Exam Flashcards
(127 cards)
1
Q
Three main components of early atmosphere
A
H2O, CO2, N2
2
Q
Source of early atmosphere
A
Volcanic
3
Q
What happened to the oxygen produced by photolysis?
A
Consumed by oxidation of reducing materials
4
Q
Proto-ocean formed…
A
4 billion years ago
5
Q
4 records of photosynthesis
A
stable isotopic record of oxygen, banded iron formations, red bed sediments and stromatolites
6
Q
Has shelf, slope and rise
A
Continental margin
7
Q
Flattest place on Earth
A
Abyssal plains
8
Q
How are guyots formed?
A
Erosion of seamount tops
9
Q
Age of oldest oceanic crust
A
180 million years old
10
Q
Average spreading subduction rate
A
10-100mm/a
11
Q
Why do some smaller sediments have slower settling velocities?
A
They have a higher surface area so ‘stick’ together
12
Q
Where do 60% of riverine lithogenic sediments come from?
A
The Tropics
13
Q
How fast do ferromanganese nodules grow?
A
1-4mm/Ma
14
Q
Coccolithophores, foraminifera and pteropods are …. biogenic sediments
A
calcerous
15
Q
Diatoms and radiolarians are … biogenic sediments
A
siliceous
16
Q
Distribution of volcanic sediments
A
globally
17
Q
Most insignificant marine sediment
A
Cosmogenic
18
Q
Lysocline is where
A
calcite starts to dissolve
19
Q
CCD depth
A
4-5km
20
Q
Two types of bulk emplacements
A
slumps and turbidity currents
21
Q
… of rain falls over ocean
A
78%
22
Q
Steady states have
A
inputs=outputs
23
Q
size/(input/output)
A
Residence time
24
Q
… of radiation emitted by surface reabsorbed by water in atmosphere as long-wave radiation
A
90%
25
Surrounds ions to dissolve them due to dipole-ion interactions
Hydration sheath
26
Average sea water salinity (0/00)
35
27
Total Dissolved Solids in seawater
3500 mg l-1
28
Most abundant ions in seawater
Sodium and bicarbonate
29
What adds bicarbonate to rivers as there is little in rain?
Dissolution of rocks such as limestone
30
Why is there little silica in seawater?
It's used by marine organisms such as radiolaria
31
What is salinity?
The concentration of all dissolved substances in seawater expressed in ppt as a dimensionless ratio
32
Why is salinity fairly uniform?
Mixing from ocean currents as long residence times
33
Where is the highest salinity
20-30 degrees N/S
34
How is salinity measured?
Measuring electrical conductivity using a salinometer
35
K, Na, Ca, Mg and Si provided to seawater from where?
Weathering of crustal rocks
36
Volcanism provides what elements?
Cl and S
37
What can be a salinity sink and source?
Hydrothermal vents
38
Evaporate formation, aerosol formation, adsorption and, sedimentation and burial are what?
Salinity sinks
39
How many tonnes of salt do rivers carry to oceans each year?
4 billion
40
Example of secondary minerals formed by weathering
orthoclase to kaolinite and dissolved silica
41
Seawater pH is...
8.3-8.5
42
Dissolved seawater constituents...
contribute to salinity
43
Particulate seawater constituents...
accumulate as sediments and break down on the seafloor
44
Dissolved salts, ions, nutrients, minerals, trace elements, DOM (e.g. DOC) and dissolved gases...
Pass the 0.45 micrometre filter (dissolved constituents)
45
Sediments, dust, ash, exoskeletons, living and dead organic matter...
Retained by 0.45 micrometre filter (particulate constituents)
46
Has the shortest element residence time
Al 2+
47
Major constituents are conservative so...
they remain unchanged by chemical or biological reactions
48
Zooplankton package phytoplankton waste into faecal pellets to be consumed by bacteria called
Marine snow (macroscopic aggregation)
49
Total incoming insolation
340 wm-2
50
Trade winds are
easterlies
51
Wind driven currents move from
friction and pressure gradients
52
At right angles to wind from Coriolis force
Ekman transport
53
Geostrophic flow when what 2 forces in balance?
Pressure gradient and Coriolis force
54
Anticyclonic in N. Hemisphere
Clockwise circulation
55
Why does Western Boundary intensification occurs?
Coriolis stronger in higher latitudes so affects westerlies more than Trade winds so higher pressure gradient when pushing water west
56
In unstable layering density...
decreases with depth
57
Lower latitudes have what type of layering?
Stable
58
Thermohaline circulation driven by...
density differences
59
75% of clean water has what temperature and salinity
0-5 degrees C and 34-35 0/00
60
Deep and bottom layers over...
2km
61
A water mass is a ...
large body from common source region with little changes in salinity and temperature and slow mixing between water masses
62
In MOC after water down wells where does it flow?
Along Western boundaries
63
MOC draws...
warm water northward
64
Why does upwelling occur at the Southern Ocean?
Westerlies around the Antarctic so Ekman transport directed left. Water moves northwards and this must be replenished from depth
65
Why is the Southern Ocean important?
Sole place on Earth where all water masses involved in MOC come together, mix and transform
66
El Nino/La Nina temperature anomaly of +/- 0.5 degrees is a standard measure known as what?
