GCE O/L Geography flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Continental vs oceanic crust

Continental crust is thick (30–70 km) and granitic, so it is less dense. Oceanic crust is thin (5–10 km) and basaltic, so it is denser and subducts beneath continental crust at convergent boundaries.

Divergent plate boundary

A boundary where two plates move apart. Magma rises to fill the gap, forming new oceanic crust at mid-ocean ridges or rift valleys on land, and causing shallow earthquakes and volcanic activity.

Subduction zone

A convergent boundary where a denser oceanic plate sinks beneath a less dense plate. It produces deep ocean trenches, fold mountains, volcanoes and powerful earthquakes along the descending plate.

Three rock types

Igneous rocks form from cooled magma or lava. Sedimentary rocks form from compacted deposited layers. Metamorphic rocks form when existing rocks are changed by heat and pressure.

Freeze-thaw weathering

Water enters cracks in rock, freezes and expands, then thaws and contracts. Repeated cycles widen the crack until fragments break off, a form of mechanical weathering common in cold upland areas.

River meander and oxbow lake

A meander is a bend in a river caused by faster erosion on the outer bank and deposition on the inner bank. When a meander loop is cut off, the abandoned curve becomes an oxbow lake.

Weather versus climate

Weather is the short-term condition of the atmosphere at a place, such as today's rain. Climate is the average pattern of weather over about 30 years.

Relief rainfall

Moist air is forced to rise over a mountain, cools, condenses and produces rain on the windward slope. The leeward side receives little rain and is called a rain shadow.

Convectional rainfall

Strong surface heating makes warm, moist air rise rapidly. It cools and condenses into tall cumulonimbus clouds, producing heavy showers and thunderstorms, typical of tropical afternoons.

Environmental lapse rate

The rate at which temperature falls with height in the lower atmosphere, about 6.5 °C per 1,000 metres. It explains why upland areas are cooler than lowlands at the same latitude.

Food chain and web

A food chain shows energy passing from producer to consumer to decomposer. A food web links several chains together, showing that organisms depend on many species for food.

Tropical rainforest biome

A hot, wet biome near the equator with high rainfall all year, high temperatures and dense layered vegetation. It has high biodiversity and rapid nutrient recycling in the warm, damp soil.

Natural increase

The difference between the birth rate and the death rate of a population, expressed per 1,000 people per year. A positive value means the population grows without migration.

Population pyramid

A graph showing the number or percentage of males and females in each age group. Its shape reveals birth rates, death rates, life expectancy and migration history.

Dependency ratio

The number of people aged under 15 and over 64 divided by the number aged 15–64, multiplied by 100. It shows how many dependants each 100 working-age people support.

Push and pull factors

Push factors are negative conditions that drive migrants away, such as war or unemployment. Pull factors are attractive conditions, such as jobs or services, that draw migrants to a destination.

Settlement hierarchy

An ordering of settlements by size and service provision, from hamlet to village, town, city and conurbation. Larger settlements offer more services and have a larger sphere of influence.

Urbanisation

The rising proportion of a country's population living in towns and cities. It is driven by rural-to-urban migration and natural increase in urban areas, especially in developing countries.

Four economic sectors

Primary activities extract raw materials, secondary activities manufacture goods, tertiary activities provide services, and quaternary activities involve knowledge, research and information work.

Intensive versus extensive farming

Intensive farming uses high inputs of labour, capital or fertiliser on a small area to raise yields. Extensive farming uses low inputs over large areas, such as ranching on marginal land.

Footloose industry

An industry that is not tied to raw material sources or markets because its products are light and easily transported, so it can locate where labour or amenities are best.

Renewable versus non-renewable energy

Renewable energy comes from sources that are naturally replenished, such as solar, wind and hydro. Non-renewable energy comes from finite stores such as coal, oil and gas.

Tourism impacts

Tourism brings income, jobs and foreign exchange but can cause cultural change, seasonal employment, footpath erosion, litter and damage to habitats if visitor numbers are unmanaged.

Sustainable development

Development that meets the needs of the present without compromising the ability of future generations to meet their own needs, balancing economic, social and environmental considerations.

Human Development Index

A composite measure of development combining income per person, education (years of schooling) and life expectancy. It ranges from 0 to 1, with higher values indicating greater development.

Appropriate technology

Technology suited to local conditions: low cost, simple to use and repair with local materials and skills, such as solar panels, hand pumps or fuel-efficient cooking stoves.

Map scale 1:50,000

One centimetre on the map represents 50,000 centimetres, or 500 metres, on the ground. One kilometre on the ground is therefore two centimetres on the map.

Six-figure grid reference

A location given by three digits for the easting and three for the northing. The first two digits of each give the grid square; the third gives the position within that square.

Contour lines

Lines joining points of equal height above sea level. Closely spaced contours show steep slopes; widely spaced contours show gentle slopes; the pattern reveals valleys and ridges.

Mean, median and mode

The mean is the total divided by the number of values. The median is the middle value when data are ordered. The mode is the most frequently occurring value.

Sampling techniques

Random sampling picks sites without bias, systematic sampling uses regular intervals along a line or grid, and stratified sampling selects sites in proportion to sub-groups in the study area.

River discharge formula

Discharge is the volume of water passing a point per second. It equals the cross-sectional area of the channel (width × mean depth) multiplied by the water velocity.

Fieldwork enquiry sequence

Identify a question and hypothesis, collect and record data, present it in graphs or maps, analyse patterns, draw a conclusion and evaluate the method's accuracy and limitations.