Geology 10 Chapter 13
A(n) _____ is a broad gently sloping surface formed by the coalescing of alluvial fans.
bajada
The "horns" in a _______ dune point in a downwind direction.
barchan
_______ 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 mesa is capped by sedimentary rocks while a butte is capped by a lava flow.
false
Since many desert regions have internal drainage, runoff collects on the valley floors as bajadas.
false
A large dune type is the _______ (or seif) dune, which forms a ridge parallel to prevailing wind direction.
longitudinal
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
U.S. deserts in Nevada and northern Arizona are largely the result of the Sierra Nevada Mountains ____.
rain shadow
Which of the following would not be a control on desert development?
rain shadow
Because sand grains are heavier than clay and silt particles, sand grains move close to the ground in a leaping pattern called ______.
saltation
The steep downwind face of a sand dune is called the ______.
slip face
_______ has extensive loess deposits up to 100 meters thick.
China
A desert is any region which has a dry or arid climate with a low rainfall of less than 25 cm per year.
true
Dune types are influenced by wind velocity.
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
Sand grains found in dunes are commonly _______.
well sorted and well rounded
A transverse dune is a relatively straight, elongated dune oriented parallel to wind direction.
false
Wind-blown sand may sculpt isolated pebbles, cobbles, or boulders into ____.
ventifacts
The angle of repose of sand-sized particles falling from the air is _____ degrees.
34 degrees