OceansOceans

Seas of LifeSeas of Life

What are Oceans?What are Oceans?

• List characteristics of the List characteristics of the oceans:oceans:– LargeLarge– WavesWaves– TidesTides– Salt waterSalt water– Plant and animal lifePlant and animal life– DeepDeep

What Are Ocean What Are Ocean Waves?Waves?

• Ocean waves are movements Ocean waves are movements where water particles where water particles alternately rise and fall.alternately rise and fall.

How Do Waves Move?How Do Waves Move?

• Water waves have Water waves have twotwo motions:motions:– The The forward progress of the forward progress of the

energyenergy of the wave. of the wave.– The The circular motion of the water circular motion of the water

particlesparticles as they rise and fall. as they rise and fall.

Wave MotionWave Motion

Parts of WavesParts of Waves

• Crest = the top of a waveCrest = the top of a wave

• Trough = the bottom of a waveTrough = the bottom of a wave

How Are Waves How Are Waves Measured?Measured?

• Wave LengthWave Length ( (FrequencyFrequency)= the )= the distance from crest to crest.distance from crest to crest.

• Wave HeightWave Height ( (AmplitudeAmplitude)= the )= the distance from crest to trough.distance from crest to trough.

How Do Waves Break?How Do Waves Break?• In open water waves roll.In open water waves roll.

• Waves break in shallow water Waves break in shallow water as the bottom of the wave has as the bottom of the wave has friction with the ocean floor, friction with the ocean floor, but the top continues at the but the top continues at the same speed.same speed.

Effects of Breaking Effects of Breaking WavesWaves

• SurfSurf is the turbulent water caused by breaking waves.

• SwashSwash is the motion of water up the beach and backwashbackwash is the water running back down the beach and under the next wave.

• Rip currentsRip currents are strong narrow currents that flow straight out to sea through the surf zone.

Topography of the Sea Topography of the Sea FloorFloor

• The crust of the sea floor is covered in many places with layers of sediment.

• Terrigenous sedimentTerrigenous sediment is land sediment that has settled on the ocean floor.

• Pelagic sedimentPelagic sediment is sediment made up of fine-grained clays and skeletons of microscopic organisms. – This covers 75% of the ocean bottom and

can take up to 50 years to settle.

• OozesOozes are sediments of microscopic shells.

OozeOozess

Topography of the Sea Topography of the Sea FloorFloor

Continental ShelfContinental Shelf is a gently sloping surface which extends under the ocean from the shoreline to a depth of about 100-200 meters.

Continental SlopeContinental Slope is relatively steep, extending downward as deep as 2 km from the shelf.

Continental RiseContinental Rise is a wedge of sediment that extends from the lower part of the slope to the deep ocean floor.

Sea Floor TopographySea Floor Topography

• Abyssal plains Abyssal plains are the flat regions of the deep ocean floor at the base of the rise.

• Submarine canyonsSubmarine canyons are v-shaped valleys that run across continental shelves and down continental slopes.

• Mid-ocean ridgesMid-ocean ridges are undersea mountain ranges in the ocean basins.

• TrenchesTrenches are deep ocean chasms parallel to the edge of a continent or island arc.

Sea Floor TopographySea Floor Topography

• SeamountsSeamounts are volcanic mountains rising 1000m above the ocean floor over a hot spot.

• GuyotsGuyots are volcanic islands that have stopped growing and have been flattened by wave action.

AtolAtol

How Do Waves Form?How Do Waves Form?

• Waves generally form in one of three ways:– Wind– Underwater earthquakes– Large amounts of ice or land

falling into the water.

How do Waves Form? How do Waves Form? Wind WavesWind Waves

• Waves are usually formed by Waves are usually formed by wind creating friction with the wind creating friction with the surface of the water.surface of the water.– With high enough wind speed a With high enough wind speed a

wave forms.wave forms.– Increased wind speed = Increased wind speed =

increased wave height.increased wave height.

