Carolina bays are elliptical to circular depressions concentrated along the

East Coast of the United States The East Coast of the United States, also known as the Eastern Seaboard, the Atlantic Coast, and the Atlantic Seaboard, is the region encompassing the coast, coastline where the Eastern United States meets the Atlantic Ocean; it has always pla ...

within coastal

New York New York most commonly refers to: * New York (state), a state in the northeastern United States * New York City, the most populous city in the United States, located in the state of New York New York may also refer to: Places United Kingdom * ...

New Jersey New Jersey is a U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

Delaware Delaware ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic and South Atlantic states, South Atlantic regions of the United States. It borders Maryland to its south and west, Pennsylvania to its north, New Jersey ...

Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...

Virginia Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

South Carolina South Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders North Carolina to the north and northeast, the Atlantic Ocean to the southeast, and Georgia (U.S. state), Georg ...

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

, and north

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

.Kaczorowski, R. T. (1977) ''The Carolina Bays: a Comparison with Modern Oriented Lakes'' Technical Report no. 13-CRD, Coastal research Division, Department of Geology, University of South Carolina, Columbia. In Maryland, they are called Maryland basins. Within the

Delmarva Peninsula The Delmarva Peninsula, or simply Delmarva, is a peninsula on the East Coast of the United States, occupied by the majority of the state of Delaware and parts of the Eastern Shore of Maryland and Eastern Shore of Virginia. The peninsula is l ...

, they and other coastal ponds are also called Delmarva bays.Coleman, D. (2001
''Delmarva Bays: Natural Enigmas.''Maryland Department of Natural Resources
, Annapolis. Maryland.

Origin of name

The name "Carolina bay" is sometimes attributed to the writings of the English explorer John Lawson, who explored North Carolina, South Carolina, and Georgia during the early 18th century. This attribution, however, is not correct. Lawson described visiting a swamp that contained bay trees, but there is no indication that he wanted to name the swamp with the word "bay". Furthermore, Lawson said that this swamp had steep margins and that he could see mountains to the west from the vicinity of the swamp. Thus, it seems more likely that this swamp was an inter-dune depression among the

Carolina Sandhills The Sandhills or Carolina Sandhills is a 10-35 mi wide physiographic region within the U.S. Atlantic Coastal Plain province, along the updip (inland) margin of this province in the states of North Carolina, South Carolina, and Georgia. The e ...

, rather than a Carolina bay. Nevertheless, bay trees are present in some Carolina bays. The earliest scientific description of Carolina bays is by L. C. Glenn (1895), who used the term "bay" (which he described as "lake-like expanses") to refer to these features near the town of

Darlington, South Carolina Darlington is a city located in Darlington County, South Carolina, United States. In 2010, its population was 6,289. It is the county seat of Darlington County. It is part of the Florence, South Carolina metropolitan area. Darlington is known f ...

. Glenn put quotation marks around the word "bay" but did not use the phrase "Carolina bay". A subsequent publication by F.A.Melton and William Schriever (1933) used the phrase "The Carolina Bays" (with quotation marks around the word "Bays"). Later, G. R. MacCarthy (1937) published a paper titled "The Carolina Bays", using this phrase throughout the publication (without quotation marks, and with a capital "B" for the word "Bays").

Geographic extent

Carolina bays are present in the U.S.

Atlantic Coastal Plain The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

from New York to north Florida. In Maryland, they are called Maryland basins. Within the

, they and other coastal ponds are also called Delmarva bays.

Geomorphology

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, many in groups aligned in a northwest–southeast direction. Generally, the southeastern end has a higher rim composed of white sand.

Orientation

According to published papers and monographs, the average trend of the long axes of Carolina Bays varies from N16°W in east-central Georgia to N22°W in southern South Carolina, N39°W in northern South Carolina, N49°W in North Carolina, and N64°W in Virginia. Within this part of the Atlantic Coastal Plain, the orientation of the long axes of Carolina bays varies by 10 to 15 degrees. If the long axes of these Carolina bays, as measured by Johnson (1942), are projected westward, then they generally converge in the area of southeastern

Indiana Indiana ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Michigan to the northwest, Michigan to the north and northeast, Ohio to the east, the Ohio River and Kentucky to the s ...

and southwestern

Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...

