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EAS 210 > CHPTR 8 Geological Time > Flashcards

CHPTR 8 Geological Time Flashcards

1
Q

principals of relative dating (7)

A
  1. superposition
  2. original horizontality
  3. lateral continuity
  4. cross-cutting relationships
  5. inclusions
  6. contact metamorphism
  7. fossil succession
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2
Q

Nicolas Steno

A

Discovered
superposition
original horizontality
lateral continuity

for relative dating of rocks

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3
Q

uniformitarianism

A

if we see a geological process today and we see evidence of it in the past; they’re probably the same thing

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3
Q

principal of superposition

A

in a sequence of undeformed sedimentary rocks, each layer is older than the one above and younger than the one below

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3
Q

original horontality

A

most rocks form at a horizontal angle
if rocks are tilted, it is because something happened between deposition and now

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4
Q

lateral continuity

A

if a layer of sediment initially extends latarallly in all directions but is now separated by an erosional feature it can be assumed that it was originally continuous

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5
Q

cross cutting relationships

A

intrusions are younger than the rocks they intrude

a fault is younger than the rock that it has fractured

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6
Q

principal of inclusions

A

a layer containing an inclusions is younger that the inclusion

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7
Q

unconformity represents?

A

“lost time”

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8
Q

nonconformity

A

boundary between sedimentary and igneous contact - causes inclusions

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9
Q

angular unconformity

A

angled/horizontal boundary between sedimentary layers

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10
Q

disconformity

A

horizontal/horizontal boundary between sedimentary layers

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11
Q

principal of contact metamorphism

A

metamorphism has to occur after the rock has formed

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12
Q

William Smtih

A

produced first geological map using fossil succession

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13
Q

index fossils

A

fossils that are present in a wide geographic range and a short time span

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14
Q

John Joly + how old he thought the Earth was

A

studied amount of salt in ocean + compared it to the rate that salt enters the ocean from rivers to determine the age of the Earth

99 million
(this was a minimum)

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15
Q

Lord Kelvin + how old he thought the Earth was

A

estimated the rate at which a sphered would cool by conduction of heat

20 - 400 million

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16
Q

what was Lord Kelvin’s mistake (2)

A
  1. heat is transported by convection and conduction in the Earth
  2. radioactive decay generates heat
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17
Q

half life

A

time it takes for half the atoms in a sample to decay

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18
Q

alpha particle

A

2 neutrons, 2 protons

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19
Q

parent atom

A

atom has not lost an alpha particle yet

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20
Q

daughter atom

A

atom has lost an alpha particle

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21
Q

When does radioactive dating clock start

A

when a grain crystallizes from the magma

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22
Q

How do we use radioactivity to date rocks

A
  1. crystals form in magma with just parent atoms
  2. nothing can enter or the leave the crystal grain
  3. we can check after 1 half life and see that half of the parent atoms have decayed
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23
Q

mass spectrometer (+how we use it to date rocks)

A
  • vaporizes rock sample
  • accelerates sample as a beam of ions
  • sample is deflected around corner by large magnet
  • heavier ions are deflected less
  • count the number of ions with different weights (parent vs. daughter)
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24
Q

What happens in terms of radioactive dating if we melt or metamorphosize a rock

A

the clock “resets”

ie. daughter atoms can escape

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25
Q

What type of rock does radioactive dating work best on

A

igneous

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26
Q

Order of decreasing geological time scale

A

Eon - era - period - epoch

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27
Q

Hadean Eon defining features

A

magma ocean
no signs of life

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28
Q

Archean Eon defining features

A
  • first cratons formed
  • evidence of water from zircon grains
  • prokaryotes in ocean
  • stromatolites with photosynthesis
  • no oxygen
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29
Q

why did the Archean eon have no oxygen

A

all oxygen produced reacted with the large amounts of iron in the ocean to form banded iron

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30
Q

Proterozoic eon defining features

A
  • early life
  • cratons join to form continents
  • iron is gone from the ocean and oxygen accumulates
  • 2 supercontinents joined then later broke up
  • ended with the snowball Earth
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31
Q

Proterozoic types of life

A

early on; eukaryotes developed
by the end; first multicellular plants and animals

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32
Q

Phanerozoic

A
  • visible life
  • Pangea supercontinent joined then eventually separated
  • 5 major mass extinctions + evolution
  • includes paleozoic, mesozoic, cenozoic era
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33
Q

