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Ocean Waves & Tides. Waves. The result of repeated and periodic disturbances that cause energy to be transported through water. Very little water is transported. Wind Turbidity currents Earthquakes. Wind Generated waves. Size of the wave is determined by:
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Waves The result of repeated and periodic disturbances that cause energy to be transported through water. Very little water is transported. • Wind • Turbidity currents • Earthquakes
Wind Generated waves Size 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 ocean’s surface the wind blows. • Longer the wind blows- bigger waves • Stronger the wind blows- higher the waves • Greater the fetch- bigger waves
Types of Waves Waves 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 Wave Waves begin as ripples (capillary)- wind blows Ripples become chop – small waves Chop becomes organized: • Smaller waves are eaten by larger waves • Faster waves overtake slower waves Swell- large rolling waves of the deep ocean. • organized, symmetrical wave • the crest and trough are smooth curves of equal size and shape.
Characteristics of progressive waves: Parts of a wave are: • Wave crest • Wave trough Wave 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 tsunami
Tsunamis Caused by • Seizmic action (earth quakes) • Volcanic action
Tsunamis • Move outward from center of source • Start in Deep Water (heavy volume & mass) • No high waves until shallower water • Moves faster when in deeper water • closer to land ---- slows down, higher waves
Ocean Currents Move like Rivers Movement Caused by • Heat energy from sun • Wind Energy • Coriolis effect (rotation of Earth) Characteristics: salinity, density, temperature
Gulf Stream: • Along East Coast of USA • Strong, warm, salty water Humboldt: • Along West Coast of S. America • COLD brings minerals, nutrients to surface
Ocean Currents • Influence weather and climate by transferring heat from tropical to polar areas • Distribute nutrients • Scatter organisms (even people)
Currents • Maintain their paths like rivers • Force of gravity causes dense water to sink, less dense water rises • Density is influenced by temp and salinity
Spring Tides • Additive affect of gravity on water • Highest hightides • Lowest low tides
Neap Tide • 90 Degree angle of • sun • Earth • Moon • Alternate 2 wk intervals
Compare Spring and Neap Tides Notice that the bulges follow the moon!
Tidal Cycle Each 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.
Storm Surges • An abrupt bulge of water driven ashore by a tropical storm or storm surge. • Crest of storm surge can go 25 - 40 feet above sea level • Not measured as wave—only 1 crest
Seiche(pronounced saysh) • A standing wave in a smaller body of water • First studied in Switzerland’s Lake Geneva • Water 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
Barrier Islands • Some 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 erosion • Barrier against strong storm surges • Provide habitat (land) for wildlife • Separate ocean water from shallow channels between the barrier island and the shore—making a different habitat for aquatic life.
Cycle of Barrier Island Formation • Active Delta • Abandonment • Detachment • Submergence
1. Active Delta • Delta actively builds land, depositing sediment from the channel to the Gulf of Mexico
2. Abandonment The 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. Detachment The combined effects sea level rise + subsidence (relative sea level rise) cause the barrier to detach -> become an island.
4. Submergence Rising sea level continues Barrier island is now more submerged Becomes a shoal beneath the water
5. Reoccupation If natural conditions prevailed, (they haven’t), the River’s distributions could bring more sediment to build a new delta lobe. The cycle would continue.
