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Geology > weathering and sedimentary rocks (LEC 4) > Flashcards

weathering and sedimentary rocks (LEC 4) Flashcards

1
Q

most common external processes,
hint: weathering

A

weathering
erosion
mass wasting (movement of rock/soil downslope)

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2
Q

what is weathering

A

breakdown of earth’s materials

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3
Q

when rocks are broken down, particle size ____________ and surface area _____________
words: increases, decreases

A

decreases
increases

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4
Q

what are the types of weathering

A

mechanical and chemical

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5
Q

what is mechanical weathering chemical weathering

A

*physical breakdown of rocks without changing the composition
*breakdown of rocks by chemical reactions mainly reactions with air
or water and resulted in one or more new compounds

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6
Q

examples of mechanical weathering

A
  • frost action (freezing and thawing)
  • pressure release (sheeting)
  • biological activity
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7
Q

important agents of chemical weathering:

A
  • atmospheric gases (mainly oxygen)
  • water (the most important agent)
  • organic acids (produced by plants and decaying of organic matter)
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8
Q

chemical weathering mechanisms (3)

A
  1. dissolution
  2. oxidation
  3. hydrolysis
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9
Q

sources of acids (3)

A

1) carbonic acid is produced from the CO2 in the atmosphere
2) sulphuric or nitrous acids are introduced in acid rains
3) various organic acids are released into soil as organisms decay

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10
Q

oxidation reactions are very slow in dry environments, what speeds up the oxidation reactions

A

water

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11
Q

factors affecting the chemical weathering rate (2)

A

rock characteristics
climate

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12
Q

___________ silicate in the rock, increases its resistance to weathering
high silicate content results in low rate of chemical weathering

A

increasing

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13
Q

high temperature = high/low weathering
dry climate = high/low weathering

A

high
low

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14
Q

old rocks > small particles > sediments > SOIL

A

slay

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15
Q

soil: parent materials can be either _________ (residual soil) or ________________ (transported soil)

A

bedrock; unconsolidated materials

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16
Q

climate is the most influential parameter for soil formation
hot, wet climate = ______ layer of chemically weathered soil
cold, dry climate = ______ layer of mechanically weathered soil

option: thin/thick

A

thick
thin

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17
Q

the optimum topography for soil formation is flat, why

A

because of low moisture content and high erosion in a steep slope will create poorly developed soil

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18
Q

soil horizons are separated layers that
differ from one another in _____, _______, _______, and _______

A

colour, texture, structure, and composition

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19
Q

define eluviation

A

when water percolates downward,
it carries FINE PARTICLES to a deeper zone

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20
Q

soil colour is generally a reflection of its composition:
high organic matter = what colour?
high Fe = what colour?

A

black or brown
red or yellow color

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21
Q

high particle size = high _________

A

leachate

22
Q

which rocks are the only rocks that contain fossils

A

sedimentary rocks

23
Q

calcite, iron oxide, silica, what are these?

A

the most common cements

24
Q

identification of cements:
________ = bubble with dilute HCl
________ = the hardest cement
________ = orange or dark red color

A

calcite
silica
iron oxide

25
Q

two main types of marines and their depths

A

shallow marine (less than 200 m depth)
deep marine (more than 200 m depth)

26
Q

name the continental environments (3)

A

alluvial fan
sand dunes
playa lake

27
Q

name the transitional environments (3)

A

tidal flats
beach
delta

28
Q

sedimentary rocks are classified based on their composition into three main types:

A

*clastic (detrital) :pieces of rocks derived by mechanical or chemical weathering
*chemical (crystalline): dissolved compounds in solution precipitate due to evaporation or
oversaturation.
*biological (bioclastic): remains of living
organisms or plants or materials produced by
organic (biological) precipitation

29
Q

three characteristics of clastic sedimentary rocks that can give us information about their deposition environment:

A
  • particle size
  • sorting
  • roundness
30
Q

the final deposit reflects the combined influence of environmental
energy and sediment availability

A

idk how to create a question from this……. LOL

31
Q

well sorted sediment (the grains in the sample are about same size) = deposited by _______
poor sorted sediment (the grains in the sample are different sizes (mixture of
large and small sizes) = deposited by _______

options: water, wind

A

wind
water

32
Q

main types of clastic sedimentary rocks (5)

A
  • mudrocks
  • shale
  • sandstone
  • conglomerate
  • breccia
33
Q

mudrocks are the _____ common type of sedimentary stone, they form from sediments deposited in a quiet water environment (lakes, lagoons, deep-ocean basin)

A

most

34
Q

why is groundwater usually underlain by shale bed

A

shale consists of very small particles which result in microscopic pore spaces which don’t permit water to infiltrate, restricting the
movement of groundwater through the shale rock

35
Q

types of sandstones (composition) (3)

A
  • quartz sandstone
  • arkose
  • wacke
36
Q

main types of clastic sedimentary rocks

A

conglomerate and breccia

37
Q

precipitate can be inorganic or organic material:
inorganic = _____________
organic = _____________

A

chemical sedimentary rock
biological sedimentary rock

38
Q

examples of:
chemical precipitates
biological precipitates

A

*ex. halite, calcite, and gypsum
halite: dissolved sodium and dissolved chloride, when concentrated enough, produce sodium chloride (halite).
*fossil remains of plants and animals

39
Q

common chemical sedimentary rocks (4)

A

limestone
dolostone
chert
evaporites

40
Q

_______ soluble minerals precipitate first

options: more/less

A

less

41
Q

stages of coal formation:
(accumulation of plant remains) >
1. plant material (plants remains) >
(partial oxidation by bacteria) >
2. peat (soft brown materials) >
(shallow burial increase in T&P) >
3. lignite (soft brown coal) >
(deep burial, the water and volatiles are pressed out) >
4. bituminous [hard, more compacted black coal (rock)]

A

that was not a question :)

but just memorize it like so:
1. remains → partial oxidation
2. p(EAT) → soft brown
3. l(IGNITE) → brown coal
4. bit[(L)uminous] → black coal

42
Q

carbon content in different coal stages

A

peat >
lignite (carbon content = 25 to 35%) >
bituminous (carbon content = 45 to 86%) >
anthracite (carbon content = 86 to 97%)

43
Q

sedimentary structures are features formed from sediments during or shortly after deposition. common types of sedimentary structures:

A
  • bedding
  • mud cracks
  • ripple marks
44
Q

bedding: beds or strata are layers of sediments accumulated in various depositional environments. three main types of bedding:

A
  • parallel-bedding
  • cross-bedding
  • graded-bedding
45
Q

parallel-bedding: the layers are parallel and typically horizontal
so what is cross-bedding

A

when the layers are inclined to horizontal

46
Q

what are graded-beds

A

when the particles within a single layer gradually change from coarse at the bottom to fine at the top

47
Q

what are mud cracks

A

when wet mud is exposed to air and dries up, it cracks

48
Q

what are ripple-marks

A

small waves of sand on the surface of a sediment layer by the action of moving water or air

49
Q

fossils are the remains or traces of prehistoric life now preserved in rock
* fossils are generally found in _______ rock and rarely in _______ rock, but never in _______ rock

A

sedimentary
metamorphic
igneous

50
Q

define leaching

A

when water percolates downward,
it carries dissolved INORGANIC MATTER to a deeper zone

Geology (14 decks)

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