The Mystery of the Carolina Bays

First Aerial Photo of the Carolina Bays taken in 1930's

When viewed from above, much of the landscape of South Carolina is clearly covered in mysterious oval depressions that aren’t obvious from ground level. Known as “Carolina Bays”, nobody really knows how these unique geological features were formed. Carolina bays are elliptical depressions concentrated along the Atlantic seaboard within coastal Delaware, Maryland, New Jersey, North Carolina, South Carolina, Virginia, Georgia, and north central Florida. In Maryland, they are called Maryland Basins.

Carolina bays are isolated wetlands in natural shallow depressions that are largely fed by rain and shallow groundwater. Carolina bays vary in size from one to several thousand acres. About 500,000 of them are present in the classic area of the Atlantic Coastal Plain. Often found in groups, these bays have an elliptical shape and generally a northwest to southeast orientation. The bays have many different vegetative structures, based on the depression depth, size, hydrology, and subsurface. Many are marshy; a few of the larger ones are (or were before drainage) lakes. Some bays are predominantly open water with large scattered pond cypress, while others are composed of thick, shrubby areas, with vegetation growing on floating peat mats. Generally the southeastern end has a higher rim composed of white sand.

Average water depth and soil type have a large influence on the types of plants found in and around Carolina bays. They are named for the bay trees frequently found in them Many bays also contain trees such as black gum, sweet gum, magnolia, bald cypress and maple, and shrubs such as sumac, button bush, gallberry and red bay. Also common in Carolina bays are water lilies, sedges and various grasses.

A popular theory from the 1930s and ’40s held that they were formed all at the same time by a prehistoric meteor shower. However, only a couple of meteor fragments have been found in or near Carolina bays. Alternative, more exotic theories have linked the Carolina bays to glaciers, to Artesian wells, to Indian tribes collecting and burning peat or to swirling schools of spawning fish while the Coastal Plain was submerged by the Atlantic Ocean before the Ice Ages. Currently, the consensus theory holds that the bays formed from pools of water, left behind by the receding ocean, which were then sculpted into their consistent oval shapes by prevailing winds.