. At the northern end of the distribution of Carolina bays, within the

and

, the average orientation of the long axes abruptly shifts by about 112 degrees to N48°E. Farther north, the orientation of the long axes becomes, at best, distinctly bimodal, exhibiting two greatly divergent directions, and, at worst, completely random, lacking any preferred direction. Plate 3 of Rasmussen and Slaughter,Rasmussen, W. C., and T. H. Slaughter (1955) "The ground water resources, in The water resources of Somerset, Wicomico, and Worcester Counties". ''Bulletin no. 16'', Maryland Geological Survey, Baltimore, Maryland. which is reproduced as Figure 51 of Kacrovowski, illustrates the disorganized nature of the orientations of the long axes of Carolina bays in

Somerset Somerset ( , ), Archaism, archaically Somersetshire ( , , ) is a Ceremonial counties of England, ceremonial county in South West England. It is bordered by the Bristol Channel, Gloucestershire, and Bristol to the north, Wiltshire to the east ...

, Wicomico, and

Worcester Worcester may refer to: Places United Kingdom * Worcester, England, a city and the county town of Worcestershire in England ** Worcester (UK Parliament constituency), an area represented by a Member of Parliament * Worcester Park, London, Engl ...

counties, Maryland. At the southern end of their distribution, the Carolina bays in southern Georgia and northern Florida are approximately circular in shape. In this area, they have a weak northerly orientation.

Stratigraphic setting

Most Carolina bays consist of a few meters of sand and/or mud that rest on an

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...

above a harder

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

that does not show signs of deformation or other disturbance. The composition and the age of this harder substrate varies from location to location.

Stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithost ...

relations of some Carolina bays with fields of eolian dunes in river valleys suggest that Carolina bays formed episodically during different times at different places. For example: :In some places, Carolina bays are inset into fields of eolian dunes in river valleys, and thus these Carolina bays must be younger than the underlying eolian dunes. One such example is Dukes Pond, which is a Carolina bay that is inset into eolian dunes in the valley of the

Ohoopee River The Ohoopee River is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed April 21, 2011 river in east-central Georgia in the United States. It is a tributary of the Altamaha River, which ...

( Tattnall County, Georgia). These eolian dunes have yielded an optically stimulated luminescence date of ~23,600 years, and thus this Carolina Bay must be younger than this OSL date. Another example is Bear Swamp, which is a Carolina bay that is inset into eolian dunes in the valley of the

Great Pee Dee River The Pee Dee River, also known as the Great Pee Dee River, is a river in the Carolinas of the United States. It originates in the Appalachian Mountains in North Carolina, where its upper course, above the mouth of the Uwharrie River, is known a ...

( Marion County, South Carolina). :In other places, Carolina bays are overlain by eolian dunes that are now vegetated, and thus these Carolina bays must be older than the overlying eolian dunes. One such example is Big Bay, which is a Carolina bay that is overlain by eolian dunes in the valley of the

Wateree River } The Wateree River, about 75 mi (120 km) long, is a tributary of the Santee River in central South Carolina in the United States, which flows to the Atlantic Ocean. It was named for the Wateree Native Americans, a tribe who had migrat ...

( Sumter County, South Carolina). These eolian sand dunes at Big Bay have been dated by optically stimulated luminescence techniques at 29,600 ± 2,400 to 33,200 ± 2,800 BP, and thus this Carolina bay must be older than these dates.

Stratigraphy within the Carolina bays and sand ridges

Cores taken within several Carolina bays have revealed a stratigraphy of a few meters of sand and/or mud resting on a unconformity above a harder substrate. Carolina bays for which the stratigraphy has been described in some detail include

Lake Mattamuskeet Lake Mattamuskeet is the largest natural lake in North Carolina. It is a shallow coastal lake, averaging 2–3 ft (0.61–0.91 m) feet in depth, and stretches long and wide. Lake Mattamuskeet lies on the Albemarle-Pamlico Peninsula. Lak ...

( Hyde County, North Carolina), Wilson's Bay ( Johnston County, North Carolina), Herndon Bay (

Robeson County Robeson County ( )Talk Like a Tarheel
, from the North Carolina C ...

