Ocean Waves

Ocean Waves & Tides

WavesThe result of repeated and periodic disturbances that cause energy to be transported through water.Very little water is transported.WindTurbidity currentsEarthquakes

Wind Generated wavesSize of the wave is determined by:The duration of the wind-how long it blows.The strength of the wind- how fast it blows.The fetch- the distance over the oceans surface the wind blows.Longer the wind blows- bigger wavesStronger the wind blows- higher the wavesGreater the fetch- bigger wavesTypes of WavesWaves are classified according to their wave-length:Wave period: Time in seconds between the passage of successive wave crests or troughs at a stationary point.

Progression of a WaveWaves begin as ripples (capillary)- wind blowsRipples become chop small wavesChop becomes organized:Smaller waves are eaten by larger wavesFaster waves overtake slower wavesSwell- large rolling waves of the deep ocean.organized, symmetrical wavethe crest and trough are smooth curves of equal size and shape.

Wave Spectrum

Characteristics of progressive waves:Parts of a wave are:Wave crest Wave troughWave parameters:Wave height (H)Wave amplitude (1/2 H)Wave length (L)Wave period (P)Wave period provides a basis for classifying waves as capillary waves, chop, swells, and tsunamiBeaufort Scale

TsunamisCaused by Seizmic action (earth quakes) Volcanic action

TsunamisMove outward from center of sourceStart in Deep Water (heavy volume & mass)No high waves until shallower water Moves faster when in deeper watercloser to land ---- slows down, higher wavesOcean Currents Move like Rivers

Movement Caused by Heat energy from sunWind EnergyCoriolis effect (rotation of Earth)

Characteristics: salinity, density, temperatureGulf Stream:Along East Coast of USAStrong, warm, salty waterHumboldt:Along West Coast of S. AmericaCOLD brings minerals, nutrients to surface

Ocean CurrentsInfluence weather and climate by transferring heat from tropical to polar areasDistribute nutrientsScatter organisms (even people)CurrentsMaintain their paths like riversForce of gravity causes dense water to sink, less dense water risesDensity is influenced by temp and salinitySpring Tides

Spring Tides

Additive affect of gravity on waterHighest hightidesLowest low tidesNeap Tide

90 Degree angle of sunEarth MoonAlternate 2 wk intervalsCompare Spring and Neap Tides

Notice that the bulges follow the moon!Tidal CycleEach cycle is 24 hour + 50 minutes (the moon rises 50 minutes later each day!)

Each high tide is about 12 hours apart.Each low tide occurs at mid-point between high tides.

There are 2 high tides and 2 low tides each day.

Storm SurgesAn abrupt bulge of water driven ashore by a tropical storm or storm surge.Crest of storm surge can go 25 - 40 feet above sea levelNot measured as waveonly 1 crest

Seiche(pronounced saysh)A standing wave in a smaller body of waterFirst studied in Switzerlands Lake GenevaWater level would rise and fall at regular intervals during wind storms

(Think -------bath tub sloshing!)Barrier Islands A small, thin strip of beach Parallel to the shore

Some are formed when sediments accumulate on submerged rises parallel to shore

A Typical Barrier Island

Barrier IslandsSome form when a river deposits sediment over a long period of time.A river can change course several times and forme different lobes.The Mississippi River Delta is a good example.

Why are Barrier Islands important?Protect shoreline from erosionBarrier against strong storm surgesProvide habitat (land) for wildlifeSeparate ocean water from shallow channels between the barrier island and the shoremaking a different habitat for aquatic life.Cycle of Barrier Island FormationActive DeltaAbandonmentDetachmentSubmergence

1. Active DeltaDelta actively builds land, depositing sediment from the channel to the Gulf of Mexico

2. AbandonmentThe delta is no longer active and erosional forces are at work on the headland, forming sandy spits on either side of the old channel.

3. DetachmentThe combined effects sea level rise + subsidence (relative sea level rise) cause the barrier to detach-> become an island.

4. SubmergenceRising sea level continuesBarrier island is now more submergedBecomes a shoal beneath the water5. ReoccupationIf natural conditions prevailed, (they havent), the Rivers distributions could bring more sediment to build a new delta lobe.

The cycle would continue.