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GEO 101 > geologic time > Flashcards

geologic time Flashcards

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1
Q

James Hutton

A

recognized the immensity of Earth history and the importance of time as a component in all geologic processes in the late 18th century

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2
Q

Sir Charles Lyell

A

demonstrated that Earth had experienced many episodes of mountain building and erosion, which must have required great spans of geologic time in the 19th century

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3
Q

Cambrian time was how many million years ago

A

540

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4
Q

numerical date

A

the number of years that have passed since an event occurred

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5
Q

relative date

A

the chronological order of events, determined by placing rocks and structures in their proper sequence or order

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6
Q

Nicolas Steno (1638-1686)

A

a Danish anatomist, geologist, and priest, was the first to recognize a sequence of historical events in an outcrop of sedimentary rock layers`

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7
Q

Principle of Superposition

A

A principle which states that in any undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below

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8
Q

Principle of Original Horizontality

A

A principle by which layers of sediment are generally deposited in a horizontal or nearly horizontal position

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9
Q

Principle of Lateral Continuity

A

A principle which states that sedimentary beds originate as continuous layers that extend in all directions until they grade into a different type of sediment or thin out at the edge of a sedimentary basin

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10
Q

Principle of Cross-Cutting Relationships

A

the geologic principle which states that geologic features that cut across rocks must form after the rocks they cut through

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11
Q

Principle of Inclusion

A

The principle which states that a rock mass adjacent to one containing inclusions must have been there first in order to provide the rock fragments and is therefore the older rock mass

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12
Q

conformable

A

referring to rock layers that were deposited without interruption

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13
Q

unconformity

A

a surface that represents a break in the rock record, caused by erosion and nondeposition

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14
Q

angular unconformity

A

an unconformity in which the older strata dip at an angle different from that of the younger beds

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15
Q

disconformity

A

a type of unconformity in which the beds above and below are parallel

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16
Q

nonconformity

A

an unconformity in which older metamorphic or intrusive igneous rocks are overlain by younger sedimentary strata

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17
Q

fossils

A

the remains or traces of organisms preserved from the geologic past

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18
Q

paleontology

A

the systematic study of fossils and the history of life on earth

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19
Q

permineralization

A

when mineral-rich groundwater permeates porous tissue such as bone or wood, minerals precipitate out of solution and fill pores and empty spaces

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20
Q

petrified wood

A

permineralization with silica, often from a volcanic source such as a surrounding layer of volcanic ash

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21
Q

mold

A

When a shell or other structure is buried in sediment and then dissolved by underground water, a mold is created.

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22
Q

cast

A

If these hollow spaces are subsequently filled with mineral matter, a mineral or rock replica of the organism, called a cast, is created

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23
Q

carbonization

A

the process that is particularly effective at preserving leaves and delicate animal forms

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24
Q

impression

A

film of carbon is lost from a fossil preserved in fine-grained sediment, a replica of the surface, called an impression, may still show considerable detail

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25
Q

amber

A

the hardened resin of ancient trees

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26
Q

tracks

A

animal footprints or trails made in soft sediment that later turned into sedimentary rock

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27
Q

burrows

A

tubes in sediment, wood, or rock made by an animal. These holes may later become filled with mineral matter and preserved. Some of the oldest-known fossils are believed to be worm burrows.

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28
Q

coprolites

A

fossil dung and stomach contents that can provide useful information about the size and food habits of organisms

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29
Q

gastroliths

A

highly polished stomach stones that were used in the grinding of food by some extinct reptiles

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30
Q

two specific conditions increase the probability that an organism will be fossilized

A

a rapid burial in sediment after death, and the possession of hard parts

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31
Q

correlation

A

the process of establishing the equivalence of rocks of similar age in different areas

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32
Q

principle of fossil succession

A

a principle by which fossil organisms succeed one another in a definite and determinable order, and any time period can be recognized by its fossil content

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33
Q

index fossils

A

a fossil that is associated with a particular span of geological time

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34
Q

fossil assemblage

A

the overlapping ranges of a group of fossils (assemblage) collected from a layer. by examining such an assemblage, the age of the sedimentary layer can be established

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35
Q

earths age

A

4.6 billion years

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36
Q

deep time

A

immense space of geologic time

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37
Q

where is practically all of an atom’s mass?