Precambrian eons

A

Hadean
Archean
Proterozoic

34
Q

Paleozoic era defining features

A
  • hard shells animals, fish, amphibians, reptiles
  • assembly of pangea
  • ended with a great mass extinction
35
Q

Mesozoic era defining features

A
  • mammals and dinosaurs
  • pangea begins to break up
  • sea levels rise
  • end defined by the meteor impact/volcano activity that killed the dinosaurs
36
Q

cambrian explosion

A

many species arriving then disappearing during the beginning of the paleozoic era

37
Q

kt boundary

A

Cretaceous–Tertiary boundary; iridium rich clay layer (which is evidence of an asteroid impact)

38
Q

Chicxulub

A

the asteroid that killed all of the dinosaurs (ended the mesozoic era)

39
Q

Describe the structure of the Asteroid crator

A

a crator with a mountain in the centre; due to the Earth rapidly rebounding

40
Q

evidence for the gulf of Mexico being the asteroid crator

A
  • circular pattern of gravity anomalies
  • drilling revealed strange rocks
  • seismic data shows a crater
  • the age of the impact structure is the same age as the end of the mesozoic era
41
Q

cenozoic era defining features

A
  • mammals develop without dinosaurs
  • Pangea breaks up
  • formation of Alps and Himalayas
42
Q

Quaternary Period

A

the current ice age;

can be broken into
pleistocene epoch
holocene epoch

43
Q

pleistocene epoch defining feature

A

start of ice age until the last retreat

44
Q

holocene epoch defining features

A

modern day
- the 6th mass extinction
- interglacial interval

45
Q

global boundary stratotype section and point (GSSP)

A

markers to show boundaries between eras

46
Q

Beginning of the Hadean eon

A

4567 Ma

47
Q

End of Hadean eon

A

4000 Ma

48
Q

Beginning of Archean eon

A

4000 Ma

49
Q

End of Archean eon

A

2500 Ma

50
Q

Start of Proterozoic eon

A

2500 Ma

51
Q

End of Proterozoic eon

A

541 Ma

52
Q

Start of Phanerozoic eon

A

541 Ma

53
Q

Start of paleozoic era

A

541 Ma

54
Q

End of paleozoic era

A

250 Ma

55
Q

start of mesozoic era

A

250 Ma

56
Q

end of mesozoic era

A

65 Ma

57
Q

Start of cenozoic era

A

65Ma

58
Q

Start of Quaternary period

A

2.6 Ma

59
Q

Alberta geology from the Quaternary period

A

thin layer of glacial deposits
some alluvial deposits
soil

60
Q

Alberta geology from the Phanerozoic eon

A
  • sedimentary rocks of WCSB
  • thickens from East to West
  • contains hydrocarbons
61
Q

Alberta geology from the Pre Cambrian eons

A
  • igneous and metamorphic rocks
  • crystalline basement
  • Archean and Proterozoic aged rocks
62
Q

WCSB

A

western canada sedimentary basement

63
Q

Alberta geology from specifically Hadean

A

no geological history in Alberta

64
Q

Alberta geology from specifically Archean

A

some basement rocks form (cratons)

65
Q

Alberta geology from specifically Proterozoic

A
  • the rest of basement rocks form
  • Archean and Proterozoic cratons join to form North America
66
Q

Which part of Alberta are Archean rocks found

A

SE Alberta

67
Q

Which part of Alberta are Proterozoic rocks found

A

NW Alberta

68
Q

Sequence of eons

A

Hadean, Archean, Proterozoic, Phanerozoic

69
Q

sequence of eras in phanerozoic eon

A

paleozoic, mesozoic, cenozoic

70
Q

which era is quaternary in

A

cenozoic

71
Q

which era is neogene in

A

cenozoic

72
Q

which era is paleogene in

A

cenozoic

73
Q

which era is cretaceous in

A

mesozoic

74
Q

which era is jurassic in

A

mesozoic

75
Q

which era is triassic in

A

mesozoic

76
Q

which era is permian in

A

paleozoic

77
Q

which era is pennsylvanian in

A

paleozoic

78
Q

which era is mississippian in

A

paleozoic

79
Q

which era is devonian in

A

paleozoic

80
Q

which era is silurian in

A

paleozoic

81
Q

which era is ordivician in

A

paleozoic

82
Q

which era is cambrian in

A

paleozoic

83
Q

the first period of the paleozoic era

A

cambrian

EAS 210 (20 decks)

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