BCS Written Geography cheat sheet

Rock cycle: igneous (cooling magma), sedimentary (compaction of deposits), metamorphic (heat/pressure); each can transform into the others.

Weathering: mechanical (frost shattering, exfoliation) versus chemical (hydrolysis, carbonation, oxidation); carbonation dissolves limestone to form karst.

Fluvial transport follows competence (largest clast size) and capacity (total load); deposition occurs where velocity and discharge fall.

Glacial landforms: cirque, arête, U-shaped valley, moraine, drumlin, esker; till is unsorted, outwash is sorted by meltwater.

Plate boundaries: divergent (ridges, rift valleys), convergent (trenches, fold mountains, subduction), transform (strike-slip faults).

Air pressure falls with altitude; wind flows from high to low pressure, deflected by Coriolis force (right in Northern Hemisphere, left in Southern).

Köppen climate groups: A tropical, B dry, C temperate, D continental, E polar; classification uses temperature and precipitation thresholds.

Ocean currents: thermohaline circulation driven by temperature and salinity; upwelling brings nutrient-rich water to the surface.

Biogeography: biomes are controlled by climate; net primary productivity peaks in tropical rainforest and declines toward deserts and poles.

Demographic transition stages: high birth/high death, early expanding, late expanding, low stationary, then declining population.

Natural increase rate = (births − deaths) per 1,000 population; doubling time ≈ 70 ÷ annual growth rate percentage.

Population pyramid shape indicates structure: broad base = youthful population, narrow base = ageing population.

Dependency ratio = (population under 15 + over 64) ÷ working-age population (15–64) × 100.

Malthus argued population grows geometrically while food grows arithmetically; Boserup argued population growth induces agricultural intensification.

Push factors (poverty, conflict, unemployment) versus pull factors (jobs, security, services) explain migration flows.

Ravenstein's laws: most migrants move short distances, rural-to-urban, and return migration occurs.

Settlement hierarchy: hamlet, village, town, city, conurbation, megacity; higher-order settlements offer rarer, more specialised functions.

Economic sectors: primary (extraction), secondary (manufacturing), tertiary (services), quaternary (knowledge); development shifts employment toward tertiary.

Von Thünen model: land use intensity and rent decline with distance from market; perishable goods locate nearest.

Weber's least-cost location: firms minimise transport plus labour costs, modified by agglomeration economies.

Resources classify as renewable, non-renewable, and flow resources; reserves are known deposits economically recoverable at current prices.

Energy: fossil fuels dominate global supply; hydropower, solar, wind, and nuclear are low-carbon alternatives.

Industrial location factors: raw materials, power, transport, labour, market, and government policy.

Comparative advantage: regions specialise in goods they produce at lower opportunity cost, raising total trade output.

Resource curse: resource-rich states may show slow growth, weak institutions, and dependence on volatile commodity prices.

Bangladesh lies roughly 20°34′–26°38′N and 88°01′–92°41′E; the Tropic of Cancer crosses near the centre.

Physiographic units: Barind Tract, Madhupur Tract, Chittagong Hill Tracts, Sundarbans, and the Ganges–Brahmaputra delta plain.

Three main rivers: Padma (Ganges), Jamuna (Brahmaputra), and Meghna; the Meghna empties into the Bay of Bengal.

Climate: tropical monsoon with hot wet summer (June–October), cool dry winter, and pre-monsoon thunderstorms (nor'westers/kalbaishakhi).

Floods: monsoon river floods, flash floods in the northeast, and storm surges in coastal districts; embankments and polders are key defences.

Agriculture: rice (aus, aman, boro), jute, tea in Sylhet, and shrimp in coastal Khulna–Satkhira.

Cyclones form in the Bay of Bengal, usually in April–May and October–November, making the coastal belt highly vulnerable.

Largest continents by area: Asia, Africa, North America, South America, Antarctica, Europe, Australia.

Major mountain belts: Himalayas, Andes, Rockies, Alps, and Atlas; Andes is the longest continental range.

Deserts: Sahara (largest hot desert), Gobi (cold desert), Atacama (driest), Thar, and Kalahari.

World rivers: Nile and Amazon rank among the longest; Amazon has the largest discharge and drainage basin.

Climate zones shift with latitude; tropical rainforest near the equator, savanna, desert, temperate, and tundra toward the poles.

Time zones: Earth rotates 360° in 24 hours, so 15° of longitude equals one hour.

Major straits: Malacca, Gibraltar, Bering, and Hormuz; key canals: Suez and Panama.

Map scale: representative fraction (1:50,000), statement (1 cm = 0.5 km), and linear bar scale.

Large-scale maps show small areas in great detail; small-scale maps show large areas with less detail.

Map projections distort shape, area, distance, or direction; Mercator preserves direction, equal-area projections preserve area.

Latitude lines (parallels) run east–west; longitude lines (meridians) run north–south and converge at the poles.

Contours join points of equal elevation; closely spaced contours indicate steep slopes, widely spaced ones indicate gentle slopes.

Grid reference: eastings are read before northings; six-figure references give 100 m precision on a 1:50,000 map.

Isopleth maps join points of equal value (isotherms, isohyets, isobars); choropleth maps shade administrative units by value.

Remote sensing: passive sensors detect reflected or emitted energy (sunlight, heat); active sensors emit their own signal (radar, lidar).

Electromagnetic spectrum bands: visible, near-infrared, thermal infrared, and microwave; water absorbs near-infrared strongly.

