Landforms Ch 6.2

The major erosional force in the desert is

water and fluvial processes.

Small sized sand that is blown in a strong wind will produce ripples that are

widely spaced

Buttes, mesas, and inselbergs represent

erosional remnants of a once extensive and continuous rock layer.

a layer of wind-blown clay and silt derived from glacial deposits is

loess

The formation of desert pavement

involves both wind and water

A crescent-shaped dune with anchoring vegetation is called a

parabolic dune

a large dune that results from winds shifting in all directions is a

star dune

Wind-blown loess deposits are only derived from glacial and periglacial sources

False

T/ F The Colorado River system is experiencing a drought that is more severe than any in the historic record.

True

Desertification is not caused by which of the following? a. overgrazing b. climate change c. erosion and salinization of crop land d. deforestation e. All of these

e. All of these

A continuous depositional apron, or __________, may form if individual alluvial fans coalesce into one sloping surface. This feature contrasts with a __________, which is an erosional surface along a mountain front where bedrock is covered by a thin veneer of alluvium.

bajada; pediment

Relatively small dunes that are crescentic in shape are termed __________ dunes.

barchan

a crescent-shaped due with horns pointed downwind is

barchan dune

Linear dunes and seif dunes are oriented

perpendicular to the wind.

Which of the following is not true of alluvial fans? a. They often serve as good sources of groundwater. b. They frequently occur in the eastern United States. c. The largest sized sediment is found near the top of the fan, and the smallest near the bottom. d. They are depositional features.

b. They frequently occur in the eastern United States

Which of the following terms is not a correct reference to a desert pavement? a. gibber plain b. lag gravels c. sand seas d. reg desert

c. sand seas

A wind-sculpted accumulation of sand is a

dune

For purposes of discussing eolian processes, the wind acts like a

fluid

The loess deposits in North America are derived from __________, and those in China are derived from __________.

glacial and periglacial regions;

Which side of a dune typically has a slope angle equal to that of the angle of repose for sand?

leeward

Significant loess deposits are found in the a. Mississippi and Missouri valleys. b. eastern Washington region. c. Ukraine in the former Soviet Union. d. Loess Plateau of China, some 300,000 km2 (115,800 mi2). e. All of these regions contain loess.

e. All of these regions contain loess.

A 50 kmph (30 mph.) wind blowing for 24 hours moves how much sand over 1m2 (1yd2)

1000 kg (2200 lbs.)

saltation is responsible for approx. how much transport of particles by wind

80%

Approx. how much of the world dessert areas are covered with sand

10%

Longitudinal sand dunes are oriented parallel to the prevailing wind

True

Abrasion is usually confined to a zone which extends up to __________ above the ground

1 m (3.28 ft.)

Desert pavement is formed by

deflation

Pebbles can be moved by __________ in a process known as __________.

saltating particles; surface creep

In which region of the United States. are eolian processes most effective?

southwest

T/F Soils formed from loess tend to be infertile

False

Elongated, streamlined ridges aligned parallel to the most effective wind direction are called

yardangs

Water is essential to the formation of a desert pavement

True

The often-sited work on eolian processes is The Physics of Blown Sand and Desert Dunes written by

Ralph A. Bagnold

Which of the following grain sizes is most readily moved by the wind? a. large b. intermediate c. small

b. intermediate

Addition of more dams on the Colorado River would result in __________ available water because __________.

both less; some of the impounded water would seep into rock and become unavailable and less; some of the water would evaporate

The spatial distribution of Earth's dry regions are attributable to all of the following factors except a. subtropical high-pressure cells between 15° and 35° N and S latitudes. b. rain shadows to the lee of mountain ranges. c. the equatorial low-pressure region and the ITCZ. d. great distances from moisture-bearing air masses.

c. the equatorial low-pressure region and the ITCZ.

Which of the following is not another name for an alluvial fan? a. qanat b. karex c. foggara d. gibber plain

d. gibber plain