Carolina Bays and the 

Shapes of Eddies 

By C. WYTHE COOKE 

A SHORTER CONTRIBUTION TO GENERAL GEOLOGY 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 254-I 

Presenting corroborative evidence 

that the elliptical Carolina bays 

were shaped by tidal eddies and 

that the shape of the ideal 

eddy is elliptical 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1954: 
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Sec"retary 

GEOLOGICAL SURVEY 

W. E. Wrather, Director 

For sale by the Superintendent of Documents, U. S. Government Printing Office 

Washington 25, D. C. - Price 70 cents (paper cover) 
CONTENTS 

Abstract __________________________________________ _ 

Hypotheses of origin _______________________________ _ 

Ideal outlines of an eddy ___________________________ _ 

Structures built by eddies ___________________________ _ 

Stationary tidal eddies _________________________ _ 

Eddy-built bars or Neptune's racetracks __________ _ 

Occurrence of eddy-built bars _______________________ _ 

Relation to Lhe contemporary sea leveL __________ _ 

Silver Bluff (6-foot) sea leveL ___________________ _ 

Talbot (42-foot) sea leveL ______________________ _ 

Penholoway (70-foot) sea leveL ____________ ~ ____ _ 

Page 

195 

195 

196 

199 

199 

199 

200 

200 

200 

202 

202 

Occurrence of eddy-built bars-Continued 

Wicomico (100-foot) sea leveL __________________ _ 

Okefenokee (145-foot) sea leveL ______________ -_-_ 

Sunderland (170-foot) sea leveL _________________ _ 

Coharie (215-foot) sea leveL ____________________ _ 

Hazlehurst (270-foot) sea leveL _________________ _ 

Summary _________________________________________ _ 

Practical applications ______________________________ _ 

Literature cited _________________________ --- ----- ----

Index ____________________________________________ _ 

ILLUSTRATIONS 

[Plates follow index] 

PLATE 41. Halfmoon Island and vicinity, Accomac County, Va. A low spit partly surrounding a tidal eddy. 

Page 

202 

203 

204 

204 

204 

204 

205 

205 

207 

42. Island Bay and vicinity, Accomac County, Va. Sand bars probably formed around a tidal eddy, now partly silted up. 

43. Elliptical ridges at Rumbley, Somerset County, Md. 

44. Elliptical marshes 3 miles east of Crisfield, Md. 

45. Elliptical clearings 2 miles west of Westover, Md. 

46. Pee Dee Islands, Marion County, S. C. Traces of two complementary fixed eddies. 

47. Cottonpatch Bay, Horry County, S. C. Trace of a fixed eddy. 

48. A group of bays in Horry County, S. C. Traces of eddies in a tidal lagoon. 

49. An area in Brunswick County, N. C., 4 miles northw.est of Southport. 

50. Mill Bay, Florence County, S.C. 

51. Big Sister Bay, Marion County, S. C. 

52. Big Horsepen Bay, Marion County, S.C. 

53. Jacks Bay, Darlington County, S.C. 

Page 

FIGURE 22. Axis and path of precession of a rotating disk _______ ------------------------------------------------------ 197 

23. Passive position of a rotating disk __________________ ------------------------------------------------------ 197 

24. Ideal shapes of eddies----------------------------------------------------------------------------------- 198 

25. Determination of the direction of elongation of a precessing eddy------------------------------------------- 198 

III 

293429-54 

A SHORTER CONTRIBUTION TO GENERAL GEOLOGY 

CAROLINA BAYS AND THE SHAPES OF EDDIES 

By C. WYTHE CooKE 

ABSTRACT 

All classes of matter have gyrostatic properties following the 

universal laws of motion. Liquids moving in a curved path 

react in the same way as solids, though the manifestation appears different because particles of a liquid are able to move 

independently of one another. So, if the plane of rotation of a 

liquid is tilted, the circular orbits of the particles are distorted 

into ellipses because the horizontal components of the centrifugal force vary in intensity according to the direction. 

An eddy, like a spinning flywheel, resists any couple that tends 

to alter the direction of the axis of rotation. The application 

of such a couple causes the axis either to precess or to set its 

direction parallel to the axis about which it is forced to turn. 

