Question 1

"Desert pavement" results from ___________.

Accepted Answer

Desert pavement results from deflation, which is the removal of fine-grained particles by wind leaving behind larger rocks and pebbles. Over time, these larger particles become arranged in a tight mosaic-like pattern known as desert pavement. Choices B, C, and D are not responsible for the formation of desert pavement.

Question 2

How does a blowout differ from a lag deposit?

Accepted Answer

A blowout occurs when wind erosion removes sediment from an area, causing the ground surface to be lowered. A lag deposit, on the other hand, is formed when brief floodwaters remove fine sediment and sand, leaving behind coarser material in depressions or low points in the ground surface. Saltative eruptions of fine sediment are not related to either phenomenon.

Question 3

Which of the following is NOT necessary for the formation of calcrete?

Accepted Answer

Warm or hot daytime temperatures are not necessary for the formation of calcrete. The other three factors (leaching of soluble mineral constituents by water, precipitation of soluble mineral constituents, and the flow or wicking of water within the ground) are necessary for the formation of calcrete.

Question 4

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

Accepted Answer

Deserts have low humidity and little precipitation, which greatly slows down the chemical weathering process.

Question 5

Two other names for desert washes (dry gullies)are ____________.

Accepted Answer

The term "arroyo" is commonly used in the southwestern US, while "wadi" is more commonly used in the Middle East, but both refer to dry gullies or desert washes. The other options, barchans and inselbergs, refer to different landforms: barchans are crescent-shaped sand dunes, while inselbergs are isolated rock formations rising above a plain.

Question 6

Native Americans produced petroglyphs by etching into ____________.

Accepted Answer

Native Americans produced petroglyphs by etching into rocks that had been coated with desert varnish, a dark, often shiny layer that forms on the surface of the stone in arid environments. This technique allowed the lighter rock beneath to be exposed, creating a contrast that made the designs visible.

Question 7

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

The removal of desert-varnished clasts during the formation of channels would expose lighter colored material, causing the more recent channels to appear lighter in color compared to the general surface of the fan. Option B is unlikely as it suggests that plant growth only occurs in areas between recent channels, which is not always the case. Option C is unlikely as it suggests that a large amount of dark-colored material was transported out of the canyons during recent storms, which is not supported by the information provided in the image. Option D is not a plausible explanation for the lighter color of the recent channels in the alluvial fan complex.

Question 8

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 rock that has been significantly reshaped on multiple surfaces by saltation-related processes (such as wind-blown sand) is called a ventifact. These rocks often have concavely shaped surfaces separated by sharp edges, as the wind erodes away the softer parts of the rock, leaving behind harder ridges.

Question 9

Because of little rainfall,the majority of physical weathering and transport of sediments in deserts is accomplished by the wind.

Accepted Answer

The answer of Because of little rainfall,the majority of physical...

Question 10

Which feature in the the photo below would a geologist study to infer that running water was the primary agent to have formed the landscape in the photo?

Accepted Answer

The dendritic patterns in the photo are a characteristic feature of landforms that have been shaped by running water.

Question 11

Why would the Antarctic ventifact shown below be black?

Accepted Answer

The ventifact is black because it is coated with desert varnish. Desert varnish is a dark coating that forms on rocks in arid environments, such as the Antarctic.

Question 12

Which two terms go together?

Accepted Answer

Lag deposit and deflation go together because deflation is a geological process where wind removes finer particles, leaving behind coarser materials known as lag deposits.

Question 13

Two means of sediment transport by wind are ____________.

Accepted Answer

The answer of Two means of sediment transport by wind...

Question 14

Saltation of sand involves ____________.

Accepted Answer

Saltation of sand is the movement of grains traveling short distances (approximately 0.5 m) in the air by wind. The term "saltation" comes from the Latin word "saltus," which means "jumping." During saltation, sand grains are lifted into the air by wind, bounce off the surface, and then settle back down. This process contributes to the formation and movement of sand dunes.

Question 15

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

Desert-adapted vegetation typically has low water uptake to conserve water, not high initial uptake.

Question 16

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 ____________.

Accepted Answer

The deserts in the western United States, such as the Mojave and Sonoran Deserts, are primarily due to their location within the rain shadow of mountain ranges like the Sierra Nevada and Rocky Mountains. These ranges block moisture from reaching the regions to their east, leading to arid conditions.

Question 17

Which of these factors allows the bouncing of sand grains to exceed 0.5 m in height (off the ground)during saltation?

Accepted Answer

The answer of Which of these factors allows the bouncing...

Question 18

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

Accepted Answer

The answer of During heavy rainstorms,rates of physical weathering and...

Question 19

Desert varnish is caused by ____________.

Accepted Answer

Desert varnish is a dark coating found on rocks in arid regions, formed by the deposition of clay minerals and iron and manganese oxides, which are altered by microorganisms.

Question 20

Why is the land surface higher underneath the clumps of vegetation?

Accepted Answer

The answer of Why is the land surface higher underneath...

Quiz 17: Dry Regions: the Geology of Deserts