Earth’s OceansEarth’s Oceans

Chapter 15Chapter 15

Grade 8 Earth ScienceGrade 8 Earth Science

Data Collection and Analysis Data Collection and Analysis (15.1)(15.1)

• At the surfaceAt the surface– Sonar (sound navigation and ranging)Sonar (sound navigation and ranging)

•Help scientists learn about topography of sea floorHelp scientists learn about topography of sea floor

•Uses sound wavesUses sound waves

•Calculate depth by measuring how long the sound Calculate depth by measuring how long the sound takes to hit the bottom and come backtakes to hit the bottom and come back

•FormulaFormula– (time)(1500m/s)/2(time)(1500m/s)/2– 1500m/s is constant velocity that sound travels in water1500m/s is constant velocity that sound travels in water

Data Collection and AnalysisData Collection and Analysis

• At the SurfaceAt the Surface– Side-scan sonarSide-scan sonar

•Directs sound waves at ocean floor at an angleDirects sound waves at ocean floor at an angle

•Helps get a picture of underwater hillsHelps get a picture of underwater hills

– TOPEX/PoseidonTOPEX/Poseidon•Use floats that contain sensors Use floats that contain sensors

•Measures temperature, salinity, concentration Measures temperature, salinity, concentration of gases and nutrients in surface waterof gases and nutrients in surface water

Data Collection and AnalysisData Collection and Analysis

• In the Deep SeaIn the Deep Sea– SubmersiblesSubmersibles

•Underwater vessels that can carry people Underwater vessels that can carry people and instruments into the deepest waterand instruments into the deepest water

•Used to observe animalsUsed to observe animals

•Used to observe geologic featuresUsed to observe geologic features– Hydrothermal ventsHydrothermal vents

•Used to collect sediments from the seafloor Used to collect sediments from the seafloor for further studyfor further study

Data Collection and AnalysisData Collection and Analysis

• ComputersComputers– Collects and analyzes data fromCollects and analyzes data from

•SatellitesSatellites

•Float sensorsFloat sensors

– Produces models that scientists can Produces models that scientists can studystudy•Simulate Earth’s changing climateSimulate Earth’s changing climate

•Simulate tides, tsunamisSimulate tides, tsunamis

•Simulate dispersion of coastal pollutionSimulate dispersion of coastal pollution

Origin of OceansOrigin of Oceans

• HypothesisHypothesis– Water originated from either a remote Water originated from either a remote

source or a local source, or bothsource or a local source, or both•Comets could have contributed to waterComets could have contributed to water

– Tail of ice Tail of ice

•MeteoriteMeteorite– Composed similar to cometComposed similar to comet– Bombardment of earth over time could have Bombardment of earth over time could have

contributed to water accumulationcontributed to water accumulation

Origin of OceansOrigin of Oceans

• VolcanismVolcanism– A mechanism that could have allowed existing A mechanism that could have allowed existing

water from within the earth to risewater from within the earth to rise– Eruptions emit gasesEruptions emit gases

• Water vaporWater vapor

• Carbon dioxideCarbon dioxide

– Young earth was hotter with far more eruptions Young earth was hotter with far more eruptions than todaythan today• Could have released huge amounts of water vapor Could have released huge amounts of water vapor

which condensed to oceanswhich condensed to oceans

Distribution of Earth’s WaterDistribution of Earth’s Water

• Oceans contain 97% of Earth’s waterOceans contain 97% of Earth’s water

• Frozen ice caps contain 3%Frozen ice caps contain 3%

• Over geologic time the percentage of Over geologic time the percentage of ice has variedice has varied– From near 0% to 10%From near 0% to 10%

The Blue PlanetThe Blue Planet

• 71% of Earth’s surface covered with water71% of Earth’s surface covered with water– Makes Earth look blueMakes Earth look blue– Average depth of oceans: 3800 mAverage depth of oceans: 3800 m– Landmasses like islandsLandmasses like islands– Most landmasses in Northern hemisphereMost landmasses in Northern hemisphere

