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Physical Geography A-level > Weathering > Flashcards

Weathering Flashcards

1
Q

Strata are horizontal…

A

layers of material.

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2
Q

Weathering is a breakdown of…

A

rock in situ-it is not taken away(erosion).

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3
Q

Physical/Mechanical weathering results in…

A

disintegration of a rock, producing angular fragments of the same rock.

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4
Q

Biological weathering is a form of…

A

disintegration(mechanical) and decomposition(chemical). The processes are interrelated.

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5
Q

Chemical weathering involves…

A

granular disintegration on the particle level, creating altered rock substances.

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6
Q

Freeze-thaw weathering can be found in areas…

A

of temperature change above or below 0 degrees, which can be either diurnal or seasonal.

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7
Q

Joints are cracks in a rock in…

A

vertical position.

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8
Q

Lines of weakness are cracks in a rock in…

A

horizontal position.

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9
Q

During freeze-thaw, water percolate…

A

into joints and freezes.

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10
Q

The volume of frozen water expands by…

A

9%.

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11
Q

The expansion of frozen water…

A

forces the rock apart. Over time, the joints get larger.

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12
Q

Frost shattering can happen if…

A

the rock is filled with a lot of water-the rock instantly breaks apart.

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13
Q

Salt crystallisation can be found in…

A

hot desert regions where low rainfall and high temperatures cause salt to accumulate just below the surface.

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14
Q

When water enters joints, salts such as…

A

sodium sulphate or sodium carbonate can be formed. These salts can expand by about 300%, putting pressure on the joints.

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15
Q

Another form of salt crystallisation can be when…

A

the water evaporates, salt crystals are left behind.

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16
Q

(salt crystallisation)As the temperature rises, the salt…

A

expands and exerts pressure on the rock.

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17
Q

Occasionally, salt crystallisation can occur in areas of…

A

polar regions, when salt is deposited form snowflakes.

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18
Q

The rate of disintegration of rock is related to…

A

porosity and permeability of the rock.

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19
Q

The combination of freeze-thaw and…

A

salt crystallisation produces the highest rates of breakdown.

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20
Q

Exfoliation can be found in hot…

A

desert areas, where there is a large diurnal temperature change.

21
Q

Rocks are poor conductors of heat, therefore…

A

exfoliation occurs only in the outer layers.

22
Q

During a day, there are heavy rates of insolation, causing…

A

the rock to expand as it heats up. The rock will undergo stress. The lines of weakness will grow inside the rock.

23
Q

During the night, there is no insolation, causing…

A

the rock to return to its original shape.

24
Q

As the rock heats up again, the outer layer…

A

of rock breaks off, as it starts to expand again.

25
Q

The exfoliation needs small amount of…

A

moisture to undergo the weathering, showed by Griggs 1936.

26
Q

Pressure release is also known as…

A

dilatation.

27
Q

Pressure release starts when…

A

overlaying rocks are removed by erosion. This causes the underlying rock to expand(isostatic change) and lines of weakness are formed to release pressure.

28
Q

When the rocks come up as the pressure is released,

A

horizontal pseudo-bedding planes are formed.

29
Q

Vegetation roots may…

A

physically break down rocks.

30
Q

Water is a key medium for…

A

chemical weathering.

31
Q

Chemical weathering is most effective…

A

sub-surface weathering, since percolating water gained organic acids.

32
Q

Carbonation-solution occurs on rocks with…

A

calcium carbonate, such as chalk and limestone.

33
Q

(carbonation)Rainfall combines with dissolved…

A

CO2 to form a weak carbonic acid. CO2 + H2O = H2CO3

34
Q

Carbonic acid reacts with…

A

Calcium carbonate(calcite) and forms calcium bicarbonate, which is soluble and removed by percolating water.

35
Q

The equation for the formation of calcium bicarbonate:

A

CaCO3 + H2CO3 = Ca(HCO3)2

36
Q

Hydrolysis occurs on rocks with…

A

orthoclase feldspar, mostly granite.

37
Q

Feldspar reacts with…

A

acid water and forms kaolinite-china clay, potassium hydroxyl and silicic acid.

38
Q

The equation for the formation of kaolinite:

A

2KAlSi3O8(feldspar) + 2H2O = Al2Si2O5(OH)4 (kaolinite) + K2O(potassium hydrxyl) + 4SiO2(silicic acid)

39
Q

The silicic acid and hydroxyl are…

A

removed in the solution, leaving kaoline behind as end product.

40
Q

Other minerals in the granite such as…

A

quartz and mica remain in the kaoline.

41
Q

Hydration is the process when…

A

certain pervious minerals absorb water, expand and change.

42
Q

During hydration, anhydrate…

A

absorbs water to become gypsum, it expands by about 0.5 %, creating hydrostatic pressure.

43
Q

Oxidation happens when…

A

Fe in rocks reacts with oxygen, resulting in rusting.

44
Q

After oxidation, ferrous rocks break…

A

into ferric material-bits of iron breaks off the rock.

45
Q

To start chelation, dead vegetation…

A

must be decomposed by microbes.

46
Q

(chelation)Precipitation mixes with…

A

nutrients from decomposed vegetation and humic acid is formed, which is very fertile and it is very acidic.

47
Q

The chelation continues by solution…

A

weathering, where humic acid reacts with rocks.

48
Q

The Basal surface of weathering is the maximum…

A

depth to which weathering penetrates. It makes the boundary between the weathered and unweathered rock.

Physical Geography A-level (33 decks)

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