Chapter 19 Desserts And Winds

Front 1

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

Back 1

inselberg

Front 2

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

Back 2

evaporites and claystone

Front 3

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

Back 3

alluvial fan

Front 4

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

Back 4

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

Front 5

______% of the earth's land is dry climate

Back 5

30%

Front 6

Name the 2 types of dry climates

Back 6

arid (dessert) and semi-arid (steppe)

Front 7

Steppe

Back 7

One of the two types of dry climate. A marginal and more humid variant of the desert that separates it from bordering humid climates.

Front 8

Rainshadow desert

Back 8

A dry area on the leeward side of a mountain range. (clouds are blocked by mountains coming from the windward side of the the mountain ranges) Many middle-latitude deserts are of this type.

Front 9

Windward

Back 9

facing the wind

Front 10

Leeward

Back 10

sheltered from the wind (often by clouds)

Front 11

Ephemeral stream

Back 11

A stream that is usually dry because it carries water only in response to specific episodes of rainfall. Most desert streams are of this type.

Front 12

_____ is the most significant agent of erosion in deserts

Back 12

Water

Front 13

deflation

Back 13

The lifting and removal of loose material by wind.

Front 14

dessert pavement

Back 14

A layer of closely spaced coarse pebbles and gravel that cover barren, rocky deserts to form a relatively smooth surface..

Front 15

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 erosional agent?

Back 15

Wind

Front 16

ventifact

Back 16

A cobble or pebble polished and shaped by the sandblasting effect of wind. (often more angular)

Front 17

In the desert environment, how are ventifacts created?

Back 17

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

Front 18

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

Back 18

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

Front 19

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

Back 19

saltation

Front 20

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

Back 20

leeward side

Front 21

What is cross bedding?

Back 21

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

Front 22

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

Back 22

slip face

Front 23

parabolic dune

Back 23

A sand dune that is similar in shape to a barchan dune except that its tips point into the wind. These dunes often form along coasts that have strong onshore winds, abundant sand, and vegetation that partly covers the sand.

Front 24

transverse dunes

Back 24

A series of long ridges oriented at right angles to the prevailing wind; these dunes form where vegetation is sparse and sand is very plentiful.

Front 25

barchanoid

Back 25

A type of dune that forms scalloped rows of sand oriented at right angles to the wind. This form is intermediate between isolated barchans and extensive waves of transverse dunes.

Front 26

what is a steppe

Back 26

semiarid region

Front 27

what is a desert

Back 27

arid region

Front 28

How do cold ocean currents influence some subtropical deserts?

Back 28

When air is cooled from below it resists the upward movement needed for cloud formation and precipitation. Thus, they receive no rain.

Front 29

Why do middle lattitude dry regions exits?

Back 29

They are often sheltered by rain because of large landmasses and are far from the ocean. also mountains play a part

Front 30

In which hemisphere are middle latitude deserts most common? Explain.

Back 30

Northern hemisphere because the southern hemisphere lacks land area

Front 31

ephemeral stream

Back 31

a stream that only carries water after it rains (only for a day or so it holds water)

Front 32

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

Back 32

In dry climates the weathering rate is significantly slower

Front 33

What is the most important erosional agent in deserts

Back 33

Water (not Wind)

Front 34

Interior drainage

Back 34

A system of streams that converge in a closed basin and evaporate without reaching the sea.

Front 35

Bajada

Back 35

A combination of 2 or more alluvial fans along a mountain front

Front 36

Playa lake

Back 36

temporary lakes in a mountain valley basin

Front 37

Playa

Back 37

dry flat lake bed that remains in a mountain basin

Front 38

inselbergs

Back 38

Isolated erosional remnants of a mountain in th later stages of a formation of a desert

Front 39

Describe the features and characteristics associated with each stage in the evolution of mountainous desert

Back 39

Early stage- Playa lakes and alluvial fans (large mountains and basins)

Middle stage- Playa and Bajada (due to more erosion

Late stage- Playa, salt flats, and inselbergs (after all or most of the mountains in the area are gone)

Front 40

bed load

Back 40

to sediment particles rolling, sliding, or tumbling along the surface in this case (more often stream beds)

Front 41

saltation

Back 41

the movement of hard particles such as sand over an uneven surface in a turbulent flow of air

Front 42

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

Back 42

suspended load is sediment carried in air for hour or even days often more fine particles

Front 43

how high are sands carried in the desert

Back 43

1 meter at most

Front 44

deflation

Back 44

the erosion of soil as a consequence of sand and dust and loose rocks being removed by the wind

Front 45

blowouts

Back 45

are sandy depressions in a sand dune caused by the removal of sediments by wind often in a smaller radius than deflation

Front 46

desert pavement

Back 46

a layer of coarse particles on the the surface

Front 47

abrasion

Back 47

is the mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind

Front 48

yardang

Back 48

a streamlined wind sculpted landform that is oriented parallel to the prevailing wind

(More mass on top and thin base, it is odd looking)*

Front 49

why is wind erosion relatively more important in dry regions that in humid areas

Back 49

because there is less water so wind is more often used to form the landscape (water still dominates but wind is more useful)

Front 50

What factor limits the depths of blowouts?

Back 50

the water table because of damp ground and vegetation

Front 51

Briefly describe two hypotheses used to explain the formation of desert pavement

Back 51

1st. Over time deflation lowers the face and coarse particles become concentrated

2nd. over time windblown dust accumulates at the surface and gradually sifts downward. Placing sand under the rocks or pebbles

Front 52

dunes

Back 52

wind blown sand deposits or ridges

Front 53

slip face

Back 53

leeward slope of the dune or the steeper part of the dune

Front 54

cross bedding

Back 54

layering within a stratum and at an angle to the main bedding plane. (/////////// relative to --------)

Front 55

barchan dunes

Back 55

sand dunes shaped like crescents and with their tips pointing downwind or with the wind

Front 56

transverse dunes

Back 56

sand dunes that are long ridges that form perpendicular to the prevailing wind

Front 57

barchanoid dunes

Back 57

a combination of both transverse and barchan dunes (long ridges perpendicular to the wind that have a waving shape to them)

Front 58

longitudinal dunes

Back 58

long ridge dunes parallel to the wind

Front 59

parabolic dunes

Back 59

dunes that are partially covered in vegetation. They have a crescent shape and their tips point toward the wind.

Front 60

how do sand dunes migrate?

Back 60

sand accumulates until sand falls down the slip face and then that process repeats until the dune gradually migrates down wind.

Front 61

list all 6 dunes

Back 61

star, barchan, barchaniod, transverse, parabolic, and longitudinal

Front 62

loess

Back 62

deposits of windblown silt