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Oceanography
1. The oceans have evolved over the history of the earth
Describe modern oceans in terms of average temperature, mean depth, average salinity and average density
Feature
Average
temperature
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Description
Approx 3.8˚C (75% of ocean is at depth
therefore low average)
Vary according to depth and latitude
Vary less than that of land because of
the high heat capacity (able to take
in/lose heat without changing temp too much
compared to earth i.e. dessert boiling in day
freezing at night)
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Average
depth
Average
salinity
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transparent – this property called
transmissibility)
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Mixing of surface water and deep
water allows for heat to be distributed
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Approx 3.75km (3800m)
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Average of 35%0
Total amount of dissolved solids
(grams) in 1000 grams (1kg) of water
Mainly made up of sodium and
chlorine (table salt)
Salinity and temp closely related (i.e.
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evaporation which causes cooling and
increased salinity)
Average
density
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1.027 g/cm (grams per cubic centimetre)
Pressure
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Humans can travel to about 3-4 atms
(atmospheres)
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Changes with depth
Sun can effectively heat just the top
layer or photic zone (as ocean is
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Distinct layering observed
Surface/mixed layer most influenced
by sun/climate – range of 15 - 18˚C
Thermocline (500 – 1000m) – drops with
depth and temp ranges from 4 - 15˚C
Deep water layer – ranges from 4 – 1˚C (pressure and salinity allows for -˚)
Enormous range with a max of 11km
at Mariana Trench
Increases with depth
Varies greatly due to evaporation, ice
melting, mixing with freshwater
High salinity occurs in secluded areas
and the subtropics (Mediterranean Seas)
Low salinity occurs in the north (Baltic
sea) and around continents (coastal areas)
Middle layer = Halocline
increases with depth but depends on
other factors i.e. increased salinity and
pressure and decreased temps (all
present at depth) = increased density
middle layer = Pycnocline
Increases with depth (due to weight of
water above)
Process and present secondary information to produce a flow chart illustrating the movement of water,
carbon and oxygen between the oceans and the atmosphere
 Oceans are a key part of the hydrological cycle with the oceans absorbing huge amounts of solar
energy thus increasing water temp and promoting evaporation
 Evaporated sea water is the main source of atmospheric water vapour which then supports life
 Also a huge exchange of materials such as water, oxygen and carbon.
 Carbon dioxide in the atmosphere is dissolved in water taken up by marine organisms and used in
photosynthesis
 Oxygen in the atmosphere is dissolved in water and taken up by marine organisms and used in
respiration
 Water evaporates from oceans when it is heated and then falls back on land and runs back into the
oceans. Water is also spilt during photosynthesis and oxygen gas is released into the atmosphere or
the ocean
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Identify the area covered by oceans and explain how this influences conditions on the earth’s surface
 71% of the worlds surface is covered by oceans (361 million square kilometres)
 The biggest oceans are the Pacific, Indian, Atlantic and Southern
 Water plays a significant role in the climate of the planet as ocean moderates atmospheric temps
 Oceans absorb half the suns energy reaching earth and the ocean is able to transport heat by
currents which distribute heat away from equatorial, tropical regions towards polar regions and by
carrying cold water from polar regions towards the tropics (Cold ocean = cold atmosphere and vice versa)
 Australia’s climate variability is strongly influenced by the Pacific Ocean
 S hemisphere has a milder climate because there is a larger surface area and volume of ocean water
 Influences of currents are referred to as El Nino (dry) and La Nina (wet)
 Always remove lots of CO2 from atmosphere - this is used in photosynthesis of marine organisms
Identify the probable origins of the oceanic waters
 Oceans formed a few thousands years after the earth and atmosphere but the composition has not
changed in a significant way as the composition of the atmosphere has – physical and chemical
properties of the ocean have stayed very stable for 1.5 billion years
 Two main theories for the origin of the oceans:
1. Degassing/Out gassing – atmosphere and oceans formed gradually. Many volcanic
eruptions released CO2 and water vapour into the atmosphere and when surface temp of
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earth cooled before boiling point of water (4 bya), rain began to fall and continued to fall for
centuries. As this water drained into hollows in the earth’s surface, the primeval ocean
came into existence. Formation of oceans helps the earth’s temp (due to its high heat capacity)
Gravity prevents water leaving the planet and because volcanism continued through history
of earth, volume of oceans increase. Most likely to be correct.
2. Comets – recent theories suggest large ice comets frequently bombarded the earth's
atmosphere and vaporized above the earth's surface. Such comet rain supplied the earth's
initial water mass as well as many of the basic compounds necessary for the origin of life.
Given the current rate of collisions, 4 billion years represents a sufficient time span to
enable oceans to reach their present day volume. Not as likely to be correct (as comets contain
high levels of deuterium however earth's water do not contain high levels of deuterium )
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Regardless of the origin, as the earth cooled, water vapour from the atmosphere cooled and
condensed and formed rain. As this rain fell on the fresh solid surface of the earth, it dissolved
some of the soluble minerals from the rocks – eventually this slightly saline water ran into large
depressions on the earth's surface to form the ocean basins
Earth's oldest rocks include sedimentary strata (NB sedimentary rocks always form in water therefore)
which indicates that as far back as 4 billion years ago, there was liquid water on the surface
Compare the evolution of the oceanic waters with the evolution of the atmosphere and explain how and why
the two are linked
 The original atmosphere formed at the same time as the earth due to residual gasses left from its
formation from a solar nebula – these gases were largely hydrogen and helium
 Soon after the atmosphere began to change as a result of degassing and a dense atmosphere
emerged from vapour and gases that were expelled during degassing – these gases may have
consisted of hydrogen, water vapour, methane, carbon monoxide and carbon dioxide
 Degassing contributed to changing atmosphere as the volcanic activities produced new gases and it
is thought that a strong solar wind blew them away in addition to plants using CO2 to produce
oxygen as well as bacteria releasing nitrogen (more a decrease of other gases than an increase of nitrogen)
Atmosphere
Origin
Gases present
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First Atmosphere
Residual gasses from
formation
Hydrogen
Helium
Volcanic Atmosphere
Degassing
Hydrogen
Methane
Carbon Monoxide
Carbon Dioxide
Water vapour
Present Atmosphere
Life processes
(photosynthesis)
Oxygen
Nitrogen
The early water vapour present in the volcanic atmosphere would not have condensed as it was
still too hot however dense clouds would have formed.
The most important feature of the ancient environment was an absence of free oxygen
About 3 billion years ago cyanobacteria began to photosynthesis creating oxygen and as this
oxygen increased, the carbon dioxide decreased
In the upper atmosphere, some oxygen molecules absorbed energy from UV rays and split to form
single oxygen atoms. These atoms combined with remaining oxygen molecules to form ozone and
consequently an ozone layer which was very efficient at absorbing UV rays
As a result of this evolution of cyanobacteria, the earth acquired an atmosphere and an ocean
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Salt in the oceans has accumulated over 3 billion years however as rivers flow into it carrying
dissolved salts from soil erosion – oceans should be far saltier than they are i.e. simultaneous with
the salt entering the sea, there must be an equal amount of salt leaving the sea.
