AP Intermediate Geography (BIEAP) cheat sheet

Earth's layers by depth: crust (0-35 km continental, 5-10 km oceanic), mantle to 2900 km, outer core (liquid, 2900-5150 km), inner core (solid, 5150-6371 km).

Crust-mantle boundary is the Mohorovičić discontinuity (Moho); core-mantle boundary is the Gutenberg discontinuity.

P-wave velocity drops sharply at the outer core because it is liquid; S-waves cannot pass through the outer core, producing the S-wave shadow zone beyond 103°.

Isostasy: lighter sial crust floats on denser sima; Airy model varies root thickness, Pratt model varies density at a constant depth.

Wegener's continental drift evidence: jig-saw fit, matching fossils (Glossopteris), tillites, and ancient fold belts across the Atlantic.

Sea-floor spreading (Hess): new oceanic crust forms at mid-ocean ridges and moves away symmetrically, recorded by magnetic striping and reversed polarity bands.

Plate boundaries: divergent (ridges, rift valleys), convergent (trenches, island arcs, fold mountains), transform (conservative, e.g. San Andreas).

Earthquake focus is the point of origin underground; epicentre is the surface point directly above; P-waves arrive first, then S-waves, then surface waves.

Weathering types: physical (frost shattering, exfoliation), chemical (hydrolysis, carbonation, oxidation), biological (root wedging, burrowing).

Karst features form in soluble limestone: sinkholes, dolines, uvalas, poljes, stalactites (ceiling), stalagmites (floor), pillars when they join.

Fluvial landforms: V-shaped valley and waterfalls in youth; meanders, ox-bow lakes, floodplains and deltas in old age; alluvial fans at piedmont zones.

Glacial erosional features: cirque, arête, horn, U-shaped valley, hanging valley, roche moutonnée; depositional: moraine, drumlin, esker, outwash plain.

Aeolian landforms: barchan (crescent, horns downwind), seif dune (longitudinal), yardang, zeugen, mushroom rock; loess is wind-deposited silt.

Soil profile horizons: O (organic litter), A (topsoil, humus), E (elution/leaching), B (illuviation, accumulation), C (weathered parent rock), R (bedrock).

Soil orders (USDA): Entisols (recent, little horizonation), Inceptisols (weak development), Alfisols (moderate leaching, clay B horizon), Aridisols (dry), Mollisols (dark grassland), Oxisols (tropical, highly weathered).

Laterite soils form under alternating wet-dry tropical conditions with intense leaching of silica and accumulation of iron and aluminium oxides; they harden on exposure.

Insolation varies with latitude, season, and angle of incidence; the tropics receive the most, poles the least, driving the global heat budget.

Pressure belts: equatorial low (ITCZ/doldrums), subtropical highs (horse latitudes), subpolar lows, polar highs; winds blow from high to low pressure, deflected by Coriolis force.

Coriolis deflection is to the right in the Northern Hemisphere and left in the Southern; it is zero at the equator and maximum at the poles.

Planetary winds: trade winds (NE and SE), westerlies, polar easterlies; monsoon is a seasonal reversal linked to differential heating of land and sea.

Air masses classified by source: cP, cT, mP, mT; fronts are cold, warm, occluded, or stationary; mid-latitude cyclones form along polar fronts.

Ocean salinity averages about 35 parts per thousand; highest in subtropical high-evaporation zones, lowest near equator and at high latitudes.

Thermohaline circulation is driven by temperature and salinity differences; cold, salty water sinks at high latitudes and drives deep currents.

El Niño is anomalous warming of the eastern equatorial Pacific with weakened trade winds; La Niña is the reverse; both shift global rainfall patterns.

Demographic transition stages: high stationary (high birth and death), early expanding (death falls), late expanding (birth falls), low stationary (both low).

Population growth rate = (births - deaths) + net migration, expressed per 1,000 population per year; natural increase excludes migration.

Doubling time is approximated by the rule of 70: 70 divided by annual percentage growth rate.

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

Population pyramid shapes: expansive (broad base, high birth), constrictive (narrow base, low birth), stationary (columnar).

Settlement types: compact/nucleated, dispersed, and linear; rural sites favour water, fertile soil, and defensible ground; urban sites favour route nodes and ports.

Christaller's central place theory: hexagonal market areas, threshold population, and range of a good determine service hierarchy.

Primate city: the largest city is more than twice the size of the second city, concentrating national functions.

Von Thünen model: land use rings around a market reflect transport cost versus land rent; perishables and bulky goods near the centre.

Agricultural systems: shifting cultivation, subsistence intensive, plantation, commercial grain farming, dairy, and market gardening; each reflects climate and market access.

Weber's least-cost location: industries locate where transport and labour costs are minimised; material index = weight of localised inputs / weight of product.

Industrial location factors: raw materials, power, labour, market, transport, capital, and government policy; footloose industries are not tied to materials.

Alfred Weber distinguishes material-oriented (weight-losing) and market-oriented (weight-gaining) industries; bulk-gaining industries locate near markets.

Transport costs fall with distance (tapering principle); break-of-bulk points are where cargo is transferred between modes.

Trade balance = value of exports - value of imports; favourable balance is a surplus, unfavourable is a deficit.

Comparative advantage: a country gains by specialising in goods it produces at lower opportunity cost, even if it is less efficient overall.

India's physiographic divisions: Himalayas, Indo-Gangetic Plain, Peninsular Plateau, Coastal Plains, and Islands (Andaman and Nicobar, Lakshadweep).

The Western Ghats and Eastern Ghats meet at the Nilgiri Hills; the Deccan Trap region of Maharashtra yields black cotton (regur) soil.

The southwest monsoon (June-September) brings most rainfall; the northeast monsoon (October-December) supplies the Coromandel coast, including coastal Andhra Pradesh.

Andhra Pradesh physiography: Coastal Andhra plain, Eastern Ghats (Nallamala, Velikonda, Kondapalli ranges), and the Rayalaseema plateau.

Major Andhra Pradesh rivers: Godavari and Krishna, both rising in the Western Ghats and forming large deltas; minor rivers include Pennar, Tungabhadra, and Vamsadhara.

Andhra Pradesh economy: rice as the principal crop, plus cotton, sugarcane, chillies, and aquaculture; Visakhapatnam is a major port and industrial centre.

Kolleru Lake lies between the Godavari and Krishna deltas; Pulicat Lake straddles the Andhra Pradesh-Tamil Nadu border; Chilika is in Odisha.

Araku Valley and the Paderu region of Visakhapatnam district are known for coffee and tribal agriculture; the Godavari delta is a rice granary.

Map scale types: representative fraction (1:50,000), statement (1 cm = 0.5 km), and linear bar; larger denominators mean smaller-scale maps.

Scale conversion: multiply map distance by the denominator to get ground distance; 1:50,000 means 1 cm on map equals 500 m on ground.

Contour lines join points of equal elevation; closely spaced contours indicate steep slopes, widely spaced indicate gentle slopes; V-shapes pointing upstream mark valleys.

Grid references: eastings are read before northings (right, then up); a four-figure reference locates a 1 km square, a six-figure reference a 100 m square.

Survey of India topographical sheets use a 1:50,000 scale with 20 m contour intervals; conventional signs show settlements, roads, and drainage.

Map projections: Mercator preserves shape (conformal) but exaggerates polar area; conical suits mid-latitude countries; cylindrical suits world maps.

Field study methods include transect walks, quadrat sampling, questionnaire surveys, and sketch mapping; observations should be recorded with date, location, and instrument.

Cross-section drawing: transfer contour intersections along a straight line to graph paper, plot elevation, and connect points to show the terrain profile.