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GEOL200 > Week 2- Origin, life cycle and sediments of the ocean > Flashcards

Week 2- Origin, life cycle and sediments of the ocean Flashcards

1
Q

When was the beginning of the universe?

A

14 billion yrs ago

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2
Q

When was earth formed?

A

4.5-4.6 bya

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3
Q

What is Accretion?

A

Bits come together to form the earth

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4
Q

How do we know that the earth is that old?

A

Rocks
Uranium led dating

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5
Q

Earth’s first atmosphere

A

Mainly H and He stripped solar wind

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6
Q

Earth’s second atmosphere

A
  • Mainly CO2 and water vapour (H,N and sulphur-based gases)
  • Formed by outgassing (burping gases to the surface)
  • earth starts to become solid but is not yet liveable
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7
Q

Ocean formation

A
  • 3.8-4.2 Ga
  • water vapour cools and forms droplets, rain falls to earth and fills depressions
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8
Q

Early life on earth

A

Cyanobacteria (blue green algae)
3.5 Ga

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9
Q

Great oxidation event

A

Cyanobacteria photosynthesize and produce O2, creating the third atmosphere
2.4 Ga

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10
Q

Where did life most likely originate?

A

At hydrothermal vents in the early ocean

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11
Q

Why did life mostly originate in hydrothermal vents?

A

Protected from meteorites that hit the ocean surface
Warm, alkaline environment (ideal conditions)
Created self-assembling protocells

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12
Q

What type of organism lived at hydrothermal vents?

A

Extremophiles (achaea)
- live in extreme conditions and metabolize sulphur

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13
Q

Stromatolites importance

A

Led to the accumulation of breathable oxygen and evolution of multicellular life

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14
Q

What is the Wilson cycle?

A

Explains how oceans are created and destroyed
400 million year cycle

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15
Q

Which stages of the wilson cycle are opening the basin?

A

Stage A, B and C

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16
Q

What stages of the wilson cycle are closing the basin?

A

Stage D, E, F

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17
Q

Wilson cycle Stage A: Embryonic

A

Rifting: earth’s crust is stretching and cracking; fissures form, faulting occurs
- rift valley forms
- subsidence (early stage of ocean formation)

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18
Q

Example of Stage A

A

East Africa rift

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19
Q

Wilson cycle Stage B: Juvenile

A

Oceanic rift zone: going to be an ocean forming
- widening of rift valley
- crust is thinning
- subsidence and connection to ocean (ocean water comes in to fill rift valley

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20
Q

Example of stage B

A

Red sea

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21
Q

Wilson cycle stage C: Mature

A
  • Continued lateral spreading of rift valley
  • Widening generation of new ocean crust
  • Increasing sedimentation
  • Geologically passive margins
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22
Q

Example of stage C

A

Atlantic
*every year is gets wider

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23
Q

Wilson cycle stage D: Declining

A
  • Convergence (ocean starts getting smaller)
  • Increasing subduction
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24
Q

Example of stage D

A

Pacific
*pacific plate is sub ducting underneath the Asian plate

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25
Q

Wilson cycle stage E- Terminal

A
  • Continents moving together
  • Subduction of ocean crust
  • Narrowing of sea
  • volcanic eruptions, earthquakes, uplift and mountain building
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26
Q

Example of stage E

A

Mediterranean sea

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27
Q

Wilson cycle stage F- Suturing

A
  • Continent collision; ocean completely gone
  • Uplift of continental crust
  • Subduction of oceanic crust
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28
Q

Example of stage F

A

Himalayas
*Indian plate has slammed into the Eurasian plate

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29
Q

Proof of Wilson cycle

A

Limestones (form in marine environment) found on top of Mt. Everest

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30
Q

What are sediments?

A

Particles (grains) of organic or inorganic matter that accumulate in a loos, unconsolidated form

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31
Q

What scale is the grain size of sediments measured on?

A

Wentworth scale

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32
Q

Types of sediments grain size

A

Fine grained (small)
Coarse grained (large)

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33
Q

Sedimentary rock

A

Occurs when sediments are lithified/cemented together

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34
Q

Size of common marine sediments (SMALL-LARGE)

A
  1. Clay
  2. Silt and sand
  3. Pebbles
  4. Cobbles
  5. Boulders
    *last three are considered gravel
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35
Q

What can grain size tell us?

