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wave (in the earth sciences)

wave, in oceanography, an oscillating movement up and down, of a body of water caused by the frictional drag of the wind, or on a larger scale, by submarine earthquakes, volcanoes, and landslides. In seismology, waves moving though the earth are caused by the propagation of a disturbance generated by an earthquake or explosion. In atmospheric science, waves are periodic disturbances in the air flow.

Oceanographic Waves

In a body of water, waves consist of a series of crests and troughs, where wavelength is the distance between two successive crests (or successive troughs). As waves are generated, the water particles are set in motion, following vertical circular orbits. Water particles momentarily move forward as the wave crest passes and backward as the trough passes. Thus, except for a slight forward drag, the water particles remain in essentially the same place as successive waves pass. The orbital motion of the water particles decreases in size at depths below the surface, so that at a depth equal to about one half of the wave's length, the water particles are barely oscillating back and forth. Thus, for even the largest waves, their effect is negligible below a depth of 980 ft (300 m).

The height and period of water waves in the deep ocean are determined by wind velocity, the duration of the wind, and the fetch (the distance the wind has blown across the water). In stormy areas, the waves are not uniform but form a confusing pattern of many waves of different periods and heights. Storms also produce white caps at wind speeds c.8 mi per hr (13 km per hr). Major storm waves can be over a half mile long and travel close to c.25 mi per hr (40 km per hour). A wave in the Gulf of Mexico associated with Hurricane Ivan (2004) measured 91 ft (27.7 m) high, and scientists believe that other waves produced by Ivan may have reached as much as 132 ft (40 m) high. Waves of similar heights, sometimes called rogue waves, most commonly occur in regions of strong ocean currents, which can amplify wind-driven waves when they flow in opposing directions; sandbanks may also act to focus wave energy and give rise to rogue waves.

When waves approach a shore, the orbital motion of the water particles becomes influenced by the bottom of the body of water and the wavelength decreases as the wave slows. As the water becomes shallower the wave steepens further until it "breaks" in a breaker, or surf, carrying the water forward and onto the beach in a turbulent fashion. Because waves usually approach the shore at an angle, a longshore (littoral) current is generated parallel to the shoreline. These currents can be effective in eroding and transporting sediment along the shore (see coast protection; beach).

In many enclosed or partly enclosed bodies of water such as lakes or bays, a wave form called a standing wave, or seiche, commonly develops as a result of storms or rapid changes in air pressure. These waves do not move forward, but the water surface moves up and down at antinodal points, while it remains stationary at nodal points.

Internal waves can form within waters that are density stratified and are similar to wind-driven waves. They usually cannot be seen on the surface, although oil slicks, plankton, and sediment tend to collect on the surface above troughs of internal waves. Any condition that causes waters of different density to come into contact with one another can lead to internal waves. They tend to have lower velocities but greater heights than surface waves. Very little is known about internal waves, which may move sediment on deeper parts of continental shelves.

Just as a rock dropped into water produces waves, sudden displacements such as landslides and earthquakes can produce high energy waves of short duration that can devastate coastal regions (see tsunami). Hurricanes traveling over shallow coastal waters can generate storm surges that in turn can cause devastating coastal flooding (see under storm).

Seismic and Atmospheric Waves

Seismic waves are generated in the earth by the movements of earthquakes or explosions. Depending on the material traveled through, surface and internal waves move at variable velocities. Layers of the earth, including the core, mantle, and crust, have been discerned using seismic wave profiles. Seismic waves from explosions have been used to understand the subsurface structure of the crust and upper mantle and in the exploration for oil and gas deposits. Atmospheric waves are caused by differences in temperature, the Coriolis effect, and the influence of highlands.

