OceanographyThe OceansOceanographyOceanography is the scientific study of Earths OceansOceanographers study:Chemical compositionTemperatureMovement of ocean waterSeafloor sedimentsTopographyMarine Life

Earths WaterOceans contain 97% of water found on Earth3% is located in frozen ice caps(Greenland, Antarctica)Sea level has risen and fallen due to warming and cooling of the EarthTectonic ProcessesEarths OceansEarth is known as the Blue Planet71% of the surface is covered by waterAverage Depth is 3800 metersMost landmasses are in the Northern Hemisphere81% of the Southern Hemisphere is water

Oceans and SeasOceans make up around 70% of the Earths surfaceDivided into 4 Oceans:Pacific-LargestAtlantic-Between the Americas and Europe and AfricaIndian-3rd largest between Africa, Asia and AustraliaArctic-North of the Arctic Circle

Oceans and SeasThe Arctic and Antarctic areas are covered by sea iceIce is less dense than water therefore ice crystals form at the surfaceParts break up in the summer

Oceans and SeasSeas are parts of the ocean that are partially landlockedBlack SeaMediterranean SeaCaribbean SeaBering SeaSeas that are completely landlocked have a different composition(More salt water)Caspian SeaAral Sea

Studying The OceanThe Challenger-Late 1800s, British research shipInvestigated ocean currents, water temperature, sediments, topographyUsed nets, dredges and other toolsMeteor- German ship in the 1920sUsed sonar, first to map the Mid-Atlantic Ridge

Ocean OriginThe Earth is believed to be 4.6 Billion years oldThe Oceans are thought to be about that oldAncient lava flows suggest this

Formation of the oceansOne hypothesis suggests that water was released from Earths interior by volcanism(out gassing)As the Earth cooled this water vapor condensed and filled the oceansFormation of the OceansThe second hypothesis says that the water came from cometsThe impact of comets releases water

Chemical Properties of SeawaterProperties of SeawaterSeawater is a solution of salts dissolved in waterSalinity is the concentration of all salts in seawaterMeasured in grams of salt per kilogram of water or pptThe average salinity is about 35 ppt

Seawater is a solution of salts dissolved in waterSalinity is the concentration of all salts in seawaterMeasured in grams of salt per kilogram of water or pptThe average salinity is about 35 pptProperties of SeawaterProperties of SeawaterMost of the salt is NaCl which splits about in solutionOther ions: Sulfate, Magnesium, Calcium, Potassium, Bicarbonate

Variations in SalinityThe highest salinity is found in subtropical regions(20-30 latitudes)The rate of evaporation exceeds the rate of precipitationPolar regions have lower salinitiesVariations in SalinityHigher salinities are found in enclosed seas near deserts such as the Mediterranean Sea, Red SeaThe Baltic Sea receives fresh water from rivers, lower salinityEstuaries are partly enclosed bodies of water at the mouths of rivers. Very low salinities(2-10 ppt)

Addition of SaltThe salinity of the oceans has remained fairly consistent over timeVolcanoes release chlorine and sulfur dioxide which dissolve in waterWeathering of continental rocks generates other ions in seawater

Removal of SaltWhen water evaporates ions stay behind and form mineralsWhen organisms die ions in their shells, bones and death accumulate on the ocean floorDensityPure water has a density of 1 g/mlSeawater ranges from 1.02-1.03 g/mlThis is due to variations in salinity and temperatureDensity increases with increasing salinity. Density decreases with increasing temperatureThe salinity can alter the freezing point (-2 C)

Light AbsorptionWater absorbs light. Intensity decreases with depthThe absorption of different wavelengths varies as wellMarine animals may appear red near the surface but look black at a depth of 10 meters

TemperatureThe 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 seafloorAfter about 100 m of ocean to about 1000 m the temperature drops from about 22 C to about 4 C

TemperatureThe zone of rapidly decreasing of temperature with depth is called the thermoclineAfter the thermocline the temperature is uniform at roughly 4 degrees CelsiusCaused by differences in densityWater MassesCold, salty water comes from the Earths polesSea ice forms Salt ions are left behind Water underneath sea ice is dense SinksThe cold, salty water then migrates towards the equatorMovement of Ocean WaterMovement of Ocean WaterOceans are always in constant movement caused by:Variations in temperatureVariations in DensityWinds blowing across the waters surfaceGravitational pull of the Moon and the Sun

Density CurrentsThe low temperatures of water at Earths poles are responsible for the movement of seawaterSalts accumulate beneath the ice which increasing the density of the seawaterThe dense seawater sinks and moves toward the equator. This is called a density currentUpwellingUpwelling is the process where cold water from the bottom of the ocean moves toward the surfaceOccurs near continents. Winds push water away from the land which is replaced by deeper water which risesUpwelling water is rich in nutrients which supports marine life

