JCE Geography flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Divergent plate boundary
- A boundary where two plates move apart. Magma rises to fill the gap, forming new oceanic crust at mid-ocean ridges and causing shallow earthquakes and fissure volcanism.
- Subduction zone
- A convergent boundary where denser oceanic crust sinks beneath continental or oceanic crust, creating deep-sea trenches, earthquakes and chains of volcanic mountains above the descending slab.
- Conservative plate boundary
- A transform boundary where plates slide horizontally past one another. Crust is neither created nor destroyed, so earthquakes occur but volcanic activity is rare.
- Igneous rock
- Rock formed when molten magma or lava cools and solidifies. Slow cooling underground gives large crystals (intrusive); rapid cooling at the surface gives fine crystals (extrusive).
- Sedimentary rock
- Rock formed from layers of sediment that are compacted and cemented over time. It often contains fossils and is typically softer and more permeable than igneous rock.
- Metamorphic rock
- Rock changed by intense heat or pressure without melting. Minerals recrystallise, producing harder, denser rock such as marble from limestone or slate from shale.
- Chemical weathering
- The breakdown of rock by chemical reactions, especially with rainwater and acids. Carbonation dissolves limestone, while oxidation rusts iron-rich minerals, weakening the rock.
- Hydraulic action
- A form of erosion where the force of moving water traps and compresses air in cracks in rock, weakening it until fragments break away, commonly along cliffs and river banks.
- Longshore drift
- The movement of sediment along a coastline by waves approaching at an angle. Swash carries material up the beach diagonally; backwash returns it straight down.
- Constructive wave
- A low-energy wave with a strong swash and weak backwash that deposits sediment and builds up beaches. These waves usually form in calm weather with a long fetch.
- Meander formation
- A bend in a river created by faster flow eroding the outer bank (river cliff) and slower flow depositing sediment on the inner bank (slip-off slope), which amplifies the curve.
- Waterfall formation
- A step in a river bed where resistant rock overlies softer rock. The softer rock erodes faster, undercutting the hard cap rock, which collapses to form a plunge pool and steep drop.
- Drainage basin
- The whole area drained by a river and its tributaries, bounded by watersheds. Inputs are precipitation; outputs are evapotranspiration and river discharge to the sea.
- Storm hydrograph
- A graph showing river discharge over time after rainfall. It shows the rising limb, peak discharge and recession limb; urbanisation and impermeable rock shorten the lag time.
- Birth rate
- The number of live births per 1,000 people in a population per year. It is high in countries with early marriage, limited contraception and agrarian economies.
- Natural increase
- The growth of a population caused by births exceeding deaths, calculated as birth rate minus death rate. It excludes the effect of migration.
- Population pyramid
- A graph showing the age and sex structure of a population. Wide bases indicate high birth rates; narrow tops indicate low life expectancy or an ageing society.
- Demographic transition model
- A four- or five-stage model tracing how birth and death rates change as a country develops, from high stationary through early and late expanding to low stationary.
- Push factor
- A negative condition in a source area that encourages people to leave, such as unemployment, poverty, conflict, drought or land shortage.
- Pull factor
- A positive condition in a destination area that attracts migrants, such as higher wages, better schools and hospitals, security, or family networks.
- Urbanisation
- The rising proportion of a country's population living in towns and cities. It results from rural-to-urban migration and from natural increase within urban areas.
- Squatter settlement
- An unplanned, often illegal housing area on the edge of a city, lacking secure tenure and basic services such as piped water, sanitation and paved roads.
- Megacity
- An urban area with a population exceeding ten million people. Most megacities are now in Asia and Latin America rather than in high-income countries.
- Human Development Index
- A composite index scoring health (life expectancy), education (years of schooling) and income (GNI per capita). Each component scores 0–1 and the three are averaged geometrically.
- GNI per capita
- Gross national income divided by population: the total income earned by a country's residents, including net income from abroad, per person. Often adjusted for purchasing power.
- Informal sector
- Economic activity that is unregistered and untaxed, such as street trading or waste picking. It employs a large share of workers in many low-income cities.
- Sustainable development
- Development that meets present needs without compromising the ability of future generations to meet theirs, balancing economic growth, social welfare and environmental protection.
- Map scale
- The ratio of map distance to real distance. On a 1:50,000 map, 1 cm represents 500 m on the ground; a larger-scale map shows more detail over a smaller area.
- Contour lines
- Lines on a map joining points of equal height above sea level. The interval is constant; closely spaced contours mean a steep slope, widely spaced ones a gentle slope.
- Grid reference
- A coordinate locating a point on a map. A four-figure reference gives a one-kilometre square; a six-figure reference gives a 100-metre square within it.
- Relief rainfall
- Rainfall caused when moist air is forced to rise over hills or mountains. It cools, condenses and rains on the windward slope, leaving a drier rain shadow beyond.
- Convectional rainfall
- Rainfall produced when strong surface heating makes moist air rise rapidly, cool and condense into towering cumulonimbus clouds, often with heavy showers and thunder.