Weathering

Question 1

tallis slope

Answer 1

slope of highly angular rock fragments

Question 2

4 main factors on weathering

Answer 2

water, chemical enviro., pressure, temp.

Question 3

equifinality

Answer 3

different processes leading to the same rock type or formation

Question 4

4 key components in the weathering system

Answer 4

process, materials, form and environment

Question 5

4 important effects of rock breakdown

Answer 5

soil formation, landscape and landform evolution, prepares rock for erosion and transportation, dissolved nutrients

Question 6

4 products of weathering systems

Answer 6

physical particles, chemicals dissolved in water in form of ions, oxides, clay minerals from chemical trans of minerals

Question 7

explain weathering feedback

Answer 7

landforms produced by weathering will influence further weathering-> increased surface area makes rock break down more quickly

Question 8

3 types of weathering

Answer 8

physical, chemical, biological

Question 9

explain dilation weathering

Answer 9

removal of overlying material over an igneous dome leads to pressure release, joints and fractures, top layer breaks up-> more uplift

Question 10

two features formed from dilation

Answer 10

exfoliation dome, exfoliation sheet

Question 11

explain thermoclasty

Answer 11

driven by sun, forest fires, lightning strikes. thermal shock when temp. changes so rapidly that rock cracks.
fatigue failure, repeated app. of stress
granular disintegration- grain by grain weathering

Question 12

how much does water expand by when frozen

Answer 12

9%

Question 13

what temp is needed for effective ice expansion in freeze-thaw

Answer 13

-22C

Question 14

difference between macro and microgélivation

Answer 14

macrogélivation: large blocks get broken off, microgélivation: granular disintegration and flaking

Question 15

explain salt crystal weathering

Answer 15

water evaporates to leave salt behind, grows, wedges rock apart
micropores allow movement of saline solution into pores
causes flaking, alveoli

Question 16

what are tafoni

Answer 16

larger alveoli (cavernous weathering)

Question 17

where does salt weathering mostly occur

Answer 17

desert and coastal environments

Question 18

explain hydration weathering

Answer 18

water into rock, water molecules attach to crystalline structure of mineral, expansion when hydrated, mineral grains flake off

Question 19

which out of the two main controls is most influential on weathering

Answer 19

climate but can be overtaken by material factors

Question 20

substance that increases the proton conc. of water

Answer 20

acidic/proton donor

Question 21

substance that decreases the proton conc. of water

Answer 21

proton acceptor/base

Question 22

what is the most common proton donor in nature

Answer 22

carbonic acid

Question 23

redox potential (Eh)

Answer 23

ability of a chemical species to bring about an oxidation or reduction reaction

Question 24

what is solubility in natural environments dependent on

Answer 24

pH and Eh, both of which are influenced by temp.

Question 25

give characteristics of water that allows it to weather physically

Answer 25

high cohesiveness, high surface tension, high capillarity, freely changes from solid to liquid to gas

Question 26

slaking

Answer 26

alternate wetting and drying that causes materials to disintegrate and crumble

Question 27

explain hydrolysis

Answer 27

chemical reaction between mineral and slightly acidic water to break bonds of a partic. substance. congruent dissolution: metal cations selectively replaced in the crystal lattice and minerals altered into clay minerals

Question 28

what minerals are especially affected by hydrolysis

Answer 28

feldspars

Question 29

what minerals can carbonation weather

Answer 29

carbonate, silicate and ferro-magnesium minerals

Question 30

why is limestone dissolved more quickly beneath soil

Answer 30

soil carries a higher conc. of dissolved CO2

Question 31

how does temp affect carbonation

Answer 31

partial pressure of CO2 falls with a rise in temperature so colder temps may lead to more weathering. (but other factors at play)

Question 32

how do oxidation and reduction transform substances

Answer 32

addition and removal of oxygen

Question 33

what is chelation

Answer 33

metal ions are kept in solution and prevented from precipitating within plant roots-> causes the removal of these cations by ion exchange, replaced by hydrogen ions which acidify soils

Question 34

give example of bacteria that weathers rock

Answer 34

cyanobacteria cause locally concentrated weathering and erosion

Question 35

function of lichens

Answer 35

communities of fungi and algae, bioprotectors, can promote weathering by excreting organic acids or prevent it by producing oxalic acid (quite insoluble coating on limestone)

Question 36

resistates

Answer 36

unaltered primary materials basically immune to a specific process that survive while surrounding rocks are weathered away

Question 37

what are secondary materials

Answer 37

weathering products of primary materials

Question 38

what determines the composition of clay material in secondary materials

Answer 38

the initial material and the intensity/duration of weathering

Question 39

how are sandy regoliths formed

Answer 39

minerals less susceptible to weathering continue to break down into smaller fragments

Question 40

what causes thermal shock (type of thermoclasty)

Answer 40

sudden temp change doesnt allow time to expand/contract quickly enough. adjacent crystals heat and expand at diff rates

Question 41

give factors that can prevent or slow down freeze-thaw

Answer 41

increased pressure during ice formation can lower freezing point and slow further freezing, impurities slow down freezing, rocks not at near saturation

Question 42

does salt weathering occur through shock or fatigue

Answer 42

fatigue

Question 43

what are the three main processes at work in salt weathering

Answer 43

crystallisation, hydration, differential thermal expansion

Question 44

what is granular disaggregation

Answer 44

salt weathering of some rocks results in larger grains formed

Question 45

what is efflorescence

Answer 45

the near-surface accumulation of salt

Question 46

contour scaling

Answer 46

the accumulation of salt in the subsurface zone leads to surface layer blistering and falling away

Question 47

cavernous weathering

Answer 47

salt weathering creates hollows where salts are retained, microclimates= moister and cooler, deeper absorption of salt = further weathering

Question 48

how can fungi and lichens weathering through hydration

Answer 48

turgor pressure

Question 49

5 methods of physical weathering

Answer 49

1. unloading, dilation, pressure release 2. thermal expansion and contraction (thermoclasty) 3. freeze-thaw 4. salt crystal growth 5. hydration

Question 50

grus

Answer 50

accumulation of angular, coarse-grained fragments resulting from granular disintegration (usually in arid regions)

Question 51

why is salt weathering more common in coastal and desert enviros

Answer 51

great temp range and moisture containing salt exists