Fire Island is a barrier island, which is believed to have developed as a spit of sediment formed from an eroding headland after the end of the last ice age. Its sand comes from two sources: the eroding cliffs and bluffs of Montauk to its east, and from offshore sources which were deposited by retreating glaciers and remain from earlier inlet deltas.

Fire Island's coastline is constantly being shaped and re-shaped by wind and water. Littoral drift, offshore bottom currents, wind, inlet formation, tidal delta growth, and occasional overwash are all essential to maintain a dynamic equilibrium on a barrier island.

 

Barrier islands are one of the most common and distinguishable features of the Atlantic coast. These important environments protect the mainland from storm events and wave action, while providing a vital ecosystem for many species. Features such as sand dunes, maritime forests, inlets, lagoons, back-barrier marshes, and vegetation constitute these fragile coastal systems. Without intervention, barrier islands maintain a state of dynamic equilibrium between sediment exchange, wave energy, and sea-level rise.

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

Global climate change is one of the critical natural resource issues that concerns the National Park Service. At Fire Island National Seashore, the major repercussion of changing temperatures lies in sea-level rise. The National Park Service and the United States Geological Survey are currently developing Coastal Vulnerability Index (CVI) maps for coastal parks to identify coastal areas sensitive to sea-level rise.

• Coastal Vulnerability Assessment of Fire Island National Seashore (FIIS) to Sea-Level Rise
  USGS Publication  03-439

A series of Science Synthesis Papers was published in 2005 to support the preparation of a General Management Plan for Fire Island National Seashore.

• The Coastal Geomorphology of Fire Island: a Portrait of Continuity and Change
  (Fire Island National Seashore Science Synthesis Paper)
  by Norbert P. Psuty, Michele Grace, and Jeffrey P. Pace, Rutgers University
  
• Bay Shoreline Physical Processes, Fire Island
  (Fire Island National Seashore Science Synthesis Paper)
  by Karl F. Nordstrom, Rutgers University
  Nancy L. Jackson, New Jersey Institute of Technology