wave tidal wave by liaoqinmei


									Ocean Waves
 wave a periodic disturbance in a solid,
  liquid, or gas as energy is transmitted
  through a medium
 two basic parts—a crest and a trough
 wave period the time required for two
  consecutive wave crests to pass a given
 wave height: vertical distance between
  crest and trough
 Wavelength: distance between two crest
  or troughs
Wave Energy
 Longer wind blows the more energy is
  transferred into the water = larger waves.
 Wave movement:
    ◦ Energy in waves move from water molecule
      to water molecule in the direction of the
    ◦ circular motion
    ◦ in a single wave period, each water particle
      moves in one complete circle
    ◦ Only the energy not the water moves across
      the surface of the ocean.
Wave Size
   Three factors determine the size of a
    ◦ Speed of the wind, the length of time the wind
      blows, and fetch.
    ◦ fetch the distance that wind blows across an
      area of the sea to generate waves
   Whitecaps:
    ◦ When winds blow the crest of a wave off
    ◦ reflect solar radiation, they allow less
      radiation to reach the ocean
Waves and the Coastline
   Breakers
    ◦ Wave moves into
      shallow water.
    ◦ The bottom of the wave
      is slowed by friction
    ◦ The top of the wave
      continues to move at its
      original speed.
    ◦ the top of the wave
      topples over and forms a
      breaker, a foamy mass of
      water that washes onto
      the coastline.
Start of Wave Sequence
End of Wave Sequence
   Refraction:
    ◦ The bending of the
      wave crest in response
      to changes in wave
    ◦ Shallow ocean water =
      slower speeds
    ◦ Deeper ocean water =
      faster speeds
Undertows and Rip Currents
   Undertow:
    ◦ Water carried onto a beach by breaking
      waves is pulled back into deeper water gravity
   Rip currents:
    ◦ form when water from larger breakers
      returns to the ocean through channels that
      cut through underwater sandbars that are
      parallel to the beach.
Rip Current
Longshore Currents
 currents form when waves approach the
  beach at an angle
 currents flow parallel to the shore.
 Great quantities of sand are carried by
  longshore currents
 These sand deposits form low ridges of
  sand called sandbars.
Longshore Currents

Longshore Currents

 giant seismic ocean waves
 Most are caused by earthquakes on the ocean floor, but
  some can be caused by volcanic eruptions and underwater
 Nick name is tidal wave, but they are not caused by tides
 has a tremendous amount of energy
    ◦ In open ocean water they travel at a rate of around 760Km per
      hour or 483mph, that similar to the speed of a jet aircraft.
 Not dangers in open water, but when they come into
  shallower the energy is transferred into height = destruction
 The arrival of a tsunami may be signaled by the sudden
  pulling back of the water along the shore


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