This photograph was taken from the ocean looking toward the shore. In the foreground is the swash of the incoming wave. Above that is the foreshore, or zone in which the swash and backwash continually sweep. The neutral colored area is the summer berm and at the top of the photograph is a cliff made up of glacial till. In the middle of the picture is a dark line. This is the trough of the longshore current, created by the oblique motion of the waves across the beach face, that sets in motion a tiny river parallel to the beach. In this trough the turbulence of the water holds sand grains in suspension and carries them along the shoreline until it reaches an area where the shoreline undergoes a sharp landward bend.

Sand is defined as particles of earth materials between .0625 and 2.0mm in diameter. Particles larger than that are known as pebbles, rocks and boulders. Particles smaller than that are silt, with diameters between 1/256 and 1/16mm, and clay, which has diameters less than 1/256mm. The water turbulence, created by the waves dragging on the ocean floor and breaking on the beach, suspends the sand, silt and clay. Here the turbulence subsides and the sand grains fall to the ocean floor creating an underwater sand bar. The clay and silt, being smaller in size, remain in suspension only to fall out in the very still waters of salt marshes. Along the shoreline, additional deposition by beach drifting and the motion of the swash and backwash build the sand bar above the surface where it is known as a sand spit. Almost always, this spit has a curved form, bending toward the land at its outer tip. In this manner, the Provincetown sand spit was created.    
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