F2 - Surface and Internal Processes of the Rock Cycle - Key Idea 1

Question 1

What is weathering?

Answer 1

The breakdown of rock in situ (no movement)

Question 2

What are the three types of weathering?

Answer 2

Physical - Freeze Thaw, Insolation
Chemical - Carbonation, Oxidation, Hydrolysis
Biological - Chemical and Physical types

Question 3

Freeze Thaw

Answer 3

Need - Water, fluctuating temperatures of below and above 0’C, precipitation/rainfall, joints in the rock, repeated action
Location - Scotland
Product - Scree/Lithic fragments
Process:
- water gets into joints in the rock after it is precipitated down
- when the temperature falls below 0* the water freezes and expands by ~9%
- this causing pressure to build which forces the joint apart, the temperature increases again and the ice melts
- this process is repeated until the piece of rock breaks off

Question 4

Insolation (onion skin)

Answer 4

Need - Largely fluctuating hot and cold weather (no fixed temp), repeated action, joints in the rock
Location - South Africa
Product - Scree/Lithic fragments
Process:
- the temperature rises during the day and causes the rock to get very hot and expand
- at night the temperature dramatically drops and causes the rock to get cold therefore the rock contracts
- this is repeated and causes the rock to get weaker, joints then start to appear
- rocks begin to peel off/break off due to the weakened state of the rock

Question 5

Carbonation

Answer 5

Need - Limestone, rock made out of Calcium Carbonate (Calcite CaCO3), carbonic acid, joints in rock

Question 6

Oxidation

Question 7

Hydrolysis

Question 8

Biological- Physical

Question 9

Biological-Chemical

Question 10

Erosion

Answer 10

The break down of rocks during or due to transportation (movement)
Movement is caused by: rivers, wind, oceans/seas, gravity, and ice

Question 11

Abrasion

Answer 11

Grains rub on the channel or on other grains

Question 12

Attrition

Answer 12

Grains bump into each other or the channel

Question 13

Corrosion

Answer 13

Where limestone dissolves due to coming into contact with an acid ????

Question 14

Transportation

Answer 14

The movement of sediment (the products of weathering and erosion)

Question 15

Traction

Answer 15

Grains are in constact contact with the bed
Round in shape - roll
Long in shape - slide
Resistant/new minerals

Question 16

Saltation

Answer 16

Grains sometimes in contact with the bed sometimes not
They bounce
Resistant/new minerals

Question 17

Suspension

Answer 17

Grains never in contact with the bed
They hang in the transporting mode
Resistant/new minerals

Question 18

Solution

Answer 18

Dissolved in the transport mode e.g. water
Ions in solution

Question 19

Movement and changes

Answer 19

The sediments follow the direction of the current
Movement of the sediments is dependent on the: size of the grains, the density of the grains and the velocity of the current
Decrease in current - t to deposited, sa to t, su to sa, so stays the same/slows down with the current
Increase in current - t to sa, sa to su, su+so just move quicker (but size doesn’t change)

Question 20

Seposition

Question 21

Evaporates

Question 22

Estuary

Question 23

Sedimentary rock descriptions

Answer 23

Size (grains)
Shape (grains)
Sorting
Colour
Composition
Cement/Matrix

Question 24

Size (grains)

Answer 24

Size of the average grain
You need a description and measurement
Coarse (mm, cm), medium (um), fine (<187um)
High energy (little transport and erosion) ———> low energy (lots of transport and erosion)

All medium grains are sandstones
Anything to fine to see is made of clay minerals

Question 25

Shape (grains)

Answer 25

Very well rounded - lots of transport and erosion Rounded Sub-rounded Sub-angular Angular Very angular - little transport and erosion

Question 26

Sorting

Answer 26

How similar the grain sizes are to each other Very well sorted ( all roughly the same size) - long transport and lots of erosion Well sorted Moderately sorted Poorly sorted Very poorly sorted (lots of different sizes) - short transport and little erosion

Question 27

Colour

Answer 27

Can’t say grey or dark/light grey Can say blue grey or dark/light blue grey You need a colour as well as grey if you say grey

Question 28

Composition

Answer 28

The percentage of the minerals + etc within the rock

Question 29

Cement/Matrix

Question 30

Foramtion

Question 31

Conglomerate

Answer 31

Size - coarse/small pebbles to large pebbles, 7mm-29mm (size depends on example given) Shape - rounded Sorting - very poorly sorted Colour - beige grey Composition - lithic fragments ?% Cement/Matrix - sand matrix but also a calcite cement Breccia is the same apart from the shape where the grains would be angular instead of round

Question 32

Orthoquartzite Desert Sandstone

Answer 32

Size - coarse 1mm or 750um (size depends on example given, very fine ODS is 375um, very coarse ODS is 1500um/1.5mm) Shape - very well rounded Sorting - very well sorted Colour - brick red Composition - quartz 90%, orthoclase 5% (white), lithic fragments 5% (black) Cement/Matrix - hematite and quartz cement (red and hard)

Question 33

Shale - and easy example even though it looks hard

Answer 33

Size - fine <187um Shape - too fine to see (clay minerals are long and thin/**Lath** shaped so could say this) Sorting - very well sorted Colour - dark blue grey Composition- clay minerals 100% Cement/Matrix - none

Question 34

Sedimentary Environments - Deserts

Answer 34

Arid (dry) Playa lake Wadi Alluvial fan Sand dunes

Question 35

Playa lake

Answer 35

Low energy Ions in solution - evaporation due to heat and wind - salts precipitate in order of solubility • calcite - bottom and side • gypsum - side and top • halite • bittern salts

Question 36

Playa lake - sedimentary rock

Answer 36

Mudstone - laminations and desiccation cracks • size - fine <187um • shape - too fine to see/lath shaped • sorting - very well sorted • composition - 100% clay minerals • colour - red/brown • cement/matrix - none

Question 37

Desiccation cracks

Question 38

Sand dunes

Answer 38

Aeolian (wind) Medium energy

Question 39

Sand dune - sedimentary rock

Answer 39

Orthoquartzite desert sandstone - cross bedding and asymmetrical ripples • size - medium 0.5-1.5mm • shape - very well rounded • sorting - very well sorted • composition - 90% quartz, 5% orthoclase, 5% lithic fragments • colour - brick red • cement/matrix - hematite cement Grains are frosted by attrition - dull/pitted surface

Question 40

Cross bedding

Question 41

Asymmetrical ripples

Question 42

Laminations

Question 43

Wadi