They’re not really bays — often, they don’t even have water in them — and they’re not all in North and South Carolina, although eastern North Carolina contains up to 80 percent of them. Carolina bays are, nevertheless, a crucial feature of the Cape Fear region, and their origins pose one of its foremost mysteries.
Carolina bays are shallow, sand-lined depressions, almost uniformly oval-shaped and almost always oriented along a uniform northwest-to-southeast axis. Most are only a few hundred, or perhaps a few thousand, feet in diameter, although Lake Waccamaw in Columbus County — generally considered the largest known Carolina bay — covers 8,938 acres and has 14 miles of shoreline. About 900 are of notable size.
Bladen County has the largest concentration of Carolina bays, with more than 1,200 known. White Lake, Jones Lake, Singletary Lake and Bay Tree Lakes are all examples of Carolina bay lakes. Carolina bays are also found in New Hanover, Brunswick and Pender counties, though. Many Wilmington neighborhoods — notably, Pine Valley — were built over former Carolina bay areas. Three small Carolina bays lie within Wilmington’s Halyburton Park. A number of Carolina bay bogs also lie in the vicinity of Boiling Spring Lakes in Brunswick County.
As many as 500,000 Carolina bays, however, are scattered in an arc from southern New Jersey, Delaware and Maryland (where they’re sometimes called “Maryland basins”) all the way to Georgia and north-central Florida; most can be found in the Coastal Plain between Fayetteville and Darlington, S.C. Some sources claim they are related to the “Grady ponds” or “Citronelle ponds” of Alabama and Mississippi. Various efforts have been made to link them to networks of oriented lakes in other parts of the world.
The name comes from the number of species of bay trees — sweet bay, loblolly bay and red bay — which often grow in profusion near the bays. Longleaf pines are often common near Carolina bays, and because their soil often highly acidic and nutrient poor, Carolina bays are often home to insectivorous plants, such as the Venus’ flytrap, bladderwort, butterwort and sundew.
Many of the bays are not lakes but bogs or periodic wetlands. As such, they are often important to migrating waterfowl, such as herons, egrets and wood storks. Dragonflies, green anole lizards and green tree frogs are often abundant in Carolina bay areas. In some drained-out bays, the peat at the bottom will extend to a depth of 11 to 50 feet. Below the peat is generally a rim or natural lining of white sand.
The unique nature of Carolina bays was first noted by South Carolina geologist Michael Toumey in 1849, followed by geologist L.C. Glenn in 1895, although their uniform orientation did not become clear until aerial photographs became available in the 1930s.
No completely satisfactory explanation has been found for why Carolina bays formed, or why they share the same orientation.
A popular theory from the 1930s and ’40s held that they were formed all at the same time by a prehistoric meteor shower. (Intriguingly, a Waccamaw Siouan legend tells how a bright ball from the sky created Lake Waccamaw.) William F. Prouty, the longtime chairman of the geology department at the University of North Carolina at Chapel Hill, spent years trying to prove the meteor-impact hypothesis, and a 1933 article in Harper’s magazine, “The Comet That Hit the Carolinas,” did much to popularize the theory.
Other geologists, however, noted that only a couple of meteor fragments have been found in or near Carolina bays. (In North Carolina, most meteorites are found farther inland, in the Piedmont.) Magnetic field surveys of the bays, moreover, do not match up with the results found for known meteor craters. In recent years, the impact theory has been revived, with some geologists suggesting that the culprit was a comet, similar to the Tunguska event in Siberia in 1908. (Comets, which are largely made of frozen gas, would have left few traces.)
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.
Radiocarbon dating of Carolina bay sediments have yielded ages of 27,000 to 50,000 years, with a considerable margin of error. Dating by the Optically Stimulated Luminescence (OSL) method have found sand rims of some Carolina bays as sold as 80,000 to 100,000 years. (Some sources claim Lake Waccamaw is as much as 250,000 years old.)
For more information, see the University of Georgia “Carolina Bays Fact Sheet.”
Date posted: April 29, 2009