Waves and Beaches
• Movement of air (disturbing force) across the
ocean causes waves to form
• Splash waves can be generated by coastal
landslides or icebergs calving
• Seismic sea waves or Tsunamis can be formed by
underwater avalanches, volcanic eruptions, or
fault slippage
• Tides are a vast, low, predictable wave created by
the sun and moon and spin of the earth
• Waves can also be created by ships creating a
wake
Wave Properties
• Ocean waves are Orbital waves which involves
components of both longitudinal and
transverse waves
• Also known as body waves because energy is
transferred through a body of matter
• Crest- high part of the wave
• Trough- low part of the wave
• Still water level- half way between crest and
trough
Wave Properties cont.
• Wave Height- measured top of crest to bottom
of trough
• Wave Length- measured crest to crest or
trough to trough
• Wave period- time it takes one wavelength to
pass a point, typical between 6 and 16 sec.
• Frequency- number of crests passing a fixed
point per unit of time
Water Properties cont.
• Waves break when steepness exceeds 1:7
ratio, a wave 7 meters long can only be 1
meter high or it breaks, near shore or open
ocean,
• Wave Base- Point at which the circular orbital
motion dies out with depth ( surge ) usually ½
wavelength
• Floating oil rigs, Bridges are designed so that
most of their mass is below the wave base
Wave Properties cont.
• Energy in a wave determined by:
– Wind speed- mph or kph
– Fetch- distance wind blows, 100s-1000s of miles
– Duration- time wind blows,hours- days
• 10% of the waves in a fully developed sea will be
twice the average height
• Swell- waves moved out of the storm area move
faster than the wind, steepness decreases become
long crested waves, travel great distances
Wave Properties cont.
• The circular orbit in a wave is slower in the
bottom half or trough than the top crest half
so a floating object does not return to its exact
spot, moves slightly forward (Wave Drift )
• Deep water waves are faster than shallow
water waves which drag on the ocean bottom
and slow down
• The longer the wavelength the faster the wave
Breaking Waves
• Waves entering shallow water drag their base on
the bottom and slow, waves move closer and
wavelength decreases, wave height increases
• When the front bottom of the wave touches the
ocean bottom and stops, the upper part of the
wave runs up over the front increasing height and
falls foreward
• Spilling Breakers- slower waves from dragging on
bottom
• Plunging Breakers-fast waves going from deep to
shallow water suddenly
PIPELINE
MAVERICKS
RINCON
Rogue Waves
• Massive solitary waves occur when normal ocean
waves are not large
• In a 6.5 ft sea a 65 ft wave may appear
• 1 wave in 23 twice average height
• 1 in 1175 will be 3 times average
• 1 in 300,000 will be 4 times average
• Probably caused by constructive wave
interference, 2 or more waves combining
• 10 large ships lost every year, 1000 total yearly