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Edexcel · 1GB0
Mean
The sum of a set of values divided by the number of values: xˉ=∑xn\bar{x}=\frac{\sum x}{n}xˉ=n.
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Meander
A bend in a river channel, with erosion usually occurring on its outer bank and deposition on its inner bank.
Mean erosion rate
The average distance lost through erosion per unit of time, calculated by dividing total retreat by elapsed time.
Mechanisation
The replacement of human labour with machinery.
Megacity
An urban area with a population of more than 10 million people.
Metamorphic rock
Rock changed from an existing rock by heat and pressure without melting.
Methane (CH₄)
A greenhouse gas released by activities including cattle farming, rice cultivation and natural gas extraction.
Migration
Seasonal movement between areas, often to find food or more favourable climatic conditions.
Milankovitch cycles
Long-term cycles in the shape of Earth's orbit, its axial tilt and the direction of its axis, which alter the distribution and timing of solar energy received by Earth.
Mining concession
Permission granted by a government to explore for or extract minerals in a specified area.
Misfit stream
A river or stream that is too small to have formed the valley it occupies, such as a small stream in a glacial U-shaped valley.
Mitigation
Actions that reduce greenhouse gas emissions or increase their removal, limiting climate change.
Modernisation theory
Rostow’s explanation that countries develop through five successive stages as investment, industry and consumption increase.
Monsoon
A seasonal change in winds that brings a distinct wet season to much of India.
Mouth
The place where a river enters the sea, a lake or another river.
Multilateral aid
Aid provided through an international organisation that brings together resources from several countries, such as the World Bank.
Multiplier effect
The wider increase in economic activity when an initial investment creates jobs and income, which generate further spending and employment.
National migration
Movement of people between places within the same country, also called internal migration.
National park
An area designated and managed to conserve its natural environment, often while allowing controlled recreation.
Natural increase
Population growth caused by births exceeding deaths.
Natural levee
A raised bank of deposited sediment beside a river channel, built up through repeated flooding.
Negative multiplier effect
A reinforcing sequence in which lost jobs or spending reduce demand for other businesses and services, causing further decline.
Neo-colonialism
Continued economic or political dominance over an independent country, without direct colonial rule.
Net migration
The number of people moving into an area minus the number moving out during a particular period.
NGO
A non-governmental organisation: an organisation independent of government that works towards particular social or environmental aims.
Non-renewable resource
An energy resource with a finite stock that is not replaced fast enough to keep pace with human use. Coal, oil and natural gas are examples.
Nucleated settlement
A settlement in which buildings are grouped closely together.
Nutrient cycle
The movement of nutrients between living organisms, dead organic material and soil.
Nutrient cycling
The movement of nutrients between living organisms, dead organic material and the soil.
Ocean current
A large-scale flow of seawater that transports water and heat energy.
615 key terms
