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GEOL 200 > week 2-ave > Flashcards

week 2-ave Flashcards

1
Q

what is bathymetry?

A

the study of ocean floor contours

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1
Q

how do we know what the ocean floor looks like?

A

bathymetry

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1
Q

what does bathymetry do?

A
  • measures the depth of the ocean
  • illustrate maps of ocean floor
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2
Q

what is depth sounding and why was it inaccurate?

A
  • lowering of the rope with a weight

inaccurate:
- only measures single point of the ocean floor
- is very slow
- impact of pressure that squashes the rope and gives an artificially short measurement

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3
Q

why is lidar not used to measure depth of ocean floor?

A

-Lidar can’t penetrate water very well
-contour maps are used instead

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4
Q

what are the 3 S’s of bathymetry?

A
  • sonar
    -satelite
    -seismic
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4
Q

what are marine provinces?

A

specific regions of the ocean that relate to the geography of the ocean floor

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5
Q

divergent boundary and 2 examples

A
  • where plates are moving apart (such as mid ocean ridges)
    -ex. Mid Atlantic Ridge
    -ex. East Pacific Rise
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6
Q

convergent boundary and example

A
  • ## where plates are moving together, such as deep-ocean trench (one has to move under the other)
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6
Q

why do we get mountain building with convergent boundaries?

A

they do not want to go under each other because they have the same density

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7
Q

what is sonar bathymetry and what are limitations?

A

-bouncing sound down to the ocean floor & measuring it)
-any biological life will interfere and it takes a lot time

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8
Q

echosounding vs side scan echosounding

A

-echosounding uses hull mounted (bottom) beam to get image or sea floor bathymetry
-side scan sonar instrument is towed behind a boat, has a wider profile but there is a data gap directly below the instrument

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9
Q

Satellite bathymetry

A

-ideal, not always possible, more $$
- measures the water surface not the ocean floor and can detect changes in the surface of the ocean like water displacement
-can quickly measure same areas over and over again

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10
Q

Seismic bathymetry

A

-uses lower frequencies & strong signals
-one boat makes sound source, other boat measures seismic reflection
-delay in signals determines depth

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11
Q

what are the 3 main parts of the ocean?

A
  1. mid-ocean ridge
    2.deep ocean basin
  2. continental margin
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12
Q

mid-ocean ridge

A

interconnected mountain chain along divergent plate boundaries (longest mountain chain in world)

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13
Q

continental margin

A

dynamic, interaction of water running off land and into the ocean

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14
Q

what is marie tharp’s contribution to mapping mid-ocean ridges?

A

-used data from german ship that took 14 profiles of the south atlantic
-she was the first to map the unseen topography of the ocean floor on a global scale
-proved mid-ocean ridges exist:

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15
Q

what was mary tharp’s evidence?

A
  • if two land masses drifted apart they would leave a gap (mary drew deep v like parts)
    -where there were ocean ridges there were earth quakes
    -the pattern of scars = evidence of continental drift
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16
Q

how much of the earth’s surface is mid-ocean ridges?

A

23%

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17
Q

why does the North West Mid Ridge Channel occur/why is it unique?

A

This deep sea canyon is unique because cold dense water goes down & the accumulation of the coldest water = cold surface water creates perfect line channel through millions of years of flow

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18
Q

difference between oceanic ridge & oceanic rise?

A
  • rate of spread (rise moves faster)
    -spreading faster so it does not have time to profile, it is much flatter
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19
Q

How old is the east pacific rise and mid atlantic ridge

A

EP- 30 million years
MAR- 100 million years

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20
Q

what is the tallest mountain?

A

Mauna Kea (tallest from ocean floor to peak)

