WBCHSE HS Geography cheat sheet

Weathering is in-situ breakdown; erosion involves transport. Frost shattering dominates above the snow line, carbonation acts on limestone, hydrolysis on granite feldspar, oxidation on iron-rich basalt.

Rock cycle links the three classes: igneous intrusive (granite, coarse) vs extrusive (basalt, fine); sedimentary clastic/organic/chemical; metamorphic limestone to marble, sandstone to quartzite, shale to slate, coal to graphite.

Divergent boundary gives mid-oceanic ridge and rift valley; ocean-continent convergence gives trench, volcanic arc and fold mountains; transform boundary gives faults such as the San Andreas.

Davisian cycle: youth (V-shaped valleys, rapids, waterfalls), maturity (wide valleys, meanders, flood plain, peneplain remnants absent), old age (peneplain with monadnocks).

Karst landforms: swallow hole, doline, uvala, polje, lapies, stalactite from the roof, stalagmite from the floor, pillar where the two join.

Glacial landforms: cirque, arete, horn, roche moutonnee, U-shaped valley, hanging valley, lateral/medial/terminal/ground moraine, drumlin, esker, kame.

Aeolian landforms: barchan (horns point downwind), seif or longitudinal dune, yardang, mushroom rock, inselberg, pediplain, loess deposits.

Seismic waves: P is longitudinal, fastest, travels through all media; S is transverse, only through solids, creating a shadow zone beyond 103 degrees; L waves are surface waves and most destructive. Focus lies inside the Earth, epicentre on the surface directly above.

Dry air by volume: nitrogen 78.08%, oxygen 20.95%, argon 0.93%, carbon dioxide about 0.04%; water vapour varies from near zero to about 4%.

Troposphere: mean lapse rate 6.5 degrees C per km, temperature ceasing to fall at the tropopause (about 8 km over poles, 18 km over the equator). The stratosphere warms upward because ozone absorbs ultraviolet radiation.

Pressure belts: equatorial low (ITCZ or doldrums), subtropical high (horse latitudes), subpolar low, polar high; surface winds are trades, westerlies and polar easterlies.

Coriolis deflection is proportional to 2 times the angular velocity times wind speed times sine of latitude: zero at the equator, maximum at the poles. Geostrophic wind flows parallel to isobars where pressure-gradient force balances Coriolis force.

Tropical cyclone requirements: sea-surface temperature of 27 degrees C or more, high humidity, weak vertical wind shear, latitude 5 to 20 degrees, and sufficient Coriolis force. The eye is a zone of subsiding air and calm.

Koppen first letters: A tropical, B dry, C warm temperate, D cold forest, E polar; second letters f (no dry season), m (monsoon), w (winter dry), s (summer dry), W desert, S steppe, h hot, k cold.

Indian monsoon mechanism: northward migration of the ITCZ, Tibetan Plateau heat low, tropical easterly jet aloft, withdrawal of the subtropical westerly jet south of the Himalaya, and ENSO-related Walker circulation changes.

Rainfall types: convectional (equatorial afternoon thunderstorm), orographic (windward slope wet, leeward rain shadow), cyclonic or frontal (temperate depressions). Relative humidity falls as temperature rises for a fixed vapour content.

Mean ocean salinity is about 35 parts per thousand; maximum in subtropical high-pressure belts (Red Sea about 40, Dead Sea about 240); lower near the equator and at high latitudes because of rainfall and ice melt.

Vertical structure: mixed surface layer, then the thermocline (roughly 100 to 1000 m) where temperature drops sharply, then the cold deep zone; the halocline marks a rapid salinity change and the pycnocline a rapid density change.

Tides: semidiurnal, diurnal and mixed types. Spring tide at new and full moon gives the maximum range; neap tide at quadrature gives the minimum. Funnel-shaped estuaries such as the Hooghly magnify tidal range.

Waves are described by crest, trough, wavelength, period and height. A wave breaks when its height-to-wavelength ratio exceeds about 1:7, or when depth is less than half the wavelength.

Warm currents: Gulf Stream, Kuroshio, Brazil, East Australian, Agulhas. Cold currents: Labrador, Canary, Benguela, Humboldt (Peru), California. Cold water meeting warm water produces fog and rich fisheries, as at the Grand Banks.

El Nino is anomalous warming of the eastern tropical Pacific with a weakened or reversed Walker cell, bringing drought to Indonesia and Australia and floods to Peru; La Nina is the reverse phase.