• Water only covers 61% of surfaceWater only covers 61% of surface

– Southern HemisphereSouthern Hemisphere• 81% surface covered81% surface covered

• All oceans-All oceans-– One vast, interconnected body of waterOne vast, interconnected body of water

Sea LevelSea Level

• Global Sea LevelGlobal Sea Level– Level of the oceans’ surfaceLevel of the oceans’ surface

•Has risen and fallen hundreds of metersHas risen and fallen hundreds of meters– Response to melting glaciersResponse to melting glaciers– Tectonic forces pushing continents up or downTectonic forces pushing continents up or down– Rising or sinking seafloorRising or sinking seafloor

Major OceansMajor Oceans

• Three major oceansThree major oceans– AtlanticAtlantic

• water above arctic circle is known as Arctic Oceanwater above arctic circle is known as Arctic Ocean

– PacificPacific• Largest, contains half Earth’s seawaterLargest, contains half Earth’s seawater

– IndianIndian

• Ocean surround Antarctica is the Southern Ocean surround Antarctica is the Southern OceanOcean

• Polar Oceans (Arctic and Southern)Polar Oceans (Arctic and Southern)– Covered with snow pack year roundCovered with snow pack year round

• No warm summers to thaw themNo warm summers to thaw them

Ocean and Atmospheric Ocean and Atmospheric InteractionInteraction

• Provide moisture and heat to Provide moisture and heat to atmosphereatmosphere– Influence large-scale circulation patternsInfluence large-scale circulation patterns– Warm ocean water aide formations of Warm ocean water aide formations of

•HurricanesHurricanes•Tropical cyclonesTropical cyclones• Influences position of jet streamInfluences position of jet stream•Plays a role in El NinoPlays a role in El Nino

• Huge supply of carbon dioxideHuge supply of carbon dioxide– Oceans keeps amount of CO2 in checkOceans keeps amount of CO2 in check

SeawaterSeawater

Chapter 15.2Chapter 15.2

Seawater Seawater

• Chemical Properties of SeawaterChemical Properties of Seawater– ContainsContains

•Dissolved gasesDissolved gases– OxygenOxygen– Carbon dioxideCarbon dioxide

•Dissolved nutrientsDissolved nutrients– NitratesNitrates– PhosphatesPhosphates

– Chemical properties vary with location Chemical properties vary with location and depthand depth

Chemical Properties of Chemical Properties of SeawaterSeawater• SalinitySalinity

– The amount of dissolved salts in seawaterThe amount of dissolved salts in seawater– Expressed as grams of salt per kilogram of Expressed as grams of salt per kilogram of

waterwater•Parts per thousand (ppt)Parts per thousand (ppt)

– Total salt content of water averages 35 pptTotal salt content of water averages 35 ppt•Most abundant salt is sodium chlorideMost abundant salt is sodium chloride

•Other saltsOther salts– ChloridesChlorides– MagnesiumMagnesium– PotassiumPotassium– CalciumCalcium

Variations in SalinityVariations in Salinity• Actual salinity vary form place to placeActual salinity vary form place to place

• Subtropical regionsSubtropical regions– More evaporation than precipitationMore evaporation than precipitation– Can be as high as 37 pptCan be as high as 37 ppt

• Equatorial regionsEquatorial regions– Abundant precipitationAbundant precipitation– Salinity lowerSalinity lower

• Polar regionsPolar regions– Seawater diluted by melting iceSeawater diluted by melting ice– Can be as low as 32 or 33 pptCan be as low as 32 or 33 ppt

Variations in SalinityVariations in Salinity

• EstuariesEstuaries– Large rivers empty into the oceansLarge rivers empty into the oceans– Fresh water dilutes seawaterFresh water dilutes seawater– Salinity lowSalinity low

Sources of Sea SaltSources of Sea Salt

• Geologic evidence indicate salinity of Geologic evidence indicate salinity of oceans similar to ancient oceansoceans similar to ancient oceans

• SourcesSources– Sulfur dioxide and chlorineSulfur dioxide and chlorine

•Gases released from volcanoesGases released from volcanoes

– Sodium and calciumSodium and calcium•From the weathering of crustal rocksFrom the weathering of crustal rocks

