Weathering

Question 1

Strata are horizontal…

Answer 1

layers of material.

Question 2

Weathering is a breakdown of…

Answer 2

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

Question 3

Physical/Mechanical weathering results in…

Answer 3

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

Question 4

Biological weathering is a form of…

Answer 4

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

Question 5

Chemical weathering involves…

Answer 5

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

Question 6

Freeze-thaw weathering can be found in areas…

Answer 6

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

Question 7

Joints are cracks in a rock in…

Answer 7

vertical position.

Question 8

Lines of weakness are cracks in a rock in…

Answer 8

horizontal position.

Question 9

During freeze-thaw, water percolate…

Answer 9

into joints and freezes.

Question 10

The volume of frozen water expands by…

Answer 10

9%.

Question 11

The expansion of frozen water…

Answer 11

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

Question 12

Frost shattering can happen if…

Answer 12

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

Question 13

Salt crystallisation can be found in…

Answer 13

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

Question 14

When water enters joints, salts such as…

Answer 14

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

Question 15

Another form of salt crystallisation can be when…

Answer 15

the water evaporates, salt crystals are left behind.

Question 16

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

Answer 16

expands and exerts pressure on the rock.

Question 17

Occasionally, salt crystallisation can occur in areas of…

Answer 17

polar regions, when salt is deposited form snowflakes.

Question 18

The rate of disintegration of rock is related to…

Answer 18

porosity and permeability of the rock.

Question 19

The combination of freeze-thaw and…

Answer 19

salt crystallisation produces the highest rates of breakdown.

Question 20

Exfoliation can be found in hot…

Answer 20

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

Question 21

Rocks are poor conductors of heat, therefore…

Answer 21

exfoliation occurs only in the outer layers.

Question 22

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

Answer 22

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

Question 23

During the night, there is no insolation, causing…

Answer 23

the rock to return to its original shape.

Question 24

As the rock heats up again, the outer layer…

Answer 24

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

Question 25

The exfoliation needs small amount of...

Answer 25

moisture to undergo the weathering, showed by Griggs 1936.

Question 26

Pressure release is also known as...

Answer 26

dilatation.

Question 27

Pressure release starts when...

Answer 27

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

Question 28

When the rocks come up as the pressure is released,

Answer 28

horizontal pseudo-bedding planes are formed.

Question 29

Vegetation roots may...

Answer 29

physically break down rocks.

Question 30

Water is a key medium for...

Answer 30

chemical weathering.

Question 31

Chemical weathering is most effective...

Answer 31

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

Question 32

Carbonation-solution occurs on rocks with...

Answer 32

calcium carbonate, such as chalk and limestone.

Question 33

(carbonation)Rainfall combines with dissolved...

Answer 33

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

Question 34

Carbonic acid reacts with...

Answer 34

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

Question 35

The equation for the formation of calcium bicarbonate:

Answer 35

CaCO3 + H2CO3 = Ca(HCO3)2

Question 36

Hydrolysis occurs on rocks with...

Answer 36

orthoclase feldspar, mostly granite.

Question 37

Feldspar reacts with...

Answer 37

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

Question 38

The equation for the formation of kaolinite:

Answer 38

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

Question 39

The silicic acid and hydroxyl are...

Answer 39

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

Question 40

Other minerals in the granite such as...

Answer 40

quartz and mica remain in the kaoline.

Question 41

Hydration is the process when...

Answer 41

certain pervious minerals absorb water, expand and change.

Question 42

During hydration, anhydrate...

Answer 42

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

Question 43

Oxidation happens when...

Answer 43

Fe in rocks reacts with oxygen, resulting in rusting.

Question 44

After oxidation, ferrous rocks break...

Answer 44

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

Question 45

To start chelation, dead vegetation...

Answer 45

must be decomposed by microbes.

Question 46

(chelation)Precipitation mixes with...

Answer 46

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

Question 47

The chelation continues by solution...

Answer 47

weathering, where humic acid reacts with rocks.

Question 48

The Basal surface of weathering is the maximum...

Answer 48

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