Desert Definitions (E) Flashcards
Desert
Dry, hot landscape fewer than 250mm of rain per year
Desert Margin
An area oh the edge of a desert
Arid
Dry
Aridity index
Number for the indicator of the degree of dryness
Insolation
Energy from the sun (sunlight)
ITCZ
InterTropical Convergence Zone
Band of low pressure at equator
Diurnal temperature range
The temperature range from day to night
Aeolian
Caused by wind
Weathering
Breaking down of material by weather
Erosion
Breaking down of material by wind or water
Saltation
Form of transport, matter to heavy to be carried is dropped repeatedly ‘bounces’
Flash flood
Quick/ sudden flood
Sheet flood
A layer of water covering an area moving together
Cyclonic
Large air mass that rotates
Anticyclonic
An area of high atmospheric pressure
Potential evapotranspiration
The amount of maximum evaporation of water possible
Surface runoff
Water which cannot infiltrate the soil
Prevailing wind
The main direction of wind
Sediment budget
Balance between sediment added and removed
Depositional landforms (2 examples)
Sand dunes , alluvial fans
Erosional landforms
Desert pavements
Messa buttes
Water balance
Balance of water entering + leaving (precipitation and evapotranspiration)
Continentality
The placement of deserts, due to how inland they are
Rain shadow effect
Where mountain ranges block it from raining on one side
Orographic effect
When air is forced to rise due to high topography
Biomass
Amount of alive matter
Xerophyte
Cacti, needs little water
Xerophyte
Cacti,needs little water
Halophyte
Salt tolerant plant
Pyrophyte
Plants adapted to survive fire
Phreatophyte
Long wide root system (large area covered )
Soil
Loose surface matters that covers most land
Thermal fracture
Expansion +contraction breaks rock, cause temperature
Salt weathering
Water evaporates leaving salt crystals behind which as they form cause rock to crack
Groundwater
Water stored underground, aquifers
Frost shattering
pressure of freezing water breaks water
Freeze-thaw
Water in crack freezes , crack expands ect
Hydration
Chemical weathering minerals in rock cause the rock to swell and break
Oxidation
Chemical weathering , iron oxidises causing rust and rock breaking
Carbonation
Chemical weathering, co2 reacts with minerals in rocks
Exfoliation
Thin layers removed of rocks as cracks form parallel to rocks surface
Granular disintegration
Grain by grain breakdown of rock. Very Small pieces fall off
Block disintegration
The splitting of rocks along the joints into blocks
Deflation
Removal of solid particles by wind
Abrasion
Polishing of rocks by wind carrying sand
Suspension
Light matter carried by wind + water
Saltation
Bouncing of carried material, to heavy to be carried but not light enough to be suspended
Surface creep
Slow movement of heavy matter
Exogenous river
River originates outside desert
Endoreic river
Water enters desert and stops there creating a lake
Ephemeral river
Temporary rivers created by sudden heavy rainfall
Delta
Flat, low lying plain, forms at mouth of river formed from sediment carried
Permeable
Water can enter
Impermeable
Water cannot enter
Mass movement
The movement of material down a slope due to gravity
Rock fall
Rock falling from cliff face due to weathering
Debris flow
Fast moving landslides
Pediments
Sheet flood on a wide gently sloping rock face
Playas
Deflation becomes a temporary lake, salt plain
Mesa
Wider than it is taller
Butte
Taller than it is wide
Inselbergs
A hill of hard volcanic rock that has resisted weathering and remained as land around it eroded away
Wadis
Abrasion by ephemeral streams
Alluvial fans
When water slows + drops sediment after leaving a narrow area
Bahadas
Multiple alluvial fans
Deflation hollow
Air removes sediment leaving large shallow area
Desert pavement
Wind picks up all small sediment leaving large shallow area
Yardang
Differential erosion
alongside one another
Zeugen
Abrasion
Above one another , form rocks looking like mushrooms
Ventifacts
Rock shaped, smoothed by wind carying sediment
Eddy/ eddies
Circular current of water
Barchan dune
Drop in energy, formed in wind direction
Seif dune
Drop in energy initially a barchan dune then secondary wind shapes it like an S
Green Sahara
When Sahara had trees + lakes = 11,000-5,000 years ago
Land degradation
Land loses water, soil fertility
Overgrazing
Over eating of plants by cattle ect
Over cultivation
Overuse of farm land for crops
Deforestation
Removal of trees
Irrigation
Pipes carrying water for crops
Desertification
Land becomes a desert
Strategy : resilience
The ability to cope with a hazard
Strategy mitigation
Reducing risk of loss from an undesirable event
Strategy adaptation
Adjustments in systems to respond to a hazard
Erg
Broad area of land covered by sand with little or no vegetation
Reg
Stony plains (large desert pavements)
Hamada
Hard rocky plateaus, most sand removed
Plateaux
Flat land
Fog harvesting
Nets catch water, deserts then can have water supply - need to be by the sea
Leaching
Chemicals entering the water system