The rotation of the earth is constantly turning the axis of 

rotation of an eddy out of its initial direction in space. Consequently, the axis of rotation of the eddy either precesses about 

the horizontal east-west diameter of the eddy or the axis becomes 

parallel to the axis of the earth. In either position the plane 

of rotation of the eddy is tilted, and the outline of the eddy 

becomes elliptical. 

The ideal shape of a precessing eddy is an ellipse whose 

shorter diameter, b, divided by its longer diameter, a, equals the 

cosine of the latitude, f/J. The direction of elongation extends 

northwestward in the Northern Hemisphere and northeastward 

in the Southern Hemisphere at such a bearing from the north 

(a) that cot a= cos f/J. The ideal proportions of a fixed eddy 

are b: a.=sin ¢J; the direction of elongation is N. 45° W. in the 

Northern Hemisphere and N. 45° E. in the Southern. 

A sand bar, Halfmoon Island, partly surrounding a tidal eddy 

in Chesapeake Bay has the proportions and orientation of the 

ideal precessing eddy. Other bars of similar shape are more 

or less filled with salt marshes like the fresh-water bogs called 

the Carolina bays. The Carolina bays have the proportions and 

orientation approximating those of the ideal fixed eddy. They 

occur at various altitudes within the tidal ranges of several 

marine terraces. The most symmetrical of the Carolina bays 

are interpreted as the sites of former tidal eddies. 

HYPOTHESES OF ORIGIN 

Webster's Dictionary records as one definition of the 

word bay "a tract of land (usually of prairie more or 

less surrounded by woods) containing a deep accumulation of humus, muck, or peat." The word is widely 

used in this sense throughout the Southeastern States, 

particularly in the Coastal Plain, where it is applied to 

all shapes and sizes of hogs. The term "Carolina bay," 

coined by Melton and Schriever ( 1933) and as used 

here, applies particularly to ovate, oval or elliptical 

bays, many of which are partly enclQsed by low sandy 

ridges. Prouty ( 1952, p. 170) states that there are 

hundreds of thousands of such elliptical, sand-rimmed, 

and oriented depressions in the Coastal Plain between 

northern Florida and New Jersey. 

Probably all geologists who have investigated the 

Carolina bays would agree that they have passed 

through a stage as lake or pond, though the basins are 

now more or less boggy. Some bays still enclose bodies 

of open water. The differences of opinion about them 

relate chiefly to the origin of the lake basins and of the 

rims. Melton and Schriever (1933) and Prouty .(1952) 

attribute these features to a shower of meteorites, 

Johnson ( 1942) to upwelling artesian springs, and 

Grant (1945) to the hovering of fishes while spawning. 

In the present writer's opinion (Cooke, 1933, 1940, 

1943, 1945a), nearly all the bays are original hollows 

in the surface of marine terraces ; and the sandy rims 

are bars, beaches, spits, and dunes built by currents, 

waves, and winds. The purpose of the present paper is 

to explain why these secondary features are elliptical. 

Proponents of the meteoritic hypothesis were impressed by the elliptical shape, the parallel orientation, 

and the conspicuousness of the rims when viewed from 

the air. These characteristics reminded them of a 

meteorite shower. Their subsequent investigations 

have consisted chiefly. of the search for magnetic 

anomalies that might indicate buried meteorite fragments. When these searches proved inconclusive, 

Prouty ( 1935) proposed as a modification that airshock waves from small missiles might blow out large, 

shallow holes. This hypothesis is dismissed by the 

present writer as implausible. 

The great abundance of the bays, their occurrence 

far above the areas of artesian flow; and the impossibility of maintaining an artesian head in the surficial 

strata are convincing arguments against Johnson's 

artesian -spring hypothesis. 

