Stratigraphy and Siliciclastic Sediments (L25-31)

Question 1

What can critical zone processes be summarised as?

Answer 1

Biosphere-, lithosphere-, hydrosphere-, atmosphere interactions

Question 2

Which interfaces does the critical zone consist of?

Answer 2

Land surface
Vegetation
Soils
Groundwater

Question 3

What is chemical weathering?

How does it work?

Answer 3

Dissolution of soluble minerals

CO2 dissolves in rainwater forming carbonic acid, which dissolves rocks on contact

Question 4

What is hydrolysis?

Answer 4

Breaking down of chemical compounds

Question 5

What cycle do sediments and sedimentary rocks reflect?

Answer 5

Weathering
Erosion
Transport
Deposition

Question 6

When do sediment grains move?

Answer 6

Lift + drag > gravity + cohesion + adhesion

Fluids exceed critical velocity

Question 7

How can sediment grains move?

Answer 7

Grain rolling
Grain saltation
Grain suspension

Question 8

Why do fluids tend to sort grains by properties?

Answer 8

Critical velocity is specific to grain size and density

Question 9

Granular sediments:
Definition
Behaviour
Structures most seen in?

Answer 9

Coarser than fine silt
Individual grains -> sorting leads to patterns
Sand

Question 10

Outline the structures seen with increasing flow regime

Answer 10

Ripples
Dunes
Washed-out and humpbacked dunes
Upper plane bed
Antidunes
Chute-and-pool

Question 11

Cohesive sediments:
Definition
Behaviour
Grain actions depend on?

Answer 11

Finer than fine silt
Individual grains bind together/fall apart, and take on/lose water
Local chemistry, biology or physical composition

Question 12

Clay minerals:
Derived from
Composition
Form
Consequences of form

Answer 12

Breakdown of feldspars and other silicates
Hydrated aluminosilicates
Platy
Surface tension, hard to erode and deposit