Key term
AQA A-Level Geography 7037
Water and Carbon Cycles
Topic overviewSystems, Stores and FlowsMass Balance in Water and Carbon StoresFieldwork and the Rainforest Case StudyMeasures of Central Tendency and DispersionSpearman's Rank, Chi-Square and Data AnalysisScatter Graphs, Triangular Graphs and Logarithmic ScalesAtlas, Thematic and Flow-Line MapsOS Maps, Sketch Maps and Field SketchesRemote Sensing, GIS and Big DataQualitative Data, Questionnaires and InterviewsSampling, Accuracy and Measurement ErrorData Misuse and Research EthicsThe Global Water StoresEvaporation, Condensation and Cloud FormationPrecipitation and Cryospheric ProcessesThe Drainage Basin as an Open SystemInfiltration and Overland FlowThe Water Balance EquationFlood HydrographsHuman Impacts on the Water CycleThe Global Carbon StoresPhotosynthesis, Respiration and Carbon TransferFarming, Land Use and Carbon SinksGreenhouse Gases and Links between the CyclesFeedback Loops and Climate ChangeCarbon Sequestration and MitigationMass Balance in a Drainage BasinUnit Conversion and Flux CalculationsLine Graphs, Bar Graphs and Pie ChartsWater and Carbon Cycles in the Tropical RainforestThe Amazon rainforest case studyStores within a River CatchmentTransfers and the Controls on Catchment HydrologyThe River Eden catchment case study
Hot Desert Systems and LandscapesLandscape
Topic overviewDeserts as Systems: Inputs, Stores, Flows and FeedbackDesert Climate, Soils and VegetationThe Aridity IndexEnergy, Sediment and Geomorphic Processes in DesertsThermal Fracture and Rock BreakdownDeflation, Abrasion and Aeolian TransportDesert Water Sources and Ephemeral StreamsDeflation Hollows, Yardangs and ZeugenBarchan and Seif DunesWadis, Bahadas and PedimentsPlayas, Inselbergs and Landscape DevelopmentObservation, Measurement and Mapping in DesertsDeath Valley hot desert case studyThe Causes and Definition of DesertificationEnvironmental Impacts of DesertificationHuman Impacts and Responses to DesertificationDesertification on the Yatenga plateau, Burkina Faso
Coastal Systems and LandscapesLandscape
Topic overviewEnergy Inputs to the Coastal SystemCoastal Flows and FeedbackWaves, Tides and Sediment CellsMarine Erosion and Transport ProcessesCliffs, Notches and Wave-Cut PlatformsBeaches, Spits and BarsSand Dune Formation and SuccessionEstuaries, Mudflats and SaltmarshSea Level Change and Coastlines of SubmergenceEmergent Coastlines and Present Sea Level RiseHard Engineering at the CoastSoft Engineering and Managed RetreatThe Holderness coast case studyThe Sundarbans and the Ganges–Brahmaputra delta
Glacial Systems and LandscapesLandscape
Topic overviewGlaciers as Systems: Inputs, Stores and FlowsIce-Albedo and Negative FeedbackDynamic Equilibrium, Landforms and LandscapesThe Glacial Mass Budget and Ice MovementThe Distribution of Cold EnvironmentsClimate, Soils and Vegetation in Cold EnvironmentsCorrie FormationGlacial Troughs and Hanging ValleysRoches Moutonnées, Drumlins and ErraticsMoraines, Till and Fluvioglacial LandformsPeriglacial Landforms and ProcessesThermokarst and Landform DistributionThe Fragility of Cold EnvironmentsImpacts and Management of Cold EnvironmentsFieldwork Skills in Glaciated EnvironmentsGlacial Case Study RequirementsCwm Idwal and the Ogwen valley case studyAlaska as a contrasting glaciated landscape
HazardsHazards or ecosystems
