Deserts

Question 1

What characteristics define the
environment of a desert?

Answer 1

Little rainfall (<10”/year), little vegetation and few people, physical weathering dominated, great variation in sand and rock.

Question 2

The most important agent of
transportation in a desert is …?

Answer 2

wind

Question 3

What are differences between the
processes of abrasion and deflation?

Answer 3

Abrasion-type of sand erosion typically near the surface, shaping of forms and stones.

Deflation-type of wind erosion where sand is blown away but pebblers remain.

Question 4

What is desert “armor”? How is it formed?

Answer 4

Derert armor is the accumulation of pebbles after the wind has blown all the sand away.

Question 5

Particles may be moved by the wind in
three different ways. Name them.

Answer 5

Surface creep, saltation, suspension

Question 6

How does sediment that travels in
suspension differ from sediment that
travels by saltation?

Answer 6

Suspension travels in the air and saltation travels right above the surace of the ground (hopping dybamics).

Question 7

What are ventifacts, and how are they
formed?

Question 8

What are the names for the various types
of sand dunes, and how do they differ in
shape (or form)?

Answer 8

Transverse-wind at 90 to crest. Horizontal shape.

Barchan- shaped like a boomerang; sand is sparse;”horns” point down

Star or Seif - variable wind directions. Incongruous shape.

Question 9

How can the direction of the wind be
determined from the form of the three
different types of sand dunes?

Question 10

What is the angle of repose?

Answer 10

The angle with respect to the horizontal at which the downwind side of the sand dune comes to rest.

Question 11

Describe the process by which a sand
dune “migrates” across the desert floor.

Question 12

What is “cross bedding”? How can the
direction of cross-bedding reveal the
direction the wind is blowing at the time
the cross beds were made?

Question 13

What is a “China wall” (with respect to a
desert dune)?

Answer 13

A wall that is steeper than 35 degrees. Chinese walls are built by reversing winds.

Question 14

Where are the highest sand dunes in the
US?

Answer 14

The Great Sand Dunes National Park in CO

Question 15

Where are the highest sand dunes in the
world?

Answer 15

Namibian Dunes in Southwest Africa. 300 meters

Question 16

What are the names of the major zones of
climate on Earth? Be able to identify them
on a global map.

Answer 16

Tropical, arid, temperate, and polar

Question 17

Be able to name and identify the major
deserts of the world that are “subtropical”,
“continental”, and “rainshadow”.

Answer 17

Subtropical-

Continental-

Rainshadow-

Question 18

Explain how wind circulation at the
equator controls the location of the arid
zone of climate in the subtropics.

Answer 18

Warm air rises, drops rain and then the wind takes the air north and south of the equator.

Question 19

Describe how mountain ranges control
the flow of moist air and cause the
formation of “rainshadow” deserts.

Answer 19

the air gets cooler as it rises and precipitates before it travels over the peak of the mountain. Therefore very small amount of rain makes it to the other side and the formation of rainshadow desert is the result.

Question 20

What are alluvial fans, and where do they
occur?

Answer 20

When shedding sediment slows down at the bottom of a mountain and smoothes out over the basin. They occur at the bottom of a canyon stream.

Question 21

What are playas, and when do they
occur?

Answer 21

An area of flat, dried-up land, esp. a desert basin from which water evaporates quickly.

They occur when snowmelt accumulates at the bottom of a desert mountain.

Question 22

What features of deserts on Earth have
been documented on Mars?

Answer 22

Transverse dunes, barchan dune fields, alluvial fan