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Fall 2018 > Geology 101 Quiz 7 > Flashcards

Geology 101 Quiz 7 Flashcards

1
Q

most of our oil, natural gas, and coal comes from

A

sedimentary deposits

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2
Q

almost everything we know about past life on this planet comes from

A

sediments & sedimentary rocks

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3
Q

fossils do not survive melting (and are often lost during metamorphism as well), so we depend on ? to preserve a record of past life

A

sedimentary systems

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4
Q

sedimentary rocks can form in one of two ways

A

1) by accumulation and lithification of particles

2) by precipitation from solution

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5
Q

clastic sediments (also called detrital)

A

sediment formed by the accumulation of particles

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6
Q

chemical sediments (or biochemical)

A

sediments formed by precipitation of dissolved ions

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7
Q

“biochemical” simply means

A

organisms aided in precipitating minerals from solution

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8
Q

? sediments are about ten times more abundant on Earth than ? sediments

A

clastic 10x more abundant than chemical

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9
Q

the composition and appearance of clastic sediments is determined by

A

composition of the source rock, weathering conditions, distance of transport, mode of transport

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10
Q

with more aggressive weathering, there will be fewer ? minerals and more ? minerals

A

fewer primary, more secondary

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11
Q

with more aggressive weathering, the grains are more

A

rounded

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12
Q

the longer the travel distance, the more ? will take place

A

weathering

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13
Q

long travel distance tends to result in

A

a decrease in easily weathered primary minerals, more secondary minerals, breakdown of larger particles, and rounding of grains

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14
Q

modes of transport

A

by wind, water, or ice

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15
Q

the mode of transport will affect

A

weathering conditions and the degree of sorting sediments are likely to experience

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16
Q

sorting

A

the degree to which grains are of a similar size

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17
Q

poorly sorted sediments

A

large range of grain sizes

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18
Q

well sorted sediments

A

smaller range of grain sizes

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19
Q

wind as a mode of transport

A

wind can normally only pick up clay, silt, and sand size particles; as the wind slows, the larger particles will fall out first resulting in well sorted deposits

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20
Q

sand dunes

A

example of wind as a mode of transport; typically occur in deserts and near beaches

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21
Q

loess

A

wind blown deposits of glacial silt; here in Mississippi; pulverized rock dried out after the ice age, allowing winds to pick up the loose material

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22
Q

desert pavement

A

not technically deposited by wind, but created by wind; as wind blows over desert sediments, the finer grains are picked up and blown away; gravel and larger rocks are left behind in what looks like a pavement of gravel on the surface

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23
Q

wind is most effective in ? climates

A

dry

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24
Q

why is wind most effective in dry climates

A

water causes particles to stick together and supports vegetation that protects the underlying sediment from blowing away

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25
Q

water as a mode of transport

A

water is effective in carrying even large boulders during floods; as water slows, the larger particles drop out first resulting in well sorted deposits

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26
Q

water moving on the (inside/outside) edge of a bend moves faster

A

outside

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27
Q

water on the inside edge slows and drops some of its sediment in well sorted

A

sand bars

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28
Q

wind will tend to etch the surfaces of the grains, giving them a

A

frosted appearance (how best to tell whether ancient dunes were deposited by wind or by water)

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29
Q

ice as a mode of transport

A

transport by ice means transport by glaciers; glaciers are the bulldozers of erosion - everything in its path is pushed forward and left in a mixed heap when the glacier retreats

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30
Q

moraines

A

bulldozed glacial deposits with very angular particles and that are very poorly sorted

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31
Q

glacial outwash deposits

A

as a glacier melts, water will carry sediments away and form more sorted deposits

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32
Q

the composition and appearance of chemical sediments is determined by

A

ion concentrations, temperature, water pressure, presence of oxygen, presence of organisms

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33
Q

examples of ions that will only precipitate if the concentration of ions is very high

A

Na+ and Cl-

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34
Q

examples of ions that will precipitate at low concentrations of ions

A

Ba2+ and SO4 2-

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35
Q

if seawater is cold,

A

calcite may precipitate

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36
Q

if seawater is warm,

A

a polymorph (aragonite) may precipitate instead

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37
Q

calcite becomes more soluble at higher

A

water pressure (lower depth)

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38
Q

sediments found on the deep ocean floor are not likely to be made of

A

calcite (sediments could be silica though)

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39
Q

the presence of oxygen can be important for some minerals such as those containing iron:
if oxygen is present, ? may form, but if oxygen is absent, ? may form instead

A

Fe2O3 hematite

FeS2 pyrite

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40
Q

organisms can be divided into

A

microorganisms and macro-organisms

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41
Q

micro-organisms

A

require a microscope to see

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42
Q

macro-organisms

A

visible without magnification

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43
Q

reefs grow because

A

the organisms build a new calcite shell above the old and move into the new space - only the surface layer is “living”

44
Q

sedimentary environment (AKA a depositional environment)

A

a geographical location characterized by a particular combination of geologic processes and environmental conditions

45
Q

elements that characterize a sedimentary environment

A

geographic location and plate tectonic setting, transport agent and medium, organic processes and organisms that modify sediments, climate

46
Q

examples of clastic environments

A

beach, river (fluvial), glacial, desert, lakes (lacustrine), deltas, and the deep sea

47
Q

where would we expect to find shell fragments and sand dunes

A

beach clastic environments

48
Q

where would we expect to find flood plain deposits and sand bars

A

river (fluvial) clastic environments

49
Q

where would we expect to find moraines and outwash deposits

A

glacial clastic environments

50
Q

where would we expect to find desert pavement and sand dunes (with etched grains)

