Deck 18: Deserts and Winds

Question 1

In a dry, fault-originated, basin and range area like the Okanagan Valley of BC and Washington, which environmental conditions are associated with steep mountain slopes and ephemeral streams?

A)Faulting is probably still active in the mountain rain shadow, producing a semi-arid climate.
B)Faulting ceased millions of years ago, resulting in an arid desert.
C)Faulting is probably still active, resulting in a steppe area with a rainy season.
D)Faulting ceased millions of years ago, resulting in moderate rainfall but very hot climate.

Answer 1

A

Question 2

Which one of the following is the best measure of the wetness or dryness of a region?

A)total annual precipitation
B)mean annual temperature
C)difference between annual precipitation and evaporation potential
D)percentage of precipitation that falls during the summer months

Answer 2

C

Question 3

Which Canadian dryland area receives the least precipitation (<50 mm/yr)?

A)SE Alberta and SW Saskatchewan
B)eastern Arctic especially Ellesmere Island, Nunavut
C)Okanagan Valley, B.C.
D)central Yukon

Answer 3

B

Question 4

Desert and steppe lands cover about what percentage of Earth's land area?

A)10%
B)66%
C)30%
D)3%

Question 5

Stream channels in dry lands that only carry water in response to infrequent rainfall or snowmelt events are called ________.

A)ephemeral
B)playas
C)rills
D)washboards

Question 6

How are sand grains transported by the wind?

A)high in the moving air column as suspended load
B)by saltation as bed load in the first metre above the land surface
C)by deflation of abraded desert pavement
D)by being picked up in swirling dust devils and carried to distant blowouts

Question 7

Rainshadow deserts are common in the lee of major mountain ranges such as in ________.

A)vast, dry, steppe lands like the Great Plains and central America
B)north central Africa
C)the dry valleys of the Okanagan and farther south in eastern California and Nevada
D)Europe north of the Alps

Question 8

What is the cause of Canada's Arctic deserts like those on Cornwallis and Ellismere Islands?

A)permanent high pressure and dry north polar easterlies
B)a rainshadow from the Mackenzie Mountains in the Northwest Territories
C)overgrazing by musk oxen and melting of the Arctic ice cap
D)subtropical high from the descending limb of the Tropic of Cancer's Hadley cell

Question 9

Which exerts the greatest amount of erosion and sculpting of landforms in deserts?

A)fast moving, descending, dense, cold dry air from the upper atmosphere
B)rainfall and running water
C)suspended silt load in perpetual dust storms of traversing winds
D)saltating bed load sand in great sandstorms of traversing winds

Question 10

Which of the following best describes the climatic factors that cause low latitude deserts like the Sahara in Africa?

A)Cool, dry air aloft is descending; surface winds are blowing toward the equator.
B)Warm, humid air aloft is descending; surface winds blow away from the equator.
C)Warm, humid air is rising; surface winds are calm.
D)Cool, dry air at the surface is rising causing winds to blow away from the equator.

Question 11

Most dry lands lie between ________ degrees north and south of the equator.

A)40 and 50
B)20 and 30
C)5 and 10
D)0 and 5

Question 12

Which of the following statements about deserts is true?

A)Although rainfalls are infrequent, erosional and deposition related to water is important in deserts
B)Deserts are located where there are ascending air masses and low atmospheric pressure
C)Deserts are defined by their sand content
D)Deserts are always located in hot, humid coastal areas

Question 13

Which one of the following statements is true?

A)Desert landscapes are monotonous, relatively flat areas covered to various depths with sand.
B)Deserts and dry lands are concentrated in areas of ascending air masses and relatively low atmospheric pressures.
C)Despite infrequent rainfalls, erosional and depositional features of running water are important in desert landscapes.
D)Rainshadow deserts occur where air masses descend after first having risen to cross a mountain range.

Question 14

________ have rainfall amounts and soil moisture contents between those of true deserts and humid lands.

A)Tundras
B)Steppes
C)Shelves
D)Sabkhas

Question 15

Which one of the following statements concerning rock weathering is true?

A)Warm temperatures and high soil moisture contents accelerate chemical weathering.
B)Low temperatures and high soil moisture contents accelerate chemical weathering but inhibit mechanical weathering.
C)Warm temperatures and low soil moisture contents both promote rapid rates of mechanical weathering.
D)Low temperatures and low soil moisture contents promote oxidation.

Question 16

Which of the following drylands lies in the rainshadow caused by prevailing Pacific westerlies and the high peaks of the Coast Mountains and North Cascades?

A)Okanagan Valley
B)Atacama
C)Patagonian
D)Sonoran

Question 17

Which one of the following is a low-latitude desert characterized by high atmospheric pressures and descending air masses (not rain shadow deserts).

