Deck 17: Dry Regions: the Geology of Deserts

Question 1

The definition of a desert depends on a region's ________.

A) latitude
B) elevation
C) aridity
D) temperature

Answer 1

C

Question 2

The figure below illustrates the formation of a ________.

A) coastal desert
B) subtropical desert
C) rain-shadow desert
D) continental-interior desert

Answer 2

A

Question 3

Why is water a very effective agent of erosion in deserts?

A) The action of running water is not lessened by vegetation cover in deserts.
B) The hotter water temperature in deserts carries more energy.
C) Deserts have many more small streams than other landscapes.
D) Slopes are steeper in deserts,making running water more powerful.

Answer 3

A

Question 4

The Atacama Desert in Chile is a desert primarily because it is located ________.

A) in the subtropics
B) near the South Pole
C) near the center of a large continent
D) next to a cold ocean current

Question 5

Deserts represent ________ of the Earth's land surface.

A) less than 5 percent
B) about 10 percent
C) about 25 percent
D) more than 50 percent

Question 6

Isolated mountains that stick up above large expanses of desert alluvium are called

A) inselbergs
B) playas
C) mesas
D) desert pavement

Question 7

The petroglyph in the image below is carved into _______,revealing the lighter-colored bedrock underneath.

A) basalt
B) desert varnish
C) caliche
D) salt

Question 8

Many desert streams are ephemeral,meaning

A) they are supplied by groundwater and not by rainfall.
B) they only carry water after rainfall events,and most of the time they are dry streambeds.
C) they only occur on north-facing slopes.
D) they quickly evaporate when the sun is shining.

Question 9

The Great Basin deserts found in the western United States are primarily the result of being located ________.

A) in the subtropics
B) within the rain shadow of one or more mountain ranges
C) near the center of a large continent
D) next to a cold ocean current

Question 10

What is the main feature of atmospheric circulation at 20° to 30° north and south latitude?

A) Cool,dry air sinks,becoming drier as it heats up.
B) Warm,moist air rises,increasing in relative humidity as it rises.
C) Warm,dry air rises,becoming cooler.
D) Cool moist air sinks,providing abundant rainfall.

Question 11

To qualify as a desert,a region must ________.

A) be hot,with a mean annual temperature greater than 25°C (77°F)
B) be arid,with less than 15 percent of the ground surface vegetated
C) have a mean annual temperature greater than 25°C and less than 5 cm annual rainfall
D) have no rainfall three out of four seasons

Question 12

The highest recorded temperatures on the Earth occur in

A) mid-latitude,rain shadow deserts.
B) mid-latitude,continental interior deserts.
C) low-latitude,low-elevation rainforests.
D) low-latitude,low-elevation deserts.

Question 13

Continental interior deserts occur because

A) there are no rivers in the interior of continents to provide water vapor.
B) air masses lose much of their moisture before reaching continent interiors.
C) continent interiors are located at low latitudes where air rises.
D) atmospheric circulation in the interior of continents is characterized by dry sinking air masses.

Question 14

Caliche and calcrete are terms for

A) economically important cement mineral resources mined from desert regions.
B) unique desert soils where grains of regolith are cemented together.
C) dark mineral deposits that develop on rock exposures in deserts.
D) faceted rocks carved by wind erosions in desert landscapes.

Question 15

Coastal region deserts are most likely to occur along coastlines adjacent to ________ ocean currents.

A) warm
B) cold
C) upwelling
D) nutrient-rich

Question 16

The Gobi in Mongolia is a desert primarily because it is located ________.

A) in the subtropics
B) in a polar region
C) near the center of a large continent
D) next to a cold ocean current

Question 17

The colors of the landscape in desert regions are controlled by ________.

A) what type of desert it is
B) the air temperature
C) the season of the year
D) the composition of the bedrock

Question 18

Much of the land area north of the Arctic Circle is considered to be a desert because

A) summer temperatures can get very hot.
B) the Arctic Ocean provides cold water currents.
C) it is extremely arid.
D) there is no rain; only snowfall.

Question 19

Desert climates associated with a rain shadow are found ________.

A) on the windward side of mountain ranges
B) on the leeward side of mountain ranges
C) in the middle of flat plains
D) along continental coastlines

Question 20

A desert may form along a coastline because a ________.

A) warm current warms and dries the air
B) warm current forces hot air inland
C) cold current cools and dries the air
D) cold current forces hot air inland

Question 21

Talus aprons represent accumulations of ________.

A) angular debris at the base of a hill
B) lag deposits
C) coarse sediment in a deflation basin
D) loess at the edge of a desert

Question 22

Playas are important resources for minerals such as

A) feldspar.
B) olivine.
C) borax.
D) quartz.

Question 23

What is talus?

A) thick crusts of cemented soil
B) angular rocky debris at the base of a cliff
C) the formal term for sand dunes
D) rocks with faceted faces abraded by wind

Question 24

A(n)________ consists of sand and gravel deposited by ephemeral distributary channels that occur where a gully or a canyon discharges from its mouth.

A) alluvial fan
B) ventifact
C) wadi
D) yardang

Question 25

Which letter corresponds to talus in this image?