Topic overviewNatural Hazards: Types, Perception and ResponsesThe Park ModelThe Hazard Management CycleThe Internal Structure of the EarthPlate Tectonic Theory and Plate MovementPlate Margins and SeismicityWhere Vulcanicity OccursVolcanic Hazards and Eruption MagnitudeVolcanic Prediction, Impacts and ResponsesA Recent Volcanic EventHow Earthquakes HappenSeismic Hazards, Distribution and MagnitudeEarthquake Prediction, Impacts and ResponsesFocus, Epicentre and Seismic VulnerabilityThe 2011 Tōhoku earthquake and tsunamiTropical Storm Formation and IntensificationTropical Storm Hazards, Distribution and MagnitudeThe Impacts of Tropical StormsManaging Storm Risk in Contrasting PlacesTyphoon Haiyan and Hurricane Maria comparedWildfires and Vegetation TypeWeather Conditions and Wildfire RiskCauses of IgnitionPrimary, Secondary and Environmental Impacts of WildfiresSocial, Economic and Political Impacts of WildfiresShort- and Long-Term Responses to WildfiresWildfire Preparedness, Prevention and AdaptationThe 2018 Camp FireThe Philippines as a multi-hazard environmentLiving with Vesuvius in the Naples area
Ecosystems Under StressHazards or ecosystems
Topic overviewBiodiversity Levels and Causes of DeclineBiodiversity Loss and Ecosystem ServicesEcosystem Structure, Trophic Levels and Food WebsEcosystem Inputs, Outputs, Stores and TransfersBiomass, Net Primary Production and SuccessionNutrient Cycling, Climate and SoilEnvironmental Controls and Ecosystem FeedbackBiomes and the Tropical Rainforest EnvironmentRainforest Stratification and AdaptationsSavanna Climate, Soils and AdaptationsHuman Impacts on the Tropical RainforestHuman Impacts on the SavannaSuccession and Climatic ClimaxTemperate Deciduous WoodlandPlagioclimax and Heather MoorlandCoral Reef Conditions, Services and StressesHuman Pressures and Coral Reef ManagementThe Great Barrier Reef: Extent and BleachingCrown-of-Thorns Starfish and Reef TourismLocal Ecosystems: Heathland, Parkland, Ponds and DunesAdaptations to Dry EnvironmentsAgriculture, Urbanisation and Invasive SpeciesEcological Change and Conservation StrategiesSustainability and Stakeholder ConflictStudying Local Ecosystems and Ecological ChangeThe Sefton Coast sand dunes case studyEcological change in Borneo
Global Systems and Global Governance
Topic overviewGlobal Flows of Capital, Labour, Goods and InformationGlobal Patterns of Production and DistributionTransport and Communications in GlobalisationSecurity, Tariffs and Trade BarriersForms of Global InterdependenceUnequal Flows and Global StabilityWorld Trade Patterns and Market AccessTransnational CorporationsTrade in Food and Manufactured GoodsCase Study: A Transnational CorporationWhat Global Governance MeansScales of GovernanceThe Global CommonsThe Physical Character of AntarcticaThe Southern Ocean and Climate Threats to AntarcticaThreats to Antarctic ResourcesThe Antarctic TreatyUNEP, NGOs and the Limits of Antarctic GovernanceBenefits and Costs of GlobalisationConflict, Environmental Costs and Critiquing Globalisation
Changing Places
Topic overviewWhat Place MeansEndogenous Factors: Location, Physical and Built SettingEndogenous Factors: Demographic and EconomicExogenous Factors, Relationships and ConnectionsContinuity and Change in PlacesLocal and Contrasting Place StudiesDetroit as a contrasting place studyMigration, Investment and Cultural Change in PlacesPolicy as an External Force on PlaceThe Legacy of Past ConnectionsGlobal Networks and Changing Place CharacteristicsInequality and Access between PlacesLived Experience and Shaping Place MeaningsRepresenting Place and Contested MeaningsThe Requirements of a Place StudySources for Place Studies
Contemporary Urban EnvironmentsHuman option
Topic overviewUrbanisation and Its Related ProcessesThe Drivers of UrbanisationDeindustrialisation, Decentralisation and Regeneration PolicyMegacities and World CitiesWhat Shapes Urban FormCultural Diversity and Urban SegregationNew Urban Landscapes and the Post-Modern CityEconomic Inequality within CitiesManaging Urban Inequality and DiversityEmployment Programmes and Top-Down StrategiesThe Urban Heat Island and Urban PrecipitationUrban Winds and Air QualityImpermeable Surfaces and Urban CatchmentsUrban HydrographsSustainable Urban Drainage SystemsRiver Restoration and the Benefits of SUDSWho Delivers River RestorationCheonggyecheon river restoration in SeoulSources and Composition of Urban WasteRecycling, Recovery and Waste DisposalLandfill and Incineration ComparedUrban Air and Water PollutantsDereliction and Pollution in Contrasting CitiesManaging Urban Pollution and DerelictionThe Local Environmental Impact of CitiesDimensions of Urban SustainabilityCompact Form, Mixed Use and LiveabilityContrasting Urban Case Studies
