Deck 21: Dry Settings: the Geology of Deserts

Question 1

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

A)greater in humid climates than in deserts,because dry desert soils can soak up all of 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 deserts and in humid climates

Answer 1

B

Question 2

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

Answer 2

A

Question 3

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

Answer 3

B

Question 4

Vegetation in the desert consists of ____________.

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

Question 5

Most regions that are now deserts have _____________.

A)been deserts throughout the geologic past
B)experienced other climates in the geologic past

Question 6

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

Question 7

Desert varnish consists of ____________.

A)pesticide and other pollutant residues
B)dusts of iron and magnesium oxides
C)dust deposits affected by microorganisms
D)carbonate cements with iron impurities,for example,siderite.

Question 8

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

Question 9

Some of the physiographic features that cause extreme aridity may be found together within a single desert,but the deserts found in the western United States are primarily due to 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

An arroyo is a steep-sided,linear trough produced by ____________.

A)normal faulting or other extensional processes
B)wind erosion of more susceptible layers
C)scouring erosion by water and sediment during flash floods
D)cliff retreat

Question 11

The highest recorded temperature on 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 12

The most expansive hot deserts on 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

Question 13

The Atacama of 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 14

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 15

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 16

As compared to humid climates,rates of chemical weathering in deserts are ____________.

A)much faster
B)much slower
C)very similar

Question 17

The Gobi of 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

Which statement about desert life is correct?

A)Mammals,unlike reptiles and birds,very rarely inhabit deserts.
B)Mammals are the most common desert inhabitants among vertebrates,and are most active at midday.
C)Mammals survive in deserts,but are less conspicuous than birds and reptiles because they are generally less active at midday.
D)Herbivorous mammals are found in desert environments,whereas carnivorous mammals are not.

Question 19

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 20

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

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

Question 21

The geometry of sand dunes is strongly influenced by the ____________.

A)strength of the wind
B)consistency of wind direction
C)abundance of sand
D)All of the above are correct.

Question 22

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

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

Question 23

In most deserts,the scarcity of rainfall means that the majority of physical weathering and erosion is accomplished by the wind.

Question 24

Although deserts have historically been sparsely populated regions,the arid southwestern states have comprised one of the fastest-growing regions in the United States since World War II.

Question 25

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

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

Question 26

Chimneys (also called hoodoos)and yardangs differ in that ____________.

A)yardangs are formed by erosion of water and chimneys by evaporation
B)chimneys are formed by evaporation and yardangs by erosion of water
C)chimneys are fossilized trunks of saguaro and other large cactus,and yardangs are not
D)chimneys are remnants of physical erosion and yardangs are remnants of wind erosion

Question 27

Which of the following are adaptations of plants that help them survive in deserts?

A)a thick waxy outer coating and needle-like 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)All of the above are correct.

Question 28

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 wind
D)the mixing of mineral sand and salt to form a weakly cemented soil

Question 29

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 30

Calcrete (caliche)forms in desert climate through the dissolution and reprecipitation of ____________ during and after rainstorms.

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