Spatial resolution is the ground area per pixel; higher resolution means smaller pixels and finer detail.

NDVI = (NIR − Red) ÷ (NIR + Red); values near 1 indicate dense vegetation, near 0 bare ground.

GIS layers: vector (points, lines, polygons) and raster (grid cells); overlay, buffer, and spatial join are core operations.

GPS uses satellite trilateration; four satellites are needed to fix position and time.

Supervised classification uses training samples; unsupervised classification groups pixels by spectral similarity.

Disaster cycle: mitigation, preparedness, response, and recovery; risk = hazard × vulnerability ÷ capacity.

Hazard types: geological (earthquake, landslide), hydro-meteorological (flood, cyclone, drought), and biological.

Greenhouse gases: carbon dioxide, methane, nitrous oxide, and fluorinated gases; CO2 dominates long-term warming.

Eutrophication: nutrient runoff (nitrogen, phosphorus) causes algal blooms and oxygen depletion.

Environmental impact assessment predicts effects before a project is approved; mitigation reduces or offsets impacts.

Deforestation and wetland loss raise flood risk by reducing infiltration and water storage.

Early warning systems (cyclone warnings, flood forecasting) reduce loss of life when linked to evacuation.

Rock cycle: igneous, sedimentary, and metamorphic rocks transform through cooling, compaction, and heat/pressure.

Weathering is mechanical or chemical; carbonation dissolves limestone to form karst.

Fluvial transport depends on competence and capacity; deposition occurs where velocity falls.

Glacial landforms include cirque, arête, U-shaped valley, moraine, and esker.

Plate boundaries are divergent, convergent, and transform.

Köppen climate groups A, B, C, D, E are defined by temperature and precipitation.

Thermohaline circulation is driven by temperature and salinity; upwelling brings nutrients to the surface.

Biomes are controlled by climate; net primary productivity peaks in tropical rainforest.

Demographic transition stages run from high birth/high death to low stationary and declining population.

Natural increase rate = (births − deaths) per 1,000; doubling time ≈ 70 ÷ growth rate percentage.

Population pyramid shape reveals youthful or ageing structure.

Dependency ratio = (under 15 + over 64) ÷ working-age population × 100.

Malthus saw geometric population growth against arithmetic food growth; Boserup saw population inducing intensification.

Push and pull factors explain migration flows.

Ravenstein's laws: most migrants move short distances and rural-to-urban.

Settlement hierarchy runs hamlet, village, town, city, conurbation, megacity.

Economic sectors are primary, secondary, tertiary, and quaternary; development shifts employment toward tertiary.

Von Thünen model: land-use intensity declines with distance from market.

Weber's least-cost location minimises transport plus labour costs.

Resources are renewable, non-renewable, or flow; reserves are economically recoverable deposits.

Fossil fuels dominate energy supply; hydropower, solar, wind, and nuclear are low-carbon alternatives.

Industrial location depends on raw materials, power, transport, labour, market, and policy.

Comparative advantage raises total trade output through specialisation.

Resource curse links resource wealth to slow growth and volatile prices.

Bangladesh spans roughly 20°34′–26°38′N and 88°01′–92°41′E.

Physiographic units include Barind Tract, Madhupur Tract, Chittagong Hill Tracts, Sundarbans, and the delta plain.

Main rivers are the Padma, Jamuna, and Meghna.

Climate is tropical monsoon with hot wet summer, cool dry winter, and pre-monsoon nor'westers.

Floods include monsoon river floods, flash floods, and coastal storm surges.

Crops include rice, jute, Sylhet tea, and coastal shrimp.

Bay of Bengal cyclones peak in April–May and October–November.

Continents by area: Asia, Africa, North America, South America, Antarctica, Europe, Australia.

The Andes is the longest continental mountain range.

Sahara is the largest hot desert; Atacama is the driest.

The Amazon has the largest discharge and drainage basin.

Climate zones shift from tropical rainforest at the equator to tundra near the poles.

15° of longitude equals one hour of time difference.

Key straits include Malacca, Gibraltar, Bering, and Hormuz.

Map scale can be shown as a representative fraction, statement, or bar scale.

Large-scale maps show small areas in detail; small-scale maps show large areas with less detail.

Projections distort shape, area, distance, or direction; Mercator preserves direction.

Parallels run east–west; meridians run north–south and converge at the poles.

Contours join equal elevations; close spacing means steep slope.

Eastings are read before northings in grid references.

Isopleth maps join equal values; choropleth maps shade units by value.

Passive sensors detect reflected or emitted energy; active sensors emit their own signal.

Water absorbs near-infrared strongly; vegetation reflects it.

Spatial resolution is ground area per pixel.

NDVI = (NIR − Red) ÷ (NIR + Red); values near 1 mean dense vegetation.

GIS data are vector (points, lines, polygons) or raster (grid cells).

GPS uses satellite trilateration; four satellites fix position and time.

Supervised classification uses training samples; unsupervised groups pixels by spectral similarity.

Disaster cycle: mitigation, preparedness, response, and recovery.

Risk = hazard × vulnerability ÷ capacity.

Hazards are geological, hydro-meteorological, or biological.

Greenhouse gases include CO2, methane, nitrous oxide, and fluorinated gases.

Eutrophication follows nutrient runoff and causes oxygen depletion.

Environmental impact assessment predicts effects before project approval.

Deforestation and wetland loss raise flood risk by reducing infiltration and storage.