Lecture 2 - Geology of Ontario + Flashcards
(123 cards)
1
Q
what are the four layers of ontario
A
precambrian - Canadian shield (plate collision and mountains) , lower paleozoic (tropical seas), pleistocene (glaciations), present day (built landscape)
2
Q
how long ago was layer II deposited
A
600-350 Ma
3
Q
what is layer II made of
A
shield covered by younger sedimentary rocks in southern ontario
4
Q
what is layer I known as
A
the Canadian shield
5
Q
where are paleozoic sedimentary rocks exposed
A
along the niagara escaprtment
6
Q
how long ago was layer I deposited
A
3-2.6 Ba
7
Q
formation of the Niagara Escarpment formed
A
rocks are 400-500 Ma, but the actual escarpment as a landform is young. it was formed by glacial and fluvial erosion, which includes Niagara Falls today
8
Q
how fast has niagra falls eroded in how long
A
10 km in over 12,500 years, which is quite rapid in geological time
9
Q
cap rock
A
resistant rocks on top of more easily eroded rocks where water flows. cap rock is lockport dolostone, and the easily eroded rocks are rochester shale at NF
10
Q
how do falls/escarptments retreat
A
undercutting below cap rocks leads to erosion of the softer rocks, and eventually the breaking off of the cap rock
11
Q
what are the exposed layers of the hamilton escarpment
A
ancaster, gasport, rochester, irondequois, reynales, thorold, grimsby
12
Q
who developed the first clean labs to measure Pb isotopes
A
Clair Petterson
13
Q
how old is the canyon diablo metetoerite
A
4.55+/-70 Ma
14
Q
what established the age of the solar system
A
canyon diablo meteorite dating
15
Q
absolute geologic age
A
understanding when events actually happened “how old is it?”
16
Q
what rock is best for geologic aging
A
igneous
17
Q
relative geologic age
A
understanding when events occurred relative to one another. “Which came first?”
18
Q
stratigraphy
A
the part of geology that deals with the formation, character, sequence, distribution, and correlation of sedimentary rocks and the fossils contained in them
19
Q
stratum/strata
A
single beds/layers of beds
20
Q
stratigraphic succession
A
the vertical sequence of layering strata
21
Q
what did nicolas steno do (1636-1686)
A
realized shark teeth were entombed in sedimentary rocks rather then grown within them. and that crystalss formed in liquid state originally in igneous rocks. invented the basic laws of stratigraphy
22
Q
principle of original horizontality
A
beds of sediment laid down in water form horizontal or near-horizontal layers. layers now eroded were once continuous.
23
Q
principle of superposition
A
sedimentary layers are deposited in time sequence, with the oldest on the bottom and the youngest on the top
24
Q
principle of lateral continuity
A
strata extend continuously in all directions until they are terminated by thinning at the edge of a basin, end abruptly at a barrier to sedimentation, or grade laterally into a different sediment type
25
what is an example of eroded original horizontality
the tapeats sandstone layer in the grand canyon has been eroded by the colorado river
26
uniformitarianism
the theory that changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes. "the present is the key to the past"
27
principle of cross-cutting relationship
states that a rock unit, sedimentary body, or fault that cuts another geologic unit is younger than the unit that was cut
28
principle of included fragments
fragments of rock within a larger rock unit are older than the rock in which they are enclosed
29
three types of unconformities
disconformity, angular unconformity, and nonconformity
30
disconformity
layers above and below the unconformity are parallel to one another
31
what is the great unconformity
the Canadian shield is 2.5 billion years old and the next layer ontop is only 5 million years.
32
angular unconformity
younger beds overlie tilted or folded beds
33
nonconformity
younger beds overlie older metamorphic or plutonic rocks
34
stratigraphic correlation
matching of strata from one region to another. using the study of lithostratigraphy
35
lithostratigraphy
study of rock types (lithology)
36
formations
distinctive rock units that can be mapped over a large area. they are usually names after a type locality where the rocks were first described.
37
sub-divisions of formations
they are sub-divided into members.
38
lumping of formations
formations are lumped together to form groups
39
how are stratigraphic layers zoned and arranged
according to relative time of deposition using the range of fossils
40
geologic range of fossils
time interval between dirst and last appearance of each species
41
zone (biozone)
a stratigraphic interval defined by its fossil content, and usually given the name of a characteristic fossil present in that interval
42
chemostratigraphy
using ratios of chemical isotpes. excursions in chemical signatures (ex. isotopic ratios) can record global environmental changes
43
magnetostritigraphy
stratigraphic correlation on the basis of magnetic properties
44
study of earths magnetostritigraphy
changes in magnetic polarity directions recorded in rocks and sediments. polarity of the earth's magnetic field is recorded at the time of deposition. the fine-grained magnetic minerals (magnetite) orient themselves when settling from suspension with the earth's magnetic field. it is applicable only in certain environments, such as the deep sea.