Population and the EnvironmentHuman option
Topic overviewThe Physical Environment and PopulationGlobal Food Production and Agricultural SystemsTropical Wet and Semi-Arid ClimatesZonal Soils: Chernozems and LatosolsSoil Erosion and Its ManagementWaterlogging, Salinisation and Soil StructureThe Dimensions of Food SecurityStudying Climatic Types and Zonal SoilsGlasgow: place and health case studyHealth, Morbidity and the Epidemiological TransitionPhysical Environment and DiseaseMalaria: Distribution, Impacts and ManagementCoronary Heart Disease and Non-Communicable DiseasesGlobal Health Initiatives and Disease StudiesThe Demographic Transition ModelFertility, Population Structure and the Demographic DividendMigrant Types and Causes of MigrationPush and Pull Factors in MigrationThe Components of Population ChangeOptimum Population and Resource DemandEcological Footprint and Population–Resource TheoriesOzone Depletion and Human HealthClimate Change, Heatwaves and Vector-Borne DiseaseClimate Change, Food Supply and NutritionGlobal Population ProjectionsJapan's population decline
Resource SecurityHuman option
Topic overviewStock and Flow Resources and ReservesResource Certainty and Development StagesResource Frontiers, Peaks and Sustainable DevelopmentEnvironmental Impact AssessmentGlobal Production and Consumption of Energy and MineralsThe Geopolitics of Energy, Minerals and WaterWater Sources and DemandWater Supply StrategiesThe Colorado River water supply schemeThe Costs of Supply and Managing DemandWater Conflict and Major Supply SchemesEnergy Types, Mix and Physical Controls on SupplyTNCs, National Interests and Energy ImpactsIncreasing Energy Supply: Unconventional, Nuclear and RenewableReducing Energy DemandEnvironmental Impacts and Sustainability of EnergyThe Alberta oil sands developmentChoosing a Mineral Ore Case StudyDemand for and Occurrence of Mineral OresThe Environmental Cost of Mineral ExtractionThe Bingham Canyon copper mineSustainability in Mineral SupplyAlternative Energy FuturesAlternative Water FuturesMineral Ore FuturesDrivers of Resource TransitionsResource Security and Human Welfare
Hot Desert Systems and Landscapes
Barchan and Seif Dunes
- 4 things to know
- Component 1
Overview
Recall questions on the shape of a barchan dune, why its horns advance faster and how sand moves up, over and down it, and on seif dunes, the two-directional wind regime that forms them and the direction in which they elongate.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
How does sand move down the leeward side of a barchan dune?
Key term
In which direction does a seif dune elongate relative to wind patterns?
Process
Explain how sand moves across a barchan dune.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define a barchan dune.
Model answer
A crescent-shaped dune with horns pointing downwind, formed where sand supply is limited and wind direction is consistent.
- 2
Why do the horns of a barchan dune advance faster than the centre?
Model answer
The horns have less sand volume, so they move more quickly.
- 3
How is sand transported up a barchan dune?
Model answer
Sand is transported up the gentle windward slope via saltation.
- 4
What happens to sand when it reaches the crest of a barchan?
Model answer
Sand accumulates at the crest.
- 5
How does sand move down the leeward side of a barchan dune?
Model answer
Sand avalanches down the steep leeward slip face.
- 6
What are seif dunes?
Model answer
Linear, elongated dunes aligned parallel to the dominant wind direction, often formed by bidirectional winds.
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