Weathering and soils

Question 1

What is weathering?

Answer 1

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

Question 2

What is mechanical weathering?

Answer 2

mechanical breakdown into smaller pieces

Question 3

What is chemical weathering?

Answer 3

decomposition by chemical alteration

Question 4

What is erosion?

Answer 4

physical removal of the weathered material

Question 5

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

Answer 5

Tectonic, hydraulic, exfoliation, unloading, cooling

Question 6

What are joints within rock?

Answer 6

weakness that can be exploited by other processes

Question 7

What is exfoliation of rock?

Answer 7

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

Question 8

What type of rock does exfoliation usually occur in?

Answer 8

granites (can lead to rounded outcrops)

Question 9

What 2 types of secondary processes can exploit joints?

Answer 9

Ice wedging (freeze thaw)
Salt wedging

Question 10

How does ice wedging exploit joints on rock?

Answer 10

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

Question 11

How much can water increase in volume upon freezing?

Answer 11

9-10%

Question 12

Where is salt wedging most likely to occur?

Answer 12

arid settings

Question 13

What is the process of salt wedging?

Answer 13

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

Question 14

What are some example of biogenic weathering?

Answer 14

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

Question 15

What is scree?

Answer 15

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

Question 16

What is talus?

Answer 16

talus cones – landforms made up of scree

Question 17

What can chemical weathering be thought of as?

Answer 17

minerals equalising with the environment

Question 18

What is the main type of chemical weathering?

Answer 18

dissolution

Question 19

What are the different types of chemical weathering?

Answer 19

Hydration/dehydration
Hydrolysis
OILRIG

Question 20

How can dehydration/hydration weather a material?

Answer 20

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

Question 21

What is the dehydration example with gypsum?

Answer 21

when hydrated gypsum looses water turns to anhydrite

Question 22

What is hydrolysis?

Answer 22

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

Question 23

What makes rain water slightly acidic?

Answer 23

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

Question 24

How do calcium carbonate ad hydrogen cations interact?

Answer 24

hydrogen can replace calcium cation through substitution (limestone dissolution)

Question 25

What can hydrogen ions do to solids?

Answer 25

can alter into different solids with different mechanical properties

Question 26

What is oxidation and reduction?

Answer 26

Oxygen is lose of electrons Reduction is gain of electrons

Question 27

Where does most oxygen occur?

Answer 27

O2 dissolved in water

Question 28

What factors can control chemical weathering?

Answer 28

Temperature Moisture pH eH

Question 29

How can temperature control chemical weathering?

Answer 29

higher temp= more energy for reactions

Question 30

How can moisture control chemical weathering?

Answer 30

most weathering needs water - more water = stringer weathering

Question 31

How can pH control chemical weathering?

Answer 31

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

Question 32

What is eH?

Answer 32

the redox potential

Question 33

What is the redox potential?

Answer 33

likelihood of the gin or loss of electrons

Question 34

What are the physical parameters of weathering?

Answer 34

Climate Drainage Relief

Question 35

How is climate a parameter of weathering?

Answer 35

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

Question 36

How is drainage a parameter of weathering?

Answer 36

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

Question 37

How is relief a parameter of weathering?

Answer 37

higher relief, speed of drainage and mass-wasting increases

Question 38

What is mass wastage?

Answer 38

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

Question 39

What can trees do to scree slopes?

Answer 39

The roots can bind materials having a stabilising effect

Question 40

How can grain size affect weathering?

Answer 40

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

Question 41

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

Answer 41

surface area will increase Volume remains the same

Question 42

What composition of rock are more resistant to weathering?

Answer 42

Felsic - quartz rich closer to earth surface conditions

Question 43

What composition of rock is least resistant to weathering?

Answer 43

Mafic- olivine furthest from surface conditions

Question 44

Is there any isolation of weathering cycles?

Answer 44

No

Question 45

What is the main weathering cycle?

Answer 45

carbonate-silicate cycles

Question 46

What can soil be called the bridge between?

Answer 46

life and the inanimate world

Question 47

What are mineral fragments and weathered rock called?

Answer 47

Regolith

Question 48

What is soil?

Answer 48

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

Question 49

What controls the formation of soil?

Answer 49

parent material Time Climate Plants/animals Topography

Question 50

How do you describe soil profile?

Answer 50

divided into horizontal layers called horizons

Question 51

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

Answer 51

Mature will have well developed horizons Immature might not have horizons

Question 52

How many orders of soil are there?

Answer 52

12

Question 53

What 2 soil horizons are in the top soil?

Answer 53

O A

Question 54

What is the O horizon in soil?

Answer 54

loose partly decayed organic matter

Question 55

What is the A horizon in soil?

Answer 55

mineral matter mixed with some humus

Question 56

What is the E horizon in soil?

Answer 56

Zone of eluviation and leaching

Question 57

What soil horizon is classified as the sub-soil?

Answer 57

B

Question 58

What is soil horizon B?

Answer 58

Accumulation of clay transported from above layers

Question 59

What is soil horizon C?

Answer 59

partially altered parent material

Question 60

What do you find below horizon C?

Answer 60

parent material

Question 61

What is parent material in soil?

Answer 61

weathered rock or deposit soil forms from