Quiz 13: Deserts and Wind Action

A desert is any region which has a dry or arid climate with a low rainfall of less than 25 cm per year.

The world's best-known deserts lie in a belt 10-15 degrees centered at latitude of 30 degree (North and South).

Some of the world's deserts are the result of the rain shadow effect of mountain ranges.

The Basin and Range province is characterized by rugged mountain ranges bounded by faults.

Thin rocky soil and slow rates of creep make desert topography steep and angular.

In passing over a dune, wind scours sand from the downwind or slip face.

Because sand-sized grains are heavier than silt or clay-sized grains, sand moves close to the ground in a series of short hops called saltation.

Dune sand throughout the world is composed of the stable mineral quartz.

Most sand dunes are asymmetric in cross section with a gentle slope facing the wind and a steeper slope on the downwind side.

A butte is a narrow valley with a narrow bottom and flat sides.

Rapid down cutting of desert stream channels produces narrow canyons with vertical walls and flat gravel-strewn floors.

A mesa is capped by sedimentary rocks while a butte is capped by a lava flow.

Where sand supply is limited a barchan dune generally develops.

Dune types are influenced by wind velocity.

Since many desert regions have internal drainage, runoff collects on the valley floors as bajadas.

A transverse dune is a relatively straight, elongated dune oriented parallel to wind direction.

A pediment is an erosional surface underlain by solid rock, while a bajada is depositional and is underlain by sediment.

Ventifacts are rocks with rounded water-abraded surfaces.

A playa lake is a deep long-lasting desert lake.

Loess is a deposit of wind-blown silt primarily composed of unweathered angular grains of quartz and feldspar.

_____ is the dominant agent of erosion in desert regions. A) Wind B) Frost action C) Running water D) Actions of the geosphere E) A combination of all of these.

How do deserts form in coastal tropical regions? A) rain shadow B) cold ocean currents C) continental interiors D) ascending air E) drought

Because of their low rainfall, intermittent stream flow, and dry stream beds, desert lack ____. A) through-flowing streams B) vegetation C) mammals D) runoff E) transverse dunes

Not all deserts are hot. Descending air near the North and South poles creates ____ deserts. A) rain shadow B) cold ocean current C) sparse D) polar E) All deserts are hot.

Desert stream channels called ____ are characterized by narrow canyons with vertical walls and flat, gravel-strewn floors. A) dry streams B) intermittent channels C) desert streams D) stream beds E) arroyos

This area of the desert southwest is characterized by mostly flat-lying beds of sedimentary rock over 1,500 meters above sea level. A) Colorado Plateau B) Basin and Range C) Great Salt Lake D) Interior Desert E) Butte province

High-speed winds can cause ____, clouds of sand moving rapidly near the land surface. A) dust clouds B) sand storms C) dust devils D) bajadas E) deflation

A _____ is a depression on the land surface caused by wind erosion which may have a pillar left at the center. A) mesa B) loess C) blowout D) plateau E) deflation basin

This agent of erosion and deposition is most effective on fine sediment that is dry. A) flash floods B) wind C) frost action D) desertification E) dry wash

The Colorado Plateau is marked by peculiar, step-like bends in rock layers called ____. A) hogbacks B) mesas C) monoclines D) cuestas E) buttes

____ is a hard shiny coating of dark iron and manganese oxides and clay minerals that form on rock surfaces in arid environments. A) Deflation coating B) Desert armor C) Ventifact D) Desert varnish E) Corona

A(n) _____ is a broad gently sloping surface formed by the coalescing of alluvial fans. A) bajada B) pediment C) playa D) cuesta E) mesa

A(n) ____ is a gently sloping erosional surface, commonly covered with a veneer of gravel, cut into the solid rock of a mountain. A) bajada B) pediment C) cuesta D) arroyo E) playa

When the desert sun dries a lake, a very flat surface underlain by hard mud-cracked clay called a _______ may form. A) bajada B) alluvial fan C) playa D) pediment E) cuesta