45
what are the four geologic eras often used
cenozoic, mesozoic, paleozoic, precambrian
46
which geologic era was the Niagara Escarpment made in
paleozoic
47
what period were the dinosaurs from
jurrasic
48
largest geochronologic time unit
eon
49
what are the four eons
phanerozoic, proterozoic, archean, hadean
50
what is the precambrian
proterozoic, archean, and hadean. it is an informal unit of time
51
what time range is the phanerozoic eon
531 Ma to now
52
what time range was the proterozoic eon
2.5Ga to 541 Ma
53
what time range was the archean eon
4Ga to 2.5 Ga
54
what time range was the hadean eon
4.54 Ga to 4.0 Ga
55
what are the four geologic time units
eon, era, period, epoch
56
what eon, era, period, epoch are we in
phanerozoic, cenozoic, quaternaty, holocene
57
what is hadean named after and why
greek god hates because it literally looked like hell
58
what percent of earths history is phanerozoic
12%
59
what was the time range of the paleozoic era
541Ma to 252 Ma
60
what was the time range of the mesozoic era
252Ma to 66 Ma
61
what is the time range of the cenozoic era
66 Mz to today
62
what is the time range of the holocene epoch
11.8 Ka to today
63
what is the second largest geochronic time unit
eras
64
how many eras are they and how are they divided
10 eras, with three in the phanerozoic eon
65
what are the three phanerozoic eras
paleozoic era, mesozoic era, and cenozoic era
66
what is the third largest geochronic time unit
periods
67
how many periods are there, and how may in the cenozoic
22 total with three in the cenozoic
68
what three periods are in the cenozoic era
paleogene, neogene, and quaternary
69
what is the time range of the paleogene period
66Ma to 23 Ma
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what is the time range of the neogene period
23Ma to 2.6Ma
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what is the time range of the quaternary period
2.6 Ma to present
72
How did earth get to how it is today
started as molten, there was differentiation of materials according to density, formation of the earths layers, huge impact creates the earths moon, and then the atmosphere started to originate
73
how long ago did the earth form from the condensation of the condensation of material from the solar nebula
4.5 Ba
74
Conditions in the hadeon eon
likely that almost the entire earth was molten magma - magma ocean. it began to cool over a few 100 million years, forming igneous rocks in the process. it was very hot from the residual heat from planetary accretion and the atmosphere has no oxygen
75
what has been happening to the temperature of the earth since the hadeon era
it has been slowly cooling down internally
76
what is komatitte
a type of basalt (ultramafic - rich in iron and magnesium). it is quite dense, and formed the earliest ocean crust at temperatures above 1100 Celcius. The spreading centres were probs produced by convection currents in the mantle
77
how were convection currents driven in the hadeon eon
it is not fully understood, but by the heat of the core. some of the earliest crust may have sunk to form the outer core
78
ocean crust density
3 g/cm^3
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continental crust density
2.7 g/cm^3
80
what is bowen's reaction series
an idealized progression of minerals produced by cooling basaltic magma. the low end of the scale is 700 deg, and all minerals crystallize into solid rock. The high end of the scale is 1250 deg, and all the minerals exist in a molten state
81
where are mafic rocks found on the bowens reaction series
on the high end in high temperatures
82
where are felsic rocks found on the bowens reaction series
on the low end in low temperatures
83
how does the bowens reaction series affect magmas?
lavas erupted early from a magma body may be basalt (mafic), as they cooled in high temperatures. they would be rich in iron, magnesium, and calcium.
lavas erupted late from a magma body may be andensites (felsic). they would be low in sodium, potassium, and silica
84
which temperature of rock cooling results in richness of magnesium, calcium, and iron
high temperature
85
formation of early oceans time
some time before 4Ga
86
formation of early oceans process
ocean crust formed underwater, adding lots of water to lavas. the melting of wet crust at subduction zones formed andesitic magmas.
87
where did water on earth first come from
outgassing from magmas. likely came as components in many many comets. comet water has similar isotopic composition to ocean water.
88
how did continental crust develop
the continued subduction of sediments and water with basaltic oceanic crust creates more felsic magmas over time, which creates continental crust. This lead to patches of continental crust.
