through Nashik, Ahilyanagar, Chhatrapati Sambhajinagar (the Jayakwadi dam at Paithan, reservoir Nath Sagar), Jalna, Beed, Parbhani and Nanded, then into Telangana. Its tributaries in Maharashtra include the Pravara (with the old Bhandardara or Wilson dam), Darna, Kadwa, Sindphana, Purna and Manjara. From Vidarbha, the Wardha (with its tributary the Penganga) and the Wainganga (Gosikhurd dam, Bhandara) unite as the Pranhita, which joins the Godavari on the Maharashtra–Telangana border near Sironcha in Gadchiroli.

The Krishna rises at Mahabaleshwar (Satara) and flows south-east past Wai, Karad (where it meets the Koyna at the Preeti Sangam) and Sangli into Karnataka. The Koyna dam (reservoir Shivsagar) at Koynanagar powers one of India's largest hydroelectric projects; its water is dropped westward through tunnels to generating stations, and the area is seismically active (1967 quake). Other Krishna tributaries in the state: Venna, Warna and the Panchganga (Kolhapur). The Bhima rises at Bhimashankar (Pune district); its tributaries include the Indrayani (Alandi, Dehu), Mula–Mutha (Pune; Khadakwasla dam on the Mutha), Ghod, Nira and Sina. The Ujani dam on the Bhima in Solapur district is a lifeline for that dry region. At Pandharpur the Bhima is called the Chandrabhaga, and it joins the Krishna in Karnataka.

The Tapi rises at Multai in Betul district of Madhya Pradesh, enters Maharashtra and flows west through Jalgaon, Dhule and Nandurbar in a rift valley between the Satpura and the Satmala–Ajanta hills, joined by the Purna (which drains western Vidarbha), Girna and Panzara, and enters the Arabian Sea near Surat. The Narmada touches Maharashtra only briefly, along the border in Nandurbar. The Konkan rivers rise on the Sahyadri and are short and fast, with estuaries and creeks; Mumbai's drinking water comes from dams on Konkan-side rivers such as the Tansa, Vaitarna and Bhatsa. In short: everything south of the Satmala–Ajanta line drains east to the Bay of Bengal through the Godavari or Krishna, except the narrow Konkan strip.

The concept

Soil type in Maharashtra follows parent rock and rainfall. Most of the Deccan has black soil (regur or black cotton soil) formed from basalt. Its clay (montmorillonite) gives it very high moisture retention; it swells when wet and develops deep cracks when dry, which aerates it ("self-ploughing"). It is rich in lime, iron, magnesia and potash but poor in nitrogen, phosphorus and organic matter. It is deep in the valleys (Tapi, Godavari, Bhima, Krishna) and thin and stony on the uplands. Laterite forms in the high-rainfall Konkan and Ghats (Ratnagiri, Sindhudurg, Kolhapur hills) through intense leaching; it is rich in iron oxide and potash but poor in organic matter, nitrogen, phosphate and calcium, and hardens on exposure (used as building blocks). Red and yellow soils occur in eastern Vidarbha (Bhandara, Gondia, Chandrapur, Gadchiroli) over older rocks, and alluvial soils line the major rivers and the coastal deltas.

Rainfall falls off sharply from west to east and then rises again. The Konkan and the Ghats get heavy rain (often above 2,500 mm, and much more at places like Amboli and Mahabaleshwar). Just east of the Ghats, parts of Pune, Satara, Sangli, Solapur, Ahilyanagar and Nashik lie in the rain-shadow with roughly 500–750 mm, the drought-prone scarcity zone. Marathwada and western Vidarbha are moderate, and eastern Vidarbha, reached by the Bay of Bengal branch, gets more again (above about 1,200 mm) and has very hot summers. The state agricultural universities divide Maharashtra into nine agro-climatic zones: South Konkan coastal, North Konkan coastal, Western Ghat, Transition I, Transition II, Scarcity, Assured rainfall, Moderate rainfall and Eastern Vidarbha.

Crops follow soil, rain and irrigation. In the kharif season (sown with the June monsoon) the main crops are rice, kharif jowar, bajra, soybean, cotton, tur and groundnut; in the rabi season (sown October–November on stored moisture) rabi jowar, wheat and gram. The regions: Konkan — rice, Alphonso mango (GI-tagged), cashew, coconut, kokum; western Maharashtra — irrigated sugarcane (with its cooperative sugar factories), plus grapes and onion around Nashik (Lasalgaon is a major onion market), pomegranate around Solapur, and turmeric around Sangli; Marathwada — rabi jowar, cotton, soybean, tur; western Vidarbha — cotton and soybean on black soil, oranges around Nagpur and Amravati; eastern Vidarbha — rice in the tank-irrigated Bhandara–Gondia belt. Sugarcane is planted in three seasons: adsali (July–August, an 18-month crop), pre-seasonal (October–November) and suru (January–February).