, North Carolina), Big Bay (Sumter County, South Carolina), Flamingo Bay ( Aiken County, South Carolina), and Duke's Pond (Tattnall County, Georgia). Lake Mattamuskeet (Hyde County, North Carolina): Cores from within this Carolina bay revealed a 0.3–1.2 m thick unit of sand and silty sand (lacustrine deposits and paleosols) that rests on an unconformity above an undisturbed unit of gray clay and sandy clay (with marine shells and burrows) of Pleistocene age. Cores from the adjacent sand rims revealed a 2.6–2.9 m thick unit of silt, sand silt, and silty sand (interpreted as paleosols, shoreline, loess, and eolian deposits) that rests on an unconformity above an undisturbed unit of gray clay and sandy clay (with marine shells and burrows) of Pleistocene age (the same unit that was encountered in cores from within the Carolina bay). Charcoal and wood from a western sand rim (closer to the bay) yielded radiocarbon ages of ~5,760 and 1,270 years before present (BP). Organic sediment and charcoal from an eastern sand rim (farther from the bay) yielded radiocarbon ages ranging from ~7,750 to 2,780 years BP. Wilson's Bay (Johnston County, North Carolina): Cores and augers from within this Carolina bay revealed a 1.5–3.2 m thick unit of sand, sandy silt, and silty sand (lacustrine deposits) that rests on an unconformity above an undisturbed unit of saprolite (weathered felsic gneiss). These lacustrine deposits yielded a radiocarbon age of ~21,920 years BP. Cores and augers from the adjacent sand rims revealed a 1.5–4.0 m thick unit of muddy sand, sand, and gravel that rests on an unconformity above an undisturbed unit of saprolite/weathered felsic gneiss (the same unit that was encountered in cores from within the Carolina bay). Organic material within the bay yielded an age of ~21,920 radiocarbon years BP. Herndon Bay (Robeson County, North Carolina): Cores drilled into four different sand ridges associated with this Carolina bay revealed that the sand ridges are composed of 2.5–4.5 m thick accumulations of fine to coarse sand that rest on an unconformity above an undisturbed unit of black mud of Cretaceous age (Black Creek Formation). Sediment samples from sand rims associated with this Carolina bay have yielded three optically stimulated luminescence (OSL) ages of ~36,700 years ago; ~29,600 years ago; and ~27,200 years ago. Big Bay (Sumter County, South Carolina): A core (drill hole D1/2) drilled within this Carolina bay went through the following units: (1) Drilling depth 0 to 4.5 m = eolian sand sheet that overlies the Carolina bay; (2) Drilling depth 4.5 to 9.0 m = silty sand and sandy mud with abundant organic material; and (3) Drilling depth 9.0 to 10.6 m = sandy clay of Pliocene age (Duplin Formation). Sediment samples from sand rims associated with this Carolina bay have yielded four optically stimulated luminescence (OSL) ages of ~35,700 years ago; ~25,200 years ago; ~11,200 years ago; and ~2,100 years ago. Within cores of undisturbed sediments recovered from Big Bay, North Carolina, Brook and others documented well-defined pollen zones consisting of distinct pollen assemblages. They found a stratigraphically consistent series of pollen zones, which increased in age consistently with depth from Holocene Stage to the Wisconsin Stage, back into

marine isotope stage Marine isotope stages (MIS), marine oxygen-isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth's paleoclimate, deduced from Oxygen isotope ratio cycle, oxygen isotope data derived from deep sea core ...

5 Flamingo Bay (Aiken County, South Carolina): A core (C1) taken within this Carolina bay revealed a 0.94 m thick unit of quartz sand that rests on an unconformity (paleosol) above an undisturbed unit of sandy silt and clay of Eocene age. Charcoal samples within the 0.94 m thick unit of quartz sand yielded radiocarbon ages of ~4,500 to 2,500 years BP. A core (P25) taken from adjacent sand rim revealed a 1.85 m thick unit of Quaternary sand that rests on an unconformity (paleosol) above an undisturbed unit of sandy silt and clay of Eocene age (the same unit that was encountered in core C1 from within the Carolina bay). Moore et al. (2012) reported that sediment samples from sand ridges associated with this Carolina bay have yielded five OSL ages of ~15,000 years ago; ~13,100 years ago; ~11,500 years ago; ~9,200 years ago; and ~5,000 years ago. Brooks et al. (2010) reported that sediment samples from sand ridges associated with this Carolina Bay yielded OSL ages of ~108,700 years ago; and ~40,300 years ago. Duke's Pond (Tattnall County, Georgia): A sediment sample from a sand rim at the margin of this Carolina has yielded an OSL age of ~23,600 years ago. Basal peat bog sediment within this Carolina bay yielded an age of ~8,600 radiocarbon years ago.

