Chapter 13 Deserts and Wind Action
Rock debris picked up in flash floods is deposited at the base of mountains in ____.
an alluvial fan
Desert stream channels called ____ are characterized by narrow canyons with vertical walls and flat, gravel-strewn floors.
arroyos
Dunes are not just desert features, they are commonly found near ____.
beaches
A _____ is a depression on the land surface caused by wind erosion which may have a pillar left at the center.
blowout
The high runoff following sporadic desert downpours can create sudden local floods called ______.
flash floods
A ____ dune is deeply convex and its horns point upwind.
parabolic
When the desert sun dries a lake, a very flat surface underlain by hard mud-cracked clay called a _______ may form.
playa
Because sand grains are heavier than clay and silt particles, sand grains move close to the ground in a leaping pattern called ______.
saltation
This area of the desert southwest is characterized by mostly flat-lying beds of sedimentary rock over 1,500 meters above sea level.
Colorado Plateau
_______ is a thin surface layer of closely packed pebbles found in deserts.
Desert pavement
____ is a hard shiny coating of dark iron and manganese oxides and clay minerals that form on rock surfaces in arid environments.
Desert varnish
A butte is a narrow valley with a narrow bottom and flat sides.
False
A mesa is capped by sedimentary rocks while a butte is capped by a lava flow.
False
A playa lake is a deep long-lasting desert lake.
False
A transverse dune is a relatively straight, elongated dune oriented parallel to wind direction.
False
In passing over a dune, wind scours sand from the downwind or slip face.
False
Since many desert regions have internal drainage, runoff collects on the valley floors as bajadas.
False
Ventifacts are rocks with rounded water-abraded surfaces.
False
Because of their low rainfall, intermittent stream flow, and dry stream beds, desert lack ____.
through-flowing streams
Wind-blown sand may sculpt isolated pebbles, cobbles, or boulders into ____.
ventrifacts
This agent of erosion and deposition is most effective on fine sediment that is dry.
wind
_____ is the dominant agent of erosion in desert regions.
Running water
Dune types are influenced by wind velocity.
True
Loess is a deposit of wind-blown silt primarily composed of unweathered angular grains of quartz and feldspar.
True
Most sand dunes are asymmetric in cross section with a gentle slope facing the wind and a steeper slope on the downwind side.
True
Some of the world's deserts are the result of the rain shadow effect of mountain ranges.
True
The Basin and Range province is characterized by rugged mountain ranges bounded by faults.
True
The world's best-known deserts lie in a belt 10-15 degrees centered at latitude of 30 degree (North and South).
True
Thin rocky soil and slow rates of creep make desert topography steep and angular.
True
Where sand supply is limited a barchan dune generally develops.
True