The mechanism is not known but salt may have been somehow locked in seafloor sediments and
then recycled through subduction, melted, and redistributed into other minerals.
2. The shape, distribution and age of the current oceans has been determined by plate tectonics
Identify the region of the crust where new ocean basins are forming and where ocean floors are subducting
 Oceanic crust, due to its composition, is more dense and so continental crust floats higher
 The only entirely oceanic plate is the Pacific Plate
 Ocean ridges are where new oceanic lithosphere is created by upwelling convection currents which
partially melt the mantle and result in basaltic magmas which intrude and erupt at the oceanic
ridges to create new oceanic crust
 As new oceanic crust is created it is pushed aside in two directions thus the age becomes
progressively greater in both directions away from the ridge in a mirror image
 Because oceanic crust may be subducted, the age of ocean basis is relatively young and the oldest
ocean crust occurs furthest away from a ridge
 Sediment thickness also increases in both directions away from the ridge and is thickest where the
crust is oldest with the bottom layer of sediment being the oldest
 When oceanic crust collides with another plate it subducts, thus losing old crust
Outline the types of evidence used to date ocean floors
 Relative dating of ocean floors indicates that the further from the ridge, the older the rocks
 Fossils can be taken from sediment and dated using radiometrics and relative dating
 There are two other methods:
1. Using magnetism of the crust (Magnetic Timescale
- The magnetic zebra striping that can be seen on the sedimentary rocks in the ocean
are from changes in the magnetism of the earth
- A reconstruction of the history of the magnetic reversals for the last 4 million years
was made using radiometric dating and measuring the magnetic orientation of rocks
- Radiometrics not good for ocean crust because it never stays very old (subduction)
- However the magnetic timescale was already established therefore scientists
measured the magnetism of the rocks on the crust and then compared it to the
magnetic time scale
2. Looking at microfossils in seafloor sediments
- Biological processes dominate sediment formation in areas that receive little
terrigenous material (land derived)
- Inorganic debris from dead organisms turns into oozes (calcium carbonate or silica)
- The microfossils in sediment immediately overlying the basalt sea floor gives an
estimate of the age of the sea floor at that locality as the basalt is considered to be the
same age as this bottom most sediment
- Microfossils already have known eras and if a certain microfossil is found the rock
can be dated to the era the organism lived in
Assess the reliability of information used to estimate the age of ocean beds
 The magnetic timescale is reliable because calculations are done and the observed data was
matched to the theorised data
 Magnetic timescales can be used to narrow down a time range
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Microfossils are also very reliable because age and distribution of microfossils is very well studied
and already well know therefore they are easy to date however direct samples of fossils and ocean
beds are needed every time and still they only give a time period
Processes should be used in conjunction with each other to achieve enhanced accuracy of results
Outline the reasons why the oldest sea floor present on the earth today is generally less than 250 mya
 The process of sea floor spreading is constantly forming new ocean crust
 The new sea floor at MORs where magma comes to surface and forms new curst
 The process of subduction destroys old ocean floor as it is subducted under continental plates
 Ocean floor acts as a huge conveyor belt, transporting crust/sediment to subduction zones
Identify the role of plate tectonics in maintaining the equilibrium between the area of sea floor and area of
continental land present on the earth
 Seafloor is constantly being generated and destroyed but this ongoing process has not significantly
altered the total area of the seafloor that exists over time i.e. subduction and rifting happens at a
constant rate and stays in balance – some oceans are growing whilst others are shrinking
 Erosion of continental crust is a constant process and as mountains are eroded away there is a
significant change in the overlying weight of crustal material. In response to these changing forces
the underlying crustal material will gradual rise to bring back balance – known as isostatic
adjustment i.e. a piece of wood floating in water. If you cut it in half, it will still float in the middle
Discuss the reasons for, and impacts of, possible shifts in the equilibrium between the area of sea floor and
area of continental land
 The area of seafloor and continental land has remained fairly stable over the earth's history
 What has varied dramatically is the distribution of land masses and oceans
 200 million years ago the continents were combined into one large land mass called Pangaea and
surrounded by one huge ocean called Panthalassa (Pan = all, Gaea = earth, Thalasaa = sea)
 over time this single land mass spilt apart forming Laurasia and Gondwana and gradually reformed
into the continents of today
 This has resulted in the formation of new ocean basins through the formation/subduction and
redistribution of ocean floor
 On land, mountains are eroding away and this is carried down stream by rivers, some is then
deposited in river deltas as the water slows. This can cause significant loading on areas of the
crustal plate and result in the slow sinking of continental plate regions
Describe evidence for the closing of former ocean basins in terms of the presence of deep marine sedimentary
rocks in present day continental mountain belts
 One of the best examples of the presence of deep marine sedimentary rocks present in continental
mountain belts are the Himalayas
 The Himalayas formed as a result of the collision between the Eurasian and the Indo-Australian
crustal plates and the resultant folding and faulting produced the mountain belt
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India was an island but it moved north and squashed out the sea that was originally there – India
moved at rates of up to 15cm a year and pushed out the Tethys Ocean. Today Himalayas are
growing and eroding at a rate of 8cm/year (never getting bigger or smaller)
There are a number of visual clues to the origin of the crustal material making the Himalayas –
these including the layering of sedimentary rocks which formed long ago as horizontal sediments
on a sea bed and ammonite fossils (c.f. nautilus looking animal) have been found in large numbers. In
addition, volcanoes that once fringed the edges of the ocean remain.
3. There are differences in physical, chemical and biological environments within and between past
and present day oceans
Outline the origin of salinity in the earth’s seas and oceans
 No single theory explains origins of the oceans but it is mostly agreed that it was due to degassing
 Most of the oceans salts were derived from gradual processes such as the breaking up of the cooled
igneous rocks of the earth's crust by weathering and erosion, the wearing down of mountains, and
the dissolving action of rains and streams that transported their mineral washings to the sea
 A portion is due to rain, groundwater and moving surface water dissolving minerals in rocks
 Most of the salt accumulated over time due to weathering of continental rocks – as rain falls on the
land it slowly dissolved parts of the rocks and soluble salts are washed into the sea
 A simultaneous with salt entering the sea, it must be an equal amount leaving (salt never increased)
 Volatiles from the mantle are released into oceans when molten material is rapidly cooled when it
comes in contact with ocean water and in the process ions become dissolved from sediments
deposited on the ocean floor have also contributed
 Major contributing component of salinity is the Chloride Ion (Cl-1)
 3.5% of the ocean is salt
Identify data sources, plan, choose equipment and perform a first hand investigation to compare the solubility
of common salts in water of different temperatures
 Investigating Solubility and Temperature:
 Aim: to compare solubility of common salts in water at different temperatures
 Method: using a measuring spoon add solute to 20ml of water
Salt
Sodium Chloride
Sodium Sulphate
Potassium Nitrate
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Iced Water (3˚C)
6.3 grams
0.1 grams
2.1 grams
Amount Dissolved
Tap Water (21.5˚C)
6.8 grams
0.7 grams
4.4 grams
Hot Water (51˚C)
8 grams
1.2 grams
5.3 grams
Results: Sodium Chloride has more salt dissolved in each water temperature and therefore this
indicates that it has a higher solubility. Nitrate was next, with Sodium Sulphate having the least
solubility. Generally the most salt dissolved in hot water and the least in cold water
Conclusion: Hot water does dissolve the most because it contains more energy to break up other
particles. Hot water needed to be kept hot (which was hard) and cold water needed to stay cold (and
not get heated) Results were based on an average as the experiment was repeated 4 times in the class
(repetition) however this approach lacks consistency (everyone stirred their beakers differently, everyone
judged when salt had dissolved differently, etc) there were also time constraints therefore was rushed.