Additional notes on stratigraphy

In a study of several Carolina bays in North Carolina, Gamble et al. (1977) stated that drilling and coring indicated that the bedding and sediments underlying Carolina bays are undisturbed. Studies by Frey, Watts, and Whitehead have also documented that the sediments filling Carolina bays are generally undisturbed. Several cores have found that the sediments that fill Carolina bays have distinct and conformably layers or beds. The dating of the sand rims of a number of Carolina bays by optically stimulated luminescence (OSL) techniques has yielded ages ranging from ~109,000 to ~2,000 years ago, but most ages from the sand rims range from ~40,000 to ~11,000 years ago.Savannah River Archaeological Research Program Staff (2010) ''Annual review of Cultural Resource Investigations by Savannah River Archaeological Research Program.'' South Carolina Institute of Archaeology and Anthropology, Columbia, South Carolina. Radiocarbon dates have been obtained from organic matter collected from the undisturbed sediments filling Carolina bays by Bliley and Burney, Mixon and Pilkey,Mixon, R. B., and O. H. Pilkey, 1976, ''Reconnaissance geology of the submerged and emerged Coastal Plain province, Cape Lookout area, North Carolina''. Professional Paper no. 859, U. S. Geological Survey, Reston, Virginia. Thom, and Kaczorowski. Some radiocarbon dates obtained from organic matter within undisturbed sediments are greater than 14,000 BP radiocarbon in age. The radiocarbon dates range from 27,700 ±2,600 to 440 ± 50 radiocarbon years BP. Some cores have contained organic matter that was too old for dating by radiocarbon methods, resulting in "greater than" dates. For example, samples from some Carolina bays have been dated at greater than 38,000 to 49,550 radiocarbon years BP. In cases where multiple radiocarbon dates have been determined from a single core, most radiocarbon dates are typically consistent in terms of their

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithost ...

position within a core, and accumulation rates calculated from them only are rarely anomalous. Given the nature of radiocarbon dating, discordant dates occasionally occur even in undisturbed deposits, when multiple samples were dated. The occasional discordant dates by themselves are meaningless as an indicator of disturbance. The intact internal stratigraphy of the Carolina bay sediments, as indicated by paleosols and pollen zones (e.g. Big Bay) refutes such arguments. As discussed by Gaiser, radiocarbon dates reported from any Carolina bay are minimum dates for their formation. The radiocarbon dates only represent times during which organic matter accumulated and was preserved in Carolina bays. At other times, datable organic matter either might not have been preserved as sediment accumulated within them, or older organic matter might have been destroyed when the bays dried out. During times when the water table was below the bottom of a Carolina bay (e.g., possibly during glacial periods when

sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...

was 130 meters (400 ft) below present), organic matter could have been destroyed by oxidization and weathering. Also, during such times, eolian processes could have eroded any existing sediments at the bottom of Carolina bays. There are some who suggest that the oldest radiocarbon date from a Carolina bay only indicates the time when the water table rose high enough for a permanent lake or swamp to exist within it. This interpretation, however, may depend upon the nature of the overlying sediment. For example, eolian processes can bury and preserve organic matter, and thus the preservation of organic matter can occur independently of water table behavior.

Ecological significance and biodiversity

The bays have many different vegetative structures, based on the depression depth, size,

hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydro ...

