Wind Erosion and Desert Features Flashcards
Is there flowing water in deserts?
no
what is the main force/agent/source of erosion in deserts?
wind
the main erosive mechanism within wind is ____ that is carried along in it.
sand
What are the three processes moving wind-blown sediments?
- surface creep - salutation - suspension
_____ ______ rolls large sized along the ground
surface creep
_____ moves medium sized grains (in this instance _____ - sized grains)
saltation, sand
- saltation is a series of short jumps in which the particles move along with the wind
______ moves small/fine sized grains (in this instance _____ -sized grains)
suspension, dust
What does suspension of sand cause?
dust storms
______ is the process by which particles are moved across the surface of rocks and acts as sandpaper smoothing those surfaces.
Abrasion
what are features formed by wind erosion?
arches, pillars,
______ occurs in areas where there is little to no vegetation
deflation
What happens in deflation?
small particles such as clay and silt are blown away by the wind
In deflation _____ particles are blown away by the wind
small
what are the small particles that are blown away by deflation?
clay, silt
desert pavement forms from the process of _____
deflation
What are the mechanisms/processes of wind erosion?
- abrasion
- deflation
- desertification
What are the three products of abrasion?
- ventifacts -
What are the three products of abrasion?
- ventifacts
- arches
- hoodoos
Ventifacts often indicate _____ direction
wind
- Ventifacts can be important in seeing the prevailing wind directions in the present as well as in the past
What are ventifacts?
rocks that have been shaped by the wind
In the process of _______ wind-blown particles blow against the surface of rocks
abrasion
The main course of erosion in deserts is _____
wind
What are the three features that can form as a product of abrasion?
- ventifacts
- arches
- voodoos
What are the three features that can form as a product of abrasion?
- ventifacts
- arches
- hoodoos
_______ are wind-blown pillars
Hoodoos
Hoodoos can indicate wind ______.
- direction
Especially if they are older they can indicate how wind directions have been in the past and if they have changed at all
Where does deflation occur?
In areas where there is little or no vegetation
________ is the process by which small particles (such as clay and silt sized-particles) are removed by the wind and larger particles are left behind
Deflation
Deflation is the process by which ______ particles are removed by the wind and ______ particles are left behind
small, large
_____ particles, over time, will be blown away and as these particles are blown away there will be a concentration of ____ particles on the surface.
small, large
As small particles are blown away the surface _____ down in a process called _____.
drops, deflation
A product of _____ is desert pavement?
deflation
What is a product of deflation?
desert pavement
As smaller particles continue to be ______ you eventually reach the point where there are no small particles left on the surface.
removed
When no further deflation can occur _____ _____ arises.
desert pavement
What are two features or products of wind erosion?
- dunes
- floods
____ are wind deposited ridges or hills of sand
dunes
What are dunes?
wind deposited ridges or hills of sand
What is a feature of a sand dune?
- typically asymmetrical in shape
Dunes are typically asymmetrical in shape meaning that there is a ____ face and a ____ face
longer, shorter
The ______ face is the face that faces the prevailing wind direction
windward
The longer face of dunes are called the _______ face
windward
The shorter face is called the ______ face
leeward, slip
What is a feature or characteristic of the windward face?
- it faces the prevailing wind direction
What is a feature or characteristic of the leeward face?
- it is steeper
Wind blows up the ______ face and blows down the _______ leeward face
windward, leeward
Does wind blow up or down the windward face?
up
Does wind blow up or down the leeward face?
down
Are dunes constantly growing and shaping?
yes
There are many different ______ of dunes that vary based on a few different _____
types, factors
What are the types of dunes?
- Barchan
- Star
- Parabolic
- Longitudinal
- Transverse
______ dunes are crescent shaped
Barchan
______ dunes migrate across the desert as the sand continues to blow.
Barchan
______ dunes are a blown out U-shaped dunes
Parabolic
The _____ of parabolic dunes are anchored in some sort of _____ and then the wind blows out a ______ curve
legs, vegetation, concave
______ dunes form parallel to the prevailing wind direction
Longitudinal
______ dunes form perpendicular to the prevailing wind direction
transverse
Do transverse dunes form parallel or perpendicular to the prevailing wind direction?
perpendicular
Do longitudinal dunes form parallel or perpendicular to the prevailing wind direction?
parallel
Which type of dune can form when a number of barchan dunes form together into lines?
transverse
What are the three factors that influence dune formation and behavior?
- wind
- vegetation
- sand supply
In any particular desert the wind speed and direction, the sand supply, and the amount of vegetation combine to form different types of dunes.
What is a unidirectional wind?
a wind that always blows in one direction
What is no direction preferred?
wind that intermittently blows from all directions
Barchan dunes form in deserts that have a wind coming primarily from ____ direction
one
Star dunes form in areas where there is ___ _______ wind direction.
no preferred
Which type of dune tends to form in deserts that have a lot of sand?
Transverse dunes
Which type of dune tends to form in deserts that have low sand supply?
Longitudinal dunes
When there is a rain event in a desert they often result in _____ ______
flash floods
- a flash flood has a lot of water and sediment being carried over a short time. The water is muddy, has a high load, and is transporting a lot of material in a very short of time.
Why does flash flooding happen in deserts?
Because deserts are very dry, the introduction of water is going to have a strong erosive force
What features do flash floods deposit?
alluvial fans
Many alluvial fans coalesce into a ____
bajada
What is a bajada?
Many alluvial fans
e.g.
death valley
a flash flood has a lot of ____ and _____ being carried over a short time.
water, sediment
As flash floods run down a slope and empty into some valley or plane they _____ material in the shape of a fan.
deposit
If many alluvial fans begin to overlap they form a feature that is known as a _____
bajada.
The process of ______ is the creation of desert conditions in areas that were previously not deserts.
desertification
Can desertification be influenced by human activity?
yes
Is desertification a natural process?
yes
What are the signs of desertification?
- lowering water tables
- Higher salt content in soil and water
- High rates of soil erosion
- Destruction of vegetation
What is an example of desertification?
the Dust Bowl
How did the Dust Bowl occur?
poor farming practices combined with a drought caused a bit of desertification in the midwest as a lot of soil was blown away in a short amount of time
One of the great projects during the time of the Dust Bowl was to create a _____ ____ across the planes to prevent any further loss of soil
tree belt
What areas are susceptible or vulnerable to desertification?
- semi-arid areas near deserts
- poor soil management in intensely farmed areas
In semi arid areas farmers have to be _____ of soil management to prevent loss of soil in order to preserve their food source.
mindful
