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Geomorphology > Aeloan > Flashcards

Aeloan Flashcards

1
Q

what is the primary control of deserts

A

plate tectonics

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2
Q

what are deserts characterized by

A
  1. extreme dryness
  2. hot or cold temps
  3. specialized ecosystems
  4. low huma populations
  5. unique geologic processes
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3
Q

do deserts have more evaporation or precipitation

A

evaporation

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4
Q

how does evaporation affect a desert ecosystem

A

evaporation prevents surface water being permanent

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5
Q

is a desert arid or not

A

yes - extremely arid

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6
Q

how much surface is covered in vegetation in a desert

A

less than 15%

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7
Q

how much annual rainfall is there in a desert

A

less than 25 cm

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8
Q

are deserts only in hot climates

A

NO - can be in cold as well

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9
Q

where are hot deserts found

A
  1. low latitudes
  2. low elevations
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10
Q

are hot deserts found close to oceans

A

NO - far from oceans

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11
Q

where are cold deserts found

A
  1. high latitudes
  2. high elevations
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12
Q

are cold deserts found far from oceans

A

NO - found close to them

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13
Q

how much of earth’s land surface is covered by dry regions

A

30%

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14
Q

what are two common climatic types of dry regions

A

deserts (Arid)
steppes (semiarid)

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15
Q

what are often found on desert land surfaces

A
  1. exposed bedrock
  2. accumulated clasts
  3. unweather sediment
  4. precipitated salt
  5. windblown sand
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16
Q

5 types of deserts

A
  1. subtropical desert
  2. rain shadow desert
  3. costal desert
  4. continental interiors
  5. polar deserts
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17
Q

example of polar deserts

A

Antarctica

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18
Q

example of continental interior deserts

A

Gobi

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19
Q

example of costal deserts

A

Atacama

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20
Q

example of rain shadow deserts

A

western Alberta

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21
Q

example of subtropical deserts

A

Sahara

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22
Q

latitude of subtropical desert

A

20 to 30 degrees N and S

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23
Q

describe moisture pattern in subtropical deserts

A
  1. solar energy evaporates water which rises as hot, moist air
  2. as the hot air rises it cools and expands
  3. rain forms
  4. the air stripped of moisture flows N and S
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24
Q

what is earth’s largest desert

A

subtropical desert

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25
Q

describe air patterns in rain shadow deserts

A
  1. air picks up moisture as it travels over the ocean
  2. the water heavy air is driven over mountains and cools to form clouds
  3. the moisture in the air condenses and becomes rain BEFORE REACHING TOP OF MOUNTAIN to form rain forest
  4. over the mountain, the air stripped of moisture sinks, compresses and sucks water out of the land
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26
Q

type of desert

A

subtropical

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27
Q

type of desert

A

rain shadow

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28
Q

type of desert

A

costal

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29
Q

describe movement of air in costal deserts

A
  1. cool air over the cold oceans cannot hold moisture
  2. as the air interacts with land it absorbs moisture which dries the desert more
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30
Q

where is the driest place on earth

A

Atacama desert (Peru)

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31
Q

describe air movement in interior deserts

A
  1. air loses moisture as it crosses continents
  2. deserts way inland receives air that is low in moisture and would likely force water out of already dry environment
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32
Q

does air lose or gain moisture as it crosses continents

A

loses moisture

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33
Q

are interior deserts close to large bodies of water

A

NO

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34
Q

where can polar deserts be found

A

above 66 degrees North and S latitude

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35
Q

is there lots of moisture above 66 Degrees N and S

A

NO

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36
Q

describe movement of air in polar deserts

A
  1. air circulation carries dry air to polar regions
  2. such cold climates means the air cannot hold moisture
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37
Q

processes that happen in a desert

A
  1. erosion by water and wind
  2. weathering
  3. soil formation
  4. deposition
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38
Q

type of weathering that dominates deserts

A

physical weathering

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39
Q

is chemical weathering common in deserts

A

no - very few chemicals present

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40
Q

what can exposed surfaces in deserts form

A

desert varnish

41
Q

what is desert varnish

A

a dark surface coating of iron and magnesium oxides that forms by bacterial activity, dust and water

42
Q

describe desert soils

A

thin with poor defined horizons

43
Q

describe the colour of desert soils

A

like bedrock (widely coloured)

