WavesWaves

Characteristics of All Wind-generated Waves

Deep Water Waves

Shallow Water Waves

Other Water Waves

Parts of WavesParts of Waves• Crest and Trough Crest and Trough

• Wavelength (L)Wavelength (L)

• Wave Height (H)Wave Height (H)

depends on wind speed, open depends on wind speed, open distance (fetch), wind durationdistance (fetch), wind duration

• Period (T)Period (T)

Motion of Water MoleculesMotion of Water MoleculesCircularCircular motion to depth equal to motion to depth equal to

one half of the wavelengthone half of the wavelength

Deep Water Waves Deep Water Waves

• Water depthWater depth > one-half wavelength > one-half wavelength

• All wind-generated waves in open All wind-generated waves in open ocean, but many other waves, tooocean, but many other waves, too

Deep Water Waves (cont.)Deep Water Waves (cont.)

•SEASEA: within storm regions: within storm regions

– Choppy/Chaotic surfaceChoppy/Chaotic surface– Contrast with Contrast with SWELLSWELL

Deep Water Waves (cont.)Deep Water Waves (cont.)

• SWELLSWELL: outside of storm regions: outside of storm regions

– Smooth shapeSmooth shape– Sorted by wavelengthSorted by wavelength

Shallow Water WavesWaves

• Waves in Waves in water depth water depth less than less than 1/201/20 of wavelength of wavelength

• Often associated with surf zoneOften associated with surf zone

Shallow Water Waves (cont)Shallow Water Waves (cont)

Varieties of Varieties of Surf:Surf:

Consider slope Consider slope of ocean floorof ocean floor

• PlungingPlunging

• SpillingSpilling

spilling

plunging

surging

Wave Speed (L/T)

• Deep WaterDeep Water– Speed = 1.56T Speed = 1.56T – T= period or time between two T= period or time between two

successive crestssuccessive crests

Wave Speed (L/T)

• Shallow water wave speedShallow water wave speed = = 3.1 x square root Depth3.1 x square root Depth

Wave RefractionWave Refraction

• Bending of wave crestsBending of wave crests

• Waves approach beach at angleWaves approach beach at angle

• One part One part of crest reaches shallow of crest reaches shallow water first and water first and slows downslows down

• Waves become more parallel to shoreWaves become more parallel to shore

Drawing of beach…..Drawing of beach…..

Wave Refraction

Refraction along irregular Refraction along irregular coastcoast

• note note distribution of distribution of wave energywave energy

• most of energy strikes headlandsmost of energy strikes headlands

• causes erosion of headland, causes erosion of headland, deposition in baysdeposition in bays

• coastal straightening coastal straightening occursoccurs

Other Ocean WavesOther Ocean Waves

• Tsunamis Tsunamis

TsunamisTsunamis

• Seismic sea waves Seismic sea waves ( tidal waves)( tidal waves)

• disturbance of ocean floordisturbance of ocean floor– volcanic eruptionvolcanic eruption– certain earthquakescertain earthquakes– landslideslandslides

Tsunamis (cont)Tsunamis (cont)

• speed greater than speed greater than 700 km/hr700 km/hr

• wavelength greater than wavelength greater than 200 km200 km

• crests can exceed crests can exceed 30 m 30 m as reach as reach shoreshore

Information on tsunamisInformation on tsunamis

• http://http://nctr.pmel.noaa.govnctr.pmel.noaa.gov//