Chapter 16: Deserts and Wind

playa

A flat bed of clay, sometimes encrusted with precipitated salts, that forms by the complete evaporation of a playa lake.

Deflation leads to the formation of desert pavement by __________.

carrying fine sediments away and leaving a layer of larger particles at the surface

Which of the following is true about sand dunes? a. Dunes are stationary features. b. Dunes are erosional landforms, not depositional landforms. c. Dunes are more affected by water than wind. d. Dunes move over time. e. Dunes move as a single bodily mass.

d

Which of the following statements about deserts is true? a. Deserts are dominated by sand dunes. b. Wind is the most significant agent of erosion in desert regions. c. Deserts are always hot. d. Water is the most significant agent of erosion in deserts. e. Deserts are lifeless.

d

Salinization appears to be most closely located geographically to which other environmental issue?

desertification

parabolic dunes

develop along shorelines from off shore winds

rainshadow

dry region on side of mountain that is sheltered from wind

Thick soil is not found in deserts because there are fewer plants than in more _______ climates.

humid

In which climate is desertification NOT currently occurring?

humid subtropical

inselbergs

isolated, steep-sided erosional remnants that rise above desert plains

Where is the Aral Sea located?

on the border of Kazakhstan and Uzbekistan

Cross-bedded sandstone shows inclined beds in a downward direction. What part of the ancient dune do these features represent?

slip face

A desert has a drier climate than a _______.

steppe

interior drainage

streams and stream systems that flow within a closed basin and thus do not reach the ocean, as in Death Valley, California, and the Dead Sea Basin in the Middle East.

deflation

the lifting and removal of loose material

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.

bajada

What mature desert landscape feature consists of coalesced alluvial fans?

subtropical desert

What type of deserts occur at 20 degrees to 30 degrees N and S latitude?

desert

arid regions (more dry than steppe

desert pavement

A layer of coarse pebbles and gravel created when wind removed the finer material.

alluvial fan

A wide, sloping deposit of sediment formed where a stream leaves a mountain range

loess

A wind-formed deposit made of fine particles of clay and silt

bed load

Describes sediments that are too heavy or large to be kept in suspension or solition and are pushed or rolled along the bottom of a streambed

star dunes

Dunes that are isolated hills of sand that exhibit a complex, star like form. Develop where wind patterns are changing.

How does the current state of the Aral Sea affect public health?

Dust and sand from the dry sea shores cause illnesses.

ventrifacts

Individual rocks with sharp edges and smooth sides

Which of the following countries is most affected by desertification? Sudan Iran South Sudan Oman Algeria

Iran

What is the order, from most to least, of the amount of desertification among river basins in South America?

La Plata, Amazon, Orinoco

What is cross bedding?

Layers deposited on a dune slip face that are inclined in the direction of wind transport.

longitudinal dunes

Long ridges of sand parallel to wind.

What is the primary difference between the two desert pavement hypotheses?

Model 1 is based on a sediment volume decrease through time (erosion), while Model 2 is based on an increase in sediment volume through time (deposition).

Which Australian city is most at risk of encroaching desertification?

Perth

ephemeral streams

Practically all desert streams are this. This are streams that only form when there has been precipitation.

Why has the size of the Aral Sea decreased?

Rivers were diverted to provide water for cotton.

Why are farmers in the Aral Sea region primarily having trouble growing crops?

Salt and dust from the Aral Sea ruin fertile soil.

What country was responsible for the reduction in the size of the Aral Sea?

Soviet Union

abrasion

The grinding away of rock by other rock particles carried in water, ice, or wind

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.

Which of the following statements characterizes ephemeral streams? a. Ephemeral streams flow only at certain times of the year. b. Ephemeral streams flow all the time in the desert. c. Ephemeral streams generally depend on groundwater in the desert to flow year round. d. Ephemeral streams don't have any life in them. e. Ephemeral streams are streams that flow through deserts, but have their origins outside of the desert.

a

transverse dunes

a linear ridge-like sand dune that is oriented at right angles to the prevailing wind direction; form where sand-transporting winds blow from a constant direction and the supply of sand is abundant; the upwind slope of a transverse dune ridge is gentle, and the steeper downwind slip face is at the angle of repos

yardangs

a streamlined rock structure formed by deflation and abrasion; appears elongated and aligned with the most effective wind direction

playa lake

a temporary lake filled after rain, or its dry often salty bed, in a desert basin

Rocks are __________ when they are scratched by sediment particles moved by wind.

abraded

Which climate is most associated with salinization?

desert

Fine-grained surface sediments are eroded by wind during _______.

deflation

Wind erosion can cause __________, which can create shallow depressions called __________.

deflation; blowouts

________ of sediment occurs when the wind carrying the sediments stops or slows such that it can no longer hold them.

deposition

All forms of ________ remove materials from the landscape surface.

erosion

A high rate of ________ is often characteristic of a climate with high temperatures and low humidity.

evaporation

The __________ of a dune is characterized by a decrease in energy and sand avalanches, which occur due to oversteepening.

leeward side

What is the term for the rolling and bouncing of sand grains during transport?

saltation

Wind can cause sand grains that are too heavy to remain suspended in the air to bounce or roll along the ground - a process called ________.

saltation

saltation

sand skips and bounces by grain impact

barchan dunes

sand supply is limited, steady wind from one direction

suspended load

sediment carried in the air

Also known as steppe, __________ climates are a type of dry climate that contain more water than arid climates.

semiarid

steppe

semiarid regions

blowouts

shallow depressions created by deflation

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

dunes

windblown accumulations of sand

What is meant by "dry"?

yearly precipitation is not as great as the potential for evaporation.