hot arid and semi arid environments definitions Flashcards

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1
Q

semi-arid

A

having rainfall of less than 500mm per annum

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2
Q

Aridity

A

is a permanent water deficit: less than 125mm of rainfall per annum

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3
Q

subtropical high-pressure belt

A

a zone of dry, descending air (high pressure) at the poleward side of the Hadley cell, leading to arid conditions

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4
Q

subtropical high-pressure belt

A

a zone of dry, descending air (high pressure) at the poleward side of the Hadley cell, leading to arid conditions

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5
Q

continentality

A

a climate that is charecteristic of a continental area having very hot summers, very cold winters and low rainfall

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6
Q

Rain shadow effects

A

the drier conditions on the leeward side of the mountains compared with the windward side

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7
Q

desertification

A

the spread of desert-like conditions, causing land degradation in humid and semi-arid areas - involves the loss of biological and economic productivity and it occurs where climatic variability (especially rainfall) coincides with unsustainable human activities

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8
Q

diurnal

A

difference between night and day

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9
Q

salt crystal growth

A

type of mechanical weathering in areas where temperatures fluctuate around 26-28 degrees - leads to the expansion of crystals by 300% such as sodium sulphate and carbonate

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10
Q

thermal fracturing

A

form of mechanical weathering caused by repeated cycles of heating and cooling over long periods of time

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11
Q

disintergration

A

type of weathering found in hot desert areas where there is a large diurnal temperature change

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12
Q

block disintergration

A

form of mechanical weathering whereby rocks are split into blocks, caused by repeated cycles of heating and cooling over long periods of time

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13
Q

granular disintegration

A

form of mechanical weathering whereby different minerals are broken down, caused by repeated cycles of heating and cooling over long periods of time

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14
Q

hydration

A

a form of chemical and mechanical weathering whereby rocks take in water, expand and contract and over time are broken down

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15
Q

deflation

A

lowering of the surface

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16
Q

suspension

A

describes sediment that are carried aloft (in the air) without touching the ground

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17
Q

pluvial

A

a period of increased rainfall in deserts

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18
Q

Gours

A

mushroom pinnacles where the base has been undercut, and bands of hard and soft rock have been differentially sand blasted

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19
Q

Zeugens

A

wind-eroded rocks in which different different rock strata lie horizontally

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20
Q

Yardangs

A

wind-eroded rocks where hard and soft rock lie side by side. the softer rocks are worn down to form troughs while harder rocks stand up as wind-worn ridges

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21
Q

barchan dunes

A

crescent-shaped and found in areas where sand is limited but there is a constant wind supply

22
Q

parabolic dunes

A

crescent-shaped dunes that point downwind

23
Q

linear dunes

A

found in areas where there is a seasonal change in wind direction

24
Q

hydrological regime

A

describes annual and seasonal variations in the flow of water in a river

25
Q

flash floods

A

sudden floods caused by heavy downpours or storms

26
Q

sheet floods

A

fllods in which the river is not confined in an identifiable river channel, but floods over a large surface

27
Q

exogenous rivers

A

flow in arid regions but have their origin in humid areas

28
Q

endoreic rivers

A

flow into inland lakes

29
Q

ephemeral rivers

A

flow only after rainstorms

30
Q

wadis

A

generally steep-sided, flat-bottomed river valleys that vary in size from a few metres in length to over a 100km long

31
Q

Alluvial fan

A

a cone of sediment occuring between a mountain and a lowland plain

32
Q

piedmont zone

A

is a lowland area/plain generally located at the base of the mountain

33
Q

bajada

A

is formed by a number of alluvial fans merging

34
Q

pediments

A

gently sloping areas (<7 degrees) of bare rock where there is a distinct break with the mountain region

35
Q

playas

A

comprised of a thick crust of salt which has formed after water has flowed into a depression and then evaporated, leaving behind a crust

36
Q

mesas

A

plateau-like features with steep sides at their edges

37
Q

buttes

A

smaller versions of mesas. they are thinner landforms that have very steep sides and a flat top

38
Q

inselbergs

A

any isolated hills that stand prominently over a level surface

39
Q

biomass productivity

A

the amount of new organic matter produced each year by the existing biomass

40
Q

biodiversity

A

the range of habitat, species and population variety

41
Q

physical drought

A

describes water shortages over a long period of time

42
Q

physiological drought

A

describes water shortages experienced by plants despite there being sufficient soil moisture available - mainly caused by high evapotranspiration rates

43
Q

succulents

A

plants that have well developed storage tissues

44
Q

Aridisols

A

desert soils with a low organic content

45
Q

Solonchaks

A

soils with a saline horizon of NaCl (sodium chloride) - also known as white alkali soils

46
Q

Solonetz

A

soils with a horizon of Na2CO3 (sodium carbonate) - also known as black alkali soils

47
Q

salination

A

the concentration of saline salts, usually in the upper horizon of the soil. It can be toxic to plants

48
Q

overgrazing

A

when pastoralists allow too many animals to graze on a fixed area of land

49
Q

overcultivation

A

where growing of crops exhausts soil nutrients

50
Q

soil degradation

A

the decline in quantity and quality of soil