Perform a first hand investigation to demonstrate the precipitation of salts from a cooling solution and solve
problems to use this information to predict precipitation in naturally occurring bodies of water
 Aim: to observe the precipitation of salt from a cooling solution under different conditions
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Methods: make a saturated salt solution (salt used – Sodium Chloride); heat 40mL water in 100mL
beaker; add salt until no more will dissolve; divide the salt equally into 3 test tubes; cool the
saturate solution in the test tubes by leaving overnight in a) an ice water bath, b) a room at air
temp, c) placed in a thermos flask
 Results:
Test Tube
Condition
Observation
Crystal size
A
Ice water
No crystals formed as it didn’t evaporate
B
Room temp Small cube like crystals
Too small - less than 1mm
C
Thermos
Large cubic crystals
Larger – up to 2mm
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Conclusion: large crystals are observed in warm conditions whereas no crystals were formed in icy
conditions. Small crystals were formed at room temperature.
In naturally occurring bodies precipitation of water occurs in warm conditions (warm conditions =
more time taken to cool down therefore large crystals formed. Smaller crystals formed in colder conditions because
there was less time to cool down and less time to make crystals) warm, equatorial regions i.e. the
Mediterranean, would form large crystals.
Explain examples of common processes that change the salinity and temperature of oceans and small
enclosed seas
 Salinity is increased by evaporation or by freezing of sea ice (water is frozen/evaporated and salt is left)
 High evaporation rates are mostly in mid-latitudes with warm temps and low rainfall
 Salinity is decreased by rainfall, runoff or melting of ice (adding of freshwater to salt)
 Waters close to river mouths or melting ice
 Temperatures at any point in the ocean are constantly changing due to tides and currents
 Ocean is heated by the suns radiation and the sea-surface temp (SST) is normally higher than air
temp though SST does change from day to night, it is to a much lesser degree than air (desert)
 Ocean currents distribute heat and tend to equalise the heat around the world
 Deep water temps are always low
 The smallest seasonal variations of SST water occur in equatorial and polar regions
 Prevailing winds blowing from continents cool water temps and the absence of large land masses
in the S Hemisphere allows for more solar radiation to go into the ocean
 Vertical mixing in the water column is the only significant process by which temperature changes
occur at this depth
Relate the range of temperatures and salinities measured in selected areas of the Pacific Ocean to the
distribution of specific species
 Currents, topography and depth affect temps and certain temps affect animal distribution
 All animals have a thermal range (i.e. a temp range in which they can most effectively grow, reproduce and
live) and the Capelin are an example of this (an energy dense forage fish in the Smelt family)
 Capelin favour cold water and during a time period when surface waters are very warm, capelin
migrate into deeper, cooler waters. When capelin are deeper in the water column, they are less
available to surface feeding sea birds and possibly harder to catch for diving birds
 Upwelling (deep ocean currents hit a shallow shelf on the ocean floor and all cold deep water Is force upwards
bringing high concentrations of nutrients to the surface) power food chains and create an abundance f food
for fish, seabirds and marine mammals and are usually host to a multitude of organisms (birds, fish)
Describe the attenuation of light with depth in oceanic waters, and the order in which the different
wavelengths of light disappear with depth in oceans
 Shorter wavelengths of light can penetrate ocean waters deeper than long wavelengths
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This means blue and violet will be transmitted the greats depths whilst red, orange and yellow will
be absorbed in the upper layers i.e. the deeper you dive, the darker the colours will get as the red
end of the spectrum has disappeared.
Red will be absorbed within the upper 10m whilst only blue and some greens will extend beyond
100m however these will only be at a low intensity
In open ocean no sunlight penetrates water beyond a depth of 1000m
Discuss the implications of limited light for the distribution of marine plants in near-shore environments and
photosynthetic plankton in open oceans
 The distribution of marine organisms depends on the physical and chemical properties of seawater
such as temp, salinity and dissolved nutrients as well as ocean currents which carry oxygen,
wastes, spores, eggs, larvae and plankton and it also depends on the penetration of light
 Photosynthetic organisms (cyanobacteria, plants, algae) exist only in the photic zone (up to about 90m)
where light is sufficient for photosynthesis
 Only 2% of the ocean floor is in the photic zone, photosynthetic organisms in benthic (bottom)
areas are far less abundant
 Phytoplankton (photosynthetic plankton) is distributed near the surface worldwide
 Heterotrophic plankton or zoo plankton are found at all depths
 Bacteria are abundant in upper waters and in bottom deposits
 Marine plants are more likely to be found in shallow water in near shore environments where light
is abundant and temperatures are warm
4. The mass motion of oceans
Describe the four types of mass motions of water (surface currents, deep circulations, tides, tsunamis) and
identify the energy source for each
 Ocean currents
 Currents allow for the circulation of water and its contents
 The driving force of currents is frictional drag of winds; the interplay of the Coriolis force (the
deflection of water because of the spin of the earth i.e. spins anticlockwise in the S hemisphere c.f. Simpson’s );
density differences (caused by temp and salinity); configuration of continents and ocean floor and
astronomical forces like the moon
 Currents can be broken into two forms – wind driven and thermohaline (temp and salt) circulation
 Wind driven circulation is the horizontal movement of the upper waters set in motion by moving
air masses. It is fast and plays a major role in transporting surplus heat from the tropics to the poles
 Thermohaline circulation is the slow moving water mass of the deep ocean. It is a vertical
movement produced at the surface in high latitudes by temp and salinity which create high density
masses. These high density masses then sink and spread beneath the surface waters resulting in
deep water movement or circulation
 Large surface currents are mainly driven by winds that blow year around – these winds are called
the Northeast and the Southeast Trade Winds
 At mid latitudes the winds are called the Westerlys
 At the highest latitudes the winds are called the Polar Easterlys (winds blow east all year round)
 Two of the largest currents are the Antarctic Circumpolar Current (West Wind Drift – circles eastward
around Antarctica) and the Kuroshio current (travels up to 120km a day at 5km/hr just off Japan)
 The Gulf Stream is a current with a strong influence on the E. coast of the US but is actually part
of a large current system and travels at a speed of 6 – 8 km/hr
 Due to the Coriolis force currents do not flow in a straight path
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This deflection then forms circulation systems known as gyres. Gyres are closed loops formed by
currents. Major gyres are centred about 30˚ N and S of the equator.
