Upper shoreface
Encyclopedia
Upper Shoreface refers to the portion of the seafloor that is shallow enough to be agitated by everyday wave action (wave base
Wave base
The wave base is the maximum depth at which a water wave's passage causes significant water motion. For water depths larger than the wave base, bottom sediments are no longer stirred by the wave motion above....

). Below that is lower shoreface
Lower shoreface
Lower Shoreface refers to the portion of the seafloor or sedimentary depositional environment that lies below everyday wave base . In this portion of the coastal environment, only the larger waves produced during storms have the power to agitate the sea bottom...

.

Overview

Water is moved in a circular motion when a wave passes. The radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...

 of the circle of motion for any given water molecule decreases with depth. The maximum depth of influence of a water wave is half the wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

. Below that depth the water remains stationary as the wave passes. For instance, in a pool of water 1 foot deep, a wave with a 2-foot wavelength would barely be moving the water at the bottom. In the same pool, a wave with a wavelength of 1 foot would not be able to cause water movement on the bottom.

The continuous agitation of the sea floor in the upper shoreface environment results in sediments that are winnowed of the smallest grains, leaving only those grains heavy enough that the water cannot keep them suspended.
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