Altamaha Basin > Hydrology > Water Quality > Environmental Threats > Human Impacts >
       Cultural Features > Coastal Habitats > Tributaries > Plants > Animals > Sapelo Island

The broad expanse of salt marshes and tidal channels which occupy most of the area between the barrier islands and the Georgia mainland are classed as lagoonal marshes, as opposed to riverine marshes which form at the mouth of rivers such as the Altamaha. The salt marsh sediments consist mainly of reworked Pleistocene muds, eroded and redeposited by the tidal currents.

The marshes of the Georgia coast are in approximate dynamic equilibrium with sea level at present, with deposition being balanced by erosion and sea level change. Erosion and meandering of tidal creek banks is caused by tidal action, slumping and bioturbation. Erosion varies greatly from one location to another, but changes in the position of major channels are rare.