Major gyres consist of:
- Two equatorial currents moving westward on either side of the equator driven by the
trade winds (1)
- In between is a weak eastward moving equatorial counter current. The weak current is
due to the absence of wind currents at the equator (the Doldrums – very little wind).
Equatorial currents move at about 2-4miles a day which allows for max heating (2)
- When the warm currents near the continents they are deflected north and south by the
continents and the Coriolis Effect. Currents move rapidly and remain warm (3)
- At about 40˚ N and S the Prevailing Westerly winds deflect the currents to the east.
Water cools as it moves eastward (4)
- Reaching the continents, the current is again deflected by the continent and the
Coriolis effect completing the gyre (5)
Gyres are stronger to the west because trade winds sweep across the oceans surface they push
water near the equator in a westward direction through concentrated channels. When water reaches
its western margins it actually piles up to about 15cm then spills northward and southward in
strong currents flowing through tight channels. This is called western intensification.
Examples of western intensification are the Gulf Stream and the Kuroshio
Wind and the Coriolis Effect combine to cause currents to move at 45˚ to the actual wind direction.
The surface layer drags the next layer of sea water below it which is deflect even further and so on.
This is called the Eckman Spiral
This causes currents to change direction at depth
At an average win speed of 45km/hr at a depth of 100m, the water is moving slowly in the
opposite direction from that of the surface
This is considered to be the bottom limit of wind driven currents
The net result of this entire process (Coriolis Effect and Eckman Effect in the gyre) is the cause the
water to move at a right angle to the wind direction or toward the centre of the gyre
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This causes ‘hills’ up to 2m high in the centre of the gyre
The mounded water flows downward and outward from the hill under the influence of gravity but
the Coriolis Effect deflects it to the right continuously until it is flowing parallel to the hill at
which point gravity and the Coriolis Effect are balanced.
This is termed a Geostrophic Current
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Because prevailing winds along coast lines blow more or less parallel to the shoreline, they push
the water toward the shore or offshore causing sinking currents or upwelling currents (the latter is
especially important to commercial fishing as upwelling currents provide nutrients for marine life )
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The ocean is layered with differences in salinity and temp. since dense, cold water sinks and warm
water rises there is a net effect of cold polar water sinking and moving both northward and
southward toward the equator
The cold current flowing along the ocean floor displaced the warmer water upward
Usually off the Pacific coasts of N and S America and the subtropical and mid latitude west coast
of Africa, surface water moves across the coast developing an upwelling current.
This rise of cool and nutrient rich water from great depths replaces the vacating water
While in other regions like the western end of an equatorial current or along the margins of
Antarctica, accumulated water is pushed downward in a down welling current
Additionally significant mixing currents are generated along the ocean floor carrying heat energy
and salinity and travel the full extent of the ocean basins
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As waves approach a coastline they undergo a change in direction. They touch bottom and drag
causes the waves to approach nearly parallel to the shore.
Although refraction bends the waves until they are nearly parallel to the coast they nonetheless still
approach at a slight angle. This results in a long shore.
The current is caused by the slight oblique angle of the wave
The returning backwash is perpendicular to the slop of the beach and this causes grains of sand to
be moved along the shore in a zigzag path
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A wave is a smooth swell on the open ocean
The highest portion of the wave is called the crest and the lowest portion is called the trough
The horizontal distance between two crests or between two troughs is called the wave length
The vertical distance between the trough and the crest is the wave height or wave amplitude
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Tsunamis are less frequent waves reaching a height of above 40m
They are caused by underwater disturbances such as earthquakes, volcanoes and landslides. The
larger the disturbance, the larger the tsunami will be
In the open ocean, tsunamis are hard to spot however in shallow water, changes occur as the
wavelength shortens and the height increases.
The strength of the disturbance, the distance and the shape of the coastline combined determine the
tsunamis height and ultimately its destructiveness
As rapidly as tsunamis move, P waves from the earthquake move faster
From quantitative examination of seismograph records it is possible to estimate whether such a
wave will be excited by a great earthquake. It is then possible to send out warnings of the wave.
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NB – Tides from Gravity; Currents from Earth's Rotation
Present information that identifies structures found in deep-sea organisms that are inferred adaptations to
environmental conditions
 Physical characteristics of the deep are abiotic factors that deep sea life must contend with to
survive – light, pressure, temp, oxygen and food have all led to fascinating adaptations of deep sea
life used to feel, see, feed, reproduce, move and avoid being eaten by predators
 An adaptation is an alteration of the structure or function of organisms which enables them to
survive and multiply in a changed environment
 Oxygen:
- Dark cold waters of the deep are oxygen poor
- Deep sea life requires little oxygen and because there are few organisms, what
oxygen is there is not depleted
- Other organisms do not require oxygen at all, living off the hydrothermal vents
- Oxygen is transported to the deep from the surface where it sinks to the bottom when
surface temps decrease
- The minimum oxygen zone is between 500 – 1000m where the abundance of species
requiring oxygen deletes the amount of oxygen in the water
 Light:
- Deep ocean waters are black
- The only light produced is by bioluminescence (living-light – produced by a living thing)
- Bioluminescence is a chemical reaction in the creatures body that creates low level
light so deep sea life must rely on alternatives to sight
- Most often, this light is blue/green but some can produce red
- Light can be used to locate, lure and stun prey
- Lack of light creates a barrier to reproduction so bioluminescent light is also used as a
signal for potential mates. Deep sea creatures are also equipped with a strong sense of
smell so chemicals are released into the water to attract potential mates.
