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Physical Geography - Structures > Geography - Drylands > Flashcards

Geography - Drylands Flashcards

1
Q

Diversity of drylands…

A

Rocky mountains, lake beds, river valleys or desert plains…

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2
Q

How many inhabit drylands?

A

2 billion.

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3
Q

Properties of dry lands?

A

Precipitation is weak and erratic annually, with arid areas.

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4
Q

Potential Evapotranspiration

A

The amonut of transpiration that would occur if there was a sufficient water source

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5
Q

When is there deficient moisutre?

A

When PET exceeds p

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6
Q

Types of arid envrionment…

A

Hyper-arid
Arid
Semi-arid
Dry-subhumid

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7
Q

Hyper-arid

A

True deserts with a P/PET value of less than 0.05

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8
Q

Examples of hyper-arid deserts?

A

Central sahara, Arabian peninsula and Namib deserts.

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9
Q

Arid

A

Classified as between 0.05 and 0.2, with 200mm annual rainfall

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10
Q

Semi-arid

A

Between 0.2 and 0.5, with 500mm rainfall in winter and 800m rainfall in the summer.

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11
Q

What does varying precptiation effect?

A

Agriucltural practices, huamn welfare, drougth susceptibiltiy

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12
Q

Dry-subhumid

A

Areas between 0.5 to 0.65

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13
Q

What causes aridity?

A

Subtropical regions
Intercontinentiality
Mountain Shadow Effect
Western Coastlines

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14
Q

Mountain Rain Shadow Effect

A

A patch of land that desertifies due to mountain rnage blocking plant growing, rainy weather.

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15
Q

Example of cause of aridity?

A

Sahara is subtropical, intercontinental and affected by the Tibesti Massif mountains

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16
Q

Why are Central Asia and North America Arid in places?

A

Continentality so weather systems cannot penetrate these area

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17
Q

Example of currents affecting aridity…

A

Namib and Atacama deserts affected by Antartic cold ocean currents, bringing colder cliamtes to these regions supressing sea surface evaporation and rainfall.

18
Q

Example of seasonal variations of aridity…

A

Closer to the ITCZ then more susceptible to its movements and rainfall varaitions.

19
Q

What are the types of soil?

A

Aridisoil
Alfsol
Entisoil
Mollisoil
Vertisol

20
Q

What causes soil crusting?

A

High evaporation with icnreased mineral concentraiton that dry and form hard layers

21
Q

How do biological crusts form?

A

Algae and Cyanobacteria with silica and calcium carbonate.

22
Q

Hydrophytes

A

Wetland plants tolerating permenently saturated soils, foudn in very few drylands.

23
Q

Mesophytes

A

Tolerate 10-20% soil moisture, measured between its fiedl capaicity and wilting point

24
Q

Xerophytes

A

Can tolerate extreeme moisture deficieny with little as 5% moisture

25
Q

How plants adapt to arid areas?

A

Regulate dormancy and limitation of growth and reproduction to the wet seasons.

26
Q

What plants are found in deserts?

A

Rarely 10% cover, contain shrubs and grasses

27
Q

What geographical sturctures influence drylands?

A

Tectonic activity and morphology like mountainous areas or flatlands.

28
Q

Rock weathering in drylands..

A

High ET means higher mineral/salt concentration as well as the bare rock surfaces

29
Q

Most common forms of weathering in arid areas?

A

Insolation and thermal weathering

30
Q

Granular Disaggregation

A

The detachment of minerals due to stress of intercrystalline bonds being weaker than the intracrystalline bonds.

31
Q

Salt Weathering

A

This is where high precipitaiton causes high salt concentration in tnadem with limited leeching

32
Q

Why is salt crystallization favoured with higher temperatures?

A

Moisture induces increased salt volume and thermal expansion of increasing heat.

33
Q

Infilitration Excess Overland Flow

A

A for of runoff where the surface is bare rock, and can promote surface sealin/crusting inunconsolidated sediments.

34
Q

How does sedimentation occur in drylands despite low precipitation?

A

High convection and thunderstorms

35
Q

Why do drylands ONLY exhbit low channel formation?

A

Low catchment and infilitration through the bed.

36
Q

Aeloian Processes

A

Refers to wind activity and its erosion, tranportation and sediment deposition.

37
Q

Example of aeloian processes?

A

Sand dunes

38
Q

Types of dune?

A

Barchan, seif, star dunes and transverse dunes

39
Q

Barchan and Seif dunes

A

Crescent shaped and Elongated respectively

40
Q

Star dunes

A

Pyramidal sand mounds with slip faces on three or more arms that radiate from the high centre of the mound.

41
Q

Transver Dunes

A

Are symmetrical, elongated dunes lying at right angles to the prevailing wind direction

Physical Geography - Structures (10 decks)

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