44
Q

what magnifies sediment erosion in deserts

A

lack of roots = lack of stability against water erosion

45
Q

what can happen in deserts with lots of rain

A

flash floods

46
Q

does water often infiltrate the ground in deserts

A

no - often remain on the surface due to aquicludes

47
Q

where do flash floods infiltrate

A

dry stream beds

48
Q

types of loads carried by wind erosion

A
  1. surface load
  2. saltation
  3. suspended load
49
Q

describe the main types of loads in wind erosion

A
  1. surface load
    - grains moved in contact with the ground
  2. saltation
    - sand skipped and bounced by grain impact (jumping along ground)
  3. suspended load
    - sediment carried in the air
50
Q

what type of clast cannot be lifted and moved by wind

A

coarse clasts

51
Q

how do large deposits of sediments form

A

when finer sediment is removed

52
Q

what is desert pavement

A

a surface layer of stones which is resistant to erosion

53
Q

is desert pavement susceptible to erosion

54
Q

ventifacts vs yardangs

A

ventifacts
- rocks pitted, grooved or polished by wind abrasion
- caused by dust suspended by wind

yardangs
- wind sculpted bedrock

55
Q

sand blasting

A

rock or other solid object blasted by sand and dust particles suspended and being move through saltation (jumping)

56
Q

two forms of wind erosion

A

deflation
abrasion

57
Q

contrast abrasion and deflation

A

deflation
- REMOVAL of material by wind transport

abrasion
- mechanical WEATHERING of rock by wind blow sand

58
Q

what is left behind by deflation

A

large rock particles that are densely packed (desert pavement)

59
Q

what is removed by deflation

A

the top layer of fine very dry soil

60
Q

what mechanism commonly forms desert pavement

61
Q

when do blowout occur

A

when wind picks up dry fine grained sediment and leaves behind exposed areas

62
Q

what is vegetation called that remains in place as a blowout forms

63
Q

dunes

A

windblown accumulations of sand

64
Q

when does wind deposition occur

A

when wind velocity decreases

65
Q

two sides to a dune

A

windward side: side the wind blows (GENTLE SLOPE)

leeward side: side protected from wind (STEEP SLOPE)

66
Q

two types of wind deposition

A
  1. dunes
  2. loess
67
Q

what direction do dunes move

A

direction of wind movement

68
Q

types of dunes

A
  1. star
  2. barchan
  3. transverse
  4. longitudinal
  5. parabolic
69
Q

what factors determine shape of dunes

A
  1. available sand
  2. wind velocity
  3. wind direction
  4. amount of vegetation present
70
Q

what direction does sand move in dunes

A

from windward side to leeward side

71
Q

what is loess

A

deposition of very fine grain material (silt and clay)

72
Q

what is loess thought to be derived from in Europe/NA

A

glacial and periglacial sources

73
Q

what is loess thought to be derived from in China

A

desert sources

74
Q

barchan dune is what shaped

A

crescent shaped

75
Q

where does the horn point in Barchan dune

76
Q

where is the steep side on Barchan dune

A

concave side

77
Q

describe wind movement in Barchan dune

A

moves in ONE direction

78
Q

describe supply of sand needed in Barchan dunes

A

short supply

79
Q

type of dune

80
Q

type of dune

81
Q

describe shape of parabolic dune

A

deeply curved

82
Q

describe horns in parabolic dune

A

anchored by vegetation

83
Q

describe movement of wind in parabolic dune

A

one direction

84
Q

describe strength of wind in parabolic dune

A

strong winds

85
Q

what amount of sand is needed for parabolic dune

A

large sand supply

86
Q

describe how parabolic dunes are opposite barchan dunes

A

their convex side is facing downwind NOT the concave side

87
Q

type of dune

88
Q

describe shape of transverse dunes

A

straight and elongated

89
Q

describe transverse dunes to wind direction

A

perpendicular to the wind direction

90
Q

amount of sand needed for transverse dunes

A

large supply

91
Q

types of dune

A

transverse dune

92
Q

describe shape of longitudinal dunes

A

extremely long, high and straight

93
Q

describe longitudinal dunes with wind direction

A

parallel to wind direction

94
Q

type of dune

A

longitudinal

95
Q

describe shape of star dune

A

center with radiating arms

96
Q

describe wind direction for star dunes

A

changing directions

97
Q

types of desert deposition

A

alluvial fans
playas

98
Q

describe how sediments change in alluvial fans

A

near source: coarse sediments

away from source: finner

99
Q

playas

A

desert lake that have no outlet streams which collect drainage from flash floods

Geomorphology (12 decks)

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