Aeolian Processes

Question 1

What is wind as a geomorphological agent?

Answer 1

Weathering + Erosion + Transport + Deposition = Denudation

Question 2

What is wind as a geomorphological agent?

Answer 2

Erosion, Transport, Deposition
Erodes rocks and sediment
Transport available sediment
Deposits transported sediment

Question 3

Examples of hot arid zones

Answer 3

Sahara Desert - North Africa
Gobi Desert - East Asia

Antarctica - The entire continent
Patagonian desert - South America

Question 4

What is the distribution of arid zones linked to?

Answer 4

Large atmospheric cells

Question 5

Why are arid zones linked to large atmospheric cells?

Answer 5

Airflow in response to gradients in
- Heat
- Pressure

Question 6

What is the Coriolis force?

Answer 6

An apparent force that acts in moving objects in a rotating reference frame, such as the Earth
Caused by the rotation of the Earth
It deflects the path of moving objects, including wind

Question 7

What does the wind direct result from?

Answer 7

The combined action of the pressure gradient and Coriolis force

Question 8

What are large-scale climate influences?

Answer 8

Hadley cell
Maritime vs. continental
Cold ocean currents

Question 9

What are seasonal large-scale climate influences?

Answer 9

• ITCZ
• Monsoons

Question 10

What are daily large-scale climate influences?

Answer 10

Breezes

Question 11

What are Aeolian processes?

Answer 11

Sediment transported by fluid - air can be considered a fluid in this context
Random molecular motion and no fixed shape or volume

Question 12

The viscosity of air?

Answer 12

Lower viscosity 1.8x10-5 Nsm-2

Question 13

The density of air?

Answer 13

Lower density 1.3kg m-3

Question 14

Does air have efficient sediment transportation?

Answer 14

No

Question 15

What is the viscosity of water?

Answer 15

High - 1x10-3 Nsm-2

Question 16

What is the density of water?

Answer 16

1000kg m-3

Question 17

Does water have efficient sediment transport?

Answer 17

Yes

Question 18

What is sediment movement a function of?

Answer 18

Erosivity and Erodibility
+ complicating factors

Question 19

What is erosivity?

Answer 19

A function of gravity
lift and drag components

Question 20

When does sediment transport occur?

Answer 20

When the force exceeds a threshold value, commonly determined by the particle size of sediment

Question 21

What is erosivity?

Answer 21

Wind field
Contact area/ morphology
Impact from other grains

Question 22

What is sediment movement a function of?

Answer 22

Of erosivity and erodibility and complicating factors

Question 23

What is erodibility?

Answer 23

The susceptibility to wind erosion
- Particle size of surface sediments
- Plant cover
- Surface crusting
- Soil moisture

Question 24

What are the factors contributing to Aeolian landforms?

Answer 24

Wind strength (velocity and time), direction and directional variability (eg seasonal)
- Sediment - source, grain size
- Moisture/ adhesion agent
- Vegetation
- Obstacles/ geomorphology
- Humans

Question 25

Sand sediment size?

Answer 25

2 - 0.063mm or 2000 - 63 um

Question 26

What is the typical wavelength of sand dunes?

Answer 26

<1m to several 10s km, h: 10s cm to >150m

Question 27

What are the major regional controls of sand dunes?

Answer 27

wind regime and sediment supply

Question 28

What are the different types of sand dunes?

Answer 28

- Transverse dunes - Linear Dunes - Star dunes

Question 29

What are the most common sand dunes?

Answer 29

Linear dunes are most common globally c. 50% all dunes

Question 30

What are the wavelengths of ripples?

Answer 30

<1 cm to c. 25cm, h:

Question 31

What is the size of silt sediment?

Answer 31

0.063 - 0.004 mm or 63 - 4 um

Question 32

Silt landforms

Answer 32

- Loess

Question 33

What is loess?

Answer 33

Typically silt size particles but some sand and clay too Alternating layers if silt and soils

Question 34

What are Yardangs?

Answer 34

Bedrock carved by the wind abrasion (dust and sand)

Question 35

What are ventifacts?

Answer 35

Rock abraded (and pitted) by wind-driven sand

Question 36

What are pavements?

Answer 36

Or lag gravel - the material left behind as the finer material has been eroded away

Question 37

Why is dust a critical component of Earth Systems?

Answer 37

- Surface-atmosphere feedback, radiation balance & climate modulation - Ocean fertilization and CO2 breakdown - Long-distance nutrient transport & vegetation fertilization - HUman health & land use The dust cycle interacts with the ocean's biological pump and reduces atmospheric CO2 through biological processes