- A parasitic relationship for reproduction is also used when males (who are much, much
smaller than females) hook their teeth into a female and attach themselves for life. The
blood vessels of the male merges with the female’s so that he receives nourishment
from her and in turn she receives a reliable source of sperm
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Pressure:
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Considering the volume of water above the deepest parts of the ocean, pressure is one
of the most important environmental factors
- Pressure increases 1atm/10m
- Ranges from 200 – 600atms (it is 1atm on land)
- Deep sea creatures have filled swim bladders and other excess cavities with oil or
flesh saturated in oil and the flesh and bones are soft and flabby
Temperature:
- In most parts of the deep sea waters are cold and remain so (not variable like the surface)
- Organisms which dive to great depths have thick layers of fat (blubber) that act as
insulators and some organisms have developed an antifreeze substance in their blood
Food:
- The lack of light and scarce food meant new feeding mechanisms were developed
- Decaying plants and animals from upper zones provide some food as they sink
- The Lamprey and the Hagfish burrow into any carcasses that fall to the floor and
consume it from the inside out
- Some have large and expandable stomachs to hold large quantities of scarce food
- Some have can unhinge their jaws to fit a whole meal in
- Jaws have teeth pointing inwards to disallow captured prey to escape
- The viperfish and the anglerfish are equipped with a long thin modified dorsal fin
with a light on the end of it which acts as a lure for prey
Overview
Adaptations include large eyes, bioluminescence, a strong sense of smell, altered body
composition (no swim bladder), expandable stomach and jaws, absence of jaws, inward facing teeth,
lures, parasitic reproduction techniques, and colour for camouflage (often black, silvery and red in colour
– absence of red light means they are hard to see)
Explain how the oxygen supply on the ocean floor is renewed making life there possible
 Oxygen is dissolved in water when waves crash on rocks and beaches and when fresh water that
has been flowing quickly over rocks and waterfalls flows into the ocean
 Oxygen is produced in oceans when plants, algae and phytoplankton photosynthesise
 Vertical currents transport oxygen to the depths
 Chemosynthetic bacteria, living near vents, use hydrogen sulphide from the vents to fix carbon
dioxide and produce carbon based molecules – oxygen is produced in the process
Explain how long-lived materials, such as synthetic chemicals and heavy metals, that enter the sea in one
place can be found thousands of kilometres away
 Mercury and lead are two dangerous heavy metals which have been dumped into oceans
 Heavy metals are often absorbed onto fine sediments suspended into the waters and can be
transported thousands of kms away by currents
 They can also be taken up by marine organisms in bioaccumulation and this can produce
biomagnification up the food chain (bioacc – enters the food chain, biomag – increases up the food change)
Process information to explain why laws about oceans are becoming increasingly important in world society
 To protect the unique and fragile ecosystems in the ocean
 To maintain biodiversity and protect endangered species
 Economic value (fisheries etc)
 Clear boundaries minimise conflict between countries
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Laws must be placed because without guidelines, the entire ocean is affect by something that
happens in one country therefore global guidelines are needed
Discuss the implications of the movement of materials by ocean currents for the use of the oceans for waste
disposal, including pollution and ocean sewage outlets
 People once thought the oceans great volume and continuous mixing would dissipate and distribute
natural and synthetic substances highly effectively and so deep water rubbish dumping was begun
 Oil pollution i.e. from tanker oil spills, bilge cleaning and other ship operations, engine oil from
cars in runoff, air pollution, offshore oil productions, natural oil seepage from the sea floor.
 Toxic waste i.e. metals and slowly degrading chemicals from industrial, agricultural, household
cleaning, gardening, products (dioxins) Toxic wastes can be taken up, accumulated and magnified
 Coastal mining deposits and withdrawals – oceans are the sources of materials that are becoming
removed, to the detriment of ocean life
 Manmade waste i.e. garbage, cleaning water, plastics all contribute to ocean pollution. Mainly
because sewage pipes share their space with storm water drains – sewage wastes mingle with
storm water and it all flows unhindered directly into the sea. Things blowing around on streets also
enter the ocean i.e. balloons, six-pack rings and plastic bags which choke animals as well as
fishing gear which drown animals that get caught in it
 Sewage in Sydney is only partly treated and then discharged into deep water 2-4km offshore – it
does not go through secondary treatment, which is expensive and requires a lot of land. Being
dumped so far offshore allows for a decrease in the degree and frequency of bacterial
contaminations of bathing waters
 Sydney’s coastal waters have three main ocean outfall discharge areas, support fish and other
marine life that are fished by commercially and for recreation
 The risk of respiratory illness and gastrointestinal infections is much higher for people swimming
at sewage pollution affected beaches
5. The physical conditions at different depths in the oceans constitute different environments and can
support different communities of organisms
Describe what is meant by ‘community of organisms’
 A community is the set of all populations that inhabit a certain area (just biotic factors)
 Communities can have different sizes and boundaries and organisms in an area that are
interdependent on each other for food shelter and/or protection
 An ecosystem is – a higher level of organisation, the community plus its physical environment
(soil, rocks, air, sunlight) i.e. abiotic and biotic factors – the biological and physical components
affecting the community/ecosystem
 There are two basic categories of communities – terrestrial and aquatic
 These two basic types contain eight smaller units called biomes
 A biome is a large scale category containing many communities of a similar nature whose
distribution is largely controlled by climate
 Conditions in water are generally less harsh than those on land – aquatic organisms are buoyed by
water and do not have to deal with desiccation.
 Aquatic biomes are divided into freshwater (inland) and marine (saltwater or oceanic)
 Marine biome has more dissolved minerals than freshwater biome. Majority of water is marine
 Two basic categories in this biome – benthic and pelagic
 Benthic communities (bottom dwelling) are subdivided by depth – the shore/shelf and the deep sea
 Pelagic communities (swimmers of floaters suspended in the water column) include planktonic (floating) and
nektonic (swimming) organisms
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Process and analyse information of life forms at different depths in the oceans to compare the deep ocean
environment and its organisms to that in the top thirty metres of the ocean
 In the photic zone there is sunlight and an abundance of all sorts of organisms
 Further down there is no phytoplankton but a wide range of zooplankton (krill) as well as jellyfish,
some fish and squids. The majority have transparent, gelatinous bodies made up of mostly water
 So little is known about deep – all species and their reproduction/predation/defence not yet known
 It is known that there is great diversity in benthic zones even though resources are poor and it is
not as hostile as originally though but rather benign and stable as it doesn’t change much due to the
lack of waves, currents, seasons etc offering long term security to inhabitants
 Benthic organisms are small in size with a slow metabolism, slow movement, long life times and
slow sexual maturation as well as the adaptations listed above
 Base of food web is organic material that rains down from the densely populated surface waters
Deep Water
No light
Zooplankton
Little turbulence
Higher pressure
Low temperatures
More dense water
Conditions don’t change much
Shallow Water
Light up to 200m
Phytoplankton and zooplankton
Water is turbulent (currents, waves…)
Low pressure
Higher temperatures
Less dense water
More changeable conditions
Gather and process information and use available evidence to assess the range of resources provided by the
ocean including fishing and food; marine aquaculture; minerals; chemicals and power
 Fish
 Provide about 16% of the total world’s protein (higher percentages occurring in developing nations)
 86 million tons of fish were captured in 2000.
 The most common species are herring, cod, anchovy, flounder, tuna, shrimp, mullet, squid, crab,
salmon, lobster, scallops and oyster.
 Molluscs and crustaceans are also widely sought.
 The fish that are caught are not always used for food. About 40% of fish are used for other
purposes i.e. fishmeal to captive feed fish.
 Areas where ocean is very shallow contain many fish i.e. middle/southern regions of North Sea.
 Coastal up welling areas can be found off of southwest Africa and off South America’s W coast.
