Geology Chapter 19

Which of the following desert landforms is carved from solid rock rather than consisting of accumulated sediments?

Inselberg

Match the desert landform with the correct definition. Drag the terms on the left to the appropriate blanks on the right.

Inselberg−bedrock knob sticking up through sediment-filled basin. Bajada−apron of sediment along the mountain front. Playa−dry, flat lake bed created by evaporation. Alluvial fan−cone of debris at the mouth of a canyon leaving the mountains.

How do sand dunes migrate?

Sand moves up the gentler side of the dune by saltation and accumulates just beyond the crest of the dune. As more sand collects, the slope steepens, and some of the sand slides down the slip face of the dune.

Based on the precipitation data available here, which region in Washington State would be the most likely location of a rainshadow desert?

Southeastern Washington

Which of the following accurately describes the Basin and Range region of the western United States?

a region with alternating mountains and basins that have been produced by normal faulting

Barchanoid dunes are an intermediate form of __________.

barchan and transverse dunes

Which of the following is a wind deposit?

barchan dune

What size sediment can be transported by wind? CHOOSE ALL THAT APPLY.

clay sand silt

What type of rocks would you expect to find in a playa lake depositional environment?

evaporites and claystone

An isolated, heavily eroded hill or mountain that rises abruptly from a plain is a(n) __________.

inselberg

Which dunes are formed under varying wind directions, but are dominantly parallel to the average direction?

longitudinal

Star dunes exhibit __________.

many ridges radiating from a central point

Desert regions occur __________, and always have a(n) __________ climate zone adjacent to them.

on every continent; steppe

When air __________, it is compressed and warmed.

sinks

Which of the following statements about deserts is true?

Although rainfalls are infrequent, erosion and deposition related to water are important in deserts.

What is the definition of an ephemeral stream?

An intermittent stream that only has water after specific episodes of rain

Which desert location in the United States consists of alternating mountain ranges and flat-bottomed valleys as a result of fault block mountains?

Basin and Range Province

Why does wind between the equator and 30 degrees south come out of the southeast?

Cooled air moves north toward the equator and is deflected toward the west by the Coriolis effect.

Within water-deficient regions, two climatic types are recognized. What are they?

Desert and steppe

What desert feature is visible in this image?

Desert pavement

What are the two primary sources for loess?

Deserts and glacial deposits

How does the rate of rock weathering in dry climates compare with the rate in humid regions?

Dry climates have much lower rates of chemical weathering and mechanical weathering than humid climates.

Which of the following statements characterizes ephemeral streams?

Ephemeral streams flow only at certain times of the year.

What term is used to describe the effect on air movement produced by Earth's rotation?

the Coriolis effect

Deserts that lie outside of the subtropics and mid-latitude belts are most likely the result of __________.

the presence of a rainshadow

Most of the erosion that took place during the "Dust Bowl" years of the 1930s in the Great Plains of North America was the result of which of the following processes?

wind

Precipitation occurs on the __________ of the mountain range, while the __________ is dry.

windward side; leeward side

Complete the sentences below that describe the process of dune movement. Match the words in the left column to the appropriate blanks in the sentences on the right. Note that some terms will remain unused.

1. Wind bounces and rolls sand along the ground, a process called saltation. 2. Sediment carried by the wind will drop to the ground when the wind's velocity decreases. 3. The force of the wind pushes particles up the windward slope of the dune as it moves. 4. The force of gravity allows particles to slide down the leeward slope of a dune as it moves.

Traditionally, a region is defined as a desert if it receives less than ________ centimeters of rain per year.

25

Match the sand dune with the correct description. Drag the terms on the left to the appropriate blanks on the right.

Longitudinal−linear ridges of sand parallel to the prevailing wind direction. Parabolic−multiple, overlapping crescent-shaped coastal dunes with the dune tips pointing toward shore. Barchan−crescent-shaped dune with tips pointing downwind. Transverse−linear ridges of sand perpendicular to the prevailing wind. Star−dunes with complex shapes that formed as a result of various seasonal wind directions. Barchanoid−undulating sand ridges perpendicular to prevailing winds with crescent-shaped slip faces pointing downwind.

________ weathering is most common in a desert environment.

Mechanical

In which hemisphere are middle-latitude deserts more common, and why?

Middle-latitude deserts are more common in the Northern Hemisphere than the Southern Hemisphere because the Southern Hemisphere lacks extensive land areas at middle latitudes.

______ dunes form in areas where vegetation partially covers the sediment.

Parabolic

Which of the following can contain large quantities of evaporite minerals such as borate and halite?

Playa

________ refers to the bouncing motion sands will display when transported by moving water or wind.

Saltation

Which part of the wind's sediment load is visible in this image?

Suspended load

How does wind's suspended load differ from its bed load?

The bed load consists of sand-sized grains that move by saltation, whereas the suspended load consists of fine, silt- or clay-sized particles that can be carried far distances by the wind once they are initially ejected into the air.

Why does the rainshadow desert form on the downwind side of the mountains?

The moisture was precipitated from the air mass on the upwind side.

Why does air tend to rise in equatorial regions?

Equatorial regions receive more direct sunlight than other areas.

When a permanent stream such as the Nile River crosses a desert, does the river's discharge increase or decrease? How does this compare to a river in a humid area?

The discharge of the Nile River decreases when it crosses a desert, in contrast with a river in a humid area, which increases in discharge.

In the desert environment, how are ventifacts created?

Ventifacts are produced on the surface of a rock by the continued impact of very small particles carried by the wind.

A(n) __________ is a cone-shaped deposit of sediment that is deposited when a stream exits the mouth of a canyon.

alluvial fan

Which of the following describes favorable conditions for transverse dune formation?

areas with steady prevailing winds and abundant sand

Deposits of silt carried by blowing winds are referred to as ________.

loess

A rainshadow desert forms ______.

on the leeward side of a mountain

Of the following options, which is the most common type of chemical weathering in a desert?

oxidation

Other than the landforms you learned about in the video, what is another landform present in the Basin and Range Province?

sand dunes

What is the most important erosional agent in deserts?

water

At what latitudes do the large-scale, convection cells bring dry air downward toward the Earth's surface?

between 20-30° north and south

Complete the following sentences about the defining characteristics of Earth's dry regions. Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is comlete before submitting your answer. Note that some terms will remain unused.

1. Also known as steppe, semiarid climates are a type of dry climate that contain more water than arid climates. 2. Thick soil is not found in deserts because there are fewer plants than in more humid climates. 3. A high rate of evaporation is often characteristic of a climate with high temperatures and low humidity. 4. A desert has a drier climate than a steppe.

Which of the following is a difference between barchan and parabolic dunes?

A barchan exhibits a concave slip face, while a parabolic dune shows a convex slip face.

When desert pavement is produced in a desert, why do the larger particles accumulate on the surface?

The wind can move particles of only a very specific size and it takes away these small particles, concentrating the larger ones.

Why is it so difficult for wind to pick up clay-sized particles?

The wind has a near-zero velocity closest to the surface and can't pick them up.

A true desert is defined by a lack of what substance?

Water

Which of the following statements about deserts is true?

Water is the most significant agent of erosion in deserts.

What is the air that sinks at latitudes of 30 degrees north and south like?

This air is cool and dry.

Which of the following desert features has sediment-size grading similar to that in a delta?

alluvial fan