PHYSICAL GEOGRAPHY

Earth system

A group of interconnected physical components such as the atmosphere, hydrosphere, biosphere, and lithosphere that interact through inputs, outputs, stores, and flows

Systems thinking

An approach that analyses how different parts of the Earth interact and influence one another through processes and feedbacks

Positive feedback

A self amplifying process where change reinforces further change causing system instability or acceleration

Negative feedback

A stabilising process where change triggers responses that counteract the initial forcing helping maintain equilibrium

Threshold or tipping point

A critical boundary where small additional change results in a sudden and potentially irreversible shift in system behaviour

Equilibrium

A balanced state where inputs and outputs are equal either in a steady state form or constantly adjusting dynamic form

Dynamic equilibrium

A condition where the system fluctuates around a long term average but remains overall balanced

Hadley cell

A tropical circulation cell where warm air rises near the equator creating low pressure then cools and sinks around 30 degrees latitude creating high pressure

Ferrel cell

A mid latitude circulation cell driven by interactions between Hadley and Polar cells resulting in westerly winds

Polar cell

A high latitude circulation cell where cold dense air sinks at the poles then moves toward lower latitudes

Intertropical Convergence Zone ITCZ

A belt of low pressure near the equator where rising warm air creates high rainfall and shifting seasonal patterns

Pressure systems

Regions of high or low atmospheric pressure that shape wind movement and weather conditions

Trade winds

Steady winds blowing from subtropical highs toward the equator within the Hadley cell

Jet stream

A fast flowing ribbon of air in the upper atmosphere that guides storm tracks and weather systems

Monsoon system

A seasonal wind reversal caused by differential heating of land and sea leading to distinct wet and dry seasons

Greenhouse effect

The natural warming of Earth as greenhouse gases absorb and re emit outgoing longwave radiation

Enhanced greenhouse effect

Human driven increase of greenhouse gases leading to additional warming and climate change

Radiative balance

The relationship between incoming solar energy and outgoing longwave radiation which determines global temperature

Climate zone formation

The process by which global circulation latitude altitude and surface characteristics create distinctive climate types

Drainage basin

The area of land where all precipitation drains into a single river system or outlet

Watershed

The boundary that separates one drainage basin from another

Infiltration

The downward movement of water from the surface into the soil

Infiltration capacity

The maximum rate at which soil can absorb water before overland flow occurs

Throughflow

Lateral movement of water through soil toward a river channel

Percolation

The movement of water from soil into underlying rock layers

Groundwater

Water stored in permeable rocks in underground aquifers

Overland flow

Water that flows across the land surface when rainfall exceeds infiltration capacity

Baseflow

Groundwater feeding into rivers maintaining discharge during dry conditions

Storm hydrograph

A graph showing how a river responds to a rainfall event through rising limb peak discharge and falling limb

River energy

The potential and kinetic energy controlling erosion transport and deposition within a channel

Sediment transport

The movement of sediment particles by traction saltation suspension or solution

Competence

The maximum particle size a river can transport at a given velocity

Capacity

The total quantity of sediment a river can carry at one time

Weathering

The breakdown of rock in situ by mechanical chemical or biological processes

Mechanical weathering

Physical breakdown of rock through processes such as freeze thaw and exfoliation

Chemical weathering

Breakdown of rock through chemical reactions such as hydrolysis oxidation and carbonation

Biological weathering

Breakdown of rock by plant roots animals and microbial activity

Erosion

The removal and transport of material by water wind ice or gravity

Hydraulic action

Erosion caused by the force of water compressing air in cracks and weakening rock

Abrasion

Wearing down of surfaces by sediment scraping grinding or rubbing

Solution erosion

Dissolving of soluble minerals by acidic water

Plucking

Glacial erosion where ice freezes onto rock fragments and pulls them away as the glacier moves

Mass movement

Downslope movement of rock soil or debris driven by gravity such as slides flows or falls

Rockfall

Sudden freefall of rock from a steep cliff or slope

Landslide

Rapid downslope movement of rock or soil along a defined slip plane

Longshore drift

Lateral movement of sediment along a coastline caused by wave action meeting the shore at an angle

Deposition

The laying down of sediment when energy levels decrease

Convection currents

Circular movements of heated and cooled mantle material that drive plate motion

Plate boundary types

Categories of divergent convergent and conservative boundaries with different associated hazards

Subduction

The process where one tectonic plate sinks beneath another forming trenches volcanoes and earthquakes

Orogeny

Mountain building caused by compression at convergent boundaries

Elastic rebound theory

The mechanism of earthquake generation where accumulated stress is released when rocks suddenly slip along a fault

Volcanic types

Categories such as shield volcanoes composite volcanoes and fissure eruptions determined by magma composition and viscosity

Lahar

A fast moving flow of volcanic ash mud and debris triggered by rainfall melting ice or volcanic activity

Pyroclastic flow

A high speed avalanche of hot ash gas and rock fragments from explosive eruptions

Hazard

A natural event with the potential to cause harm such as an earthquake or volcanic eruption

Risk

The likelihood of harm occurring considering exposure vulnerability and capacity to respond

Biome

A large scale ecological zone defined by climate vegetation and characteristic species

Primary productivity

The rate at which plants convert sunlight into chemical energy through photosynthesis

Net primary productivity

The energy available to the ecosystem after plant respiration is subtracted from total productivity

Succession

The sequence of changes in ecosystem structure and species composition following disturbance

Pioneer species

The first organisms to colonise a newly disturbed or bare area

Climax community

A stable ecosystem that forms at the end of succession under given climate conditions

Disturbance

An event such as fire storm or human activity that disrupts ecosystem structure

Latitudinal biodiversity gradient

The pattern of increasing species richness toward the equator due to climate stability and energy availability

Ecosystem services

Benefits humans gain from ecosystems including carbon storage water regulation and biodiversity support

Cryosphere

The frozen components of the Earth system including snow ice glaciers and permafrost

Accumulation

The gain of snow and ice on a glacier through snowfall wind drift or freezing of meltwater

Ablation

The loss of ice from a glacier through melting sublimation or calving

Glacier mass balance

The difference between accumulation and ablation which determines whether a glacier advances or retreats

Internal deformation

Slow flow of glacial ice as crystals deform and slide past each other under pressure

Basal sliding

Movement of a glacier over bedrock aided by meltwater at the base

Permafrost

Ground that remains continuously frozen for at least two consecutive years

Ice albedo feedback

A climate feedback where melting ice lowers reflectivity causing more absorption of solar energy and further warming

Carbon cycle

The circulation of carbon between the atmosphere oceans land plants soils and rocks through natural and human processes

Carbon sink

A reservoir that absorbs more carbon than it releases such as forests or oceans

Radiative forcing

A measure of how different factors change the balance between incoming and outgoing energy influencing global temperature

Albedo

The reflectivity of a surface such as ice water or vegetation which affects how much solar energy is absorbed

Thermohaline circulation

Global deep ocean circulation driven by differences in water temperature and salinity controlling heat distribution

Ocean acidification

The decrease in ocean pH caused by absorption of carbon dioxide affecting marine ecosystems

Extreme weather trends

Long term changes in the frequency duration or intensity of events such as storms heatwaves and droughts