 In the open ocean, tuna and other mobile species like yellow fin can be found in large amounts.
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Minerals
Minerals mined include salt, sand, gravel, and some manganese, copper, nickel, iron and cobalt
which can be found in the deep sea - Mexico is the biggest salt extractor in the Pacific
Drilled for crude oil
Bromine extracted is used in the food, dye, pharmaceutical, and photo industries
Magnesium, recovered by an electrolytic process, is used in industrial metal alloys, especially with
aluminium; Japan and California are the main sites for its extraction.
Metal-bearing deposits on the deep-sea floor, consisting of nodules, crusts, and accumulations of
metallic sulphides from deep vents, are of potential economic interest.
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Mining for nodules which manganese, iron, copper, nickel, titanium, and cobalt are being looked
into however economic considerations and concern over management of mining operations are
slowing mining operations
Marine sulphide ores, containing iron, copper, cobalt, zinc, and traces of other metallic elements,
are deposited in large amounts by the actions of deepwater hydrothermal vents, such as occur in
the Pacific off the Galapagos Islands and on the Juan de Fuca ridge
Power
Deposits of oil and gas under the seafloor are the most valuable and sought-after fuels of the
modern world economy.
Shallow seas and small ocean basins, such as the South and East China seas, are thought to have a
high potential for large reserves.
The principal areas in the south western Pacific for offshore oil and gas exploration are in the
South China Sea but they also include the area off the Sumatran coast in Indonesia.
In the north western Pacific the main areas lie to the northwest of the island of Kyushu in Japan, in
the southern portion of the Yellow Sea and in Gulf of Chilli and in regions off Sakhalin Island.
Oil and gas wells have been drilled in the Bering Sea in the north and areas off the southern coast
of California in the eastern Pacific.
In the southern Pacific, hydrocarbon production and exploration is taking place in the Gippsland
Basin off the south eastern coast of Australia; in New Zealand's Cook Strait, its area in the Tasman
Sea, and off South Island; and in areas off Fiji.
Review the range of abiotic characteristics of an environment that determines the nature of a community
within that environment
 The range of biotic characteristics of an environment would vary depending on whether it was a
deep ocean environment or shallow water.
 They could be: temperature; salinity; dissolved gas levels in water; light wavelength and intensity;
pressure; current characteristics (speed, depth, direction); pH; substratum (bottom = sediment? rock?);
tides; waves; exposure to air
 Ocean has a particular range of abiotic factors that play varying degrees of importance in the
distribution and abundance – that is, where organisms are found and how many are there
Describe and compare examples of food chains that occur in the top layers of the oceans and those found at
great depth, explaining the differences
 Top layers of ocean have living photosynthetic organisms (i.e. sea grass, algae, phytoplankton and
cyanobacteria) at the beginning
 Deep ocean food chains have autotrophic organisms that have died and fallen to the floor or
hydrothermal vents as the energy sources
 Surface:
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Deep:
Explain, using examples, why organisms living on the ocean floor will be different from organisms living in
the top thirty metres of the ocean
 Abiotic characteristics i.e. light, pressure, temp
 Biotic characteristics members of the same species (low population density means having to mate at every
opportunity whenever they meet the opposite sex) and members of other species (must be efficient predators to
catch what little live food swims in darkness i.e. huge teeth and extendable stomachs)
Structure
Deep Sea Fish
Surface Fish
Reason for Difference
Eye
Very large
Smaller
Deep sea fish need to get as
much light as possible – a big
eye can gather lots of light
Mouth
Very large and dislocated Small teeth
Availability of food. Less food
for extendibility
in deep therefore need to get any
food that comes around
Body shape
No clear body shape –
Thin and stream lined
Surface fish they need to swim
not important but often
long distances to escape/catch
food - need to be able to swim
Dorsovetnrally flattened
Laterally flattened
fast
Body covering Gelatinous skin – helps
Scales
Scales useful for being
with pressure
streamlined and reflecting sun
for camouflage as well as
providing added armour
Bioluminescence Yes
No
Surface fish have no need – only
need where is no light
Gut
Extendable
Small
Availability of food – needs to
be able to accommodate food
when it is encountered
Colour
White, colourless, clear
Silver, yellow, colourful
Camouflage - no light at depth
and reflective
i.e. doesn’t reach
Explain how increased ocean currents and sea floor topography can change the utilisation of ocean resources
by society
 Main resources obtained = fish, crustaceans (lobsters, prawns) and molluscs (octopus, squid)
 Oil and gas are mined from offshore drilling rigs and a new venture is mining in deeper oceans for
minerals such as iron, manganese, sulphur, copper and nickel.
 Deep oceans have not been accessible for mining and fisheries but as vessels are now doing
research into the abyss more is being discovered
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Bringing minerals to the surface is expensive and is still uneconomic however with mining on land
becoming more expensive there may be a time when it is economic
When deep cold water currents meet landmasses they rise up from the sea floor carrying nutrients
This upwelling stimulates the growth of microscopic photosynthetic organisms and contributes to
the rich diversity of life found in the coastal waters
It is in these areas where commercial fishing takes place
When bathymetry is mapped and studied, we may be able to exploit benthic organisms as a food
source i.e. benthic crabs, lobsters and molluscs
6. Hydrothermal vents support unusual communities
Describe the way in which seawater is heated in circulation within newly formed ocean crust
 At MORs cracks and crevices are created as new magma comes to the surface
 As the seafloor spreading continues, the faults also provide conduits so that cold seawater can
circulate downward into the crust
 Seawater seeps into these openings and is heated by the magma that lines beneath the earth's crust
 As water is circulated through the crust, it becomes more salty – becomes brine
 The brine continues to circulate through the crust dissolving minerals the constitute the rocks it
comes into contact with
 The hot brine now becomes concentrated in dissolved elements and the composition of the fluid
has now changed, resulting in hydrothermal fluid
 The brine is heated it rises and seeks a path back into the ocean through an opening in the sea floor
 As the vent water busts out into the ocean, its temp is very high – up to 400˚ yet this water does not
boil because it is under so much pressure
 Water contains many minerals (i.e. manganese, zinc, iron, silver and copper in the form metal sulphides )
 The site is called a black or white smoker depending on the minerals extruded
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Research into hydrothermal vents is justified because it gives insight into life on other planets that
have similar, anaerobic environments; there is an economic benefit of metal sulphides as a
resource and the minerals could be harvested; there is scientific interest with the discovery of new
species; gives insight into how life may begun and you can monitor earthquake/volcanic activity
Solve problems, plan and perform an investigation to demonstrate the effect of surface area to volume ratio of
solids on their cooling rate in water
 Aim: to examine the cooling rate of different sized objects
 Methods:
- Cut agar containing indicator into three cubes with sides of 1cm, 2cm and 3cm
- Calculate and record the volume and surface area of each cube
- Place cubes in beakers of hydrochloric acid and leave for 10 min
- Cut each agar cube in half and record depth of diffusion – diffusion recorded by
amount of agar cube that is discoloured and not purple any more (indicator is purple)
 Results:
Cube side
Surface
Volume
SA:V
Depth of
Volume
% left
%
Area
Penetration
left
coloured
penetrated
coloured
by acid
1cm
6
1
6:1
3mm
0.064
6.4%
93.6%
2cm
24
8
3:1
2mm
4.096
51.2%
48.8%
3cm
54
27
2:1
1mm
21.952
81%
19%
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Conclusion: the smaller the object is, the more acid will penetrated – or i.e. the more it will be
affected by temperature – the smaller the object the faster it would cool. Large objects are less
affected by temperature/acid and take much long to cool
Discussion: models the cooling of objects in a medium i.e. seawater by exhibiting the depth of
diffusion of acid in agar cubes. The depth of infiltration of the acid models the loss of heat, from
the outside of the agar cubes, in. the cube with the greatest SA:V ratio ‘cooled down’ the fastest.