A)Sahara Desert; northern Africa
B)Atacama Desert in Chile, South America
C)Gobi Desert, China and Mongolia
D)desert valleys of the Great Basin, U.S.

Question 18

What is the cause of the Patagonian desert?

A)rainshadow from onshore south Pacific westerlies and high elevations of the Andes
B)major river diversion of Rio de Plata for irrigation in northern Argentina
C)subtropical high from descending limb of the Tropic of Capricorn's Hadley cell
D)permanent high pressure and dry south polar easterlies

Question 19

All of the following statements concerning dry lands are true except for?

A)Precipitation totals are low; dew points are lower in the summer than winter.
B)Evaporation potential exceeds actual precipitation.
C)Storms are infrequent and rainfall amounts are highly variable.
D)Wind is the dominant agent of erosion and sediment transport.

Question 20

Which one of the following concerning desert lands is false?

A)Less than 30 percent is covered with dunes and drifting sand.
B)Wind erosion and deposition are important processes.
C)Running water has little effect on shaping the landscape.
D)Most desert areas are characterized by descending wind patterns.

Question 21

All of the following are formed by abrasion except for a ________.

A)dune
B)glacial striation
C)ventifact
D)yardang

Question 22

________ dunes have scalloped sand ridges at right angles to prevailing winds with crescent-shaped slip faces pointing downwind.

A)Barchanoid
B)Star
C)Transverse
D)Parabolic

Question 23

Which one of the following statements about sand dunes is correct?

A)A dune migrates in the direction of inclination of the slip face.
B)The more gently sloping surface is the leeward slope of the dune.
C)Sand is blown up the slip face and rolls down the more gently sloping flank of the dune.
D)In a sand dune, the more gently inclined strata lie parallel to the slip face.

Question 24

________ refers to the "bouncing" mode of sand transport in a windstorm or stream.

A)Saltation
B)Ventifaction
C)Siltation
D)Deflation

Question 25

Which one of the following will effectively limit further deflation in a desert area?

A)sea level
B)desert pavement
C)the water table
D)the repose level

Question 26

A ________ is closed depression in an arid region caused by ________.

A)kettle hole, boiling desert springs
B)sinkhole, wind abrasion
C)U-shaped valley, drying chinook winds
D)blowout, deflation

Question 27

Which one of the following is determined by the angle of repose for dry sand?

A)longitudinal dune gradient angle
B)windward slope of a transverse dune
C)a vertical cut bank in loess
D)inclination angle of a dune slip face

Question 28

A single, crescent-shaped ________ dune is noted for slow rates of motion and tips pointing downwind.

A)barchan
B)transverse
C)longitudinal
D)parabolic

Question 29

________ dunes are linear sand ridges at right angles to the prevailing wind direction in coastal areas, with a steady supply of sand.

A)Transverse
B)Barchan
C)Longitudinal
D)Parabolic

Question 30

Assume that the central slip face of a barchan dune slopes downhill toward the east.What is the direction of the prevailing wind?

A)east to west
B)north to south
C)south to north
D)west to east

Question 31

How is desert pavement formed?

A)Deflation and sheet wash remove fine-sized materials leaving coarse, weathered, rock fragments concentrated at the surface.
B)Blowing wind removes fine-size soil particles; coarser particles abrades to sand size.
C)Running water deposits gravel and sand over the finer-sized soil particles.
D)Intense chemical weathering removes the sand- and silt-sized particles, leaving coarse rock debris covering the land surface.

Question 32

During a typical sandstorm, saltating sand grains reach a maximum height of about ________ above the land surface.

A)1 centimetre
B)1 metre
C)10 centimetres
D)10 metres

Question 33

Which of the following statements about wind transport is true?

A)Wind can transport boulders by saltation.
B)Wind cannot carry clay particles because they are too small.
C)Dust from the Sahara Desert can be carried across the Atlantic Ocean.
D)Saltation knocks down cacti up to 5 metres high.

Question 34

Assume that the slip face of a transverse dune slopes downhill toward the south.What is the direction of the prevailing wind?

A)east to west
B)north to south
C)south to north
D)west to east

Question 35

Wind transported bed load along the desert floor is called ________.

A)surface creep
B)desert crawl
C)floor migration
D)bed shimmy

Question 36

A ________ is formed by abrasion of rocks by windblown sand.

A)playa
B)ventifact
C)pediment
D)desert pavement

Question 37

Which type of dune resembles a transverse dune with scalloped edges pointing downwind?

A)parabolic
B)barchanoid
C)barchan
D)hemorrhoid

Question 38

What is the angle of repose for dry sand?

A)6°
B)10°
C)34°
D)67°

Question 39

Which one of the following would probably not affect the size and depth of a blowout?

