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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
mass spectrometer (+how we use it to date rocks)
- 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)
24
What happens in terms of radioactive dating if we melt or metamorphosize a rock
the clock "resets" ie. daughter atoms can escape
25
What type of rock does radioactive dating work best on
igneous
26
Order of decreasing geological time scale
Eon - era - period - epoch
27
Hadean Eon defining features
magma ocean no signs of life
28
Archean Eon defining features
- first cratons formed - evidence of water from zircon grains - prokaryotes in ocean - stromatolites with photosynthesis - no oxygen
29
why did the Archean eon have no oxygen
all oxygen produced reacted with the large amounts of iron in the ocean to form banded iron
30
Proterozoic eon defining features
- 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
31
Proterozoic types of life
early on; eukaryotes developed by the end; first multicellular plants and animals
32
Phanerozoic
- visible life - Pangea supercontinent joined then eventually separated - 5 major mass extinctions + evolution - includes paleozoic, mesozoic, cenozoic era
33
Precambrian eons
Hadean Archean Proterozoic
34
Paleozoic era defining features
- hard shells animals, fish, amphibians, reptiles - assembly of pangea - ended with a great mass extinction
35
Mesozoic era defining features
- mammals and dinosaurs - pangea begins to break up - sea levels rise - end defined by the meteor impact/volcano activity that killed the dinosaurs
36
cambrian explosion
many species arriving then disappearing during the beginning of the paleozoic era
37
kt boundary
Cretaceous–Tertiary boundary; iridium rich clay layer (which is evidence of an asteroid impact)
38
Chicxulub
the asteroid that killed all of the dinosaurs (ended the mesozoic era)
39
Describe the structure of the Asteroid crator
a crator with a mountain in the centre; due to the Earth rapidly rebounding
40
evidence for the gulf of Mexico being the asteroid crator
- 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
cenozoic era defining features
- mammals develop without dinosaurs - Pangea breaks up - formation of Alps and Himalayas
42
Quaternary Period
the current ice age; can be broken into pleistocene epoch holocene epoch
43
pleistocene epoch defining feature
start of ice age until the last retreat
44
holocene epoch defining features
modern day - the 6th mass extinction - interglacial interval
45
global boundary stratotype section and point (GSSP)
markers to show boundaries between eras
46
Beginning of the Hadean eon
4567 Ma
47
End of Hadean eon
4000 Ma
48
Beginning of Archean eon
4000 Ma
49
End of Archean eon
2500 Ma
50
Start of Proterozoic eon
2500 Ma
51
End of Proterozoic eon
541 Ma
52
Start of Phanerozoic eon
541 Ma
53
Start of paleozoic era
541 Ma
54
End of paleozoic era
250 Ma
55
start of mesozoic era
250 Ma
56
end of mesozoic era
65 Ma
57
Start of cenozoic era
65Ma
58
Start of Quaternary period
2.6 Ma
59
Alberta geology from the Quaternary period
thin layer of glacial deposits some alluvial deposits soil
60
Alberta geology from the Phanerozoic eon
- sedimentary rocks of WCSB - thickens from East to West - contains hydrocarbons
61
Alberta geology from the Pre Cambrian eons
- igneous and metamorphic rocks - crystalline basement - Archean and Proterozoic aged rocks
62
WCSB
western canada sedimentary basement
63
Alberta geology from specifically Hadean
no geological history in Alberta
64
Alberta geology from specifically Archean
some basement rocks form (cratons)
65
Alberta geology from specifically Proterozoic
- the rest of basement rocks form - Archean and Proterozoic cratons join to form North America
66
Which part of Alberta are Archean rocks found
SE Alberta
67
Which part of Alberta are Proterozoic rocks found
NW Alberta
68
Sequence of eons
Hadean, Archean, Proterozoic, Phanerozoic
69
sequence of eras in phanerozoic eon
paleozoic, mesozoic, cenozoic
70
which era is quaternary in
cenozoic
71
which era is neogene in
cenozoic
72
which era is paleogene in
cenozoic
73
which era is cretaceous in
mesozoic
74
which era is jurassic in
mesozoic
75
which era is triassic in
mesozoic
76
which era is permian in
paleozoic
77
which era is pennsylvanian in
paleozoic
78
which era is mississippian in
paleozoic
79
which era is devonian in
paleozoic
80
which era is silurian in
paleozoic
81
which era is ordivician in
paleozoic
82
which era is cambrian in
paleozoic
83
the first period of the paleozoic era
cambrian

EAS 210 (20 decks)

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