A

the nucleus

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38
Q

mass number

A

protons+neutrons

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39
Q

radioactive decay

A

the spontaneous decay of certain unstable atomic nuclei (nuclear decay)

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40
Q

alpha decay

A

An alpha particle is composed of 2 protons and 2 neutrons. Thus, emission of an alpha particle means that the mass number of the isotope is reduced by 4, and the atomic number is lowered by 2.

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41
Q

beta decay

A

electron is emitted to produce the electron plus a proton. Because the nucleus now contains one more proton than before, the atomic number increases by 1—and it’s no longer the same element

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42
Q

electron capture

A

when an electron is captured by the nucleus. The electron combines with a proton and forms an additional neutron. As with beta decay, the mass number remains unchanged. However, because the nucleus now contains one fewer proton, the atomic number decreases by 1.

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43
Q

parent

A

unstable radioactive isotope

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44
Q

daughter products

A

isotopes resulting from the decay of the parent

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45
Q

radiometric dating

A

the procedure of calculating the absolute ages of rocks and minerals that contain certain radioactive isotopes

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46
Q

half-life

A

the time required for one-half of the atoms of a radioactive substance to decay

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47
Q

uranium-238

A

lead-206

4.5 billion years half life

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48
Q

uranium-235

A

lead-207

704 million years

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49
Q

thorium-232

A

lead-208

14.1 billion years

50
Q

rubidium-87

A

strontium-87

47.0 billion years

51
Q

potassium-40

A

argon-40

1.3 billion years

52
Q

earths oldest rocks so far

A

may be as old as 4.28 billion years

53
Q

radiocarbon dating

A

dating of events from the very recent geological past (the past few tens of thousands of years) based on the fact that the radioactive isotope of carbon is produced continuously in the atmosphere

54
Q

geologic time scale

A

the division of earth history into blocks of time (eons, eras, periods, and epochs) the time scale was created using relative dating principles

55
Q

eon

A

the larges time unit on the geologic time scale, next in order of magnitude above era

56
Q

Phanerozoic eon

A

the part of geologic time that is represented by rocks containing abundant fossil evidence. The eon extending from the end of the Proterozoic eon (540 million years ago) to the present. means “visible life”

57
Q

deformation

A

general term for the processes of folding, faulting, shearing, compression, or extension of rocks as the result of various natural forces

58
Q

where does deformation of rock most commonly occur?

A

along plate boundaries

59
Q

outcrop

A

sites where bedrock is exposed at the surface

60
Q

geologic/rock structure

A

all features created by the processes of deformation from minor fractures in bedrock to a major mountain chain

61
Q

three types of tectonic structures

A

folds, faults, and joints

62
Q

stress

A

the force per unit area acting on any surface within a solid

63
Q

confining pressure

A

stress that is applied uniformly in all directions

64
Q

what is the result of confining pressure?

A

this type of force compacts mineral grains and reduces the volume of a rock body

65
Q

differential stress

A

forces that are unequal in different directions

66
Q

what is the result of differential stress?

A

deformation

67
Q

what are the three types of differential stress?

A

compressional, tensional, and shear

68
Q

compressional stress

A

differential stress that shortens a rock body

69
Q

what are compressional stresses most often associated with?

A

convergent plate boundaries

70
Q

what happens to the crust due to compressional stress?

A

crust becomes laterally shortened and vertically thickened

71
Q

tensional stress

A

the type of stress that tends to pull a body apart

72
Q

what are tensional stresses most often associated with?

A

divergent plate boundaries

73
Q

what happens to the crust due to tensional stress?

A

crust is stretched, thinned, and fractured (deep rift valleys)

74
Q

shear

A

stress that causes two adjacent parts of a body to slide past one another

75
Q

what is shear most often associated with?

A

transform plate boundaries

76
Q

what happens to the crust due to shear?

A

earth’s crust slips horizontally past one another

77
Q

strain

A

an irreversible change in the shape and size of a rock body caused by stress

78
Q

how can you infer the type of stress that deformed a rock?