A)a rise in sea level
B)a near surface water table
C)type and density of vegetation
D)areas of desert pavement

Question 40

A ________ is a crescent-shaped dune whose tips point downwind.

A)parabolic
B)transverse
C)barchan
D)star

Question 41

________ dunes are linear sand ridges roughly parallel to the prevailing wind direction in areas of moderate sand supply.

A)Longitudinal
B)Barchan
C)Transverse
D)Parabolic

Question 42

Rain shadow deserts occur mainly at middle latitudes.

Question 43

A dry climate is one in which yearly precipitation is not as great as the potential loss of water by evaporation.

Question 44

Running water is an important erosional agent in many arid lands despite infrequent rainfalls.

Question 45

Intermittent streams in dry areas of the western United States are called ephemeral.

Question 46

The tips of ________ dunes point upwind and commonly result from persistent, onshore winds in certain coastal areas.

A)parabolic
B)barchan
C)longitudinal
D)transverse

Question 47

Assume that the central slip face of a parabolic dune slopes downhill toward the west.What is the direction of the prevailing wind?

A)east to west
B)north to south
C)south to north
D)west to east

Question 48

Deposition of glacial silt from blowing winds near the ice front was responsible for ________.

A)deflation ventifacts
B)blowout pavement
C)star steppes
D)loess deposits

Question 49

About one-third of the Earth's land areas have arid to semiarid climates.

Question 50

Deserts between 30 and 45 degrees of latitude are more extensive in the southern hemisphere than in the northern hemisphere.

Question 51

Which type of dune can be up to 90 metres tall and forms under variable wind directions?

A)parabolic
B)transverse
C)barchan
D)star

Question 52

Saltation refers to evaporation of shallow, muddy waters from a playa lake.

Question 53

Steppes are the driest of the true desert lands.

Question 54

________ dunes are long, high, sand dunes parallel with the prevailing wind direction.

A)Subliminal
B)Longitudinal
C)Latitudinal
D)Transvestual

Question 55

Assume that a longitudinal dune field has its dune crests oriented north-south, with a few dunes having hooked ends closed to the north, or branching, nearly parallel ridges opening to the south.What is the direction of the prevailing wind?

A)east to west
B)north to south
C)south to north
D)west to east

Question 56

Loess deposits in the central United States and Columbia Plateau ________.

A)blew in from the dry areas in the Great Plains and southwestern desert areas
B)originated as silt sized particles in Canadian Pleistocene glacial outwash streams and freshly exposed till
C)accumulated from flooding of the Mississippi River
D)were originally deposited as barchanoid dunes and later redeposited by glaciers

Question 57

________ are complexly shaped dunes in the Sahara or Arabian deserts, formed in response to different, seasonal, wind directions.

A)Star
B)Barchan
C)Transverse
D)Parabolic

Question 58

Sand is transported by saltation both in running water and by blowing winds.

Question 59

Canada's only non-polar desert occurs in the southern Okanagan Valley of British Columbia.

Question 60

Multiple, connected, crescent-shaped coastal ________ dunes have tips pointing upwind, towards the beach.

A)parabolic
B)barchan
C)transverse
D)longitudinal

Question 61

Yardangs are streamlined, wind-sculpted ridges oriented parallel to prevailing wind direction.

Question 62

Desert pavements keep forming because deflation of the desert floor cannot be stopped.

Question 63

Transverse dunes are oriented at right angles to a shoreline.

Question 64

Blowouts are broad, shallow depressions excavated by deflation.

Question 65

Barchanoid dunes form scalloped rows of sand oriented perpendicular to wind direction.

Question 66

The steeper lee slope of a sand dune is called the slip face.

Question 67

Star dunes are isolated hills of sand formed by changing wind directions.

Question 68

In North America, loess deposits are found mainly in the dry to semiarid lands of southwestern United States and northern Mexico.

Question 69

Ventifacts are wind-abraded blowouts exceeding one kilometre in diameter.

Question 70

Sand dunes cover more than 50 percent of most desert lands.

Question 71

The dissolved load in wind is more concentrated than in streams.

Question 72

Wind is viscous enough to lift sediment grains by suction alone.

Question 73

Wind turbines 10 metres above the ground surface are subjected to relatively little abrasion by blowing sand.

Question 74

The loess in western China was derived from windblown, glacial silt and rock flour.

Question 75

Windblown loess, like sand, typically accumulates as mound-like dunes.

Question 76

Like barchans, the tips of a parabolic dune point downwind.

Question 77

Suspended load in wind includes boulders.

Question 78

The tips of a barchan dune point downwind.

Question 79

Loess consists mainly of silt-sized particles.

Question 80

The slip face of a barchan dune made of medium sand is steeper than the slip face of medium sand in a transverse dune.