Question 1

If the two counterclockwise ocean current cells shown below were to reverse their directions of flow,what would happen to the Atacama and Namib deserts?

Accepted Answer

A)  Each would probably become larger and drier. 
B)  There would probably be no significant change to them. 
C)  They would probably experience more rainfall and might disappear. 
D)  They would probably experience tectonic subsidence. 
A)  Each would probably become larger and drier. 
B)  There would probably be no significant change to them. 
C)  They would probably experience more rainfall and might disappear. 
D)  They would probably experience tectonic subsidence. C

Question 2

Based on the figure below,do deserts tend to form where air is moving up from or down toward Earth's surface?

Accepted Answer

A)  Deserts appear to be more common where air is rising up from the Earth's surface. 
B)  Deserts appear to be more common where air is sinking down toward the Earth's surface. 
C)  Deserts appear to be more common where air is traveling parallel with the Earth's surface. 
D)  The location of deserts does not have any relation to the direction of air travel. 
A)  Deserts appear to be more common where air is rising up from the Earth's surface. 
B)  Deserts appear to be more common where air is sinking down toward the Earth's surface. 
C)  Deserts appear to be more common where air is traveling parallel with the Earth's surface. 
D)  The location of deserts does not have any relation to the direction of air travel. B

Question 3

The downwind side of a dune is called the _____________.

Accepted Answer

A)  lee face 
B)  depositional slope 
C)  slip face 
D)  lag face 
A)  lee face 
B)  depositional slope 
C)  slip face 
D)  lag face C

Question 4

Which of the following is NOT a subtropical desert?

Accepted Answer

A)  the Kalahari 
B)  the Atacama 
C)  the Australian 
D)  the Arabian 
A)  the Kalahari 
B)  the Atacama 
C)  the Australian 
D)  the Arabian

Question 5

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

Accepted Answer

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 
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 6

Why do the sand dunes in the west vary from those in the east in the figure below?

Accepted Answer

A)  The average size of the sand clasts differs in the two areas. 
B)  There is slightly more rain to the east. 
C)  The material to the east is closer to an igneous-rock source area, from which the dune sediment is significantly derived. 
D)  The winds are predominantly in one direction in the west but blow more complexly in the east. 
A)  The average size of the sand clasts differs in the two areas. 
B)  There is slightly more rain to the east. 
C)  The material to the east is closer to an igneous-rock source area, from which the dune sediment is significantly derived. 
D)  The winds are predominantly in one direction in the west but blow more complexly in the east.

Question 7

What is a playa?

Accepted Answer

A)  an outcropping of bedrock within a large area of alluvium, soil, or sediment 
B)  a sand dune formed when winds blow predominantly from two different directions oriented at approximately 90 degrees to one another 
C)  a narrow gully or small canyon that intermittently contains flowing surface water 
D)  the lowest point of a basin that contains fine sediments, evaporate minerals, and occasionally standing water 
A)  an outcropping of bedrock within a large area of alluvium, soil, or sediment 
B)  a sand dune formed when winds blow predominantly from two different directions oriented at approximately 90 degrees to one another 
C)  a narrow gully or small canyon that intermittently contains flowing surface water 
D)  the lowest point of a basin that contains fine sediments, evaporate minerals, and occasionally standing water

Question 8

Which of the following is NOT true regarding wind as the primary agent of erosion in most deserts?

Accepted Answer

A)  Air masses move differently over deserts, resulting in higher pressure gradients and greater winds. 
B)  There are fewer trees, shrubs, and grasses to slow the winds, and so wind blows right over the soil/ground surface, easily eroding it. 
C)  There are fewer plant roots, to help bind soil in place. 
D)  The low soil moisture means that sand-size particles are more easily separated and blown away from one another. 
A)  Air masses move differently over deserts, resulting in higher pressure gradients and greater winds. 
B)  There are fewer trees, shrubs, and grasses to slow the winds, and so wind blows right over the soil/ground surface, easily eroding it. 
C)  There are fewer plant roots, to help bind soil in place. 
D)  The low soil moisture means that sand-size particles are more easily separated and blown away from one another.