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wave

wave / wāv/ • v. 1. [intr.] move one's hand to and fro in greeting or as a signal: he waved to me from the train. ∎  [tr.] move (one's hand or arm, or something held in one's hand) to and fro: he waved a sheaf of papers in the air. ∎  move to and fro with a swaying or undulating motion while remaining fixed to one point: the flag waved in the wind. ∎  [tr.] convey (a greeting or other message) by moving one's hand or something held in it to and fro: we waved our farewells | she waved him goodbye. ∎  [tr.] instruct (someone) to move in a particular direction by moving one's hand: he waved her back. 2. [tr.] style (hair) so that it curls slightly: her hair had been carefully waved for the evening. ∎  [intr.] (of hair) grow with a slight curl: [as adj.] (waving) thick, waving gray hair sprouted back from his forehead. • n. 1. a long body of water curling into an arched form and breaking on the shore. ∎  a ridge of water between two depressions in open water: gulls and cormorants bobbed on the waves. ∎  a shape seen as comparable to a breaking wave: a wave of treetops stretched to the horizon. ∎  (usu. the wave) an effect resembling a moving wave produced by successive sections of the crowd in a stadium standing up, raising their arms, lowering them, and sitting down again. ∎  (the waves) poetic/lit. the sea. ∎  an intense burst of a particular feeling or emotion: horror came over me in waves a new wave of apprehension assailed her. ∎  a sudden occurrence of or increase in a specified phenomenon: a wave of strikes had effectively paralyzed the government. 2. a gesture or signal made by moving one's hand to and fro: he gave a little wave and walked off. 3. a slightly curling lock of hair: his hair was drying in unruly waves. ∎  a tendency to curl in a person's hair: her hair has a slight natural wave. 4. Physics a periodic disturbance of the particles of a substance that may be propagated without net movement of the particles, such as in the passage of undulating motion, heat, or sound. See also standing wave and traveling wave. ∎  a single curve in the course of this motion. ∎  a similar variation of an electromagnetic field in the propagation of light or other radiation through a medium or vacuum. PHRASES: make waves inf. create a significant impression: he has already made waves as a sculptor. ∎  cause trouble: I don't want to risk her welfare by making waves. PHRASAL VERBS: wave something aside dismiss something as unnecessary or irrelevant: he waved the objection aside and carried on.wave someone/something down use one's hand to give a signal to stop to a driver or vehicle.DERIVATIVES: wave·less adj.wave·like adj. & adv.

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"wave." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 16 Aug. 2017 <http://www.encyclopedia.com>.

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wave

wave In physics, carriers of energy from place to place. Waves are caused by disturbances that result in some sort of oscillation. These oscillations then spread out (propagate) as waves. The velocity depends on the type of wave and on the medium. Electromagnetic waves, such as light, consist of varying magnetic and electric fields vibrating at right angles to each other and to the direction of motion; they are transverse waves. Sound waves are transmitted by the vibrations of the particles of the medium itself, the vibrations being in the direction of wave motion; they are longitudinal waves. Sound waves, unlike electromagnetic waves, cannot travel through a vacuum or undergo polarization. Both types of waves can undergo reflection and refraction, and give rise to interference phenomena. A wave is characterized by its wavelength and frequency, the velocity of wave motion being the product of wavelength and frequency. See also electromagnetic radiation; polarized light; wave amplitude; wave frequency

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wave

wave In oceanography, moving disturbance travelling on or through water, but that does not move the water itself. Wind causes waves by frictional drag. Waves not under pressure from strong winds are called swells. Waves begin to break on shore or ‘feel bottom’ when they reach a depth shallower than half the wave's length. When the water depth is about 1.3 times the wave height, the wave front is so steep that the top falls over and the wave breaks.

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wave

wave1 move to and fro, shake or sway as with the wind. The word in the above senses as at present used is not clearly evident before XVI; not certainly continuous with OE. wafian (recorded twice) make a movement to and fro with the hands, corr. to MHG. waben wave, undulate, f. Gmc. *wab̌-, repr. also by ON. vafi doubt, uncertainty, and WAVER.

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"wave." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. 16 Aug. 2017 <http://www.encyclopedia.com>.

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wave

wave2 movement in an extent of water by which a portion of it rises above the general level. XVI. alt., by assoc. with WAVE1, of ME. †wawe, earlier waze, rel. to OE. wagian, ME. wawe, sway to and fro, wave (cf. WAG1).
Hence wavy (-Y1) XVI.

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wave

wavebehave, brave, Cave, clave, concave, crave, Dave, deprave, engrave, enslave, fave, forgave, gave, grave, knave, lave, Maeve, misbehave, misgave, nave, outbrave, pave, rave, save, shave, shortwave, slave, stave, they've, waive, wave •enclave • exclave • conclave •Redgrave • architrave • Wargrave •Palgrave • palsgrave • aftershave •brainwave • heatwave • microwave

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"wave." Oxford Dictionary of Rhymes. . Encyclopedia.com. 16 Aug. 2017 <http://www.encyclopedia.com>.

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