Needs to be repeated and no control was used as results were determined on a basis of comparison
A higher surface area to volume ration will mean cooling is quicker
Crust with a lot of cracks in it compared to crust with few cracks will cool faster as more surface
area is exposed to the cool water to cool it down
Perform and investigation to assess the relationship between the rate of hatching in brine shrimp to salt water
concentration and temperature
 Salinity
 Aim: to see if differing salinity levels affect the hatching and growth of brine shrimp
 Method: poured one litre of distilled water into each of the 3 tanks; 15grams of salt was added to
one tank, 25grams to the next and 35 to the last; added 5 drops of solution to each (about 1500 eggs)
 Results:
Day
Observation
15g/L
25g/L
35g/L
Day 1
Experiment set up
Experiment set up
Experiment set up
Day 4
All hatched and free
All hatched and free
All hatched and free
swimming –1mm long
swimming –1mm long
swimming –1mm long
Day 8
Has the least alive
Has some alive
Has the most alive
Day 9
0 alive
Most alive –1mm in
Most still alive – 1mm in
length
length
Day 10
0 alive
Very few alive
Lots still alive
Day 11
0 alive
0 alive
Lots still alive
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Temp
Aim: to determine the effect of temperature on hatch rate of brine shrimp
Method: two tanks set up, filled with 1L of distilled water and set up in a well lit area; aquarium
heater placed in one tank and set to 26˚ and other tank kept at room temp approx 20˚, 35grams of
salt added to each and 2 drops of brine eggs added
Results:
Day
20˚
26˚
Day 1
No hatching
No hatching
Day 4
Some hatched
Most hatched
Day 8
Few living
Most living
Conclusion: 26˚ yielded a higher hatch and survival rate
Gather, process and present information from secondary sources that describes the processes and
characteristics of hydrothermal vents and their unique biotic communities
 Hydrothermal vent communities occur at many areas of tectonic activities i.e. the Galapagos Rift
 Temp of vent water varies greatly from between 23˚ in the Galapagos vents to around 350˚ in the
East Pacific Rise vents
 Most species live out of the main flow at temps of around 2˚
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The biomass of vent communities is high with dense colonies of tubeworms, crabs, clams,
muscles, limpets and shrimp. Many of which are endemic (i.e. koala is endemic to Aus – only found there)
Of particular interest because they flourish in the dark at high pressures and low temperatures and
are unique because they are support by chemolithoautotrophic (chemicals, from rocks, self feeders a.k.a.
self feeding bacteria that use the chemicals out of the rocks) archeans and bacteria i.e. Thiomicrospira which
form dense microbial carpets and drive their energy chiefly from oxidising hydrogen sulphide.
The giant tubeworms that inhabit the vents are unique – they are chemoautotrophs (hydrogen sulphide
most used) Hydrogen sulphide is turned into energy by bacteria that live inside the worm.
Many of the nonbacterial (eukaryote) vent species filter feed on these organisms whilst others rely
on symbiotic sulphur bacteria for energy
Includes bacteria, blind crabs, enormous tube worms, giant clams, deep sea muscles, fish, octopus
Approaching the vents temps of the usually very cold begin to average around 11˚ and particles of
copper, iron and zinc sulphides as well as hydrogen sulphide are present. No light and organic
matter around vents is hundreds of times greater around the vents than on the ocean floor. I.e. its
warmer, more nutrient filed, more populated and more organic matter.
Relate the heating of the water to the cooling of the newly formed crust
 Typically vents are found along MORs or other areas of tectonic activity
 Though abundant, vents at rifts are not continuous and are thought to occur every 10km or so
 They are closely associated with subduction zones, fracture zones and back arc basins
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Small fractures occur when crust is cooling and contracting – these cracks allow water from the
ocean to permeate the new crust. The infiltration and circulation of cold water cases the rock to
cool even further, imparting some of its heat energy onto the water
Explain the ability of hydrothermal waters (brines) to scavenge elements from rocks
 MORs occur where the ocean crust is subject to tensional forces. This causes fracture and cracks
 When the sea water flows through these cracks not only is it heated but the water also scavenges
elements as the intense pressure (typical at depth) causes minerals in basalt to corrode and leach out
into the water
 The excessive heat also contributes as heat gives water more energy to dissolve things (i.e. minerals)
Outline and describe the products and process of hydrothermal fluid discharge from deep-sea vents
 Chemicals in the ocean water are converted in the crust and hydrothermal vents
 Hydrothermal fluid is seawater with altered physical and chemical characteristics
 Hydrothermal fluid is injected back into the ocean at vents and forms the plumes
 Plumes are often black or white with the colour due to mineral particles that precipitate rapidly as
hot hydrothermal fluid mix with cold sea water (i.e. from 340˚ to 2˚)
 Black smokers consist of tiny metallic sulphide particles that precipitate out of the hot vent fluid as
it mixes with the cold sea water
 White smokers lack the metallic sulphide particles and silica and carbonate contribute to the white
Describe examples of the unique bacteria and invertebrate species that live around hydrothermal vents
 The bacteria found in the water near vents have been described as ‘white snow’ and get their
energy from oxidising sulphide
 One invertebrate that lives off these bacteria is the 1m long tube worm that have 3m tubes - Riftia
 These tubes have no obvious gut – instead they have a special organ which has dense
concentrations of chambers that contain sulphide oxidising bacteria. The animal, in turn, can digest
the bacteria and derive nutrients
 Some bivalve molluscs have sulphur oxidising bacteria as symbionts in their gills
 Typically vents have sulphur oxidising bacteria as primary producers (bottom of the food chain) and
they live both freely and as endosymbionts (living symbiotically in the body)
 Endosymbiotic invertebrates include snails, clams and worms
 The macro fauna (large animals) include crustaceans and rare fish
 The abundant molluscs and tubeworms found in Pacific vents are rare or absent in the Atlantic
 Pacific fauna also includes crustaceans, molluscs, fish, octopus, shrimp and krill
7. The type of sediment that accumulates on the floor of the deep oceans varies according to water
depth, supply of nutrients to surface waters and distance to land masses
Outline the origin, characteristics and distribution of different deep-sea sediments in the Pacific Ocean basin
 Marine sediments are products of a number of physical, chemical and biological processes
 Seds can be categorised as terrigenous (from land); biogenous (from life); hydrogenous (from water)
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Biogenous bottoms referred to as oozes
Calcareous ooze:
- Abundance of calcium shells (former foraminifera, sea urchins, snail) as well as algae such
as coccoliths that manufacture skeletons made up of calcium carbonate die and the