Question 9

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

Accepted Answer

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

Question 10

Two means of sediment transport by wind are ____________.

Accepted Answer

A)  sand load and silt load 
B)  wind load and storm load 
C)  dune load and storm load 
D)  bed load and suspended load 
A)  sand load and silt load 
B)  wind load and storm load 
C)  dune load and storm load 
D)  bed load and suspended load

Question 11

Why are there few or no deserts within 5 degrees latitude of the equator,even though this latitude averages the highest amount of sunlight of any latitiude on Earth?

Accepted Answer

A)  because the equator itself crosses almost no land masses 
B)  because the Amazon, Nile, Congo and Mekong rivers carry sufficient water to stabilize lands at these latitudes 
C)  because warm air rises up from the Earth at the equator, and hence rainfall is high 
D)  because cool air from the upper atmosphere sinks down to the land or sea surface at these latitudes 
A)  because the equator itself crosses almost no land masses 
B)  because the Amazon, Nile, Congo and Mekong rivers carry sufficient water to stabilize lands at these latitudes 
C)  because warm air rises up from the Earth at the equator, and hence rainfall is high 
D)  because cool air from the upper atmosphere sinks down to the land or sea surface at these latitudes

Question 12

How does a blowout differ from a lag deposit?

Accepted Answer

A)  A blowout is formed by saltative eruption of fine sediment. 
B)  A lag deposit is represented by a physical depression or low point in the ground surface. 
C)  A lag deposit forms in a wadi or desert wash, when briefly present floodwaters remove fine sediment and sand. 
D)  A blowout is an area where the removal of sediment by wind has lowered the ground surface. 
A)  A blowout is formed by saltative eruption of fine sediment. 
B)  A lag deposit is represented by a physical depression or low point in the ground surface. 
C)  A lag deposit forms in a wadi or desert wash, when briefly present floodwaters remove fine sediment and sand. 
D)  A blowout is an area where the removal of sediment by wind has lowered the ground surface.

Question 13

Saltation of sand involves ____________.

Accepted Answer

A)  spherical grains rolling along the surface of dunes 
B)  grains traveling short distances (approximately 0.5 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 
A)  spherical grains rolling along the surface of dunes 
B)  grains traveling short distances (approximately 0.5 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 14

Which of the following is NOT a component of desert varnish?

Accepted Answer

A)  manganese oxide 
B)  iron oxide 
C)  clay 
D)  calcium oxide 
A)  manganese oxide 
B)  iron oxide 
C)  clay 
D)  calcium oxide

Question 15

It appears as if more recent channels in the alluvial fan complex shown below are lighter in color than the general surface of the fan.What geologic process could have caused this effect?

Accepted Answer

A)  removal of desert-varnished clasts during formation of the channels, thus exposing less varnished and lighter colored material 
B)  the longer and bigger growth of plants on the areas between the recent channels, which from this far away cause the intrachannel areas to appear darker 
C)  transport of a large amount of dark-colored material out of the canyons during recent storms 
D)  the formation of inselbergs 
A)  removal of desert-varnished clasts during formation of the channels, thus exposing less varnished and lighter colored material 
B)  the longer and bigger growth of plants on the areas between the recent channels, which from this far away cause the intrachannel areas to appear darker 
C)  transport of a large amount of dark-colored material out of the canyons during recent storms 
D)  the formation of inselbergs

Question 16

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

Accepted Answer

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

Question 17

In this high-altitude photo of a desert,what are the dark grey features in the bottom right of the photo? Hint: The area that looks like water flowing from top right to bottom left of the photo is not water.

Accepted Answer

A)  volcanoes 
B)  chimneys 
C)  inselbergs 
D)  cuestas 
A)  volcanoes 
B)  chimneys 
C)  inselbergs 
D)  cuestas

Question 18

Drawing upon information in this chapter and previous chapters,which of the following would NOT be a reason why flowing water "dries up" so quickly in deserts?