Removal of Sea SaltsRemoval of Sea Salts

• Salinity doesn’t constantly increase Salinity doesn’t constantly increase because sea salts are removedbecause sea salts are removed

• Evaporation leave solid salts behindEvaporation leave solid salts behind– Organisms use this salt for shells, bones Organisms use this salt for shells, bones

and teethand teeth– Become sediments on the sea floorBecome sediments on the sea floor

Physical Properties of Physical Properties of SeawaterSeawater

• DensityDensity– Maximum density of freshwater:1.0 Maximum density of freshwater:1.0

g/cm^2g/cm^2– Salt ions add to mass of seawaterSalt ions add to mass of seawater

• Increases density of seawaterIncreases density of seawater

– Cold water more dense than warm waterCold water more dense than warm water– Seawater density rangesSeawater density ranges

•1.02 g/cm^2 to 1.03 g/cm^21.02 g/cm^2 to 1.03 g/cm^2

Physical Properties of Physical Properties of SeawaterSeawater

• Freezing pointFreezing point– Variations of salinity affect freezing Variations of salinity affect freezing

pointpoint•Lower than freshwaterLower than freshwater

– Freshwater freezes 0 degrees CFreshwater freezes 0 degrees C– Seawater freezes -2 degrees CSeawater freezes -2 degrees C

Absorption of LightAbsorption of Light

• Intensity of light decreases with Intensity of light decreases with depthdepth

• Water absorbs lightWater absorbs light

• Light penetrates upper 100 mLight penetrates upper 100 m

• Many organisms below 100 m are Many organisms below 100 m are blindblind

Temperature ProfilesTemperature Profiles• Plot changing water temperatures against Plot changing water temperatures against

depthdepth

• Vary depending on locationVary depending on location

• Three layersThree layers– Surface area 100 m thickSurface area 100 m thick

•Relatively warmRelatively warm

– Transitional layerTransitional layer•ThermoclineThermocline

– Characterized by rapidly decreasing temperaturesCharacterized by rapidly decreasing temperatures

– Bottom layerBottom layer•Cold and dark with temperatures near freezingCold and dark with temperatures near freezing

Water MassesWater Masses

• Deepwater MassesDeepwater Masses– Cold water comes from polar oceansCold water comes from polar oceans– Surface water under ice of polar oceans coolsSurface water under ice of polar oceans cools

•Cold water is more denseCold water is more dense

•Dense water sinksDense water sinks

– Three water masses Three water masses •Antarctic Bottom WaterAntarctic Bottom Water

•North Atlantic Deep WaterNorth Atlantic Deep Water

•Antarctic Intermediate WaterAntarctic Intermediate Water

Water MassesWater Masses

• Intermediate Water MassesIntermediate Water Masses– Form in relatively salty water near Form in relatively salty water near

Antarctica cools and sinksAntarctica cools and sinks– Water is slightly warmer and less denseWater is slightly warmer and less dense– Atlantic contains all three major Atlantic contains all three major

deepwater massesdeepwater masses– Pacific and Indian oceans contain the Pacific and Indian oceans contain the

two Antarctic deepwater massestwo Antarctic deepwater masses

Ocean MovementsOcean Movements

Chapter 15.3Chapter 15.3

WavesWavesWaves:Waves:

rhythmic movement that carries energy rhythmic movement that carries energy through space or matterthrough space or matter

Crest:Crest:

the highest point of a wavethe highest point of a wave

Trough:Trough:

the lowest point of a wavethe lowest point of a wave

Wave lengthWave length

the distance from crest to crestthe distance from crest to crest

WavesWaves

• Wavelength and speed increase Wavelength and speed increase when energy is addedwhen energy is added

• Only energy moves forwardOnly energy moves forward– Water moves in circlesWater moves in circles

Wave HeightWave Height

• Three factorsThree factors– FetchFetch

•Expanse of water that the wind blows acrossExpanse of water that the wind blows across

