Drylands as Systems

Question 1

Positive feedback

Answer 1

initial change brings about further change

Question 2

negative feedback

Answer 2

system is returned to normal functioning

Question 3

components or dryland systems

Answer 3

geology, sediments, water, climate

Question 4

aridity index def

Answer 4

Numerical index of dryness

Question 5

aridity index eqt

Answer 5

P/PET (all values are mean annual)

Question 6

PET: def: factors

Answer 6

Potential Evapotranspiration: amount of evaporation that would occur if sufficient water sources were available: atmospheric humidity, solar radiation and wind

Question 7

Climate in drylands

Answer 7

low annual ppt, PET higher than ppt, wind active in landscape change

Question 8

Geology in drylands

Answer 8

lithology: chemical composition, physical characteristics (porosity, permeability…)

Question 9

latitude in drylands

Answer 9

low latitudes Hadley cell, intensity of solar radiation varies (less temp polewards), cold ocean currents lat 15-30

Question 10

altitude in drylands

Answer 10

temp fall with altitude, large temp ranges, low humidity and ppt

Question 11

relief and aspect in drylands

Answer 11

leeward slopes can be dry due to rain shadow, southerly aspect make higher temp and more evapotranspiration so dryer

Question 12

availability of sediment in drylands

Answer 12

scarce sediment desert pavements are a feature, more sediment due to active weathering makes alluvial fans, bajadas and sand seas

Question 13

rain shadow

Answer 13

area of below average rainfall on the lee of an upland

Question 14

alluvial fans

Answer 14

cone of sediment deposited by a river where it leaves a steep upland course and flows onto low land

Question 15

bajada

Answer 15

series of alluvial fans that merge to form a continuous spread of sediment

Question 16

sand sea

Answer 16

vast expanse of sand dunes

Question 17

Cause and effect of Hadley Cells

Answer 17

equator sun overhead, air touching ground heats, rises and cools and vapour condenses, ppt forms, rising air replaced from N and S created high and low Pa areas, air descends at 30 lat, warms with descent making few clouds and aridity (look at diagram)

Question 18

Polar drylands

Answer 18

permafrost region no ice cover, lacking veg, low ppt because intense cold, most yr water frozen but brief summer melt leads to solifluction, freeze-thaw in fall and spring due to temps going above and below freezing

Question 19

Semi-arid environments

Answer 19

0.21-0.5 aridity index, seasonal rainfall allows settlement and agriculture, increasing dist from equator so rainy season shorter and dry season longer

Question 20

mid- and low-latitude deserts

Answer 20

tropical deserts have near same rainfall all yr, summer temps can be 80C, drainage mainly endoreic streams, mid-lats more variable in pattern

Question 21

tundra

Answer 21

treeless region in sub-Arctic and high mountain with short growing season and severe winter temp

Question 22

solifluction

Answer 22

summer meltwater in upper permafrost layers can’t drain away, lubrication means soil is moved on gentlest slopes

Question 23

hyper arid

Answer 23

<0.05

Question 24

arid

Answer 24

0.05-0.20

Question 25

semi arid

Answer 25

0.21-0.50

Question 26

sub-humid

Answer 26

> 0.50