The sand makes a temporary rest in the broad deltas that form where the out flowing fresh water collides head on with the incoming salt at flood tide. The sand at the mercy of the tides, currents and wind are shifted around twice daily as the incoming tides creep over the delta. The sand at some point will become part of a barrier island. Approximately 10,000 years ago Gray's Reef was exposed as land perhaps as an ancient barrier island itself and composed of the same materials that comprise the Appalachians. While exposed to thousands of years of rain the sand solidified to become rocky outcroppings with ledges. These features give Gray's Reef its distinctive profile which has become prime habitat for hundreds of encrusted marine flora and fauna (plants and animals). (photo: Gray's Reef NMS)