Oceanography is the scientific study of Earths Oceans
Oceanographers study: Chemical composition Temperature Movement of
ocean water Seafloor sediments Topography Marine Life
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Earths Water Oceans contain 97% of water found on Earth 3% is
located in frozen ice caps(Greenland, Antarctica) Sea level has
risen and fallen due to warming and cooling of the Earth Tectonic
Processes
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Earths Oceans Earth is known as the Blue Planet 71% of the
surface is covered by water Average Depth is 3800 meters Most
landmasses are in the Northern Hemisphere 81% of the Southern
Hemisphere is water
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Oceans and Seas Oceans make up around 70% of the Earths surface
Divided into 4 Oceans: Pacific-Largest Atlantic-Between the
Americas and Europe and Africa Indian-3 rd largest between Africa,
Asia and Australia Arctic-North of the Arctic Circle
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Oceans and Seas The Arctic and Antarctic areas are covered by
sea ice Ice is less dense than water therefore ice crystals form at
the surface Parts break up in the summer
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Oceans and Seas Seas are parts of the ocean that are partially
landlocked Black Sea Mediterranean Sea Caribbean Sea Bering Sea
Seas that are completely landlocked have a different
composition(More salt water) Caspian Sea Aral Sea
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Studying The Ocean The Challenger-Late 1800s, British research
ship Investigated ocean currents, water temperature, sediments,
topography Used nets, dredges and other tools Meteor- German ship
in the 1920s Used sonar, first to map the Mid-Atlantic Ridge
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Ocean Origin The Earth is believed to be 4.6 Billion years old
The Oceans are thought to be about that old Ancient lava flows
suggest this
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Formation of the oceans One hypothesis suggests that water was
released from Earths interior by volcanism(out gassing) As the
Earth cooled this water vapor condensed and filled the oceans
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Formation of the Oceans The second hypothesis says that the
water came from comets The impact of comets releases water
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Properties of Seawater Seawater is a solution of salts
dissolved in water Salinity is the concentration of all salts in
seawater Measured in grams of salt per kilogram of water or ppt The
average salinity is about 35 ppt Seawater is a solution of salts
dissolved in water Salinity is the concentration of all salts in
seawater Measured in grams of salt per kilogram of water or ppt The
average salinity is about 35 ppt Properties of Seawater
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Most of the salt is NaCl which splits about in solution Other
ions: Sulfate, Magnesium, Calcium, Potassium, Bicarbonate
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Variations in Salinity The highest salinity is found in
subtropical regions(20- 30 latitudes) The rate of evaporation
exceeds the rate of precipitation Polar regions have lower
salinities
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Variations in Salinity Higher salinities are found in enclosed
seas near deserts such as the Mediterranean Sea, Red Sea The Baltic
Sea receives fresh water from rivers, lower salinity Estuaries are
partly enclosed bodies of water at the mouths of rivers. Very low
salinities(2-10 ppt)
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Addition of Salt The salinity of the oceans has remained fairly
consistent over time Volcanoes release chlorine and sulfur dioxide
which dissolve in water Weathering of continental rocks generates
other ions in seawater
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Removal of Salt When water evaporates ions stay behind and form
minerals When organisms die ions in their shells, bones and death
accumulate on the ocean floor
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Density Pure water has a density of 1 g/ml Seawater ranges from
1.02-1.03 g/ml This is due to variations in salinity and
temperature Density increases with increasing salinity. Density
decreases with increasing temperature The salinity can alter the
freezing point (-2 C)
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Light Absorption Water absorbs light. Intensity decreases with
depth The absorption of different wavelengths varies as well Marine
animals may appear red near the surface but look black at a depth
of 10 meters
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Temperature The surface of the ocean waters 15 degrees C(Is
warmer near the equator) In the Polar regions the water is cold
from the surface to the seafloor After about 100 m of ocean to
about 1000 m the temperature drops from about 22 C to about 4
C
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Temperature The zone of rapidly decreasing of temperature with
depth is called the thermocline After the thermocline the
temperature is uniform at roughly 4 degrees Celsius Caused by
differences in density
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Water Masses Cold, salty water comes from the Earths poles Sea
ice forms Salt ions are left behind Water underneath sea ice is
dense Sinks The cold, salty water then migrates towards the
equator
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Movement of Ocean Water Oceans are always in constant movement
caused by: Variations in temperature Variations in Density Winds
blowing across the waters surface Gravitational pull of the Moon
and the Sun
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Density Currents The low temperatures of water at Earths poles
are responsible for the movement of seawater Salts accumulate
beneath the ice which increasing the density of the seawater The
dense seawater sinks and moves toward the equator. This is called a
density current
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Upwelling Upwelling is the process where cold water from the
bottom of the ocean moves toward the surface Occurs near
continents. Winds push water away from the land which is replaced
by deeper water which rises Upwelling water is rich in nutrients
which supports marine life
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Surface Currents Surface currents are formed by Earths global
wind systems In the tropics trade winds blow from east to west,
water moves in the same direction Mid latitudes-Prevailing
westerlies move from west to east Polar Regions-Winds move from
east to west
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Surface Currents Gyres are large circular current systems that
flow from north to south The Coriolis effect influences this 5
major gyres: 2 in the Pacific Ocean 2 in the Atlantic Ocean 1 in
the Indian Ocean
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Surface Currents When a current encounters a landmass the water
is deflected away from the equator As the warm current moves North
it cools and turns eastward Gulf Stream-Flows along the east coast
of North America
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Waves A wave is a rhythmic movement that carries energy through
space or matter Waves carry small amounts of water
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Waves Crest-Highest point of a wave Trough-Lowest point of a
wave Wave Height-Distance between the crest and trough
Wavelength-The distance between two crests or troughs Factors
influencing wave height: Wind Speed Wind Duration Fetch
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Waves Waves lose energy when they reach shallow water due to
friction As they slow they become higher and steeper Breakers are
collapsing waves
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Tides Sea level-Average height of the oceans surface
Tides-Periodic rise and fall of ocean waters caused by the
gravitational attraction of the Moon and Sun
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Tides One full tidal cycle takes about 24 Hours 50 Minutes.
