Assam HS Higher Secondary Geography cheat sheet

Endogenic processes build relief through tectonism and volcanism; exogenic processes such as weathering, erosion, transport and deposition wear relief down.

At divergent plate boundaries new crust forms; at convergent boundaries subduction or collision produces trenches, fold mountains and volcanic arcs; transform boundaries generate strike-slip faults.

Weathering is in situ breakdown: mechanical processes include frost action, salt crystallisation and exfoliation; chemical processes include carbonation, hydrolysis and oxidation.

Fluvial erosion acts through hydraulic action, abrasion, attrition and solution; deposition where velocity falls forms floodplains, levees, deltas and oxbow lakes.

Glacial landforms include cirque, arête, horn, U-shaped valley, hanging valley, moraine, drumlin and esker; coastal forms include cliff, wave-cut platform, spit, bar and tombolo.

Karst develops on soluble limestone through carbonation; characteristic features are sinkholes, caves, stalactites, stalagmites and disappearing streams.

Drainage pattern reflects rock resistance and structure: dendritic on uniform rocks, trellis on folded strata, radial on domes or volcanoes, rectangular on jointed rocks.

Stream order increases where two lower-order streams join; sinuosity = channel length / valley length; relief = maximum elevation minus minimum elevation.

Insolation is incoming solar radiation; Earth's energy budget balances absorbed shortwave radiation with outgoing longwave radiation, and albedo is the reflected fraction.

Temperature generally falls with altitude at an environmental lapse rate of about 6.5°C per km; inversion occurs when warmer air lies above colder surface air.

Pressure gradients drive wind; the Coriolis force deflects moving air, friction slows surface wind, and geostrophic wind balances pressure gradient and Coriolis force aloft.

Relative humidity = (actual vapour pressure / saturation vapour pressure) × 100; dew point is the temperature at which air becomes saturated.

Rising air cools adiabatically: the dry adiabatic lapse rate is about 10°C per km and the saturated rate about 6°C per km; condensation forms cloud and precipitation.

The South Asian monsoon arises from seasonal ITCZ migration, land-sea thermal contrast, Tibetan Plateau heating and jet-stream shifts; a break monsoon means weak rainfall over the core zone.

Tropical cyclones require sea-surface temperature above about 26.5°C, high humidity, low vertical wind shear and sufficient Coriolis effect; they weaken after landfall.

Köppen classification uses temperature and precipitation; Assam is humid subtropical (Cwa) with hot wet summers and mild dry winters.

Hydrological cycle fluxes include precipitation, interception, infiltration, overland flow, groundwater recharge, evapotranspiration and runoff; basin storage changes with input and output.

Stream discharge Q = cross-sectional area A × mean velocity V; hydrograph lag is the time between the rainfall peak and the discharge peak.

Drainage density = total channel length / basin area; bifurcation ratio = number of streams of order n / number of streams of order n+1.

Porosity is the void-volume fraction; permeability is the ability to transmit water; an unconfined aquifer has a water table, while a confined aquifer lies under pressure between aquitards.

Soil forms through interactions of climate, organisms, relief, parent material and time (CLORPT); profile horizons are O, A, E, B, C and R.

The soil texture triangle classifies sand, silt and clay proportions; loam is a balanced mixture; cation exchange capacity rises with clay and organic matter.

Erosion types include sheet, rill, gully, splash and wind deflation; conservation measures include contour ploughing, terracing, check dams, strip cropping and afforestation.

Assam soils are mainly alluvial in the Brahmaputra and Barak valleys, with laterite and red soils in uplands; acidity and flooding constrain agriculture.

Population density = total population / area, expressed as persons per km²; physiological density = population / cultivated land.

Natural increase = birth rate − death rate; growth rate includes net migration; doubling time is approximately 70 divided by annual growth rate in percent.

Dependency ratio = (population under 15 + population over 64) / population aged 15-64 × 100; sex ratio = females per 1000 males.

Demographic transition stages are high stationary, early expanding, late expanding, low stationary and declining; population pyramids show age-sex structure.

Migration is analysed using push-pull factors, distance decay, intervening obstacles and remittances; refugees cross international borders involuntarily.

