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Geology 111 > Chapter 16 > Flashcards

Chapter 16 Flashcards

1
Q

what four key factors control rates of weathering?

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

rind

A

external layer of weathred material

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3
Q

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

A

fast

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4
Q

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

A

slow

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5
Q

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

A

speed up

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6
Q

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

A

speed up

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7
Q

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

A

increase

  • constantly exposed to groundwater
  • carbonic acid
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8
Q

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

A

speed up

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9
Q

three types of weathering

A
  1. biological
  2. physical
  3. chemical
    • silicate
    • carbonate
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10
Q

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

A

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

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11
Q

three main processes of chemical weathering

A
  1. solubility
  2. acids
  3. oxidation
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12
Q

how does solubility affect chemical weathering?

A

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

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13
Q

how do acids affect chemical weathering?

A
  • H+ attacks surfaces

- natural acids erode rock

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14
Q

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

A
  • sulfuric
  • hydrochloric
  • carbonic
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15
Q

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

A

carbonic - weak acid but it is the most abundant

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16
Q

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

A

2.2 billion years ago as a result of photosynthesis

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17
Q

is silicate weathering slower or faster than carbonic weathering?

A

slower

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18
Q

products of chemical weathering

A
  1. clay minerals - kaolonite, smectite
  2. oxides
  3. salts - halite, calcite
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19
Q

main processes of physical weathering

A
  1. water/ice
  2. thermal expansion
  3. organic activity
  4. salt
  5. exfoliation
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20
Q

how does water/ice physically weather rocks?

A

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

21
Q

what is thermal expansion?

A

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

22
Q

what type of organic activity physically weathers rock?

A
  • tree roots growing through rocks

- organisms get in cracks

23
Q

how does salt physically weather rocks?

A

it expands with warming and when it absorbs water

24
Q

exfoliation

A

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

25
Q

soil

A

mineral and organic residue from weathering

26
Q

soil composition

A

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

27
Q

what are horizons?

A

zones of alteration, addition, and translocation

28
Q

order of horizons

A 
O
A
E
B
C
29
Q

O horizon

A
  • surface

- consists of organic materials

30
Q

A horizon

A
  • darkest - most humus
  • addition of organics
  • loss of material
31
Q

E horizon

A

leeched zone - clay

32
Q

B horizon

A

addition of weathering products (clay and salt)

33
Q

C horizon

A
  • parent material

- slightly altered

34
Q

5 factors of soil formation

A
  1. parent material
  2. climate
  3. topography
  4. organisms
  5. time
35
Q

4 types of soil

A
  1. oxisol
  2. alfisol
  3. aridisol
  4. mollisol
36
Q

oxisol

A
  • deeply weathered
  • very red
  • very little organic matter
  • Australia
37
Q

alfisol

A
  • woodland soil
  • Ohio soil
  • decent organic matter
38
Q

aridisol

A
  • desert soil
  • very little organic matter
  • accumulates salt
39
Q

mollisol

A
  • grassland soil

- great for agriculture

40
Q

what are the most important formation factors of oxisol?

A

climate and time

41
Q

what are the most important formation factors for alfisol?

A

climate and organisms

42
Q

what are the most important formation factors for aridisol?

A

climate

43
Q

what are the most important formation factors for mollisol?

A

climate and organisms

44
Q

what does CLORPT stand for? (Midwest example)

A 
CLimate - semi-arid
Organisms - prarie, grassland
Relief/Topography - minimal, open-prarie
Parent material -  glacial loess
Time - 18,000
45
Q

main causes of soil erosion

A
  • overgrazing 35%
  • agricultural practices (bad) 28%
  • deforestation 30%
  • fuel wood 7%
46
Q

how can we slow down soil erosion?

A
  • crop rotation
  • contour plowing
  • terracing (levels)
47
Q

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

A

24 billion metric tons

48
Q

how rapid are the rates of soil production?

A

extremely low - soil is non-renewable

49
Q

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

A

1/3

Geology 111 (9 decks)

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