How Do Waves Form?How Do Waves Form?Wind Waves continuedWind Waves continued

• Fetch = the distance that wind blows over the surface of the water.– Increased fetch = increased wave

height.

– Therefore the largest waves form on the biggest bodies of water with the strongest, longest prevailing winds.

How Do Waves Form?How Do Waves Form?Underwater EarthquakesUnderwater Earthquakes

• As underwater earthquakes shift the ocean floor, very large waves called tsunamis form as great amounts of water rise and fall around the fault line.

How Do Waves Form?How Do Waves Form?LandslidesLandslides

• As large amounts of land/ice hit the water at one time, very large waves called mega-tsunamis form as great amounts of water is pushed out of the way.

BeachesBeaches• A beachbeach is a strip of sediment (usually

sand or gravel) that extends from the low-tide line to a cliff or zone of permanent vegetation.

• The beach facebeach face is the section the waves are constantly pounding.

• Just offshore there is usually a marine marine terraceterrace, a wide, gently sloping platform that may be exposed at low tide.

• The bermberm is the wave-deposited upper part of a beach that is usually dry.

Berm and TerraceBerm and Terrace

What Are Tides?What Are Tides?

• Tides are long, slow waves that Tides are long, slow waves that result in the alternate rise and result in the alternate rise and fall of the surface level of the fall of the surface level of the oceans.oceans.– Tides can change sea level by up Tides can change sea level by up

to 60 feet.to 60 feet.

What Are What Are Tidal Tidal PoolsPools??

• Tidal pools form as high tide Tidal pools form as high tide water collects and is trapped water collects and is trapped when the tide drops.when the tide drops.

Tidal PoolsTidal Pools

How Do Tides How Do Tides Occur?Occur?

• Tides are caused by – the gravitational pull of the

moon and sun on the earth,– The rotation of the earth.

What is the Shape of the What is the Shape of the Earth?Earth?

• The gravitational forces acting on the earth flattenflatten the oceans of the earth into an oblate oblate spheresphere..

Types of TidesTypes of Tides

• High tide is the highest level the water reaches.

• Low tide is the lowest level the water reaches.

• Spring tides are more severe (higher high tides and lower low tides than normal).

• Neap tides are less severe (lower high tides and higher low tides than normal).

Spring TideSpring Tide

• Spring tidesSpring tides occur when the occur when the gravitational gravitational forcesforces of the sun and of the sun and the moon pull on the earth in the the moon pull on the earth in the same waysame way..– This combination of forces makes the This combination of forces makes the

earth earth more oblatemore oblate (less round) and (less round) and causes causes higherhigher than normal than normal high tideshigh tides and and lowerlower than normal than normal low tideslow tides..

Neap TideNeap Tide

• Neap tidesNeap tides occur when the occur when the gravitational gravitational forcesforces of the sun and of the sun and the moon pull on the earth the moon pull on the earth at at right anglesright angles to each other. to each other.– This combination of forces makes the This combination of forces makes the

earth earth more roundmore round and causes and causes lowerlower than normal than normal high tideshigh tides and and higherhigher than normal than normal low tideslow tides..

What is the What is the Intertidal Intertidal ZoneZone??

• The intertidal zoneintertidal zone is an ecosystem that exists in the area of coastline between the high tide line and the low tide line.

Life In The Intertidal Life In The Intertidal ZoneZone

• Threats to life are:Threats to life are:– Being dried up by the sunBeing dried up by the sun– Being eaten by birds and Being eaten by birds and

animalsanimals– Being washed out to seaBeing washed out to sea

Adaptations for Life in the Adaptations for Life in the ITZITZ

• Organisms adapt to the wet/dry cycle of the ITZ by various means:– Locomotion– Shells– Grip– Maintaining moisture– Hiding/burrowing

Adaptive OrganismsAdaptive Organisms

LimpetLimpet

Erosion and Deposition by Erosion and Deposition by Wave ActionWave Action

• Longshore DriftLongshore Drift is the movement of sediment parallel to the shore as waves strike the shore at an angle.