A

by observing and measuring the strain imprinted on a rock body

79
Q

three types of deformation changes (strain)

A

elastic, brittle, and ductile

80
Q

elastic deformation

A

rock deformation in which the rock returns to nearly its original size and shape when the stress is removed

81
Q

brittle deformation

A

deformation that involves the fracturing of rock. associated with rocks near the surface

82
Q

ductile deformation

A

a type of solid-state flow that produces a change in the size and shape of a rock body without fracturing. occurs at depths where temperatures and confining pressures are high

83
Q

four factors that influence how a rock deforms

A

temperature, confining pressure, type of rock, and time

84
Q

how does temperature affect deformation?

A

high temperatures-ductile

low temperatures-brittle

85
Q

how does confining pressure affect deformation?

A

higher temperatures enhance ductile behavior, and greater pressures tend to keep the rock intact—and thus more likely to bend rather than fracture

86
Q

strong, brittle rocks

A

granite, basalt, quartz sandstones

87
Q

weak, ductile rocks

A

rock salt, shale, limestone, and schist, and glacial ice

88
Q

how does time affect deformation?

A 
compressional strain (shortening) can be accommodated by ductile deformation->slow process
if stress is applied to a rock unit too quickly, the rock will deform elastically until its strength is exceeded, and then it will fracture
89
Q

folds

A

a bent layer or series of layers that were originally horizontal and subsequently deformed

90
Q

hinge line

A

imaginary axis in which each layer is bent around

91
Q

axial plane

A

surface that connects all the hinge lines of the folded strata

92
Q

anticline

A

a fold in sedimentary strata that resembles an arch

93
Q

synclines

A

a linear downfold in sedimentary strata; the opposite of anticline

94
Q

dome

A

a roughly circular unfolded structure

95
Q

what happens to an eroded dome?

A

erosion has stripped away the highest portions of the overlying sedimentary beds, exposing older igneous and metamorphic rocks in the center

96
Q

basin

A

a circular downfolded structure

97
Q

what happens to an eroded basin?

A

the youngest rocks are at the center

98
Q

monoclines

A

a one-limbed flexure in strata. the strata are usually flat-lying or very gently dipping on both sides of the monocline

99
Q

fault

A

a break in a rock mass along which movement has occurred

100
Q

strike

A

the compass direction of the line of intersection created by a dipping bed or fault and a horizontal surface

101
Q

a strike is always ______ to the direction of dip

A

perpendicular

102
Q

dip

A

the angle at which a rock layer or fault is inclined from the horizontal

103
Q

dip-slip fault

A

a fault in which the movement is parallel to the dip of the fault

104
Q

hanging wall block

A

the rock surface immediately above a fault

105
Q

footwall block

A

the rock surface below a fault

106
Q

dip-slip fault (normal fault)

A

a fault in which the rock above the fault plane has moved down relative to the rock below

107
Q

horst

A

an elongate, uplifted block of crust bounded by faults

108
Q

graben

A

a valley formed by the downward displacement of a fault-bounded block

109
Q

detachment fault

A

a nearly horizontal fault that may extend for hundreds of kilometers below the surface. such a fault represents a boundary between rocks that exhibit ductile deformation and rocks that exhibit brittle deformation

110
Q

reverse fault

A

a fault in which the material above the fault plane moves up in relation to the material below

111
Q

thrust fault

A

a low-angle reverse fault

112
Q

mega thrust fault

A

the plate boundary separating a subducting slab of oceanic lithosphere and the overlying plate

113
Q

strike-slip fault

A

a fault along which movement occurs horizontally

114
Q

transform fault

A

a major strike-slip fault that cuts through the lithosphere and accommodated motion between two plates

115
Q

oblique-slip fault

A

a fault that exhibits both dip-slip and strike-slip movement

116
Q

faut scarp

A

a cliff created by movement along a fault. it represents the exposed surface of the fault prior to modification by weathering and erosion

117
Q

slickensides

A

polished and grooved rock surfaces etched as crustal rocks slide past one another

118
Q

fault breccia

A

loosely coherent rock composed of broken and crushed rock fragments

119
Q

joint

A

a fracture in rock along which there has been no movement

120
Q

what do geologists infer if sedimentary strata are horizontal?

A

the area is undisturbed

121
Q

geologic map

A

graphic depiction of an area of geologic study, with labels and annotations

122
Q

block diagram

A

a three-dimensional view of a portion of earth’s crust that makes it possible to visualize rock layers at the surface as well as underground

GEO 101 (19 decks)

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