The removal of clay, silt, and sand particles from a land surface by wind is called _____. A) blowout B) saltation C) scour D) deflation E) depression

The "horns" in a _______ dune point in a downwind direction. A) longitudinal B) symmetrical C) transverse D) star E) barchan

The steep downwind face of a sand dune is called the ______. A) slip face B) coarsest grains C) longest dimension D) gentle slope E) upwind surface

Sand moving over a dune surface by saltation typically forms ___. A) graded beds B) ripple marks C) mud cracks D) desert pavement E) tool marks

Sand grains found in dunes are commonly _______. A) poorly sorted and well rounded B) well sorted and poorly rounded C) well sorted and well rounded D) poorly sorted and poorly rounded E) gravel sized

Which of the following would not be a control on desert development? A) rain shadow B) great distance from an ocean C) location near cold ocean currents D) areas beneath rising air masses E) climatic belts at 30 north and south latitude

U.S. deserts in Nevada and northern Arizona are largely the result of the Sierra Nevada Mountains ____. A) combined with Coriolis Force B) deflation C) volcanism D) south wind E) rain shadow

Deflation continues to deepen a blowout until it reaches ______. A) the water table B) bedrock C) extent of roots from vegetation D) sea level E) There is no lower limit to blowouts.

The expansion of deserts into once populated areas is known as ___. A) sahel formation B) desertification C) rain shadow effects D) deflation E) desert migration

A ______ is a narrow hill of resistant rock with a flat top and very steep sides found in some deserts. A) butte B) horn C) plateau D) pediment E) ridge

_______ dunes in the Sahara are as high as 200 m and as long as 120 km. A) Barchans B) Parabolic C) Transverse D) Longitudinal E) Ventifact

Loess deposits in the U.S. Midwest are derived from ____. A) the Ohio River valley B) the Rocky Mountains C) top soil loosened by agriculture D) the Sahara Desert E) glacial outwash of the Pleistocene age

Most dunes move only ____ per year. A) 10 to 15 meters B) 30 to 100 meters C) 1 to 2 kilometer D) 5 to 10 kilometers E) 10 to 100 kilometers

Wind-blown sand may sculpt isolated pebbles, cobbles, or boulders into ____. A) sand dunes B) ventifacts C) desert pavement D) desert varnish E) desert road

A ____ dune is deeply convex and its horns point upwind. A) bajada B) parabolic C) barchan D) longitudinal E) transverse

Because sand grains are heavier than clay and silt particles, sand grains move close to the ground in a leaping pattern called ______. A) slipping B) jumping C) saltation D) parabolas E) blowouts

In the United States, large areas of _____ are blanketed with a cover of loess. A) California B) Arizona and New Mexico C) the Rocky Mountains D) the Midwest E) Canada

_______ has extensive loess deposits up to 100 meters thick. A) California B) Canada C) Brazil D) Ireland E) China

A large dune type is the _______ (or seif) dune, which forms a ridge parallel to prevailing wind direction. A) barchan B) transverse C) parabolic D) longitudinal E) moon

_______ is a thin surface layer of closely packed pebbles found in deserts. A) A pediment B) Desert pavement C) A barchan D) Desert varnish E) A mesa

The angle of repose of sand-sized particles falling from the air is _____ degrees. A) 14 B) 24 C) 34 D) 44 E) 90

An area with desert conditions in the United States is ____. A) the Sahara B) the southern Appalachians C) the Colorado Plateau D) the Pacific Northwest coast E) Minnesota

The high runoff following sporadic desert downpours can create sudden local floods called ______. A) ephemeral floods B) flash floods C) spring floods D) storm surges E) desert disasters

Where sand supply is limited a _____ dune usually forms. A) blowout B) star C) longitudinal D) barchan E) seif

Dunes are not just desert features, they are commonly found near ____. A) glaciers B) beaches C) rivers D) folds E) exposed rock

Rock debris picked up in flash floods is deposited at the base of mountains in ____. A) an alluvial fan B) a barchan dune C) a playa D) an arroyo E) a meandering river