89
how long ago did continental crust develop
4.4 Ga in the zircon age
90
what is the earliest evidence of water
4.4 Ga zircon has stable oxygen isotope rations indicating that zircon reacted with water. evidence that deep oceans had formed by 3.8 Ga
91
what was water from meteorites like
meteorites were canbonaceous chondrites (felsic), containing up to 20% H2O. it was locked up in clay minerals. Just like how most of earths water is currently locked up in the crust
92
early atmosphere composition
not exactly known
- abundant hydrogen
- no free oxygen
- anoxic or reducing
- high CO2 levels
93
modern atmosphere composition
- nitrogen
- oxygen (21%)
- argon
- carbon dioxide (0.03%)
- water vapor
- other gasses
94
when did oxygen start to build up in the atmosphere
early archean (3.8 - 3.4 Ga)
95
what two processes built up oxygen
photochemical dissociation and photosynthesis (more in terms of volume)
96
photochemical dissociation
water molecules split by UV radiation in upper atmosphere (2H2O + UV -> 2H2 + O2)
97
photosynthesis in early photosynthetic organisms
cyanobacteria and other algae take up CO2 for energy and release oxygen
98
cyanobacteria and how old they are
earliest forms of life. recognized in 3.5 Ga old Archean rocks. algal mats build to form stromatolites
99
banded iron formations (BIFs) formation
Because Fe was more prevalent in ocean during archean period as it was released from abundant hydrothermal vents at mid-ocean ridges. cyanobacteria produced some oxygen. the oxygen and dissolved iron combine to form insoluble iron oxide which precipitated out forming thin layer of ocean floor. the alternating times of oxygenated (red) and non oxygenv(black/grey) events.
100
what year rocks are BIFs in
common in rocks 3.0-1.8 Ga old, and absent in younger rocks.
101
what did early weathering of rocks do
reduced CO2 in the atmosphere, drawing it down. the weathering of igneous rocks (Ca-silicates) produces calcium carbonate and silica. water and co2 react to make carbonic acid/rainwater that reacts with rocks to create new stuff
102
what are the oldest fossils and first evidence of life
cyanobacteria (blue-green algae) that is 3.5 billion years old
103
what are the suggester older fossils
microfossils (tubes) in BIF deposits in Quebec. They are possibly 3.8 -4.28 Ga
104
what elements are able to produce life
carbon, oxygen, hydrogen, nitrogen, phosphorous, and sulphur, all of which are abundant in the solar system
105
what did the Miller-Urey experiment do
simulated conditions on early Earth and produced organic compounds (amino acids) from inorganic materials as an analogue of early Earth
106
micelle
a ball of chain molecules, single lined
107
what is the importance of extremophiles to getting life where it is
extremophiles give a lot of pathways with how we could get to where we are now because of the extreme living conditions they can take
108
what would be the evolution of how cells cam to be
chain molecule consisting of a hydrophillis phosphate attached to a fatty acid chain were attracted to other fats, and combines to form balls or sheets. Sheets then form a single layer ball, or a bilayer ball with a vesicle in the middle, which is similar to a cell wall.
109
bilayer ball (liposome)
bilayer sheet in the form of a ball, has a vesicle in the middle
110
what played a role in the origin of life
concentration of reagents makes polymers
clay or pyrite substrates can also aid in polymerizing organic molecules
rewetting can cause bilayers to form liposomes
wetting and drying concentrates, reagents, and protocells that can replicate may become self-selected for improvement
111
lithotropes
live in environments like rocks where they can oxidize inorganic compounds. live off of geochemical energy and consume hydrogen
112
where might have early bacteria lived
in and on rocks. they were found in granites in sweden over 3600 m below the surface
113
where on earth did early life forms flourish
probably in oceans because salts, solvents, mixing of element create organic compounds. life probably developed at hydrothermal vents at mid-ocean ridges
114
life at hydrothermal vents
temps greater than 100 deg, no light, energy from chemosynthesis, microbes (hyperthermophiles), and no fossils from early spreading centres (no preservation?)
115
what did prokaryotes form
stromatolies, the oldest known fossils. They are organic structures formed by trapping sediment on sticky bacterial mats. they are columnar structures.
116
cratons and shields
oldest parts of modern continents. they are the stable parts of the continental crust that have survived subduction
117
how old is the north american craton
over 600 Ma
118
exposed parts of the cratons
shields
119
platform or cover rocks
the younger rocks covering shields
120
what is the canadian sheild
ancient erosional surface. its the inside of a mountain
121
peneplaine
ancient erosoinal surface
122
what is the complex geology of cratons
they are made of different geological provinces with areas of distinct geology. each represents an ancient micro-continent (terrane) brought together by plate tectonics. they are then welded onto the craton along suture zones.
123
where are the old and young rocks on cratons
oldest rocks are in the centre and younger are along the margins
