Week 4

Question 1

Explain the aeolian processes

Answer 1

Involves the transportation, erosion, and deposition of sand and silt by wind

Question 2

Wind requires _____ velocities due to its _____ density

Answer 2

Wind requires higher velocities due to its lower density

Question 3

What are the types of sediment transport

Answer 3

traction, saltation, suspension

Question 4

Traction (type of sediment transport)

Answer 4

Larger sediments (>500 microns) roll along the ground, slowly “creeping” forward

Question 5

Saltation (type of sediment transport)

Answer 5

Sand-sized particles move in short hops, knocking smaller particles into the air

Question 6

Suspension (type of sediment transport)

Answer 6

Very small sediments (<70 microns) remain suspended in the air

Question 7

Abrasion (type of wind erosion)

Answer 7

Mechanical weathering caused by repeated impacts of airborne sediment

Question 8

Deflation (type of wind erosion)

Answer 8

Removal of loose sediment from an area by wind

Question 9

Transverse (sand dune type)

Answer 9

Straight crests perpendicular to wind direction

Question 10

Parabolic (sand dune type)

Answer 10

Curved crests perpendicular to wind direction

Question 11

Longitudinal (sand dune type)

Answer 11

Form parallel to wind direction in areas with two dominant wind directions

Question 12

Star (sand dune type)

Answer 12

Starfish-shaped dunes in environments with more than two main wind directions

Question 13

What is deflation, and how does it affect the distribution of archaeological materials on the surface?

Answer 13

Deflation occurs when wind removes fine particles (such as sand and silt), leaving behind larger archaeological materials on the surface.

This process does not shape the layer but results in a surface where coarser materials are concentrated.

Question 14

How does wind erosion affect objects and landscapes, and what features can it create that may appear anthropogenic?

Answer 14

Erosion by wind can polish and shape objects and landscapes over time, sometimes creating features that may appear anthropogenic (e.g., ventifacts).

Question 15

How can archaeological sites be buried by fine-grained sediments, and why is the source of sediments important, especially in environments with high wind activity?

Answer 15

Archaeological sites can be buried by sheets of fine-grained sediments, which are dynamic and may cover and expose materials over time.

The source of sediments is key, especially in environments with high wind activity.

Question 16

How are arid and semi-arid environments classified?

Answer 16

These environments are classified by the amount of annual rainfall.

Question 17

Hyper-arid

Answer 17

Less than 12 months of rain.

Question 18

Arid

Answer 18

Less than 50 mm annually (e.g., Atacama Desert).

Question 19

Semi-arid

Answer 19

Receives 250-500 mm annually.

Question 20

How do high-pressure cells and the orographic effect influence desert formation and aridity on one side of a mountain?

Answer 20

High-pressure cells contribute to dry, stable air, leading to desert conditions, while the orographic effect causes moisture to be lost on the windward side of a mountain, creating arid conditions on the leeward side.

Question 21

How does wind transport sediments, and what factors influence this process?

Answer 21

Wind transports sediments by overcoming the friction between particles.
Factors such as moisture, grain size, and wind velocity affect the effectiveness of sediment transport.

Question 22

What is saltation, and how does it relate to wind as a transport agent?

Answer 22

Saltation is a process where medium or fine sediment particles are lifted and moved by wind, similar to the movement of particles in rivers.

Question 23

What is suspension in the context of wind as a transport agent, and how does it contribute to environments like the Sahara?

Answer 23

Suspension is a process where finer particles, such as silt and clay, are carried long distances in the air by wind, contributing to the formation of dusty environments like the Sahara.

Question 24

How are sand dunes formed, and what role does wind play in their creation?

Answer 24

Sand dunes are formed in sandy environments through wind transport, where sand grains accumulate and migrate, shaping the dunes over time.

Question 25

What factors influence the different types of sand dunes, such as barchan, parabolic, and star dunes?

Answer 25

The types of sand dunes vary based on wind direction, sediment supply, and environmental conditions, leading to different formations like barchan, parabolic, and star dunes.

Question 26

What causes dune migration, and how do erosion and deposition contribute to this process?

Answer 26

Dune migration occurs as erosion happens on the windward side of the dune and deposition takes place on the leeward side, causing dunes to slowly move across landscapes.

Question 27

How does wind activity affect the preservation and stratigraphy of archaeological objects?

