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Earth System- 29992 > Weathering and soils > Flashcards

Weathering and soils Flashcards

1
Q

What is weathering?

A

physical and chemical breakdown of rocks and minerals at the Earth’s surface.

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2
Q

What is mechanical weathering?

A

mechanical breakdown into smaller pieces

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3
Q

What is chemical weathering?

A

decomposition by chemical alteration

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4
Q

What is erosion?

A

physical removal of the weathered material

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5
Q

What processes can lead to the production of joints via mechanical weathering?

A

Tectonic, hydraulic, exfoliation, unloading, cooling

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6
Q

What are joints within rock?

A

weakness that can be exploited by other processes

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7
Q

What is exfoliation of rock?

A

after a stress release spalling off of sheets of material from the outer surface

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8
Q

What type of rock does exfoliation usually occur in?

A

granites (can lead to rounded outcrops)

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9
Q

What 2 types of secondary processes can exploit joints?

A

Ice wedging (freeze thaw)
Salt wedging

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10
Q

How does ice wedging exploit joints on rock?

A

Water from rain or condensation will flow into cracks in rocks when it freezes it will expand forcing the rock to fracture

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11
Q

How much can water increase in volume upon freezing?

A

9-10%

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12
Q

Where is salt wedging most likely to occur?

A

arid settings

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13
Q

What is the process of salt wedging?

A

gypsum or halite precipitates in pores and joints wedging them apart as salt crystals grow

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14
Q

What are some example of biogenic weathering?

A

plant roots into joints (slow as plant grows)
Animals can bore into rock

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15
Q

What is scree?

A

collection of broken up pieces of rock (loose/ unconsolidated)

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16
Q

What is talus?

A

talus cones – landforms made up of scree

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17
Q

What can chemical weathering be thought of as?

A

minerals equalising with the environment

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18
Q

What is the main type of chemical weathering?

A

dissolution

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19
Q

What are the different types of chemical weathering?

A

Hydration/dehydration
Hydrolysis
OILRIG

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20
Q

How can dehydration/hydration weather a material?

A

loss or gain of water can affect a minerals mechanical properties (make them weaker)

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21
Q

What is the dehydration example with gypsum?

A

when hydrated gypsum looses water turns to anhydrite

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22
Q

What is hydrolysis?

A

substitution of hydrogen ions in solution in acidic waters for cations in solid minerals

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23
Q

What makes rain water slightly acidic?

A

dissolved CO2 interacts with water to form carbonic acid (part of limestone dissolution)

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24
Q

How do calcium carbonate ad hydrogen cations interact?

A

hydrogen can replace calcium cation through substitution (limestone dissolution)

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25
Q

What can hydrogen ions do to solids?

A

can alter into different solids with different mechanical properties

26
Q

What is oxidation and reduction?

A

Oxygen is lose of electrons
Reduction is gain of electrons

27
Q

Where does most oxygen occur?

A

O2 dissolved in water

28
Q

What factors can control chemical weathering?

A

Temperature
Moisture
pH
eH

29
Q

How can temperature control chemical weathering?

A

higher temp= more energy for reactions

30
Q

How can moisture control chemical weathering?

A

most weathering needs water - more water = stringer weathering

31
Q

How can pH control chemical weathering?

A

H+ ions are needed for hydrolysis
Rainwater- 4-6.5 Ocean-8 (weathering more prevalent on land)

32
Q

What is eH?

A

the redox potential

33
Q

What is the redox potential?

A

likelihood of the gin or loss of electrons

34
Q

What are the physical parameters of weathering?

A

Climate
Drainage
Relief

35
Q

How is climate a parameter of weathering?

A

changes globally
Past events - snowball
Moving weather belts
Warm temp more weathering
Cold- freeze thaw

36
Q

How is drainage a parameter of weathering?

A

well drained environments experience more continuous weathering as weathering reactions require weathering products to be removed

37
Q

How is relief a parameter of weathering?

A

higher relief, speed of drainage and mass-wasting increases

38
Q

What is mass wastage?

A

with increased altitude mass will become more unstable and prone to collapse

39
Q

What can trees do to scree slopes?

A

The roots can bind materials having a stabilising effect

40
Q

How can grain size affect weathering?

A

increased surface area of finer grained rocks/minerals means they weather faster than than larger grained rocks/minerals

41
Q

What will happen to surface area and volume as a material in weathered?

A

surface area will increase
Volume remains the same

42
Q

What composition of rock are more resistant to weathering?

A

Felsic - quartz rich closer to earth surface conditions

43
Q

What composition of rock is least resistant to weathering?

A

Mafic- olivine furthest from surface conditions

44
Q

Is there any isolation of weathering cycles?

A

No

45
Q

What is the main weathering cycle?

A

carbonate-silicate cycles

46
Q

What can soil be called the bridge between?

A

life and the inanimate world

47
Q

What are mineral fragments and weathered rock called?

A

Regolith

48
Q

What is soil?

A

combination of mineral and organic matter, water, and air and the portion of the regolith that plants live from

49
Q

What controls the formation of soil?

A

parent material
Time
Climate
Plants/animals
Topography

50
Q

How do you describe soil profile?

A

divided into horizontal layers called horizons

51
Q

What might be the difference in soil profile between a mature and immature soil?

A

Mature will have well developed horizons
Immature might not have horizons

52
Q

How many orders of soil are there?

A

12

53
Q

What 2 soil horizons are in the top soil?

A

O
A

54
Q

What is the O horizon in soil?

A

loose partly decayed organic matter

55
Q

What is the A horizon in soil?

A

mineral matter mixed with some humus

56
Q

What is the E horizon in soil?

A

Zone of eluviation and leaching

57
Q

What soil horizon is classified as the sub-soil?

A

B

58
Q

What is soil horizon B?

A

Accumulation of clay transported from above layers

59
Q

What is soil horizon C?

A

partially altered parent material

60
Q

What do you find below horizon C?

A

parent material

61
Q

What is parent material in soil?

A

weathered rock or deposit soil forms from

Earth System- 29992 (24 decks)

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