WAVES disturbance caused by the movement of energy from a source through some medium (solid, liquid or gas). THERE ARE MANY DIFFERENT SIZES AND SHAPES OF WAVES

Global Wave Height

Rogue Wave

Hawaii, 66’ wave

Types of Waves Chaotic Waves Ocean Swells Ocean Breakers

Swell – mature, regular, wind waves

WAVES Because the wave form moves forward these are called progressive waves

Wind wave – ratio of height to wavelength (wave steepness) = 1 to 7

WAVES The energy is moving at the speed of the wave, but NOT the water

Fig 9-1, g

Fig 9-3, p.201

Orbits The diameter of the orbits diminishes rapidly with depth Wave motion in deep water is negligible past ½ the wavelength

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WAVES The parcel of water moves in a circular motion = orbit water is displaced very little across the sea surface as the illusion of a wave suggests

Components… Crest Trough Wavelength Height Frequency Fetch Wavebreak Refraction Period

Fig 9-2, g

Wave fetch – uninterrupted distance over which the wind blows w/o significant change in direction.

Fig 9-15, g Wavebreak – ratio of wave height to water depth is 3 to 4

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Wave Refraction When waves do not approach parallel to shore… The wave line will bend to become more parallel to shore

Fnft Wave refraction

Wave crests bend 90 degrees as they move around point (Hawaii) = refraction

Stoke’s Drift or Mass Transport Small net movement of water in the direction of the wave

Figure not from book

Classifying Waves disturbing force = the energy that cause waves to form restoring force = the dominant force trying to return surface water to flatness wavelength

Wave energy as a function of wave period

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types of waves “swell” (capillary wave) Shallow water wave Deep water wave

Wave Types Capillary waves –Wind –Surface tension – <1.73cm

Fig. 9-6, g

Capillary waves interrupt the smooth surface, deflect upward, Slow & cause winds energy to be transferred into the water. A= crest; B=trough

Swell – mature, regular, wind waves

Fnft Deep water wave Shallow water wave

Deep vs Shallow Water waves The orbits of water molecules in a wave are circular only when the wave is in deep water A wave cannot “feel” the bottom if it is in water deeper than ½ its wavelength = a deep water wave

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Deep vs Shallow Water Waves ONLY WIND WAVES CAN BE DEEP WATER WAVES

Deep vs Shallow Water Waves Shallow water waves = moving in water shallower than 1/20 it wavelength Water at the bottom moves back and forth

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Deep vs Shallow Water Waves Transitional waves = travel through water deeper than 1/20 their wavelength and shallower than ½ its wavelength

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Fig. 9-5, g

How waves break at shore... A deep water waves feels bottom and becomes a transitional wave orbits become elliptical crests become peaked wave height increases wave slows down wave length decrease

Wavebreak – ratio of wave height to water depth is 3 to 4

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How waves break at shore... The wave becomes too high for its wavelength and the wave breaks The surf zone is the region between the breaking waves and the shore.

INTERFERENCE Destructive interference = cancellation effects of subtraction –When a wave crest and another wave’s trough coincide

INTERFERENCE Constructive interference = addition effects that form large crests and deep troughs –When crests coincide

Constructive Interference

Types of Waves Tsunamis Seismic Sea Waves

Types of Waves Tsunamis – long wavelength, shallow water progressive waves caused by rapid displacement of ocean water. This is caused by sudden vertical movement of earth along a fault line, causing a Seismic Sea Wave. Origination on seafloor, a “problem” for continental populations if this is close to land or in a confined space!

Tsunami A tsunami can be a wave w/ a wavelength up to 125 miles! Remember the deepest ocean basin is 7(+) miles deep…if a wave = ½ wavelength it’s still not enough “room” to move (do the math!) Problem: a tsunami wave can reach a height of over 100’

Tsunamis originate from earthquakes, volcanic explosions, or submarine landslides. On December 26, 2004, an earthquake with a magnitude of over 9.0 on the Richter scale triggered a megatsunami that affected coastlines throughout the Indian Ocean.

Fig 9-27, g

Fig 9-21, g 1946 Hawaiian tsunami

Fnft Sequence: 1957 Hawaii tsunami 5 hrs. earlier = earthquake…

Fnft 15 minutes later

Fnft 2 hrs. total duration = 56’ total wave height, $25 million in damages

Fig 9-26, g

Fig. 9-26, g