A) A
B) B
C) C
D) D

Question 26

Wind-carved elaborate mounds and ridges are termed ________.

A) mirages
B) caliches
C) sabkhas
D) yardangs

Question 27

What is a ventifact?

A) a bowl-like depression carved by wind
B) an exposed rock with facets carved by wind
C) a tool left by former civilizations that lived in deserts
D) coarse-grained sediments that are not carried in desert dust storms

Question 28

In the figure below,the sand grains are being transported by ________.

A) suspension
B) saltation
C) surface creep
D) deflation

Question 29

The slope of a pile of talus is typically _______ than the slope of an alluvial fan.

A) less irregular
B) less steep
C) steeper
D) more stable underfoot

Question 30

The figure below demonstrates the formation of a surface layer of coarse material on the surface in deserts called

A) a blowout deposit.
B) a lag deposit.
C) an arroyo.
D) badlands.

Question 31

Which of the following describes sediment deposition in alluvial fans?

A) It is where streams in valleys are dammed by large mountains.
B) It is where streams sink into the subsurface and drop their sediment load.
C) It is where dunes pile sediment against the base of a mountain.
D) It is where the slope of the stream decreases and the water slows.

Question 32

Over time,alluvial fans may merge to form a ________.

A) wadi
B) talus apron
C) playa
D) bajada

Question 33

A salt-rich flat lake bed in called a

A) wadi.
B) pediment.
C) playa.
D) bajada.

Question 34

Alluvial fans accumulate in deserts at the mouth of ________

A) canyons
B) sand dunes
C) playas
D) talus slopes

Question 35

The process of lowering the land surface by wind erosion is known as ________.

A) saltation
B) deflation
C) desertification
D) escarpment

Question 36

A mesa is most likely to form if the underlying bedrock is

A) folded sedimentary rock.
B) fault-tilted sedimentary rock.
C) flat-lying sedimentary rock.
D) igneous rock.

Question 37

Why are salt lakes salty?

A) because desert streams carry very salty water
B) because mineral springs deliver salt water to such lakes
C) because evaporation from the lakes removes water but not salt
D) because rainfall in deserts is salty

Question 38

Fine-grained sediments such as dust and silt can stay in the air and be transported by wind as ________.

A) suspended load
B) saltation
C) deflation clasts
D) desert varnish

Question 39

Most of the erosion in desert environments is caused by ________.

A) wind
B) surface water
C) groundwater
D) salt wedging

Question 40

Where would you go among the following to find a salt lake?

A) Florida
B) Utah
C) Michigan
D) Hawaii

Question 41

Explain the global-scale pattern of atmospheric circulation that leads to the formation of subtropical deserts.

Question 42

Why are flash floods so effective at transporting sediment?

Question 43

Areas with relatively scarce sand and constantly shifting winds will develop ________ dunes.

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

Question 44

What is the dominant erosional force in deserts: wind or water? Why?

Question 45

Plowing soil and overgrazing by livestock in arid regions can contribute to

A) loss of sand dunes.
B) growth of desert varnish.
C) accelerated soil erosion.
D) decreases in precipitation.

Question 46

Imagine you are a farmer moving into the Great Plains area after the Dust Bowl of the 1930s.What can you do to make the land fertile enough for farming again? What can be done to prevent a similar disaster from happening again?

Question 47

How can overpopulation contribute to desertification of a landscape?

Question 48

What is desert varnish? How does it form? Why doesn't one find desert varnish in humid climates?

Question 49

Conversion of productive land to desert is known as ________.

A) deflation
B) saltation
C) degradation
D) desertification

Question 50

The geometry of sand dunes is NOT strongly influenced by the ________.

A) strength of the wind
B) consistency of wind direction
C) abundance of sand
D) timing of the monsoon season

Question 51

Illustrate how a rain-shadow desert might form.

Question 52

Which of the following human activities will lead to desertification?

A) addition of fertilizer to soil
B) overgrazing by livestock in an area
C) over-irrigating an area
D) building a city in an area

Question 53

The movement of sand up the windward face of a dune and down the slip face causes

A) cross-bedding.
B) caliche.
C) desert pavement.
D) dust storms.

Question 54

Why is the dust derived from desert erosion a challenge to public health?

A) It suffocates plants that are downwind.
B) It can carry salts and toxic metals.
C) It contains carbon monoxide.
D) It reduces the oxygen in air.

Question 55

Which of the following hazards could lead to desertification?

A) climate change
B) earthquakes
C) landslides
D) flooding

Question 56

Contrast a lag deposit and desert pavement.

Question 57

What is a desert? Explain how a desert could be formed at one of the poles.

Question 58

The Sahel is a semiarid grassland south of the Sahara Desert that is experiencing

A) depopulation.
B) loss of desert pavement.
C) desertification.
D) seasonal flooding.

Question 59

Why is the Great Salt Lake in Utah so salty?

Question 60

Where in the United States were people affected by desertification during the Great Depression of the 1930s?

A) Appalachia
B) New England
C) Alaska
D) the western Great Plains