Surface CurrentsSurface currents are formed by Earths global wind systemsIn the tropics trade winds blow from east to west, water moves in the same directionMid latitudes-Prevailing westerlies move from west to eastPolar Regions-Winds move from east to westSurface CurrentsGyres are large circular current systems that flow from north to southThe Coriolis effect influences this5 major gyres:2 in the Pacific Ocean2 in the Atlantic Ocean1 in the Indian Ocean

Surface CurrentsWhen a current encounters a landmass the water is deflected away from the equatorAs the warm current moves North it cools and turns eastwardGulf Stream-Flows along the east coast of North AmericaWavesA wave is a rhythmic movement that carries energy through space or matterWaves carry small amounts of water

WavesCrest-Highest point of a waveTrough-Lowest point of a waveWave Height-Distance between the crest and troughWavelength-The distance between two crests or troughsFactors influencing wave height:Wind SpeedWind DurationFetch

WavesWaves lose energy when they reach shallow water due to frictionAs they slow they become higher and steeperBreakers are collapsing wavesTidesSea level-Average height of the oceans surfaceTides-Periodic rise and fall of ocean waters caused by the gravitational attraction of the Moon and Sun

TidesOne full tidal cycle takes about 24 Hours 50 Minutes. This is due to the Moon rotating around the EarthSpring Tides-When the Moon is full or new. High tides are higher than usual, low tides are lower than usualNeap Tides-The Earth, Moon and Sun form a right angle. Lower tidal rangeShoreline FeaturesShorelinesShorelines are shaped by waves, tides and currents by erosion and depositionOcean floor is shaped by tectonic processes

ErosionWave Refraction is the bending of a wave when it reaches shallow waterThis is caused by wave speed and water depthA wave will reach a headland first and will bend towards the headland

ErosionMost of the energy is concentrated on headlands, therefore they undergo erosionThis forms a wave cut platform at the base of a steep cliff

DepositionCoastal landforms are formed by sediment from eroded land that are carried to the oceans by riversWhen waves and currents slow down these sediments settle out and build coastal landformsBeachesA 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 itBeachesLongshore CurrentSediment is deposited in areas where the current slowsSandbars often form and run parallel to most beachesResult from waves breaking and dumping sediment

Longshore CurrentA longshore current is when a water approaches the shore at an anglePrevailing winds and wave patterns influence which direction it will flowLongshore currents causes and is wash up and down the beach in a zigzag pattern

Longshore CurrentGaps in the sandbars allow water to return to the ocean. This forms a rip currentBarrier Islands form when sandbars form at low tide and winds pile up sand

Barrier IslandSpit-Forms when longshore currents slow due to increased water depthBaymouth-A spit that has grown across the mouth of a bay

Spit, Baymouth Bar

Artificial Protective StructuresJetties-Walls of concrete or boulders that extend into the ocean on either side of the entrance to a harborGroins-Similar structures to jetties that trap sand on one side and not the other

Artificial Protective StructuresSeawall-An embankment built along the shore to protect the land from powerful wavesErosion increases because waves are bounced back with most of their original energy

Changes in Sea LevelSea level has fluctuated over timeRises in sea level after often attributed to melting glaciersIf the polar ice sheets melted sea level would rise about 70 metersTectonic forces can cause a change in sea level

Mapping The SeafloorSonarSonar-Emits sound pulses that the detect the depths of the ocean floorSide Scan Sonar-Sound pulses are directed toward the seafloor at an angle. Topographic features can then be mappedContinental MarginThe continental margin is an area of continental crust that lies below sea level. Continental crust is less dense than oceanic crust

Continental ShelfContinental Shelf is the portion of the continental margin that lies closest to landAverage width is about 60 kmMost of this was exposed during the last ice age

Continental ShelfThe continental slope is where the ocean floor drops steeply below the continental shelfContinental Rise forms when sediments carried down the continental slope settle at its baseOcean BasinsOcean basins are areas of the seafloor that are above the oceanic crust

Ocean BasinsAbyssal Plains are smooth parts of the ocean basinsSohm Abyssal PlainHatteras Abyssal PlainAbyssal Plains sediment has been deposited over millions of yearsOcean BasinsDeep Sea Trenches-Deep depressions in the ocean basinsMay stretch for thousands of kilometersMariana TrenchThese are sites where tectonic plates converge

Ocean BasinsMid Ocean Ridges-Chain of mountains that is broken into segments by numerous cracks(fracture zones)May emerge from the oceans surface as volcanic islandsForm when magma rises along divergent plate boundariesMid-Atlantic Ridge

Hydrothermal VentsHydrothermal Vents are rifts in mid ocean ridges that contain springs of hot waterSeawater seeps into cracks and is warmed by the magma from the mantleBlack Smokers-Eject thick, smoke like plumes of water that can reach 350 degrees Celsius

Ocean BasinsSeamounts are submerged mountains that are most likely extinct volcanoesTablemounts (guyots) are submerged mountains with flat topsThe lack of erosional processes cause these features to last forever