Accepted Answer

A)  The stream-bottom sediments are often coarse particles with correspondingly large pore spaces between them, allowing water to quickly infiltrate downward. 
B)  The water table in the desert is usually deep and is not close to the ground surface. 
C)  The air is usually dry, and so evaporation rates are usually high. 
D)  The desert-adapted vegetation common in dry washes, arroyos, wadis, and the like, has a very high initial water uptake in order to store water for dryer periods, and the roots literally "soak up water." 
A)  The stream-bottom sediments are often coarse particles with correspondingly large pore spaces between them, allowing water to quickly infiltrate downward. 
B)  The water table in the desert is usually deep and is not close to the ground surface. 
C)  The air is usually dry, and so evaporation rates are usually high. 
D)  The desert-adapted vegetation common in dry washes, arroyos, wadis, and the like, has a very high initial water uptake in order to store water for dryer periods, and the roots literally "soak up water."

Question 19

A rock that has been significantly reshaped on multiple surfaces by saltation-related processes and sometimes has concavely shaped surfaces separated by sharp edges is a(n)__________________.

Accepted Answer

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

Question 20

Which of these was NOT a contributing cause of the desertification of the Sahel?

Accepted Answer

A)  higher-than-normal temperatures 
B)  increased grazing 
C)  increased farming 
D)  disease-related death of the predominant grass types 
A)  higher-than-normal temperatures 
B)  increased grazing 
C)  increased farming 
D)  disease-related death of the predominant grass types

Exam 17: Dry Regions: the Geology of Deserts

If the two counterclockwise ocean current cells shown below were to reverse their directions of flow,what would happen to the Atacama and Namib deserts?

Based on the figure below,do deserts tend to form where air is moving up from or down toward Earth's surface?

The downwind side of a dune is called the _____________.

Which of the following is NOT a subtropical desert?

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

Why do the sand dunes in the west vary from those in the east in the figure below?

What is a playa?

Which of the following is NOT true regarding wind as the primary agent of erosion in most deserts?

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

Two means of sediment transport by wind are ____________.

Why are there few or no deserts within 5 degrees latitude of the equator,even though this latitude averages the highest amount of sunlight of any latitiude on Earth?

How does a blowout differ from a lag deposit?

Saltation of sand involves ____________.

Which of the following is NOT a component of desert varnish?

It appears as if more recent channels in the alluvial fan complex shown below are lighter in color than the general surface of the fan.What geologic process could have caused this effect?

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

In this high-altitude photo of a desert,what are the dark grey features in the bottom right of the photo? Hint: The area that looks like water flowing from top right to bottom left of the photo is not water.

Drawing upon information in this chapter and previous chapters,which of the following would NOT be a reason why flowing water "dries up" so quickly in deserts?

A rock that has been significantly reshaped on multiple surfaces by saltation-related processes and sometimes has concavely shaped surfaces separated by sharp edges is a(n)__________________.

Which of these was NOT a contributing cause of the desertification of the Sahel?

The Earth in Context

The Way the Earth Works: Plate Tectonics

Patterns in Nature: Minerals

Up From the Inferno: Magma and Igneous Rocks

The Wrath of Vulcan: Volcanic Eruptions

Pages of Earths Past: Sedimentary Rocks

Metamorphism: a Process of Change

A Violent Pulse: Earthquakes

Crags, cracks, and Crumples: Crustal Deformation and Mountain Building

Deep Time: How Old Is Old

A Biography of Earth

Riches in Rock: Energy and Mineral Resources

Unsafe Ground: Landslides and Other Mass Movements

Streams and Floods: the Geology of Running Water

Restless Realm: Oceans and Coasts

A Hidden Reserve: Groundwater

Amazing Ice: Glaciers and Ice Ages

Global Change in the Earth System

Rock Groups

A Surface Veneer: Sediments and Soils

The Rock Cycle

The Earths Interior Revisited: Insights From Geophysics

Memories of Past Life: Fossils and Evolution

An Introduction to Landscapes and the Hydrologic Cycle

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