Chapter 16

Question 1

what four key factors control rates of weathering?

Answer 1

1. properties of parent rock
2. climate - rainfall and temperature
3. presence or absence of soil
4. length of exposure

Question 2

rind

Answer 2

external layer of weathred material

Question 3

is the weathering rate for a mineral with high solubility fast or slow?

Answer 3

fast

Question 4

does a massive rock structure have a fast or slow weathering rate?

Answer 4

slow

Question 5

does more rainfall speed up or slow down the weathering rate?

Answer 5

speed up

Question 6

does a high temperature speed up or slow down the weathering rate?

Answer 6

speed up

Question 7

as the thickness of the soil layer in a rock increases, does the weathering rate increase or decrease?

Answer 7

increase

• constantly exposed to groundwater
• carbonic acid

Question 8

does high organic content in soil speed up or slow down the weathering rate?

Answer 8

speed up

Question 9

three types of weathering

Answer 9

1. biological
2. physical
3. chemical
   
   • silicate
   • carbonate

Question 10

true or false: the more stable a rock is, the slower it weathers (two examples)

Answer 10

true
halite - unstable - weathers rapidly
granite - stable - weathers slowly

Question 11

three main processes of chemical weathering

Answer 11

1. solubility
2. acids
3. oxidation

Question 12

how does solubility affect chemical weathering?

Answer 12

minerals with weak ionic bonds are more soluble therefor they chemically erode faster

Question 13

how do acids affect chemical weathering?

Answer 13

• H+ attacks surfaces

- natural acids erode rock

Question 14

what are three types of natural acids involved in chemical weathering?

Answer 14

• sulfuric
• hydrochloric
• carbonic

Question 15

which type of natural acid has the biggest effect on chemical weathering?

Answer 15

carbonic - weak acid but it is the most abundant

Question 16

when did oxygen become a part of the chemical weathering process?

Answer 16

2.2 billion years ago as a result of photosynthesis

Question 17

is silicate weathering slower or faster than carbonic weathering?

Answer 17

slower

Question 18

products of chemical weathering

Answer 18

1. clay minerals - kaolonite, smectite
2. oxides
3. salts - halite, calcite

Question 19

main processes of physical weathering

Answer 19

1. water/ice
2. thermal expansion
3. organic activity
4. salt
5. exfoliation

Question 20

how does water/ice physically weather rocks?

Answer 20

water gets inside cracks and expands 9% when it freezes, causing further fracturing in the rock

Question 21

what is thermal expansion?

Answer 21

rocks are a bad conductor of heat so the surface gets hot and expands while the inner rock stays cool

Question 22

what type of organic activity physically weathers rock?

Answer 22

• tree roots growing through rocks

- organisms get in cracks

Question 23

how does salt physically weather rocks?

Answer 23

it expands with warming and when it absorbs water

Question 24

exfoliation

Answer 24

large, flat or curved sheets of rock detach from the outcrop

Question 25

soil

Answer 25

mineral and organic residue from weathering

Question 26

soil composition

Answer 26

45% minerals 20-30% water 20-30% air 5% organic

Question 27

what are horizons?

Answer 27

zones of alteration, addition, and translocation

Question 28

order of horizons

Answer 28

``` O A E B C ```

Question 29

O horizon

Answer 29

- surface | - consists of organic materials

Question 30

A horizon

Answer 30

- darkest - most humus - addition of organics - loss of material

Question 31

E horizon

Answer 31

leeched zone - clay

Question 32

B horizon

Answer 32

addition of weathering products (clay and salt)

Question 33

C horizon

Answer 33

- parent material | - slightly altered

Question 34

5 factors of soil formation

Answer 34

1. parent material 2. climate 3. topography 4. organisms 5. time

Question 35

4 types of soil

Answer 35

1. oxisol 2. alfisol 3. aridisol 4. mollisol

Question 36

oxisol

Answer 36

- deeply weathered - very red - very little organic matter - Australia

Question 37

alfisol

Answer 37

- woodland soil - Ohio soil - decent organic matter

Question 38

aridisol

Answer 38

- desert soil - very little organic matter - accumulates salt

Question 39

mollisol

Answer 39

- grassland soil | - great for agriculture

Question 40

what are the most important formation factors of oxisol?

Answer 40

climate and time

Question 41

what are the most important formation factors for alfisol?

Answer 41

climate and organisms

Question 42

what are the most important formation factors for aridisol?

Answer 42

climate

Question 43

what are the most important formation factors for mollisol?

Answer 43

climate and organisms

Question 44

what does CLORPT stand for? (Midwest example)

Answer 44

``` CLimate - semi-arid Organisms - prarie, grassland Relief/Topography - minimal, open-prarie Parent material - glacial loess Time - 18,000 ```

Question 45

main causes of soil erosion

Answer 45

- overgrazing 35% - agricultural practices (bad) 28% - deforestation 30% - fuel wood 7%

Question 46

how can we slow down soil erosion?

Answer 46

- crop rotation - contour plowing - terracing (levels)

Question 47

how much less soil does the U.S. have each year?

Answer 47

24 billion metric tons

Question 48

how rapid are the rates of soil production?

Answer 48

extremely low - soil is non-renewable

Question 49

How much total prim topsoil is gone in the U.S.?

Answer 49

1/3