South Carolina, USA — Were they formed by the impact of a meteor striking the Earth or are they merely sink holes? The answer to how Carolina bays were formed is not something about which scientists agree.
Carolina bays are geological depressions of mysterious origin that occur throughout the Coastal Plain of the Carolinas and Georgia. They take their name from the evergreen bay trees that typically characterize them.
On March 19, Dr. Richard Porcher, a professor of biology and director of the herbarium at The Citadel, gave a presentation on Carolina bays to the Friends of Santee National Wildlife Refuge.
Porcher is an authority on the flora of South Carolina and the author of Wildflowers of the Carolina Low Country and Lower Pee Dee and co-author of A Guide to the Wildflowers of South Carolina and Low Country: The Natural Landscape.
First described around 1750 by naturalist John Bartram, a large concentration of Carolina bays is found in South Carolinas coastal plain, some 4,000, but they also occur in southeastern North Carolina and northeastern Georgia, Porcher said.
Carolina bays are isolated wetlands in natural shallow depressions, which are largely fed by rain and shallow groundwater, he said. These elliptical-shaped bays generally have a northwest to southeast orientation and vary in size from less than an acre to many acres, Porcher said. Water levels are normally lowest in autumn and highest in early spring, he said, adding that some Carolina Bays are wet all year while others fill with water, then dry up, depending on the season.
Carolina bays are wetlands that are not associated with moving water. These wetlands are rich in wildlife. I would not even begin to talk about the wildlife, amphibians, reptiles and other animals. That is a whole different field, he said.
Different researchers believe Carolina bays are 30,000 to 100,000 years old or older, Porcher said, yet scientists are not certain of their origins. One theory suggests that a meteor hit Earth thousands of years ago, breaking into pieces that made dents as they skipped across the planets surface, he said, noting that this is not a theory he accepts.
The bays are clumped and not randomly located. I have used this against a shower of meteorites because a shower of meteorites would seem to form a random pattern. These bays are discretely in certain areas, and even in a clump they seem to march in a line, Porcher said. To me, it is difficult to get that type of pattern from a shower of meteorites.
He said one of the features of the Carolina bays is normally that they have a high, elevated sand ridge along their southeastern side. In keeping with the meteorite theory, the meteorite struck and pushed out a depression, Porcher said, and as it struck, it pushed up a sand ridge. Some of these elevations have multiple sand ridges.
So, if you believe a meteorite hit, you have to believe a meteorite struck here and pushed up the first ridge. Another struck right behind it and pushed up the second and so on, he said. Some of these bays have six or seven ridges.
Another theory on the creation of Carolina bays is that they were formed over a long period of time. Some think they were formed by artisan wells, or sink holes. However, as Porcher explained, there are holes is all these theories, so the bottom line is no one theory holds water. They are puzzling, unsolved, geological phenomena, he said.
The majority of the bays have been drained for farmland, Porcher said, adding that there are two types of bays, a clay base and a peat base. The clay base holds water for a longer period of time, he said, and the plants have a period of time to establish. The peat bay has a deep layer of peat that protects the plants and gives them water during the dry season.
Porcher led a field trip to Carolina bay near the Santee National Wildlife Refuge. He explained that the bays have to be burned off periodically to reduce tree growth in the bay. The last time the area bay caught onfire, July 4, the fire was so hot and the smoke so thick that the blaze had to be extinguished to reduce the smoke along Interstate 95, Porcher said. This prevented the purging of the wood growth in the bay, so the eastern portion of the bay has wood growth along its banks.
One of the benefits of the Carolina bays is to hold water during times of high rains, Porcher said. The bays can hold a large amount of water and will prevent flooding along the coastlines, he said.
Currently, there is a program to restore the bays that have been damaged by farming, Porcher said. The benefits of Carolina bays helping to prevent flood have been recognized, he said, and efforts to restore as many bays as possible are under way.