Oceanic Nino Index
67
What is the Southern Oscillation Index?
Tahiti-Darwin monthly mean sea level pressure anomalies hPa
68
Reversed winds in El Nino mean what for Peru Current?
It's weaker so less upwelling
69
What's displaced by El Nino/La Nina?
Walker circulation
70
When North Atlantic Oscillation is in positive mode pressure differences are...
higher, so stronger storms
71
What wave type has the wave height?
Swell
72
The four factors involved in wind generated waves are...
Wind velocity, wind duration, fetch and original sea structure
73
What is significant wave height?
The mean wave height of the highest 1/3 of waves?
74
What moves across the sea surface?
Wave energy (not particles)
75
Two motions in progressive waves are...
forward and orbital
76
When does circulation not reach sea floor?
if water depth is equal to or greater than 1/2 the wavelength
77
When wave depth is equal to or less 1/20 of wavelength, what happens?
Wave motion is flatter and reaches the seafloor
78
What's the celerity?
Speed at which crests (peaks) propagate
79
What changes happens when waves approach the coast?
They slow down (become dependent on water depth for speed), refract to coastline shape and collapse as a shore breaker
80
What remains constant in a wave?
The periods
81
Why do waves refract?
Slow down due to changes in water depth. A an angle different parts of same crest have different speeds so waves end up reorientating themselves
82
What are the three types of shore breakers?
Spilling, plunging and surging
83
What wave type carries the most energy?
Tides
84
Why are tides shallow water waves, despite their long wavelengths?
Their wavelengths dwarf water depths
85
Why do different latitudes experience different tide types?
The declination of the Earth (28.5 degrees) means some areas will enter a bulge once and some twice a day
86
What is the position of celestial bodies during neap tides?
Sun and Moon and 90 degrees to each other relative to the Earth
87
What direction does the rotary tide wave move in the Northern Hemisphere?
Anti-clockwise
88
Cotidal lines...
connect points where high tide (crest of rotary wave) occur at the same time each day
89
Corange lines...
link parts of rotary wave with same tidal range
90
What three factors contribute to tidal bores?
Large tidal ranges (>5m), tapering basin geometry and water depths decreasing systematically
91
Beaches are...
active zones of sediment transportation between an erosional area above sea level and depositional below water level
92
Nearshore contains what 3 zones?
swash, surf and breaker
93
Swash zone is...
covered and uncovered by water with each surge
94
A beam is...
a prominent flat topped wave deposit
95
Backshore zone
land adjoining nearshore
96
Offshore zone
open water
97
Beach profiles can be...
swell (growth) or storm (erosion)
98
Wave setup leads to?
Rip currents (after piling of water)
99
Why do longshore currents occur?
As there is no room for orbital motion, water is transported on shore and this needs to evacuated and this arises from a water pressure gradient. They diverge at zones of maximum setup and converge at zones of minimum setups
100
Three controls on deltas are...
river, wave and tidal
101
Three ways an estuary can be formed?
glaciation, drowned rivers and tectonic activity
102
How do concentrations of conservative elements change?
Addition or removal of seawater
103
Three minor elements in seawater?
N,P and S
104
What is the removal process of components in seawater?
Removes substances from the dissolved phase and adds them to the particulate phase which can be removed from the water column via sedimentation
105
What is the removal process of adsorption?
When metal ions are attracted to the residual surface charges on particles
106
What happens to the elements in algae derived detritus that were taken up aa biological uptake in primary production?
They are released during bacterial breakdown and released at depth to be recycled
107
Mean solar irradiance in Tropics and high latitudes are...
9000 and 500 WM-1 respectively
108
What are the three factors that control angle of incidence?
Latitude, season and time of day
109
When there is low solar elevation, there is a...
high angle of incidence and high reflectance loss
110
Light attenuation controls light underwater and is the combined effects of...
absorption and scattering
111
Light attenuation is described by...
Beer-Lambert Law
112
Light intensity (I)...
decreases exponentially with depth
113
K is usually what?
0.02-0.2m-1
114
What zone is between euphotic and aphotic?
disphotic
115
What are the three optically active components of seawater?
Particulate matter, dissolved matter and water itself
116
Thee euphotic zone depth (Ze) is equal to what?
3Zs (3 x Secchi depth)
117
What does the euphotic zone depth represent?
The deepest depth primary producers can sustain themselves
118
Why is the part of the ocean south of Greenland cooling?
Freshwater inputs mean less dense water formation, destabilising MOC so less heat transported to N. Atlantic
119
How much as the deep ocean warmed?
1.4 x 10^23
120
Three types of plastic degradation?
Physical, mineralisation and biofouling/defouling
121
Compensation point (GPP=Respiration and NPP=0) represents what?
Euphotic zone depth
122
What does primary production depend on?
Mixing and stratification?
123
Why, for primary production, are tropical regions nutrient limited?
Strong permanent thermocline due to high solar irradiance all year acts as a mixing barrier?
124
Warm core rings are...
anticyclonic
125
Three types of tidal power generation
Barrages, fences and turbines
126
Three types of wave power generation
oscillating water column, float system and overtopping system
127
Advantage of current power
Stable and predictable as constant direction