A

Info about transport, depositional conditions and energy of the environment
Ex. finer grain sediments don’t require as much energy to move

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36
Q

Settling

A

Process by which grains settle to the bottom of the ocean and from a sediment layer
*can depend on grain size

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37
Q

Time is takes for sediments to reach the ocean floor

A

Sand= 2 days
Silt= 6 months
Clay= 50 yrs

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38
Q

4 sediment types

A
  1. Terrigenous (lithogenous): from land
  2. Biogenous: remains of marine organisms
  3. Hydrogenous: precipitate directly from seawater
  4. Cosmogenous: from space
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39
Q

Shallow water marine sediments

A

Neritic
- terrigenous

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40
Q

Deep water marine sediments

A

Pelagic
- Biogenous

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41
Q

Hydrogenous sediments

A

Less than 1% of the sediments in the ocean
Includes metal sulphides and manganese nodules

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42
Q

Manganese nodules

A

Polymetallic (Mn, Fe, Ni, Co, Cu)
Slow precipitation
They would not from where other sediments accumulate bc if they were covered they could not grow

43
Q

Cosmogenous sediments

A

Alien (extraterrestrial) sediments
- tektites (interplanetary dust)

44
Q

Terrigenous sediments

A

99% of sediments are terrigenous
Greatest amount in ocean close to land

45
Q

Processes involved in sedimentation

A
  1. Erosion/weathering
  2. Transportation
  3. Deposition
46
Q

What is a common component of terrigenous sediments?

A

Quartz(SiO2)

47
Q

Why is quartz important?

A
  • One of the most stable minerals on the planet
  • Can be transported ling distances
48
Q

Sources of terrigenous sediments

A
  • Volcanic eruptions
  • Wind blow sediment from desert
  • Sediment carried far out over ocean
  • River transport and discharge of eroded material
49
Q

Biogenous sediment

A

Produced by marine organisms as shells or other hard body pats that are either calcareous (CaCO3) or siliceous (SiO2)

50
Q

Where do biogenous sediments come from?

A

Tests or shells of microscopic organisms

51
Q

Microscopic organisms that contribute to biogenic sediments

A

Foraminifera
Coccolithophores
Radiolarians
Diatoms

52
Q

How do foraminifera and coccolithophores create shells?

A

Calcareous (CaCO3)

53
Q

How do radiolarians and diatoms create shells?

A

Siliceous (SiO2)

54
Q

Coccolithophores

A

Covered with small plates made of CaCo3
Create think deposits of ooze

55
Q

What is an ooze?

A

Very fine pelagic sediment that can either be calcareous or siliceous
*Must be at least 30% biogenous for it to be an ooze

56
Q

Foraminifera

A

CaCO3 secreting single-cell organisms

57
Q

Radiolarians and Diatoms

A

SiO2 secreting
Diatoms =single celled algae
Radiolarians= single-celled

58
Q

Calcite compensation depth (CCD)

A

The depth at which the amount of calcium carbonate delivered to the seafloor is equal to the amount removed by dissolution
*Marine snow is not visible below it

59
Q

CCD and dissolution

A

If CaCO3 sinks below the CCD it will dissolve
If CaCO3 remains above CCD it will accumulate

60
Q

Calcite compensation depth conditions

A

More acidic (low pH)
Lower temp
High CO2
High pressure

61
Q

Lysocline

A

Depth at which a rapid increase in dissolution occurs

62
Q

Lysocline depth in the Atlantic

A

5500m

63
Q

Lysocline depth in the Pacific

A

4500m
*shells in the pacific dissolve at a shallower depth

64
Q

Why is there variable depth of the lysocline in the Atlantic vs the Pacific?

A

Deeper in Atlantic bc it’s warmer and pH is less acidic

65
Q

What conditions lead to increased solubility?

A

Increased CO2 content (the more CO2 the more CaCO3 dissolves)
Decreased temp (leads to more CO2 held in water)
Increased pressure

66
Q

CCD and calcareous ooze distribution

A
  1. Calcareous ooze deposited on the mid-ocean ridge
  2. Calcareous ooze is covered and protected (abyssal clay and SiO2 ooze)
  3. Sea floor spreading moves calcareous ooze beneath the CCD into the deep water
67
Q

Distribution of marine sediments

A

Calcareous sediments- mid latitudes (warmer, tropical waters)
Siliceous - high latitudes (colder water)

68
Q

*****What can collecting sediment cores tell us?

A

Climate change
Geology
Earth history
Evolution of life
Verify scientific theories

69
Q

How do we know what the ocean floor looks like?