• GroinsGroins are built to protect beaches that are losing sand from longshore drifting.

• JettiesJetties are rock walls designed to protect the entrance of a harbor from sediment deposition and storm waves.

JettieJettiess

GroinGroinss

Coast and Coastal Coast and Coastal FeaturesFeatures

• The coastcoast is all the land near the sea, including the beach and a strip of land inland from it.

• Coasts change, due to drowning by glacial meltwater or tectonic forces, resulting in irregular shorelines with valleys that become short, deep, narrow bays.

• HeadlandsHeadlands are the points of land between the valleys.

HeadlandHeadlandss

What is Wave What is Wave Refraction?Refraction?

• An irregular coast with bays separated by headlands can gradually be straightened by wave action.

• Shallow water slows waves off the headlands while those same waves move faster through the deep bays.

• This bending of the wave is called wave refractionwave refraction.

Headland Headland ErosionErosion

Wave Erosion and Wave Erosion and DepositionDeposition

Wave TrainsWave Trains

Coastal Features Formed Coastal Features Formed by Wave Erosion of by Wave Erosion of

HeadlandsHeadlands• Sea cliffsSea cliffs are steep slopes that

erode as waves undercut them.• StacksStacks are erosional remnants of

headlands, and sea archessea arches are bridges of rock left after shoreline erosion.

• FjordsFjords are long, deep, steep sided bays formed by glaciers.

• EstuariesEstuaries are drowned river valleys.

Sea Sea CliffsCliffs

Tidal Tidal EstuaryEstuary

Stacks, Fjiords, ArchesStacks, Fjiords, Arches

Coastal Features Formed Coastal Features Formed by Wave Erosion of Coastsby Wave Erosion of Coasts

• SandbarsSandbars are ridges of sand that parallel the shoreline, usually underwater.

• Barrier islandsBarrier islands are sandbars that reach above sea level.

• A spitspit is a finger-like ridge of sediment that extends out into the open water.– A spit with a curved end is called a hookhook.

• Baymouth barsBaymouth bars are ridges of sediment that cut off an earlier open bay from the ocean.

• TombolosTombolos are bars of sediment that connect a former island to the mainland.

Sandbars, Spits, Baymouth bars and Sandbars, Spits, Baymouth bars and TombolosTombolos

How Did The Oceans How Did The Oceans Form?Form?

• Water came from volcanoes Water came from volcanoes (water vapor) into the air. Over (water vapor) into the air. Over millions of years this water vapor millions of years this water vapor cooled, and condensed, then cooled, and condensed, then precipitated out to form the precipitated out to form the oceans.oceans.

Where Did The Salt Come Where Did The Salt Come From?From?

• Once the oceans formed, the water cycle began.– The constant runoff, along with

erosion, dissolved many elements and minerals and deposited them in the oceans.

– Other elements were added to the atmosphere from volcanoes.

– The most abundant elements were sodium, chlorine, silicone and calcium.

What is Salinity?What is Salinity?

• SalinitySalinity is the measure of the amount of solidssolids (primarily salts) dissolveddissolved in the ocean water.– On average, in every 1000 grams

of salt water there is 35 grams of dissolved solids. (35 parts/1000)

Salinity of the Oceans Salinity of the Oceans Does NotDoes Not Change Change

• Salinity remains constantconstant because:– Constant addingConstant adding from volcanoes,

erosion, runoff etc.– Constant removalConstant removal by plants and

animals, and solids forming on the bottom.

– Addition and removal occur at the occur at the same rates.same rates.

How Does Salinity How Does Salinity Support Life?Support Life?

• Salinity is harmful to Salinity is harmful to humans yet it supports humans yet it supports marine life. How?marine life. How?– Calcium forms bones and Calcium forms bones and

shellsshells– Silicone forms shellsSilicone forms shells– Oxygen and carbon dioxide Oxygen and carbon dioxide

dissolved in the water is dissolved in the water is used for respiration of used for respiration of animals and plants.animals and plants.

