Deck 21: Dry Regions: the Geology of Deserts

Question 1

The Sahara is a desert primarily because it is located ________.

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

Answer 1

A

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

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

Answer 3

C

Question 4

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

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

Question 5

During heavy rainstorms,rates of physical weathering and erosion are ________.

A) greater in humid climates than in deserts because dry desert soils soak up all the available moisture
B) greater in deserts than in humid climates because soil tends to be more easily eroded in deserts than in humid regions
C) greater in humid climates than in deserts because vegetation tends to break up the soil
D) about equally fast in both deserts and humid climates

Question 6

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

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

Question 7

Desert climate associated with a rain shadow is 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 8

The 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 9

Very hot air just above the ground creates a wavering pool of light on the ground known as a(n)________.

A) sabkha
B) wadi
C) arroyo
D) mirage

Question 10

Compared with humid climates,the rates of chemical weathering in deserts are ________.

A) much faster
B) much slower
C) very similar
D) too variable to compare

Question 11

The most expansive hot deserts on the Earth occur in the ________.

A) tropics,at or near the equator
B) subtropics,between 20° and 30° north or south of the equator
C) temperate zone,between 30° and 50° north or south of the equator
D) latitudes higher than 50° north or south of the equator

Question 12

Coastal region deserts are most likely near ocean currents that are ________.

A) warm
B) cold
C) flowing east
D) flowing west

Question 13

Most hot deserts ________.

A) retain their high temperatures throughout the night because there is no vegetation to absorb heat from the sediment at the surface
B) cool off greatly at night because of sparse vegetation,dry air,and little cloud cover
C) cool off by no more than 8°C on most nights
D) gain additional heat at night because the desert air rises

Question 14

The measured rainfall shown in the figure below is characteristic of a ________.

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

Question 15

Deserts represent ________ of the Earth's land surface.

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

Question 16

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 17

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 18

According to the textbook,the highest recorded temperature on the Earth was in a ________.

A) tropical rainforest in Brazil
B) low-latitude,high-elevation desert in Mexico
C) high-latitude,high-elevation desert in Mongolia
D) low-latitude,low-elevation desert in Libya

Question 19

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% 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 20

At 30° north latitude,at the northern edge of tropical (Hadley)cell convection in the northern hemisphere,________.

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 21

Evaporite deposits in coastal,subtropical regions derived from the evaporation of seawater stranded above high tide are termed ________.

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

Question 22

Badlands are characterized by ________.

A) thick caliche crusts
B) closely spaced parallel drainages
C) sabkhas
D) perennial streams

Question 23

Native Americans produced petroglyphs by etching into ________.

A) rocks that had been subjected to case hardening
B) rocks that had been coated with desert varnish
C) dark basalts
D) obsidian

Question 24

Desert varnish consists of ________.

A) pesticide and other pollutant residues
B) thick coatings of iron and magnesium oxides
C) dust deposits affected by microorganisms
D) carbonate cements with iron impurities (e.g.,siderite)

Question 25

A mushroom-shaped landform consisting of a column of less-resistant rock supporting a broader extent of wind-resistant rock is termed a ________.

A) blowout
B) ventifact
C) wadi
D) yardang

Question 26

The saltation of sand involves ________.

A) spherical grains rolling along the surface of dunes
B) grains traveling short distances (approximately 1 m)in the air
C) grains traveling long distances (approximately 1-100 km)in the air by strong winds
D) the mixing of mineral sand and salt to form a weakly cemented soil

Question 27

When fine-grained sediment is blown away as shown in the figure below,the coarser sediment left behind is known as ________.

A) a sabkha
B) ventifacts
C) a lag deposit
D) talus

Question 28

Calcrete (caliche)forms in a desert climate through the dissolution and the re-precipitation of ________ during and after rainstorms.

A) manganese oxide
B) quartz
C) calcite
D) iron oxide

Question 29

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

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

Question 30

An apron-shaped pile of alluvium that forms at the mouth of a canyon is known as a(n)________.

A) playa
B) sabkha
C) alluvial fan
D) inselberg

Question 31

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 32

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

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

Question 33

A salt-encrusted muddy tidal flat is known as a ________.

A) wadi
B) pediment
C) sabkha
D) bajada

Question 34

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

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

Question 35

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 36

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

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

Question 37

As shown in the figure below,wind erosion can create a faceted rock known as a ________.

A) ventifact
B) lag deposit
C) yardang
D) wadi

Question 38

Fine-grained,wind-blown sediments are eventually deposited as ________.

A) loess
B) ventifacts
C) dunes
D) desert pavement

Question 39

A rock that has been significantly reshaped on multiple surfaces by windborne particles and sometimes has a sharp edge is a(n)________.

A) inselberg
B) ventifact
C) wadi
D) yardang

Question 40

What is an ephemeral stream?

A) A stream that flows perennially through the desert supporting lush vegetation.
B) A stream that flows perennially through the desert but supports little to no vegetation because of its high mineral content.
C) A desert stream that contains water only immediately following a rain event.
D) A steep-walled canyon that was formed by wind erosion.

Question 41

Why is the Great Salt Lake in Utah so salty?

Question 42

Conversion of productive land to desert is known as ________.

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

Question 43

The Dust Bowl event in 1933 resulted from which natural event?

A) overpopulation
B) long-term drought
C) global climate change
D) change in the course of rivers

Question 44

Which statement about desert life is correct?

A) Mammals,unlike reptiles and birds,very rarely inhabit deserts.
B) Animal life in the desert is limited to herbivores only.
C) Animals that live in the desert must be able to retain water and survive extreme temperatures.
D) Animals that live in the desert are only active at night when it is cooler.

Question 45

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

Question 46

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

Question 47

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

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

Question 48

Illustrate how a rain-shadow desert might form.

Question 49

Which of the following hazards could lead to desertification?

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

Question 50

Label the image below with the name of the type of sand dune shown.

Question 51

Which of the following human activities will lead to desertification?

A) addition of fertilizer to soil
B) diversion of water from an area
C) over-irrigating an area
D) building a city in an area

Question 52

Which of the following is NOT an adaptation of plants that helps them survive in deserts?

A) a thick waxy outer coating and needlelike leaves
B) shallow,expansive root systems that can uptake infiltrated water over a broad area
C) succulence (tissues that retain moisture for a long period of time)
D) thin-skinned seeds that can quickly germinate when it rains

Question 53

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

Question 54

Imagine you are a farmer moving into the Great Plains area after the Dust Bowl of 1933.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 55

After extensive erosion of a hill in a desert environment,the small remnant surrounded by alluvium-filled basins is known as a(n)________.

A) inselberg
B) hogback
C) questa
D) mesa

Question 56

Vegetation in the desert consists of ________.

A) cacti only
B) extensive grasslands with water-seeking deep roots
C) scattered succulents,such as cacti,with adaptations to obtain and retain as much water as they can
D) forests of tall,broad-leafed trees

Question 57

Contrast a lag deposit and desert pavement.

Question 58

Examine the images of the Aral Sea below.What happened and why?

Question 59

Deserts are defined as regions with minimal precipitation and vegetation that covers no more than 15% of the land surface.How are any plants able to survive in the desert? Describe two different adaptations.

Question 60

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