skeletal material rains down onto the sea bed and accumulates
- Ooze is extremely fine grained and composed of shells, coral, fossils and organisms
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Cal carbonate dissolves quickly under pressure and in cold water therefore not found
in deep ocean floors – never found deeper than 5km (Carbonate Compensation Depth)
- The most common pelagic (oceanic) sediment covering 48% of the worlds ocean floor
- Accumulates at about 50m/million years (rapid)
Siliceous oozes:
- Result from a dominance of siliceous (glass, opal) shell pieces made from planktonic
organisms like radiolarians and diatoms (around the size of dust)
- Organisms die and the remnant material dies and rains down onto the sea floor – for
the ooze to form they must be adequately substantial to endure the downward journey
- Extremely fine grained and has a yellowish-brown colour
- Cannot subsist without nutrients so found in areas of high productivity i.e. the polar
regions and the equator – cover about 14% of the seabed
- Siliceous ooze build up at a rate of 10m/million years
Terrigenous bottoms come from earth's crust – can be solid rock or product of weathering and
erosion of this rock and can also be referred to as lithogenous
Much of the weathering/erosion takes place on land and the seds are washed into the ocean
These seds carpet the bottom of the ocean near almost all the continents in the area called the
continental shelf (continental borderlands)
Red clays (pelagic clays):
- Accumulate in the deepest and most remote areas of the ocean
- Composition is a varied mix of fine quartz, clay minerals, less than 10% biogenic (but
may contain some i.e. bones and teeth that have fallen from above ) material, authigenic (formed in
situ) deposits precipitated directly from seawater and space dust
- Cover 38% of the sea floor and most predominant Pacific Ocean sed
- Ultimate origin is unknown but probably derive from distant rivers, volcanic ash and
wind blown dust (Aeolian origin)
Glacial Marine Seds:
- Sourced from glacial systems that have travelled from mountain ranges and
eventually reached the sea
- Once the ice meets the sea, any seds being pushed forward in the glacier/trapped in
the ice sheet are dumped into the water – i.e. glacier slides over rocks, picks up seds,
takes them to the sea
- Sediment is angular and coarse grained and derive from a range of source
- Composition depends on the rock that the glacier has travelled over
Continental margin seds:
- Originate on land and are transported to coasts via river systems and winds
- Composition and texture differ depending on origin of grain
- Hardier minerals i.e. quartz often dominate this sediment
- Texture determined by transport i.e. small, smooth grain = long period of water travel
- Contain a high portion of biogenic material as continental margins provide a habitat
for many organisms and ecosystems
- Majority occur on continental shelves/rises/margins as well as deltas and bays
Hydrogenous ocean bottoms result from dissolved materials precipitating from sea water
Most of these are manganese nodules and are composed of layers of metals such as manganese,
iron, nickel, cobalt and copper
Authigenic sed i.e. formed in situ, and occur in association with oozes and clays
They can be in the seize of a pear to that of a potato and are always on the surface of the seds
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Deposits could be a future source for metals (not yet – found in international waters, too expensive)
Thought to form from the precipitation of seawater that is supersaturated in manganese; as a result
of volcanic activity and hydrothermal vents; from decomposition of basaltic debris.
Built up layers of manganese hydroxides around a core (i.e. shark tooth, previous nodule, basalt debris)
The surface is generally smooth but sometimes rough, knobbly and irregular
Discuss the different circumstances required for the deposition of different deep-sea sediments in the Pacific
Ocean basin
 Terrigenous seds cover central/N Pacific, polar regions and all of the continental borderlands
 Deep sea clays are the only ones that can survive the extreme pressure of the deepest basins. More
rapidly deposited closer to continents. Accretion increases in times or drought or where erosion is
high due to lack of vegetation and during times of volcanic activity
 Biogenous seds are common in temperate oceans less that 4000 – 5000m deep like S Pacific, N/S
Atlantic and Indian Ocean. Quite common in high latitude floors i.e. Antarctica and the N Pacific
 Calcareous ooze can be located in shallow, warmer waters as the calcium begins to dissolve in the
CCD further down than 5km. Where foraminifera and coccoliths are plentiful i.e. where there are
nutrients and sunlight, this sediment is common
 Sil ooze - diatoms and radiolarians are most frequent in upwelling zones i.e. near the equator. Sed
tends to accumulate in waters that are colder and deeper than cal ooze.
 Hydrogenous bottoms have wide distributions but more concentrated in the Central and S Pacific
 Manganese nodules origin is still debatable as is its requirements for deposition. Only found in
deep oceans in the locality of MORs and appear to formed from minerals extruded from vents
8. Oceanographers have a range of technology available to assist the collection of data about the
oceans
Identify two of the following technologies used by oceanographers and for each one describe how they work
and the evidence they provide (echo sounders, dredges/grabs/core samplers, fish/ plankton nets,
bathythermographs, magnetometers)
 (That is, be able to identify all of them but be able to describe two)
 Most tools/methods used to study sea floors have been invented/developed within the last 50 years
 direct observation of the seafloor is difficult and time consuming
Technology
Echo sounders
Dredges, grabs and
core samplers
Fish and plankton
nets
How it works
Sound pulse is sent into water and return
echo recorded. The sound energy travels
through the water to the ocean bottom
where it is reflected back. Are attached
to the hull of a ship or tow vehicle
Physically takes the sea floor as a
sample. Corers take a core about a mile
long, grab samplers grab seds and
dredges are pulled along behind a boat
and dragged on the sea floor collecting
seds
Nets are towed behind boats to catch
plankton and fish. Mesh size appropriate
to the organism trying to catch
Evidence/data collected
Depth measured by using time it takes echo
to get to the sea floor and back. Determined
from the travel time and speed of sound in
water. Distance = speed x time/2 (/2 because
of the 2 way trip to the floor and back)
A sample of the ocean floor, rocks,
organisms and sediments
Organisms caught are counted and
identified. Size and health of organisms at
different depths and different locations
found
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Bathythermographs
(depth-temp monitor)
Magnetometers
Measures the temperature of water with
depth – a temp profile of the ocean is
taken
Detects the magnetic field in sea rocks
Input into numerical oceanography. Models
that analyse and predict ocean currents,
surface temps and other features
Shows the sea floor has different polarities
and displays this in a magnetic profile
showing these polarities
Diagrams of Technology
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