What Are Ocean What Are Ocean Currents?Currents?

• In a currentcurrent the water particles flow in one direction.– Like in rivers and oceans.

• Ocean currents distribute solar energy Ocean currents distribute solar energy around the globe.around the globe.

• There are several types of ocean currents.– Surface currentsSurface currents– Density currentsDensity currents– Turbidity currentsTurbidity currents

Surface Surface CurrentsCurrents

• A surface currentsurface current is a movement of water that affects only the upper 100 feet of seawater.– Most are caused by winds.

•Example is the Gulf Stream

How Do Surface Currents How Do Surface Currents Affect Life?Affect Life?

• Surface currents affect life through:– Weather– Marine life = food supplies

Surface Currents Affect Surface Currents Affect WeatherWeather

• Weather: surface currents Weather: surface currents affect the climates by affect the climates by distributing the heat distributing the heat energy of the oceans energy of the oceans around the globe.around the globe.

– Warm water from the tropics Warm water from the tropics is brought north as cold polar is brought north as cold polar water is brought south.water is brought south.

Surface Currents Affect Surface Currents Affect Marine LifeMarine Life

•Most life in the oceans Most life in the oceans exists close to the surface exists close to the surface because:because:– Ocean plants need light for Ocean plants need light for

photosynthesis.photosynthesis.•Light only penetrates upper Light only penetrates upper 100-200 feet100-200 feet

– Animals live near surface where Animals live near surface where food sources exist.food sources exist.

Classification of Marine Classification of Marine LifeLife

• Marine organisms are classified by the way they move.

• Marine organisms are classified as either plankton,plankton, nekton, nekton, or benthos benthos.

What are Plankton?What are Plankton?

• PlanktonPlankton = are organisms that drift.– most are microscopic.– plankton depend on dissolved

substances in the water to exist.– plankton exist where “food” is and

therefore travel with the prevailing currents.

What are Nekton?What are Nekton?

• NektonNekton = are organisms that = are organisms that swim (fish and animals).swim (fish and animals).– Since these organisms can swim Since these organisms can swim

they can search for food.they can search for food.– These organisms still tend to use These organisms still tend to use

the currents as their supply of the currents as their supply of food.food.

What are Benthos?What are Benthos?

• BenthosBenthos are organisms that live on the ocean floor.

• These organisms do not swim and some, such as corals, stay in one place their entire life. Others, such as snails and crabs, crawl along the ocean floor.

Some BenthosSome Benthos

What Are What Are Density Density CurrentsCurrents??

• Density currentsDensity currents are the are the movement of water that occurs movement of water that occurs when dense seawater moves when dense seawater moves toward areas of less dense toward areas of less dense seawater. (usually vertical)seawater. (usually vertical)

• Density currentsDensity currents are affected are affected by temperature and salinity.by temperature and salinity.

Affects of Temperature on Affects of Temperature on CurrentsCurrents

• Freshwater freezes faster (less Freshwater freezes faster (less density).density).

• As the freshwater freezes it As the freshwater freezes it increases the salinity of the increases the salinity of the surrounding seawater.surrounding seawater.

• The more dense seawater sinks and The more dense seawater sinks and pushes the less dense seawater pushes the less dense seawater away resulting in a currentaway resulting in a current.

UpwellingUpwelling

• UpwellingUpwelling is an interruption in a density current.– This usually is the upward movement of

cold water.– This happens when strong surface winds

carry warm surface water away allowing the cold deep water to come to the surface.

Coastal Upwelling

What are Turbidity What are Turbidity Currents?Currents?

• Turbidity currentsTurbidity currents are dense mixtures of water and sediment that are pulled downslope by gravity like huge avalanches. These are a major cause of canyon erosion.– TurbiditesTurbidites are the deposits made

by turbidity currents.