, and subsurface. Many are marshy; a few of the larger ones are (or were before drainage) lakes;

Lake Waccamaw Lake Waccamaw is a fresh water lake located in Columbus County, North Carolina, Columbus County in North Carolina. It is the largest of the natural Carolina Bay lakes. Although bay trees (''Magnolia virginiana L.'', ''Gordonia lasianthus Elli ...

is an undrained example. Some bays are predominantly open water with large scattered pond cypress, while others are composed of thick, shrubby areas (

pocosin Pocosin is a type of palustrine wetland with deep, acidic, sandy, peat soils. Groundwater saturates the soil except during brief seasonal dry spells and during prolonged droughts. Pocosin soils are nutrient-deficient (oligotrophic), especially in ...

s), with vegetation growing on floating peat mats. The bays are especially rich in

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

, including some rare and/or

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

. Species that thrive in the bays'

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

s include birds, such as

wood stork The wood stork (''Mycteria americana'') is a large wading bird in the family (biology), family Ciconiidae (Ciconiiformes, storks). Originally described in 1758 by Carl Linnaeus, this stork is native to the subtropics and tropics of the Americas ...

heron Herons are long-legged, long-necked, freshwater and coastal birds in the family Ardeidae, with 75 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genus ''Botaurus'' are referred to as bi ...

egret Egrets ( ) are herons, generally long-legged wading birds, that have white or buff plumage, developing fine plumes (usually milky white) during the breeding season. Egrets are not a biologically distinct group from herons and have the same build ...

s, and other migratory

waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which i ...

, mammals such as

deer A deer (: deer) or true deer is a hoofed ruminant ungulate of the family Cervidae (informally the deer family). Cervidae is divided into subfamilies Cervinae (which includes, among others, muntjac, elk (wapiti), red deer, and fallow deer) ...

, black bears,

raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the North American, northern or common raccoon (also spelled racoon) to distinguish it from Procyonina, other species of raccoon, is a mammal native to North America. It is the largest ...

skunk Skunks are mammals in the family Mephitidae. They are known for their ability to spray a liquid with a strong, unpleasant scent from their anal glands. Different species of skunk vary in appearance from black-and-white to brown, cream or gi ...

s, and

opossums Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North A ...

. Other residents include

dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of dragonflies are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threate ...

green anole ''Anolis carolinensis'' or green anole () (among other names below) is a tree-dwelling species of anole lizard native to the southeastern United States and introduced to islands in the Pacific and Caribbean. A small to medium-sized lizard, the g ...

s and green

tree frog A tree frog (or treefrog) is any species of frog that spends a major portion of its lifespan in trees, known as an arboreal state. Several lineages of frogs among the Neobatrachia suborder have given rise to treefrogs, although they are not clos ...

s. The bays contain trees such as

black gum Black gum may refer to several species of plants: * ''Nyssa sylvatica ''Nyssa sylvatica'', commonly known as tupelo, black tupelo, black gum or sour gum, is a medium-sized deciduous tree native to eastern North America from the coastal Northeas ...

bald cypress ''Taxodium distichum'' (baldcypress, bald-cypress, bald cypress, swamp cypress; ; ''cipre'' in Louisiana) is a deciduous conifer in the family Cupressaceae. It is native to the southeastern United States. Hardy and tough, this tree adapts to a w ...

, pond cypress, sweet bay, loblolly bay, red bay,

sweet gum ''Liquidambar'', commonly called sweetgum (star gum in the UK), gum, redgum, satin-walnut, styrax or American storax, is the only genus in the flowering plant family Altingiaceae and has 15 species. They were formerly often treated as a part of ...

maple ''Acer'' is a genus of trees and shrubs commonly known as maples. The genus is placed in the soapberry family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated si ...

magnolia ''Magnolia'' is a large genus of about 210 to 340The number of species in the genus ''Magnolia'' depends on the taxonomic view that one takes up. Recent molecular and morphological research shows that former genera ''Talauma'', ''Dugandiodendr ...

pond pine ''Pinus serotina'', the pond pine, black bark pine, bay pine, marsh pine, or pocosin pine, is a pine tree found along the Southeastern portion of the Atlantic coastal plain of the United States, from southern New Jersey south to Florida and west t ...

, and shrubs such as fetterbush,

clethra ''Clethra'' is a genus of flowering shrubs or small trees described as a genus by Linnaeus in 1753.sumac Sumac or sumach ( , )—not to be confused with poison sumac—is any of the roughly 35 species of flowering plants in the genus ''Rhus'' (and related genera) of the cashew and mango tree family, Anacardiaceae. However, it is '' Rhus coriaria ...