Settlement site is the actual location, influenced by water, defence and relief; situation is regional position; rural settlements may be compact, dispersed, linear or nucleated.

Economic sectors are primary extraction, secondary manufacturing, tertiary services and quaternary knowledge; industrial location depends on raw material, power, market, labour, transport and policy.

Von Thünen rings explain perishable and intensive farming near market; Weber's least-cost model weighs material index and transport orientation.

Physiographic divisions are the Himalayas, Indo-Gangetic Plain, Peninsular Plateau, Coastal Plains and Islands; each has distinct relief, drainage and resources.

The Himalayas are young fold mountains with Himadri, Himachal and Shiwalik ranges; the Indo-Gangetic Plain is alluvial and densely populated.

The Peninsular Plateau is old crystalline igneous and metamorphic terrain with Deccan Trap basalt in the northwest; the Western and Eastern Ghats flank it.

Himalayan rivers are perennial, snow-fed and antecedent; peninsular rivers are seasonal, rain-fed and often flow through hard rock.

Major soils are alluvial in northern plains and deltas, black or regur on Deccan basalt, red on crystalline uplands, laterite in heavy-rainfall areas, and arid and forest soils.

Iron ore comes from Odisha, Jharkhand, Chhattisgarh and Karnataka; coal from Jharkhand, Odisha, Chhattisgarh and West Bengal; bauxite from Odisha; mica from Jharkhand and Andhra Pradesh.

Petroleum occurs in Assam at Digboi, Naharkatiya and Moran, in Gujarat at Ankleshwar and Cambay, and offshore at Mumbai High; natural gas is associated with these fields.

Monsoon rainfall is high on the windward Western Ghats and in northeast India, low in Rajasthan and the rain-shadow Deccan; cyclones affect the east and west coasts.

Census 2011 recorded about 1.21 billion people, density of 382 persons per km², sex ratio of 943 females per 1000 males and literacy of 74.04%.

India's population is unevenly distributed; high densities occur in the Ganga plain, coastal deltas and Kerala, while low densities occur in the Rajasthan desert, Himalayas and central uplands.

Kharif crops are sown with the summer monsoon, including rice, maize, cotton and jute; rabi crops are grown in winter, including wheat, gram and mustard; zaid is a short summer season.

The Green Revolution combined high-yielding varieties, irrigation, fertiliser and mechanisation, mainly wheat in Punjab-Haryana and rice in irrigated areas.

Major industries include iron and steel at Jamshedpur, Bhilai, Rourkela and Durgapur; cotton textiles at Mumbai, Ahmedabad and Coimbatore; software at Bengaluru, Hyderabad and Pune.

Transport includes national highways linking major cities, railway zones, and major ports such as Mumbai, JNPT, Chennai, Kolkata, Paradip, Visakhapatnam and Kandla.

Regional development disparities reflect resource endowment, colonial history, connectivity and policy; hill and island regions face accessibility constraints.

Assam's economy relies on tea, petroleum, silk, tourism and agriculture; Brahmaputra bridges and National Waterway 2 improve connectivity.

Scale is map distance divided by ground distance; representative fraction (1:50,000), statement (1 cm = 0.5 km) and graphical bar are interchangeable forms.

Keep units consistent when converting scale: 1:50,000 means 1 cm on the map equals 50,000 cm on the ground, or 500 m, or 0.5 km.

Contours join points of equal elevation; a V pointing upstream indicates a valley, a V pointing downstream indicates a spur, and closed concentric contours may be a hill or depression.

Closely spaced contours indicate a steep slope; widely spaced contours indicate a gentle slope; uniform spacing indicates a uniform slope; a contour crossing a stream bends upstream.

Grid references give eastings before northings; bearings are measured clockwise from north; magnetic declination adjusts compass bearing to true north.

Choropleth maps show densities or averages by administrative unit; isopleth maps join equal values; dot maps show distribution; bar and pie graphs compare quantities.

Central tendency: mean = sum/n, median = middle value, mode = most frequent value; percentage change = (new − old) / old × 100.

Field study uses transect, quadrat, questionnaire, interview and GPS; sampling must be representative and observations recorded with date, location and sketch.