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Sedimentary Rocks and Processes Flashcards

1
Q

Define Weathering

A

The physical breaking up of rock into smaller pieces

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2
Q

Define Erosion

A

The removal of material

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3
Q

What are three physical weathering processes?

A

Freeze-thaw, Insolation, Pressure release

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4
Q

What is a biological weathering process?

A

Root growth

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5
Q

What are four chemical weathering processes?

A

Carbonation, Oxidation, Hydrolysis, Solution

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6
Q

Define Carbonation

A

Rainwater containing carbon dioxide from the air and soil reacts with carbonates to form soluble hydrogen carbonates

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7
Q

Define Freeze-Thaw

A

Water expands by 9% upon freezing so fractures filled with water are prized further apart

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8
Q

Define Insolation

A

Heating and cooling of rocks in desert regions causes minerals to expand and contract at different rates until the rock fractures

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9
Q

Define Oxidation

A

The addition of oxygen to the atomic structures of minerals or a similar chemical change

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10
Q

Define Hydrolysis

A

The addition of water molecules to the atomic structures of minerals

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11
Q

Define Root Growth

A

Plant roots growing in fractures

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12
Q

Define Solution

A

Soluble minerals dissolve and are carried away in solution

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13
Q

Define Pressure Release

A

Deeply buried rocks are compressed by the pressure of the rocks above. When the overburden is removed, the rock expands to produce stress release fractures

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14
Q

What are the three agents of erosion?

A

Wind, Water, Ice

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15
Q

Define Agent of Erosion

A

Things that move material

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16
Q

What does the Hjulstrom Curve help geologists to determine?

A

What velocity is required to erode, transport and deposit different sized clasts

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17
Q

What is the Hjulstrom Curve based on?

A

The results from an experiment with flowing water (1m depth) over flat-lying, unconsolidated sediment

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18
Q

What are three positives of the Hjulstrom Curve?

A

Uses a logarithmic scale to show a wide range of clast sizes and velocities, Describes the relationship between velocity and grain size, Uniformitarianism - present is the key to the past

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19
Q

What are three negatives of the Hjulstrom Curve?

A

Only applies to rivers 1m deep, Loose sediment on the bottom of the river only, Doesn’t take density, shape or angularity of sediment into consideration

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20
Q

What are two erosional processes that modify shape during transportation?

A

Abrasion and Attrition

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21
Q

Define Abrasion

A

Particles grind down the bedrock

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22
Q

Define Attrition

A

The particles grind against each other

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23
Q

What are the five processes of transportation?

A

Suspension, Solution, Saltation, Traction, Sliding

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24
Q

What are three ways sediment can change as it moves downhill?

A

Size, Shape, Composition

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25
Relating to size, the further a grain moves from its source...
The smaller it becomes
26
What scale can size be categorised by?
Wentworth Scale
27
Relating to shape, the further a grain moves from its source...
The more rounded it becomes
28
What is roundness described by?
Using six different classes from very angular to well rounded
29
What is shape influenced by?
The planes of weakness within the rock
30
What are the four categories on the Zingg Analysis?
Blade, Disc, Rod, Sphere
31
Relating to composition, the further a sediment moves from its source...
The more compositionally mature it becomes
32
Define Bowen's Reaction Series
Helps geologists to predict the stability of a mineral and therefore how likely it is to weather
33
The higher the temperature at which a mineral forms...
The more likely it is to be weathered
34
Using Bowen's Reaction Series, what are the four least stable minerals?
Olivine, Pyroxene (Augite), Amphibole (Hornblende), Feldspar
35
Using Bowen's Reaction Series, what are the two most stable minerals?
Quarts and Muscovite
36
What happens to the feldspars when granite is weathered?
They undergo hydrolysis to form clay
37
What happens to the biotite when granite is weathered?
Undergo hydrolysis to form clay and oxidation to form iron oxides
38
What happens to the quartz when granite is weathered?
It remains as residual minerals due to their chemical weathering resistance
39
Define Sorting
The size range exhibited by a sediment
40
What can a grain size analysis help geologists decide?
What the main method of transportation was
41
Mean Grain Size =
(∅75+∅50+∅25)/3
42
Skewness =
(∅84-∅50)/(∅84-∅16) - (∅50-∅5)/(∅95-∅5)
43
Sorting Coefficient =
(∅84-∅16)/2
44
Define Matrix
Fine grained sediment holding clasts together
45
Define Cement
A crystalline material (calcite or quartz usually) which holds grains together
46
Define Monomictic
One clast composition
47
Define Polymictic
Variety of clast compositions
48
Define Clast Supported
Clasts touch each other
49
Define Matrix Supported
Clasts are not touching
50
What are thirteen sedimentary structures which can be used as a way up indicator?
Cross bedding, Graded bedding, Ripple marks, Desiccation cracks, Flute casts, Prod marks, Roots, Burrows, Geopetal structures, Fossils in life assemblage, Included fragments, Channels, Load casts and flame structures
51
What are six sedimentary structures which can be used as a paleocurrent indicator?
Cross bedding, Imbricate structures, Ripple marks (if asymmetrical), Flute casts, Prod marks (trend), Channels (trend)
52
What are the four facies in a desert?
Scree slopes, Alluvial fan, Aeolian sand dunes, Playa lake
53
What are the four facies in a fluvial system?
Channel, Point bar, Flood plain, Ox-bow lake
54
Define Delta
Where river carry sediment into deeper relatively still water, forming the mouth of a river
55
What are five sedimentary structures found in the top set of a deltaic sequence?
Channel, Cross bedding, Laminations, Ripples, Roots
56
What are two sedimentary structures found in the foreset of a deltaic sequence?
Cross bedding, Ripples
57
What are three sedimentary structures found in the bottom set of a deltaic sequence?
Laminations, Burrows, Fossils
58
What are the four facies in a marine environment?
Beach, Tropical, Deep marine, Turbidites
59
What are four conditions required for limestone formation?
Marine water, Shallow water depth, Warm water temperature, Clear water
60
What type of limestone was formed in the Cretaceous?
Chalk
61
What type of limestone was formed in the Jurassic?
Oolitic
62
What type of limestone was formed in the Carboniferous?
Bioclastic
63
Define Turbidites
Underwater avalanche moving downhill (density driven) made from greywacke and mudstone, triggered by mass movement or an earthquake
64
Define Diagenesis
The group of processes which change a sediment into a rock, at low temperatures and pressures near the Earth's surface
65
What are the two main processes of diagenesis?
Compaction and Cementation
66
Define Compaction
Sediment is squeezed by the pressure of overlying sediment
67
What happens during compaction?
Water is lost as porosity and permeability are reduced
68
Define Cementation
Minerals crystallise in pore spaces, cementing the grains together
69
What happens to permeability during cementation?
Decreases as the grains are bound together
70
What are three minerals commonly acting as cement?
Quartz, Calcite, Iron minerals e.g. haematite

Geology (16 decks)

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