Answer 27

Archaeological objects can be buried or exposed due to wind activity, affecting their preservation and stratigraphy.

Question 28

How does deflation in archaeological contexts impact the interpretation of a site?

Answer 28

Deflation can mix artifacts from different periods, leading to challenges in accurately interpreting the chronological sequence and context of the site.

Question 29

What types of sediment are typically transported by wind, and what is an example of this in nature?

Answer 29

Wind typically transports sand, silt, and clay. An example is the Sahara Desert's dust storms.

Question 30

What happens to fine grains in wind-transported environments, and how does it affect sorting?

Answer 30

Fine grains are winnowed (blown away), leaving behind coarser grains. This leads to well-sorted deposits, where coarser grains remain as lag.

Question 31

How does wind erosion impact archaeological sites?

Answer 31

Wind erosion can cause deflation, removing finer sediments and leaving behind larger artifacts, or it can bury archaeological materials under layers of windblown sediments.

Question 32

What factors contribute to the formation of arid zones?

Answer 32

Arid zones form due to air subsidence, the position within a land mass, and the orographic effect, where mountains block moisture.

Question 33

How are hyper-arid, arid, and semi-arid environments classified based on annual rainfall?

Answer 33

Hyper-arid areas experience at least 12 consecutive months without rain, arid zones receive less than 250 mm annually, and semi-arid areas have between 250-500 mm of annual precipitation.

Question 34

When do sediments begin to move with wind?

Answer 34

Sediments move when the critical threshold friction velocity of the wind is exceeded, which depends on particle size, wind velocity, moisture, surface roughness, and other factors like salt and crusting.

Question 35

What is the effect of aeolian erosion on rocks and archaeological materials?

Answer 35

Aeolian erosion causes abrasion and grinding of rock fragments, including artifacts and lithics, creating ventifacts, which are polished rocks with faceted surfaces and elongated grooves.

Question 36

How does aeolian erosion impact landscapes and archaeological sites on a regional scale?

Answer 36

Aeolian erosion can sculpt entire bedrock exposures, forming yardangs (elongated hills), and can affect the integrity of archaeological assemblages through deflation, which removes finer grains and leaves heavier objects behind.

Question 37

How are sand dunes formed, and what factors influence their shape and movement?

Answer 37

Sand dunes form from the accumulation of windblown sand. Their shape and movement are influenced by wind strength and direction, sand supply, vegetation, and grain size.

Question 38

What factors prevent dune migration, and how does this occur?

Answer 38

Dune migration is prevented by "anchoring" through vegetation, which traps sand, or soil formation that adds stability, often influenced by human activity.

Question 39

What is loess, and what is its composition?

Answer 39

Loess is a fine-grained deposit composed of quartz, feldspar, mica, clay minerals, and carbonate grains, along with phytoliths, heavy minerals, ash, and salts.

Question 40

How is loess typically formed, and why is it easily eroded?

Answer 40

Loess forms through processes like glacial grinding, frost, weathering, and biological activity. It tends to maintain vertical faces when eroded but is easily erodible due to its fine particle size.

Question 41

What is the general geomorphology of Seaview from east to west?

Answer 41

It includes a flat coastal plain, coastal retention dune, sandy beach, internal lagoon, and barrier reef.

Question 42

What is the composition of the layer exposed near the top of the ridge at Seaview?

Answer 42

A dark, loamy, compact layer covered by aeolian sand.

Question 43

What is the relationship between erosion and deposition in coastal and dune environments?

Answer 43

Coastal and dune environments are shaped by the balance between erosion and deposition, which continuously alters the landscape.

Question 44

What are loess deposits, and what materials are they made of?

Answer 44

Loess deposits are fine-grained aeolian and colluvial sediments composed of quartz, feldspar, mica, clay minerals, carbonate grains, phytoliths, heavy minerals, ash, and salts.

Question 45

What is the typical size of loess particles?

Answer 45

Loess particles are silt-sized, ranging from 2-40 microns and are positively skewed.

Question 46

Why is loess easily erodible?

Answer 46

Loess tends to keep vertical faces when eroded and is easily erodible due to its fine grain size.

Question 47

What are the possible origins of loess?

Answer 47

Loess may originate from glacial grinding, frost action, liberation of silt, weathering, and biological processes.