Lecture 14 - Aeolian Erosion and Deposition

Question 1

What are Karstic Landscapes?

Answer 1

-The form where the exposed rock is limestone
-Limestone is principally made of calcite which is easily eroded by weak acid
-As the rock dissolves, caved and sinkholes form
-In the caves (where the environment is slightly more CO2 rich) calcite precipitates again, forming speleothems
-Speleothems form in annual layers that can be dated and their isotopic composition determined to reconstruct paleoclimates

Question 2

What is Wind?

Answer 2

-The movement of air: hot air is less dense and so rises, with cooler air taking its place

Question 3

Wind Erosion: what is Deflation?

Answer 3

-Process by which smaller particles of sand and silt are blown away, eventually leaving behind the coarser sediments in the form of a desert pavement

Question 4

Wind Erosion: what is Abrasion?

Answer 4

-When rocks are gradually eroded by the action of small sediments carried by the wind
-This can create what are known as ventifacts

Question 5

How does Wind Transportation Occur?

Answer 5

-Transportation usually concerns fine material, ie sand (2-0.05mm), silt (0.05-0.002mm) and clay (<0.002mm)
-The ability of wind to pick up a particle is dependent on wind velocity (friction with the land and density of atmosphere) and the size of the individual particle (gravity)

Question 6

What are Dunes?

Answer 6

-Form when wind velocity is reduced and sediment is deposited
-Sand grains are all a similar size
-Cross laminations (direction of bed and dipping indicates the paleo-direction of the wind)
-Cross laminations also occur is rivers so be careful!
-There are many types, their shape indicating the direction of the prevailing wind

Question 7

How is Loess useful for a Geomorphologist?

Answer 7

-Paleoclimate can be reconstructed using loess by looking at:
-grain size (wind direction/
strength)
-soil type (vegetation, rainfall)
-pollen (vegetation)
-land snail shells (temperature
and rainfall)