A

desert clastic environments

51
Q

examples of chemical sedimentary environments

A

carbonate, siliceous, swamp, soil B horizon, evaporite

52
Q

where would we expect to find calcite shells and reefs (mostly shallow ocean)

A

carbonate chemical environments

53
Q

where would we expect to find silica tests (shallow and deep ocean)

A

siliceous chemical environments

54
Q

where would we expect to find fine grained sediment and vegetation

A

swamp chemical environments

55
Q

where would we expect to find precipitated minerals (like caliche) leached from A horizon

A

soil B horizon chemical environments

56
Q

where would we expect to find precipitated minerals (like caliche) leached from A horizon

A

evaporite chemical environments

57
Q

lagoon

A

a shallow body of water partially protected from a larger lake or sea

58
Q

in arid climates where seawater washes into a lagoon and evaporates, ? can form

A

evaporite deposits

59
Q

common evaporite deposits

A

halite, gypsum, selinite, calcite

60
Q

playa lake

A

a lake with an inlet stream but no outlet that periodically dries up (usually seasonally)

61
Q

playa

A

a playa lake when it is dry

62
Q

in a playa lake, water is lost only to

A

evaporation and seepage into the ground

63
Q

mixed environments

A

where clastic and chemical sediments are being deposited together

64
Q

examples of mixed environments

A

deep sea, playa lake

65
Q

deep sea as a mixed environment

A

chemical: silica tests from swimming microorganisms
clastic: volcanic ash drifting over the ocean

66
Q

playa lake as a mixed environment

A

chemical: evaporite minerals
clastic: sand and silt washed in from the inlet stream

67
Q

bedding structures

A

features preserved in lithified sediments that provide information on the type of environment, and even the original orientation of the strata if it has been shifted

68
Q

examples of bedding structures

A

ripple marks, mud cracks, graded bedding, cross bedding, bioturbation structures, bedding sequences

69
Q

two types of ripple marks

A

symmetrical and asymmetrical

70
Q

symmetrical ripple marks

A

formed by wave action (indicated near shore environment)

71
Q

asymmetrical ripple marks

A

formed by wind or water current (indicates river environment or current in larger water body)

72
Q

mud cracks

A

indicates a shallow water environment that occasionally dries up

73
Q

in mud cracks, if a flood suddenly brings in muddy water, the mud may

A

fill the cracks before they swell and seal - if this layer is buried, the mud cracks may be preserved

74
Q

graded bedding

A

a single layer with coarse grains near the bottom grading up to finer near the top

75
Q

what type of bedding structure is common anytime sediment is mixed in water suddenly and allowed to settle?

A

graded bedding

76
Q

turbidity flow

A

sediment that begins to slide underwater, entrains water in the sediment and begins to flow rapidly down slope

77
Q

turbidite

A

deposit laid down by a turbidity flow

78
Q

graded bedding if often seen in ? flows

A

turbidity

79
Q

cross bedding

A

sloping layers in dune deposits are truncated by sloping layers in another direction

80
Q

bioturbation structures

A

“bio” means life, “turbation” means stirred up - so bioturbation refers to preserved structure that show that organisms have moved sediment around

81
Q

examples of bioturbation structures

A

preserved tracks, tunnels, or burrows

82
Q

bedding sequences

A

a pattern of layers in a specific sequence is often an indication of a particular process

83
Q

lithification (turning sediment into rock) involves

A

compaction and cementation

84
Q

compaction

A

squeezing particles closer together (especially significant for clays)

85
Q

cementation

A

precipitation of minerals between grains

86
Q

common cements

A

calcite and silica

87
Q

diagenesis

A

processes that alter sediments after deposition (including lithification)

88
Q

in addition to compaction and cementation, diagenesis also includes alteration of minerals, such as

A

changing crystal structure to turn aragonite into calcite; swapping half the Ca atoms for Mg atoms to calcite to turn it into dolomite

89
Q

sedimentary rocks are divided into two categories

A

clastic and chemical

90
Q

clastic rocks

A

conglomerates, sandstone, siltstone, mudstone and shale

91
Q

conglomerates

A

made from poorly sorted sediments, including gravel

92
Q

sandstone

A

made from sand

93
Q

siltstone

A

made from silt

94
Q

mudstone and shale

A

both made from clay (mud), but shale breaks into thin layers

95
Q

clastic rocks can also have

A

descriptive identifies or unique names

96
Q

example of descriptive identifier for mud with calcite cement

A

calcareous shale

97
Q

example of descriptive identifier for mud with silica cement

A

siliceous shale

98
Q

example of unique names for sandstone made of mostly quartz

A

quartz arenite

99
Q

example of unique names for sandstone made of quartz and feldspars

A

arkose

100
Q

chemical rocks

A

limestone, dolostone, chert, organic, iron formation, evaporite

101
Q

limestone

A

calcareous muds, shells and coral (reefs)

102
Q

dolostone

A

limestone (calcite) turned into dolomite

103
Q

chert

A

siliceous sediments (opal, chalcedony, quartz)

104
Q

organic

A

organic debris (peat, coal)

105
Q

iron formation

A

iron oxides (hematite)

106
Q

evaporite

A

evaporite minerals (halite, gypsum, selenite, calcite)

107
Q

the Mediterranean Sea and Black Sea were once

A

dried up

Fall 2018 (24 decks)

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