![]() ![]() Node = Fixed Point, Antinode = maximum displacement (Figure 7-11) Resonance Standing waves can be dangerous due to the phenomenon of resonance. Oscillate back and forth about a node i.e., a fixed point.įorm when winds blow in one direction which causes water to pile up at one end of a basin. Standing waves (seiches) do not move horizontally. Standing Waves Seas, swell, and surf are progressive waves. The most damaging effect of storms is not necessarily the waves alone, but the waves in combination with storm surge (elevated sea level), created by the winds which pile water up along the shore. Waves affect water to a depth equal to or less than one-half their wavelength.Ī special case is a tsunami, a deepwater wave generated by a submarine disturbance with incredibly long wavelengths, high wave speeds, and very short wave heights, UNTIL they feel the bottom in shallow water!Īs waves enter shallow water their wavelength shortens and their height increases. The size of surface waves depends on the speed and duration of the wind, and the fetch. Progressive waves move along the sea surface. Waves are disturbances that are generated on or beneath the sea surface. Low pressure which leads to a rise in sea level. Some of the greatest destruction comes from the storm surge or extreme high water levels due to the: Storm Surges Storms affect shorelines in a variety of ways. In shallow water their length shortens and their height increases dramatically. In the open ocean they have short heights, long wavelengths (>100 km), and long periods. Surfing Video: Condition Black Tsunamis Sudden shifting of the ocean floor due to earthquakes, volcanic eruptions, and submarine slumping. Waves Break by Spilling Plunging, or Surging (Figure 7-9) depending on the slope of the bottom When this value is about 1/7, waves begin to break. Life History of Ocean Waves (Cont.) Shore breakers (surf) are collapsing waves. Wave energy is defocused where the lines diverge. Wave energy is focused where the lines converge. Wave Orthogonals (Figure 7-8) Refraction can be assessed by drawing wave orthogonals, imaginary lines perpendicular to the wave crest. Transformation of Shallow-water Waves (Figure 7-7b) Wave Refraction (Figure 7-8a) Click here for ANIMATIONīending of the wave crest as waves enter shallow water. Waves Entering Shallow Water As waves enter shallow water: Water depths are less than 1/20 the wave length. Shallow-water Wave Transformations Interaction with the sea bottom. This leads to wave refraction and waves collapse forming surf (breakers). Transformation of Deep-water Waves: Dispersion (Figure 7-7a) Shallow Waves Affected by Bottom In shallow water, the sea bottom transforms the wave's properties. The crests build up and the troughs build down.ĭestructive Waves (Figure 7-6c) Destructive wave interference occurs when the crest of one wave coincides with the trough of another wave resulting in a cancellation. Rogue Waves? (Figure 7-6b) Constructive wave interference occurs when several wave crests or troughs coincide. This area is characterized by a "confused" sea state with extensive wave interference. Life History of Ocean Waves Waves originate in the fetch area. It is the energy of the wave, not its mass that is in motion. When wave passes, no net displacement of water. Wave Speed The speed (celerity) of the wave form can be calculated byĭividing the wavelength by the wave period. The orbits of the water molecules become elliptical. Shallow Water Waves (Figure 7-4b) Waves which interact with the sea floor are known as shallow-water waves. ![]() The orbits of the water molecules are circular. Wave Motion with Depth (Figure 7-3a) Click here for ANIMATION Motion of Water Particles Beneath Waves (Figure 7-3b) Deep Water Waves (Figure 7-4a) In deep water most waves do not interact with the sea bottom and are called deep-water waves. It is wave energy not water molecules that moves across the sea surface. The orbital motion of water particles beneath the wave. Wave Motions Two basic motions associated with an ocean wave: Surf - waves that have reached the coast, grow in height, and break Swell - more regular waves beyond area of generation Progressive Wave Types Sea - irregular waves in the area of generation Progressive Waves Wind-generated waves are progressive waves because they travel across the sea surface. Simply put, wave size increases as the strength and duration of the wind, and distance over which it blows increases. Wind Generation of Waves The type of wave generated by wind is determined by: Wave Parameters (Figure 7-1a) What Causes Waves? Wind Standing waves oscillate about a fixed point. Progressive waves move across the sea surface. Properties of Ocean Waves An ocean wave is an undulation of the sea surface. ![]()
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