This is due to the Moon rotating around the Earth Spring Tides-When
the Moon is full or new. High tides are higher than usual, low
tides are lower than usual Neap Tides-The Earth, Moon and Sun form
a right angle. Lower tidal range
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Shorelines Shorelines are shaped by waves, tides and currents
by erosion and deposition Ocean floor is shaped by tectonic
processes
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Erosion Wave Refraction is the bending of a wave when it
reaches shallow water This is caused by wave speed and water depth
A wave will reach a headland first and will bend towards the
headland
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Erosion Most of the energy is concentrated on headlands,
therefore they undergo erosion This forms a wave cut platform at
the base of a steep cliff
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Deposition Coastal landforms are formed by sediment from eroded
land that are carried to the oceans by rivers When waves and
currents slow down these sediments settle out and build coastal
landforms
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Beaches A beach is a sloping band of loose sediment at the edge
of an ocean The size of the sediments depends on the energy of the
wave that deposited it A beach is a sloping band of loose sediment
at the edge of an ocean The size of the sediments depends on the
energy of the wave that deposited it Beaches
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Longshore Current Sediment is deposited in areas where the
current slows Sandbars often form and run parallel to most beaches
Result from waves breaking and dumping sediment
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Longshore Current A longshore current is when a water
approaches the shore at an angle Prevailing winds and wave patterns
influence which direction it will flow Longshore currents causes
and is wash up and down the beach in a zigzag pattern
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Longshore Current Gaps in the sandbars allow water to return to
the ocean. This forms a rip current Barrier Islands form when
sandbars form at low tide and winds pile up sand
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Barrier Island Spit-Forms when longshore currents slow due to
increased water depth Baymouth-A spit that has grown across the
mouth of a bay
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Spit, Baymouth Bar
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Artificial Protective Structures Jetties-Walls of concrete or
boulders that extend into the ocean on either side of the entrance
to a harbor Groins-Similar structures to jetties that trap sand on
one side and not the other
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Artificial Protective Structures Seawall-An embankment built
along the shore to protect the land from powerful waves Erosion
increases because waves are bounced back with most of their
original energy
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Changes in Sea Level Sea level has fluctuated over time Rises
in sea level after often attributed to melting glaciers If the
polar ice sheets melted sea level would rise about 70 meters
Tectonic forces can cause a change in sea level
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Sonar Sonar-Emits sound pulses that the detect the depths of
the ocean floor Side Scan Sonar-Sound pulses are directed toward
the seafloor at an angle. Topographic features can then be
mapped
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Continental Margin The continental margin is an area of
continental crust that lies below sea level. Continental crust is
less dense than oceanic crust
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Continental Shelf Continental Shelf is the portion of the
continental margin that lies closest to land Average width is about
60 km Most of this was exposed during the last ice age
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Continental Shelf The continental slope is where the ocean
floor drops steeply below the continental shelf Continental Rise
forms when sediments carried down the continental slope settle at
its base
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Ocean Basins Ocean basins are areas of the seafloor that are
above the oceanic crust
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Ocean Basins Abyssal Plains are smooth parts of the ocean
basins Sohm Abyssal Plain Hatteras Abyssal Plain Abyssal Plains
sediment has been deposited over millions of years
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Ocean Basins Deep Sea Trenches-Deep depressions in the ocean
basins May stretch for thousands of kilometers Mariana Trench These
are sites where tectonic plates converge
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Ocean Basins Mid Ocean Ridges-Chain of mountains that is broken
into segments by numerous cracks(fracture zones) May emerge from
the oceans surface as volcanic islands Form when magma rises along
divergent plate boundaries Mid-Atlantic Ridge
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Hydrothermal Vents Hydrothermal Vents are rifts in mid ocean
ridges that contain springs of hot water Seawater seeps into cracks
and is warmed by the magma from the mantle Black Smokers-Eject
thick, smoke like plumes of water that can reach 350 degrees
Celsius
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Ocean Basins Seamounts are submerged mountains that are most
likely extinct volcanoes Tablemounts (guyots) are submerged
mountains with flat tops The lack of erosional processes cause
these features to last forever