, button bush,

zenobia Septimia Zenobia (Greek: Ζηνοβία, Palmyrene Aramaic: , ; 240 – c. 274) was a third-century queen of the Palmyrene Empire in Syria. Many legends surround her ancestry; she was probably not a commoner, and she married the ruler of the ...

, and gallberry. Plants common in Carolina bays are

water lilies ''Water Lilies'' ( ) is a series of approximately 250 oil paintings by French Impressionist Claude Monet (1840–1926). The paintings depict his flower garden at his home in Giverny, and were the main focus of his artistic production during ...

sedges The Cyperaceae () are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large; botanists have described some 5,500 known species in about 90 generathe largest being the "true sedges" (genu ...

and various

grasses Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivated in ...

. Several carnivorous plants inhabit Carolina bays, including

bladderwort ''Utricularia'', commonly and collectively called the bladderworts, is a genus of carnivorous plants consisting of approximately 233 species (precise counts differ based on classification opinions; a 2001 publication lists 215 species).Salmon, Br ...

butterwort ''Pinguicula'', commonly known as butterworts, is a genus of carnivorous flowering plants in the family Lentibulariaceae. They use sticky, glandular leaves to lure, trap, and digest insects in order to supplement the poor mineral nutrition they ...

pitcher plant Pitcher plants are carnivorous plants known as pitfall traps—a prey-trapping mechanism featuring a deep cavity filled with digestive liquid. The traps of pitcher plant are considered to be "true" pitcher plants and are formed by specialized ...

, and

sundew ''Drosera'', which is commonly known as the sundews, is one of the largest genera of carnivorous plants, with at least 194 species. 2 volumes. These members of the family Droseraceae lure, capture, and digest insects using stalked mucilaginous ...

. Some bays have been greatly modified by human activities including

farming Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...

, highway building, and construction of housing developments and

golf course A golf course is the grounds on which the sport of golf is played. It consists of a series of holes, each consisting of a teeing ground, tee box, a #Fairway and rough, fairway, the #Fairway and rough, rough and other hazard (golf), hazards, and ...

s. For example, Carvers Bay, a large bay in

Georgetown County, South Carolina Georgetown County is a County (United States), county located in the U.S. state of South Carolina. As of the 2020 United States census, 2020 census, the population was 63,404. Its county seat is Georgetown, South Carolina, Georgetown. The count ...

, was used as a

bomb A bomb is an explosive weapon that uses the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-transmitted mechan ...

ing practice range during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

. It has been drained and is mostly used for

tree farming A tree plantation, forest plantation, plantation forest, timber plantation, or tree farm is a forest planted for high volume production of wood, usually by planting one type of tree as a monoculture forest. The term ''tree farm'' also is used to ...

today. Others are used for

vegetable Vegetables are edible parts of plants that are consumed by humans or other animals as food. This original meaning is still commonly used, and is applied to plants collectively to refer to all edible plant matter, including edible flower, flo ...

or field

crops A crop is a plant that can be grown and harvested extensively for profit or subsistence. In other words, a crop is a plant or plant product that is grown for a specific purpose such as food, fibre, or fuel. When plants of the same species a ...

with

drainage Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess water. The internal drainage of most agricultural soils can prevent severe waterlogging (anaerobic conditions that harm root gro ...

. A study of bays located on the Delmarva peninsula estimated that 70% had been partially or fully converted to agriculture. In South Carolina, Woods Bay, on the

Sumter Sumter may refer to: People Given name * Sumter S. Arnim (1904–1990), American dentist * Sumter de Leon Lowry Jr. (1893–1985), United States Army general Surname * Rowendy Sumter (born 1988), Curaçaoan footballer * Shavonda E. Sumt ...

Florence Florence ( ; ) is the capital city of the Italy, Italian region of Tuscany. It is also the most populated city in Tuscany, with 362,353 inhabitants, and 989,460 in Metropolitan City of Florence, its metropolitan province as of 2025. Florence ...

county line near Olanta, was designated a

state park State parks are parks or other protected areas managed at the sub-national level within those nations which use "Federated state, state" as a political subdivision. State parks are typically established by a state to preserve a location on accou ...

to preserve it as much as possible in its natural state. Also, 66 Bennett's Bay, near

Manning Manning (a.k.a. Mannion, Manning) is a family name. Origin and meaning Manning is from an old Norse word — manningi — meaning a brave or valiant man; and one of the first forms of the name was Mannin; another cartography was Mannyg ...