– Wind durationWind duration•How long the wind blowsHow long the wind blows

– Wind speedWind speed•How fast the wind blowsHow fast the wind blows

Breaking WavesBreaking Waves• Waves approaches shallow water Waves approaches shallow water

• Water depth becomes less than half their Water depth becomes less than half their wavelengthwavelength– Causes changes in movement of wavesCauses changes in movement of waves

• Waves slow down and catch up with the Waves slow down and catch up with the slower wave crests aheadslower wave crests ahead

• Crest to crest wavelength decreasesCrest to crest wavelength decreases

• Crests collapse forward causing breakersCrests collapse forward causing breakers– Breakers: collapsing wavesBreakers: collapsing waves

TidesTides

• The periodic rice and fall of sea levelThe periodic rice and fall of sea level– High tide: sea level risesHigh tide: sea level rises– Low tide: sea level fallsLow tide: sea level falls

• Tidal rangeTidal range– Difference in height of high and low tideDifference in height of high and low tide

• Tide cycleTide cycle– Takes 24 hours and 50 minutesTakes 24 hours and 50 minutes

Moon Influence on TidesMoon Influence on Tides

• Gravitational attraction among Earth, Gravitational attraction among Earth, Moon and SunMoon and Sun

• Earth and Moon orbit a common Earth and Moon orbit a common center of gravitycenter of gravity

• Unbalance forces of moon and Earth Unbalance forces of moon and Earth cause tidal bulges on opposite sides cause tidal bulges on opposite sides of Earthof Earth

Sun’s Influence on TidesSun’s Influence on Tides

• Earth’s orbital motion affects tidesEarth’s orbital motion affects tides

• Lunar tides twice as large as solar Lunar tides twice as large as solar tidestides– Moon is closerMoon is closer

• Depending on the lunar cycle, solar Depending on the lunar cycle, solar tides can either make tides bigger or tides can either make tides bigger or smallersmaller

TidesTides

• Spring TideSpring Tide• During full moon or new moon Earth, the sun During full moon or new moon Earth, the sun

and the moon are aligned causing higher tidesand the moon are aligned causing higher tides

• Have a greater tidal range during winter in Have a greater tidal range during winter in Northern Hemisphere, and summer in Southern Northern Hemisphere, and summer in Southern HemisphereHemisphere

– Neap TidesNeap Tides• First or third quarter moonFirst or third quarter moon

• sun and moon are at right angles to Earthsun and moon are at right angles to Earth

• Solar tides diminish lunar tidesSolar tides diminish lunar tides

CurrentsCurrents

• Surface currentsSurface currents– Occur in the top 100 to 200 mOccur in the top 100 to 200 m– Daily velocity: 100 kmDaily velocity: 100 km– Follow predictable patternsFollow predictable patterns– Driven by wind systemsDriven by wind systems– Can also be affected by land masses Can also be affected by land masses

(continents)(continents)– Affected by Coriolis EffectAffected by Coriolis Effect

GyresGyres

• Land masses deflect currentsLand masses deflect currents– Causes them to move in circular patternsCauses them to move in circular patterns

• Five major gyresFive major gyres– North PacificNorth Pacific– North AtlanticNorth Atlantic– South PacificSouth Pacific– South AtlanticSouth Atlantic– Indian OceanIndian Ocean

GyresGyres

• Northern HemisphereNorthern Hemisphere– Circulate clockwiseCirculate clockwise

• Southern HemisphereSouthern Hemisphere– Circulate counter clockwiseCirculate counter clockwise

• Around equatorAround equator– Move toward west and deflect toward Move toward west and deflect toward

the polesthe poles

UpwellingUpwelling

• Water moving verticallyWater moving vertically

• Originate in deeper watersOriginate in deeper waters– Below the thermoclineBelow the thermocline– Usually coldUsually cold

Density CurrentsDensity Currents

• Caused by the differences of the Caused by the differences of the temperature and salinity of watertemperature and salinity of water

• Denser water sinksDenser water sinks– After water cools it moves away from After water cools it moves away from

the polesthe poles– Circulate between major ocean basinsCirculate between major ocean basins

• Less dense water risesLess dense water rises