hot arid and semi arid environments definitions

Question 1

semi-arid

Answer 1

having rainfall of less than 500mm per annum

Question 2

Aridity

Answer 2

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

Question 3

subtropical high-pressure belt

Answer 3

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

Question 4

subtropical high-pressure belt

Answer 4

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

Question 5

continentality

Answer 5

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

Question 6

Rain shadow effects

Answer 6

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

Question 7

desertification

Answer 7

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

Question 8

diurnal

Answer 8

difference between night and day

Question 9

salt crystal growth

Answer 9

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

Question 10

thermal fracturing

Answer 10

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

Question 11

disintergration

Answer 11

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

Question 12

block disintergration

Answer 12

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

Question 13

granular disintegration

Answer 13

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

Question 14

hydration

Answer 14

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

Question 15

deflation

Answer 15

lowering of the surface

Question 16

suspension

Answer 16

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

Question 17

pluvial

Answer 17

a period of increased rainfall in deserts

Question 18

Gours

Answer 18

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

Question 19

Zeugens

Answer 19

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

Question 20

Yardangs

Answer 20

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

Question 21

barchan dunes

Answer 21

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

Question 22

parabolic dunes

Answer 22

crescent-shaped dunes that point downwind

Question 23

linear dunes

Answer 23

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

Question 24

hydrological regime

Answer 24

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

Question 25

flash floods

Answer 25

sudden floods caused by heavy downpours or storms

Question 26

sheet floods

Answer 26

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

Question 27

exogenous rivers

Answer 27

flow in arid regions but have their origin in humid areas

Question 28

endoreic rivers

Answer 28

flow into inland lakes

Question 29

ephemeral rivers

Answer 29

flow only after rainstorms

Question 30

wadis

Answer 30

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

Question 31

Alluvial fan

Answer 31

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

Question 32

piedmont zone

Answer 32

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

Question 33

bajada

Answer 33

is formed by a number of alluvial fans merging

Question 34

pediments

Answer 34

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

Question 35

playas

Answer 35

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

Question 36

mesas

Answer 36

plateau-like features with steep sides at their edges

Question 37

buttes

Answer 37

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

Question 38

inselbergs

Answer 38

any isolated hills that stand prominently over a level surface

Question 39

biomass productivity

Answer 39

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

Question 40

biodiversity

Answer 40

the range of habitat, species and population variety

Question 41

physical drought

Answer 41

describes water shortages over a long period of time

Question 42

physiological drought

Answer 42

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

Question 43

succulents

Answer 43

plants that have well developed storage tissues

Question 44

Aridisols

Answer 44

desert soils with a low organic content

Question 45

Solonchaks

Answer 45

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

Question 46

Solonetz

Answer 46

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

Question 47

salination

Answer 47

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

Question 48

overgrazing

Answer 48

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

Question 49

overcultivation

Answer 49

where growing of crops exhausts soil nutrients

Question 50

soil degradation

Answer 50

the decline in quantity and quality of soil