A

Rely on the five S’s
- Soundings
- Sonar (soundwaves)
- Submersible
- Seismic
- Satellite

70
Q

Types of remote sensing

A

Detects energy reflected from Earth
Detects subtle changes in ocean surface

71
Q

What do ocean basins look like?

A
  1. Continental margin
  2. Deep ocean basin
  3. Mid ocean ridge
72
Q

Continental margin

A

Submerged outer edge of a continent

73
Q

Deep ocean basin

A

Deep sea floor beyond the continental margin

74
Q

Active continental margin

A

Narrow continental shelf, steep slope, thinner sediment cover
- seismic and volcanic activity, orogeny
- coincides w plate margins
-active techtonism occurs

75
Q

Passive continental margin

A

Wide continental shelf, gentle slope, think sediment cover
- range from volcanic activity to no volcanic activity
- does not coincide with plate margins
-far from techtonic plate

76
Q

Continental shelf

A

Relatively flat edge of a continent where a country extends to
- exposure during low sea-levels
- underlain by granitic crust
- biologically-rich, economically significant

77
Q

Continental slope

A

True edge of a continent
- starts at a shelf break
- presence of submarine canyons

78
Q

Submarine canyon

A

Narrow, steep-sided underwater valley that erodes into the continental shelf and slope
*primary transport pathways for terrigenous sediment reaching abyssal seafloor

79
Q

Deep sea fan

A

When a submarine canyon ends in a fan shaped sediment wedge
Underwater avalanche that erodes and canyons and forms turbidites

80
Q

Where are submarine canyons more common?

A

Along active continental margin

81
Q

Turbidity currents

A

Quickly moving down flow slope of dense sediment-laden water

82
Q

Fluidized flow

A

Flow of sediments start fast, depositing large sediments which pile up and eventually slows the flow down resulting in a turbidite

83
Q

Continental rise

A

Where we reach the true deep ocean
Sediment accumulation, turbidites, deep sea fans underlain by oceanic crust

84
Q

Abyssal plains

A

Flat, most featureless areas of the earth

85
Q

Suspension settling

A

Accumulation of fine-grained sediment
Occurs at abyssal plains

86
Q

How is sediment thickness controlled in an abyssal plain?

A

Age
Distance from continent and trench

87
Q

Abyssal hill

A

Elevated areas in deep ocean basins
Most abundant geomorphic feature on earth
<1000m high

88
Q

Seamounts

A
  • circular/elliptical feature
    >1000m in height
  • steep slopes
  • underwater volcano
89
Q

Guyots

A
  • flat topped
  • eroded by waves
90
Q

Trenches

A

Long, narrow depressions on the seafloor
One plate sub ducting under another plate
Formed by techtonic processes

91
Q

Island arc

A

Curving chain of volcanic islands occurring around the margin of ocean basins
Always forms on concave side of trench

92
Q

Where is the trench wall always steeper?

A

On island arc side

93
Q

Marie Tharp and mid ocean ridges

A

First to map topography of ocean floor and prove mid-ocean ridges exist

94
Q

Mid ocean ridge

A

An elevated region with a central valley on an ocean floor at the boundary between two diverging tectonic plates where new crust forms from upwelling magma
*basaltic rock

95
Q

Fast spreading ridge

A

Magma is hotter and flows easier
ex. East pacific rise

96
Q

Slow spreading ridge

A

Colder, plate more brittle (breaks and forms normal faults)
ex. northern mid- atlantic

97
Q

Transform faults

A
  • Two tectonic plates slide past one another
  • May occur in the portion of a fracture zone that exists between different offset spreading centres
  • Offsets mid-ocean ridge pattern
98
Q

Fracture zone

A

Linear feature on the ocean floor resulting from the action of offset mid-ocean ridge axis segments
- Due to plate tectonics

99
Q

Who first discovered hydrothermal vents?

A

Robert Bellard in 1977

100
Q

White smokers (hydrothermal vents)

A

Super hot water comes in contact with ocean water
30-350 degrees celcius

101
Q

Black smokers (hydrothermal vents)

A

Greater than 350 degrees celcius
Metal sulphides present

102
Q

What lives at a hydrothermal vent and what process do they perform?

A

Extremophiles
- Chemosynthesis

103
Q

Can hydrothermal vents go extinct?

A

Yes
Can lose magma source

GEOL200 (10 decks)

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