Aeloan Flashcards
1
Q
what is the primary control of deserts
A
plate tectonics
2
Q
what are deserts characterized by
A
- extreme dryness
- hot or cold temps
- specialized ecosystems
- low huma populations
- unique geologic processes
3
Q
do deserts have more evaporation or precipitation
A
evaporation
4
Q
how does evaporation affect a desert ecosystem
A
evaporation prevents surface water being permanent
5
Q
is a desert arid or not
A
yes - extremely arid
6
Q
how much surface is covered in vegetation in a desert
A
less than 15%
7
Q
how much annual rainfall is there in a desert
A
less than 25 cm
8
Q
are deserts only in hot climates
A
NO - can be in cold as well
9
Q
where are hot deserts found
A
- low latitudes
- low elevations
10
Q
are hot deserts found close to oceans
A
NO - far from oceans
11
Q
where are cold deserts found
A
- high latitudes
- high elevations
12
Q
are cold deserts found far from oceans
A
NO - found close to them
13
Q
how much of earth’s land surface is covered by dry regions
A
30%
14
Q
what are two common climatic types of dry regions
A
deserts (Arid)
steppes (semiarid)
15
Q
what are often found on desert land surfaces
A
- exposed bedrock
- accumulated clasts
- unweather sediment
- precipitated salt
- windblown sand
16
Q
5 types of deserts
A
- subtropical desert
- rain shadow desert
- costal desert
- continental interiors
- polar deserts
17
Q
example of polar deserts
A
Antarctica
18
Q
example of continental interior deserts
A
Gobi
19
Q
example of costal deserts
A
Atacama
20
Q
example of rain shadow deserts
A
western Alberta
21
Q
example of subtropical deserts
A
Sahara
22
Q
latitude of subtropical desert
A
20 to 30 degrees N and S
23
Q
describe moisture pattern in subtropical deserts
A
- solar energy evaporates water which rises as hot, moist air
- as the hot air rises it cools and expands
- rain forms
- the air stripped of moisture flows N and S
24
Q
what is earth’s largest desert
A
subtropical desert
25
describe air patterns in rain shadow deserts
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
26
type of desert
subtropical
27
type of desert
rain shadow
28
type of desert
costal
29
describe movement of air in costal deserts
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
30
where is the driest place on earth
Atacama desert (Peru)
31
describe air movement in interior deserts
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
32
does air lose or gain moisture as it crosses continents
loses moisture
33
are interior deserts close to large bodies of water
NO
34
where can polar deserts be found
above 66 degrees North and S latitude
35
is there lots of moisture above 66 Degrees N and S
NO
36
describe movement of air in polar deserts
1. air circulation carries dry air to polar regions
2. such cold climates means the air cannot hold moisture
37
processes that happen in a desert
1. erosion by water and wind
2. weathering
3. soil formation
4. deposition
38
type of weathering that dominates deserts
physical weathering
39
is chemical weathering common in deserts
no - very few chemicals present
40
what can exposed surfaces in deserts form
desert varnish
41
what is desert varnish
a dark surface coating of iron and magnesium oxides that forms by bacterial activity, dust and water
42
describe desert soils
thin with poor defined horizons
43
describe the colour of desert soils
like bedrock (widely coloured)
44
what magnifies sediment erosion in deserts
lack of roots = lack of stability against water erosion
45
what can happen in deserts with lots of rain
flash floods
46
does water often infiltrate the ground in deserts
no - often remain on the surface due to aquicludes
47
where do flash floods infiltrate
dry stream beds
48
types of loads carried by wind erosion
1. surface load
2. saltation
3. suspended load
49
describe the main types of loads in wind erosion
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
what type of clast cannot be lifted and moved by wind
coarse clasts
51
how do large deposits of sediments form
when finer sediment is removed
52
what is desert pavement
a surface layer of stones which is resistant to erosion
53
is desert pavement susceptible to erosion
NO
54
ventifacts vs yardangs
ventifacts
- rocks pitted, grooved or polished by wind abrasion
- caused by dust suspended by wind
yardangs
- wind sculpted bedrock
55
sand blasting
rock or other solid object blasted by sand and dust particles suspended and being move through saltation (jumping)
56
two forms of wind erosion
deflation
abrasion
57
contrast abrasion and deflation
deflation
- REMOVAL of material by wind transport
abrasion
- mechanical WEATHERING of rock by wind blow sand
58
what is left behind by deflation
large rock particles that are densely packed (desert pavement)
59
what is removed by deflation
the top layer of fine very dry soil
60
what mechanism commonly forms desert pavement
deflation
61
when do blowout occur
when wind picks up dry fine grained sediment and leaves behind exposed areas
62
what is vegetation called that remains in place as a blowout forms
pilar
63
dunes
windblown accumulations of sand
64
when does wind deposition occur
when wind velocity decreases
65
two sides to a dune
windward side: side the wind blows (GENTLE SLOPE)
leeward side: side protected from wind (STEEP SLOPE)
66
two types of wind deposition
1. dunes
2. loess
67
what direction do dunes move
direction of wind movement
68
types of dunes
1. star
2. barchan
3. transverse
4. longitudinal
5. parabolic
69
what factors determine shape of dunes
1. available sand
2. wind velocity
3. wind direction
4. amount of vegetation present
70
what direction does sand move in dunes
from windward side to leeward side
71
what is loess
deposition of very fine grain material (silt and clay)
72
what is loess thought to be derived from in Europe/NA
glacial and periglacial sources
73
what is loess thought to be derived from in China
desert sources
74
barchan dune is what shaped
crescent shaped
75
where does the horn point in Barchan dune
downwind
76
where is the steep side on Barchan dune
concave side
77
describe wind movement in Barchan dune
moves in ONE direction
78
describe supply of sand needed in Barchan dunes
short supply
79
type of dune
barchan
80
type of dune
Barchan
81
describe shape of parabolic dune
deeply curved
82
describe horns in parabolic dune
anchored by vegetation
83
describe movement of wind in parabolic dune
one direction
84
describe strength of wind in parabolic dune
strong winds
85
what amount of sand is needed for parabolic dune
large sand supply
86
describe how parabolic dunes are opposite barchan dunes
their convex side is facing downwind NOT the concave side
87
type of dune
parabolic
88
describe shape of transverse dunes
straight and elongated
89
describe transverse dunes to wind direction
perpendicular to the wind direction
90
amount of sand needed for transverse dunes
large supply
91
types of dune
transverse dune
92
describe shape of longitudinal dunes
extremely long, high and straight
93
describe longitudinal dunes with wind direction
parallel to wind direction
94
type of dune
longitudinal
95
describe shape of star dune
center with radiating arms
96
describe wind direction for star dunes
changing directions
97
types of desert deposition
alluvial fans
playas
98
describe how sediments change in alluvial fans
near source: coarse sediments
away from source: finner
99
playas
desert lake that have no outlet streams which collect drainage from flash floods