, in

Clarendon County, South Carolina Clarendon County is a county located below the fall line in the Coastal Plain region of U.S. state of South Carolina. As of the 2020 census, its population was 31,144. Its county seat is Manning. This area was developed for lumber and mills ...

, is a designated Heritage Preserve. Another bay in

Bamberg County, South Carolina Bamberg County is a county located in the southwestern portion of U.S. state of South Carolina. As of the 2020 census, the population was 13,311, making the rural county the fourth-least populous of any in South Carolina. Its county seat is B ...

is owned by the South Carolina Native Plant Society, which has been developing a preserve called the Lisa Matthews Memorial Bay, which is trying to preserve and increase the federally endangered wildflower '' Oxypolis canbyi'' (Canby's Dropwort) in the bay. The uplands area surrounding the bay is being restored from a

loblolly pine ''Pinus taeda'', commonly known as loblolly pine, is one of several pines native to the Southeastern United States, from East Texas to Florida, and north to southern New Jersey. The wood industry classifies the species as a southern yellow pi ...

plantation to the original

longleaf pine The longleaf pine (''Pinus palustris'') is a pine species native to the Southeastern United States, found along the coastal plain from East Texas to southern Virginia, extending into northern and central Florida. In this area it is also known as ...

. Included in the longleaf restoration is the restoration of wiregrass (''Aristida beyrichiana'') as a key understory plant. Its flammability aids in periodic burning, which is necessary for Canby's Dropwort and many of the other species unique to the environment.

Interpretations (theories of origin)

Most geologists today interpret the Carolina bays as relict geomorphological features that developed via various eolian and

lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

processes. Multiple lines of evidence, e.g.

radiocarbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotop ...

optically stimulated luminescence In physics, optically stimulated luminescence (OSL) is a method for measuring doses from ionizing radiation. It is used in at least two applications: * Luminescence dating of ancient materials: mainly geological sediments and sometimes fired pot ...

dating, and

palynology Palynology is the study of microorganisms and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and occur in sediments, sedimentary rocks, and even some metasedimentary rocks. Palynomorphs are the mic ...

, indicate that the Carolina bays predate the start of the

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

. Fossil pollen recovered from cores of undisturbed sediment taken from various Carolina bays in North Carolina by Frey, Watts, and Whitehead document the presence of full glacial pollen zones within the sediments filling some Carolina bays. The range of dates can be interpreted that Carolina bays were either created episodically over the last tens of thousands of years or were created at time over a hundred thousand years ago and have since been episodically modified.

Relict thermokarst lakes

Recent work by the U.S. Geological Survey has interpreted the Carolina bays as relict

thermokarst Thermokarst is a type of terrain characterised by very irregular surfaces of marshy hollows and small hummocks formed when ice-rich permafrost thaws. The land surface type occurs in Arctic areas, and on a smaller scale in mountainous areas such ...

lakes that have been modified by eolian and

processes. Modern thermokarst lakes are common today around Barrow (Alaska), and the long axes of these lakes are oblique to the prevailing wind direction. These lakes develop by thawing of frozen ground, with subsequent modification by wind and waves. Thus, the interpretation of Carolina bays as relict thermokarst lakes implies that frozen ground once extended as far south as the Carolina bays. This interpretation is consistent with the optically stimulated luminescence dates, which suggest that the Carolina bays are relict features that formed when the climate was colder, drier, and windier. Quaternary geologists and geomorphologists state that the features of the Carolina bays can be readily explained by known terrestrial processes and repeated modification by eolian and lacustrine processes. Also, Quaternary geologists and geomorphologists have found a correspondence in time between when active modification of the rims of Carolina bays most commonly occurred and when adjacent sand dunes were active during the

Wisconsin glaciation The Wisconsin glaciation, also called the Wisconsin glacial episode, was the most recent glacial period of the North American ice sheet complex, peaking more than 20,000 years ago. This advance included the Cordilleran Ice Sheet, which nucleated ...

