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