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21
transform faults
-feature of plate boundaries -where plates move in opposite directions -seismically active
22
fracture zones
-intraplate feature -plates move in the same direction at a slightly different rate -less seismically active than transform faults
23
hydrothermal vents
-feature discovered in east pacific rise -home to unique life forms (extremophiles) - black & white smokers and minerals found here
24
white smokers
-barium -calcium silicon -250-300 degrees celcius
25
black smokers
-metal sulphides present -350 degrees celcius
26
what do vents do?
-sea water moves through a plumping system and is converted to hydrothermal fluid -extreme temperature profile changes causes massive turbulence and energy changes
27
chemosynthesis
extremophiles and other life forms get energy from heat not sun
28
abyssal plains
- Flat, most featureless areas of the Earth - even less features than deserts - nearly 50% of planet is covered in them
29
why do abyssal plains exist?
they exist because of sediment and their distribution is influenced by continental margin type
30
abyssal hills
-elevated areas on plains -isolated or in group -volcanic origins
31
types of abyssal hills?
seamounts guyots or tablemounts
32
seamounts
-circular/elliptical feature - less than 1000m in height - relatively steep slopes
33
guyots or tablemounts
-flat topped -eroded by wave action at the ocean surface
34
how are seamounts formed?
- by hotspot volcanism (rise of a hot buyant mantle) - rise as tectonic plates moves over hotspot - extremly hot part of the mantle = less dense bc its hotter = it rises and pushes against the lithosphere (oceanic plate), which generates new mount
35
seamoAunts and bio productivity?
- high level of biological productivity because with the upwelling of cold water filled with minerals and pulling warm water down = more life
36
active margin (and features)
- narrow shelf -steep continental slope -earthquakes, volcanos, mountain building -coincides with plate margins -california, chile -(seamounts, trenches)
37
passive margin (and features)
-wide continental self -longer transitional to oceanic crust -little earthquake & volcanic activity, no mountain building -does not coincide with plate margins -louisiana - (abyssal plains)
38
features of passive margin
- thick accumulation of sediment -transitional crust, subsiding, faulted continental crust - shelf
39
why are sediments important? (5 reasons from lecture)
- contain a record of Earth's history & provide clues - marine organism distribution -paleoclimatology -climate change -circulation patterns
40
what is sediment?
- particles of organic or inorganic matter that accumulate in a loose, unconsolidated form
41
four types of sediment?
1. lithogenous 2. biogenous 3. hydrogenous 4. cosmogenous
42
lithogenos sediment
terrigenous - from land- inorganic
43
biogenous sediment
remains of marine organisms ex. shark teeth - important in deep ocean areas - close to 50% of planet is made up of this type of sediment
44
hydrogenous
- precipitated chemicals from sea water -dissolved materials/metals - water is a universal solvent that carries these minerals = chemical reaction that pulls material out from solid material
45
cosmogenous sediment
from space
46
processes of sedimentation
1. erosion (weathering) 2. transportation (ex. areas with big rainfail changes clarity/turbidity and picks up sediment) 3. deposition
47
sediment deposition layers?
sediment layers can be km thick above oceanic and continental crust
47
why are larger grains closer to land? (like quartz and glass looking sediment?)
- the bigger the grain the more energy required to transport it = why they are closer to land
48
neritic
- derived from land, larger grained
49
pelagic
derived from sea, fine grained
50
neritic lithogenous sediment
- deposited within or near continetal margins -wave action transports sediments
51
deposition
- accumulating sediments and growing - occurs in low energy environments - protected areas will have more deposition
52
erosion
-losing materals -weather -high wave activity - high energy areas have less deposition and more erosion
53
pelagic wind blown sediment
- wind blown (aeloian) sedient from desert - big wind events generate disposition - trend viewed = areas that are really dry blow sediments, not in wet areas at they stick together
54
biogenous sediment & marine ooze
tests of microscopic organisms are important component of marine ooze (testa = shell)
55
what is an ooze?
-very fine-grained pelagic sediment containing at least 30% biogenous test -calcarous or siliceous -toothpaste consistency
56
how do we know some places of land used to be oceanic crust?
-biogenous evidence found in hardened ooze on land -silliceous or calcareous deposit
57
distribution of calcareous sediment
- why do we not see it everywhere in pelagic zone = at really deep depths, calcium carbonate dissolves so it accumulates in more shallow areas
58
calcite compensation depth *recommend to look at graphs on slides to study as well-lecture 2 of week 2
-CCD is depth where all CaCO3 is dissolved -as you go down in the ocean respiration happens a lot deeper than photosynthesis happens - deep, cold, water = holds more gas = lets carbon dioxide accumulates and dissolves calcium carbonate - this is why we do not get calcium carbonate on the surface's of very deep parts of the ocean
59
How does calcium cabonate (CaCO3) deposit in places below the CCD line (not at surface but below)?
- due to seafloor spreading -as the sea floor weathers away the particles get trapped by the plate boundaries and sillica deposits protect them until the sea floor weathers away
60
why does silliceous ooze accumulate?
-cool waters and upwelling -sillica-secreting organisms live in sunlight surface waters and ooze only accumulates beneath areas where productivity & secretion is high - when the rate of supply of siliceous tests is greater than the rate at which sillica dissolves = ooze accumulates
61
ocean sediment
-mostly consists of lithogenous and biogenous -more fine-grained sediment is transported with ease by current, wave, wind - large particles need big energy to be moved and can take over 50 years to settle (clay)
62
how do we measure marine sediments?
-sample = clamshell samplet (no depth but easiest) -collect a core = piston core (drilling to seafloor) -sediment traps

GEOL 200 (13 decks)

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