Ocean floor provinces: continental shelf (about 0.1 degree slope), continental slope (about 4 degrees), continental rise, abyssal plain, mid-oceanic ridge and trench. The deepest point is Challenger Deep in the Mariana Trench, about 10,935 m.

Coral reefs require warm shallow clear salt water of about 20 to 30 degrees C; fringing reef, barrier reef and atoll represent a developmental sequence. Upwelling of nutrient-rich deep water sustains the richest fisheries.

An ecosystem is a biotic community plus its physical environment, linked by energy flow and nutrient cycling. Energy enters as insolation and leaves as heat, so the system is open with respect to energy.

Lindeman's 10 percent law: only about 10 percent of energy at one trophic level passes to the next, so food chains rarely exceed four or five links and energy pyramids are always upright.

Succession runs pioneer to seral stages to climax. Hydrarch succession begins in water (hydrosere), xerarch on bare rock (xerosere); primary succession starts on new substrate, secondary follows disturbance.

Biomes follow climate: equatorial rainforest, savanna, hot desert, mediterranean, temperate deciduous forest, taiga and tundra, with vertical zonation on mountains.

India's four biodiversity hotspots are the Himalaya, Indo-Burma, Western Ghats-Sri Lanka and Sundaland (Nicobar Islands). Sundarbans mangroves are halophytes with pneumatophores and stilt roots.

Biogeochemical cycles are gaseous (carbon, nitrogen, oxygen) with an atmospheric reservoir, or sedimentary (phosphorus, sulphur) with a lithospheric reservoir and no significant gaseous phase.

Soil profile horizons: O litter, A humus and topsoil, B zone of illuviation, C weathered parent material, R bedrock. Laterite forms under heavy leaching rainfall; black regur soil is clayey and moisture-retentive.

Crude birth rate = births per 1000 mid-year population; crude death rate similarly. Rate of natural increase = CBR minus CDR; replacement fertility is about 2.1; infant mortality counts deaths under one year per 1000 live births.

Demographic transition stages: high stationary, early expanding, late expanding, low stationary, and declining (Germany, Japan). India is in stage three with falling but still high birth rates.

Population pyramid shapes: expansive with a broad base and high growth, constrictive with a narrow base and decline, stationary with a bell shape and stability.

Census 2011, India: population 1,210.9 million, density 382 per sq km, sex ratio 943, literacy 74.04 percent, decadal growth 17.7 percent.

Census 2011, West Bengal: population 91.28 million, density 1028 per sq km, sex ratio 950, literacy 76.26 percent. North 24 Parganas is the most populous district and South 24 Parganas the largest in area.

Settlement patterns: compact or nucleated (plains, water scarcity, defence), dispersed (hills, pastoral areas), linear (along road, river or coast), circular, and checkerboard.

Christaller's central place theory uses hexagonal complementary regions, defined by range (maximum distance consumers will travel) and threshold (minimum demand needed for a service to survive), giving nested orders of settlements.

Rank-size rule: population of the nth city equals the largest city divided by n. A primate city is more than twice the second city and dominates the urban hierarchy.

Sectors: primary (extractive), secondary (manufacturing), tertiary (services), quaternary (knowledge and information), quinary (decision-making).

Cropping seasons: kharif sown with the southwest monsoon in June-July and harvested September-October (rice, jute, cotton, maize, groundnut); rabi in October-March (wheat, gram, mustard); zaid in summer.

Von Thunen's model: rings of land use around a market, driven by transport cost and perishability, from market gardening and forestry through grains to livestock and wilderness.

Weber's least-cost theory: weight-losing industries using bulky ore locate near the raw material, weight-gaining industries locate near the market; agglomeration economies modify the pure location triangle.

Iron and steel plants: Jamshedpur (TISCO, 1907), Burnpur, Durgapur, Rourkela, Bhilai, Bokaro, Salem and Vishakhapatnam, located with reference to iron ore, coking coal, limestone and water.

India's first cotton mill opened in Bombay in 1854 and the first jute mill at Rishra near Hooghly in 1855. Jute mills concentrate along the Hooghly because of water, cheap labour and port access.

Tea needs 150 to 250 cm rainfall, well-drained slopes and 15 to 30 degrees C; growing areas are Assam (Brahmaputra valley), West Bengal (Darjeeling, Dooars, Terai) and the Nilgiris.

Transport and trade: the Golden Quadrilateral links Delhi, Mumbai, Chennai and Kolkata; balance of trade equals exports minus imports; Special Economic Zones and free trade zones promote export-led growth.

Physiographic divisions of India: Himalaya, Northern Plains, Peninsular Plateau, Coastal Plains and Islands (Andaman and Nicobar, Lakshadweep).

