The summer beach is typically wider and flatter than the beach in winter.

Fire Island's beaches are composed mainly of white quartz sand of varying grain size. Occasional layers of heavy mineral sands—which include grains of garnet and magnetite—appear as colored bands among the predominantly white sediment. Occasionally, you will find pebbles or other gravel and fragments of shell on the beach.  

The particle size of beach sand is layered, depending on the energy of the depositing waves and wind.

Hard, black deposits of peat are occasionally uncovered on Fire Island's Atlantic Ocean beach.

The size and shape of the beach is always changing. While sediment is constantly being moved more or less perpendicular to or from shoreline by tidal and wave action, the predominant net movement of sediment along Fire Island's coast is parallel with the shore through the effects of longshore currents. The movement is called longshore sediment transport and its rate is dependent on wave energy and the angle at which waves strike the coast.

NPS Natural Resource Program Center

For More Information

You can learn more about coastal processes at the NPS "Views of the National Parks" web site:

• Coastal Processes
• Coastal Geology multimedia education program