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Although symmetrical ripples are also called bi-directional ripples there is a difference between them. Bi-directional ripples are rarely symmetrical due to the difference in force of the two directions, where as the wave formed or oscillation ripples form from the circular water movement pattern of
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Ripples are relatively small, elongated ridges that form on bed surfaces perpendicular to current flow. With continuous current flow in one direction, asymmetrical ripples form. Asymmetrical ripples contain a steeper slope downstream. With an alternation in current flow from one direction to the
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Symmetrical ripples form as water molecules oscillate in small circles. A particle of water within a wave does not move with the wave but rather it moves in a small circle between the wave crest and wave trough. This movement of water molecules is the same for all water molecules effected by the
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wave. The water molecules continue to do this to a depth equal to 1/2 the wavelength. The water molecule traveling in a circular pattern interacts with the sediment on the floor and moves the sediment into symmetrical ripples. These ripples can be either
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and long relatively straight crests, which may commonly bifurcate. Commonly, these crests can be truncated by subsequent flows. Their wavelength (periodicity) depends on the sediment grain size, water depth and water-particle orbits in the waves. On
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Hampton, Monty A., Torresan, Michael E., and Barber, Jr., John H., 1997, Sea-floor geology of a part of Mamala Bay, Hawaii: Pacific
Science, v. 51, n. 1, p. 54-75. Reproduced by permission of the University of Hawaii
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While wave-formed ripples are traditionally described as symmetrical, asymmetric wave ripples are common in shallow waters along sandy shores. They are produced by bottom oscillations generated by passing
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Atlantic coast beaches : a guide to ripples, dunes, and other natural features of the seashore / William J. Neal, Orrin H. Pilkey, Joseph T. Kelley. Publisher
Missoula, Mont. : Mountain Press,
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Department of Earth
Science, Preston Cloud Research Laboratory, University of California, Santa Barbara, CA 93106, United States Precambrian Research; Nov2009, Vol. 174 Issue 3/4, p215-240, 26p
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Marshak, Stephen. "Chapter 7: A Surface Veneer: Sediments, Soils and
Sedimentary Rocks." Earth Portrait of a Planet. 3rd ed. New York: W.W Norton & company, 2008. 211. Print.
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Monroe, James S., and Reed
Wicander. The Changing Earth: Exploring Geology and Evolution, 2nd ed. Belmont: West Publishing Company, 1997.
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water molecules. These ripples form parallel to the shore line. They usually display rounded troughs and rounded crests.
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directions. Symmetrical ripples are commonly found in shallow waters. Beaches are a good place to find these ripples.
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Wave-formed ripples indicate an environment with weak currents where water motion is dominated by wave oscillations.
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opposite symmetrical ripples form. Symmetrical ripples tend to have the same slope on both sides of the crest.
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the pattern of wave-formed ripples may be complicated, as a product of changing depth and wind and
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are often characterised (and thus distinguished from
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131:A=Effect of oscillatory motion in deep water
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220:Journal of Sedimentary Research
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34:or symmetric ripple, from
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176:Sedimentary structures
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135:1=Progression of wave
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187:References
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