Himalayan ranges: Trans-Himalaya (Karakoram), Greater Himalaya (Himadri), Lesser Himalaya (Himachal) and Shiwaliks, with Doon or dun valleys between the Lesser Himalaya and the Shiwaliks.

Passes: Shipki La, Nathu La, Jelep La in Sikkim, Bomdi La and Se La in Arunachal Pradesh. Himalayan rivers are perennial and antecedent; peninsular rivers are seasonal and largely consequent.

Soils: alluvial in the Indo-Gangetic plain, black regur on Deccan trap, red on crystalline rocks, laterite under heavy leaching rainfall, plus arid, forest and saline-alkaline types.

West Bengal has four divisions: the Darjeeling Himalaya, the Terai-Dooars foothill belt, the Rarh laterite upland, and the Gangetic delta including the Sundarbans.

West Bengal rivers: Bhagirathi-Hooghly (a distributary of the Ganga), Damodar, Mayurakshi, Kangsabati, Tista, Mahananda and Jaldhaka. The Damodar is known as the sorrow of Bengal.

The Damodar Valley Corporation was set up in 1948 with the Tilaiya, Konar, Maithon and Panchet dams; Raniganj and Asansol coalfields, Durgapur steel plant (1959) and Chittaranjan locomotive works anchor the industrial belt.

The Sundarbans is the world's largest mangrove forest, a UNESCO World Heritage Site, a Biosphere Reserve since 1989, and the habitat of the Royal Bengal tiger.

Risk equals hazard multiplied by vulnerability, divided by capacity. A hazard becomes a disaster only when it exceeds the community's ability to cope with its own resources.

Pollution indicators: BOD measures organic load, COD measures chemically oxidisable matter, with pH and dissolved oxygen. A river with dissolved oxygen below about 4 mg/L cannot support most fish.

Greenhouse gases: CO2, CH4, N2O, water vapour and CFCs. Over 100 years the global warming potential of methane is about 28 times and of nitrous oxide about 265 times that of carbon dioxide.

Ozone depletion: chlorine released from CFCs destroys stratospheric ozone, producing the Antarctic ozone hole. The Montreal Protocol of 1987 phased out CFCs; ozone depletion and global warming are distinct problems.

Climate governance: UNFCCC 1992, Kyoto Protocol 1997, Paris Agreement 2015 to hold warming well below 2 degrees C while pursuing 1.5 degrees C, informed by IPCC assessment reports.

Disaster management cycle: mitigation and preparedness before an event, response (rescue and relief) during it, recovery and rehabilitation afterwards, supported by land-use planning and early warning.

India's Disaster Management Act 2005 created the NDMA, SDMAs, DDMAs and the NDRF. The Sendai Framework 2015-2030 sets seven global targets for disaster risk reduction.

West Bengal hazard profile: Bay of Bengal cyclones (Aila 2009, Amphan 2020), monsoon floods and embankment breaches, landslides in Darjeeling and Sikkim, and drought in Bankura and Purulia.

Scale types: representative fraction (1:50,000), statement (1 cm = 0.5 km) and linear or graphical scale. Scale equals map distance divided by ground distance; enlarging a map increases the RF value.

Contour rules: a V or U pointing upstream marks a valley; hachures on the inside of a closed ring indicate a depression, on the outside a hill; contours never cross except at an overhanging cliff.

Slope from contours: closely spaced contours mean a steep slope, widely spaced a gentle slope, even spacing a uniform slope; a concave slope has widely spaced contours at the top and a convex slope at the bottom.

Survey instruments: chain or tape for horizontal distance, prismatic compass for bearings, plane table with alidade for field plotting, dumpy level for reduced levels, clinometer for slope angle.

Statistics: mean equals the sum of values divided by n; median is the middle value; mode is the most frequent value. Dispersion uses range, quartile deviation, mean deviation, standard deviation and coefficient of variation.

The correlation coefficient r lies between minus 1 and plus 1; r equal to zero means no linear relation; a value near plus or minus 1 means strong linear relation, but correlation does not prove causation.

Map types: choropleth (shading by administrative unit), isopleth (lines joining equal values), dot map, proportional circles or pie diagrams, flow lines and cartograms.

Remote sensing and GIS: passive sensors use reflected sunlight, active sensors (radar, lidar) emit their own energy; resolution is spatial, spectral, temporal and radiometric. Raster data form a pixel grid, vector data use points, lines and polygons; GPS fixes position by trilateration from at least four satellites.