between 15,000 and 40,000 years (Late Wisconsin) and 70,000 to 80,000 years BP (Early Wisconsin). In addition, Quaternary geologists and geomorphologists have found that the orientations of the Carolina bays are consistent with the wind patterns that existed during the Wisconsin glaciation, as reconstructed from the orientations of parabolic dunes in river valleys. Within the Atlantic Coast Plain, the orientation of the long axes of Carolina bays and the inferred direction of movement of adjacent sand dunes, where present, are generally oblique to each other. In southern Georgia and northern Florida, the orientation is matched by an inferred west to east direction of movement of Pleistocene sand dunes.Markewich, H. W., and W. Markewich (1994) ''An overview of Pleistocene and Holocene inland dunes in Georgia and the Carolinas; morphology, distribution, age, and paleoclimate''. Bulletin no. 206, United States Geological Survey, Reston, Virginia. Northward from northern Georgia to Virginia, the average inferred direction of movement of Pleistocene parabolic sand dunes systematically shifts along with the average orientation of the long axes of Carolina bays as to lie oblique to them. In the Delmarva Peninsula, the 112-degree shift in the average trend of the long axes also corresponds with a shift in the average inferred direction of movement of Pleistocene parabolic sand dunes such that their direction of movement is also oblique to the long axes, as is the case in the rest of the Atlantic Coastal Plain.

Alternative interpretations

Many alternative hypotheses have been proposed for the origin of the Carolina Bays and been examined and that are either no longer or never were viewed favorably by most geologists. These hypotheses include their origin as spring basins, enclosed soundlets, groundwater solution depressions, artesian springs, salmon redds, streamlined groundwater flow forming limestone sinks, deflation hollows, intersecting river terraces, burning peat leading to subsidence, wind modified and ponded periglacial patterned ground, and from hydrogen seepage. Some of the disfavored alternative hypotheses involve extraterrestrial events of some type. These hypotheses include meteorite impacts; shockwaves from a comet explosion; secondary impacts of glacial ice boulders ejected from a Younger Dryas impact in th Laurentide Ice Sheet; and speculative "cavitation" processes in a unproven, regional sandy, Mid-Pleistocene impact ejecta. These hypotheses are dismissed for a number of reasons including the wholesale lack of primary evidence for the extensive contemporary impact ejecta, impact processes, impactors, and suitable source impact crater for either sand or ice boulder ejecta.

Similar landforms in the Gulf of Mexico coastal plain

Other landform depressions, not widely accepted as Carolina bays, are present within the northern

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

coastal plain in southern

Mississippi Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...

and

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

, where they are known as either Grady ponds or Citronelle ponds.Bernard, H.A., and Leblanc, R.J., 1965, "Resume of the Quaternary geology of the northwestern Gulf of Mexico province", in: ''The Quaternary of the United States'' (H.E. Wright, Jr., and D.G. Frey, eds.), Princeton University Press, Princeton, New Jersey, pp. 137–185. They are also known by a variety of names such as ''pocks'', ''pock marks'', , ''lacs ronds'', and ''natural ponds.'' These features in southern Mississippi and Alabama are elliptical to roughly circular in shape. The measurement of the long axes of 200 elliptical Grady / Citronelle ponds in southwestern

Baldwin County, Alabama Baldwin County is a county located in the southwestern part of the U.S. state of Alabama, on the Gulf coast. It is one of only two counties in Alabama that border the Gulf of Mexico, along with Mobile County. As of the 2020 census, the popul ...

found a very distinct orientation tightly clustered about N25°W. Undrained depressions, circular to oval in shape and exhibiting a wide range of area and depth, are also a feature of the Gulf of Mexico coastal plain in Texas and southwest Louisiana. These depressions vary in size from in diameter. Within Harris County, Texas, raised rims, which are about high, partially enclose these depressions.Aronow, S., nda
''A Digression on the origin of some anomalous undrained depressions mostly on the Pleistocene and Pliocene surfaces in the Gulf of Mexico'' PDF version, 48 KB
Armand Bayou Watershed Working Group, The Texas Coastal Watershed Program, Houston Texas.Aronow, S., ndb
''Geomorphology and surface geology of Harris County and Adjacent parts of Brazoria, Fort Bend, Liberty, Montgomery, and Waller Counties, Texas'' PDF version, 68 KB
Armand Bayou Watershed Working Group, The Texas Coastal Watershed Program, Houston Texas.