195 
196 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

The rounding effects o£ waves and wave-induced The bays must be o£ different ages, the oldest on the 

currents during the lake stage appear to be an adequate higher terraces, which emerged first. 

explanation for the shape of the sandy shores of many Sincere thanks are due to Dr. R. B. Blizard, o£ the 

asymmetrical or crooked bays. However, a;_conSiderable Sperry Gyroscope Company, and to Pro£. Gilbert N. 

number o£ bays show such remarkable. symmetry and Plass, o£ the .Johns Hopkins University, whose frank 

such perfect parallelism (pl. 46) that randorr.ctound.;. · criticism of an earlier draft of the manuscript lead 

ing seems precluded. The strange "coincidences~''"tthat · to dra$tic·revision. It is hoped that the present version 

the ratios of the diameters of the most perfect ellipses is :q1ore intelligible though the conclusions remain 

approximate the sine o£ the latitude and that the direc- .. unchanged. 

tion o£ elongation o£ these same bays trends almost ' 

IDEAL OUTLINES OF AN EDDY exactly N. 45° W., bisecting two cardinal directio;ns, 

indicate that some cosmic cause must be involved, presumably the rotation o'fthe earth.' 

. The elliptical shapes of the bays arepossihly caused . 

by the gyroscopic effect of the rotation of the earth on · 

a rotating body of water, an eddy. As·h~s been already 

stated (Cooke, 1940, 1943, 1945a, 1950), this effect· is i 

to alter the outline of an eddy from the initial· circula:r 1 

shape to an ellipse of definite· proportions and· orient~- · 

tion. Because the proportions and trend of the more 

symmetrical Carolina bays approximate the theoretical 

features of an eddy, these bays "are conceived of as 

having once contained eddies, which to some extent 

rounded the shores~ but whose principal work was the 

building of -submerged bars. · 

This ~ypothe~is o£ origin attrib~tes the multi,p!e , 

ridges found in many bays>to changes in the·velWity : 

of the eddy, which would increase or diminish its diameter and. change. the: location ·,of bar-building .. 1

T·he 

intersection of ridges m'ight be brought· about by · a 

shifting of the center of rotation. ''iPartiar' or isolated · 

ridges· may indicate a stopping of_ the· eddy befor~ the 

building" of the bar had advanced far. toward 'completion~ ·· Pear-slraped bays, whose directl.on of elongation 

generally deviate from that of the ideal eddy, may have 

-bee:ri partly ·shaped by eddies of short duration. Occurrence of- these features :has been used as arguments 

against the theories of terrestrial origin ~-nd iii fav6r 

of the·. meteoritic hypothesis. · · 

· · • A- weakness of the eddy hypothesis as originally · 

formulated (Cobke; 1940, ·1943, 1945a) ··was ·the lack , 

of a/satisfactory mechanism for k~eping the .eddies in · 

motior/ ~long enohgh to produce noticeabh~ "·effects. 

·Strong, contirtu'(')Us: winds were postulated, but winds . are notoriously fickle." A more reliable moti~e force is " 

the power of the tides. · Tides flow continually, .. d~·y . ~Jter day, year,..after year, as long as the passages con-

.necti~g th_e tidal basin with the sea rem-ain 6pen. 

·. If tides furnished_ the motive power by which the 

·carolina bays were shaped, the rims must have been 

built in inland estuaries or on tidal flats while the 

coastal terraces on which they lie were still submerged. 

As early as 1938 it was suspected (Cooke, 1940) that 

a rotating current, an eddy' ~ends to assull_le an . elliptical shape of definite orientation. To prove this 

assumption mathematically and so to derive formulas 

for the shape and orientation of an eddy woul~ .~equire the manipulaf.ion of eornplicategjjq.yd,roq~;~·mi~al 

equations far beyond -the mathematical ability of~h~ 

writer. However, it may. be assumed· that a drop. of 

:Jiquid moving in a: curved ·path 'obeys the same laws 

of rriotioi1 as a solid partiCle· movi~g. in 'a ~urved path 

and that a rot~ting body of a liqui~ .Will be1lave iiiJ:p.e 

same~ m~;tl}ner as a r9tating_solid ~ody _ex~ept. ip.~q~r 

as its acti(}n. ·will be modified by its lack Q:f rigiditY'•t;·l· 

An eddy differs'· from a sprnning.··flywneel-:i.n ;that 

the'e~ect of~r·avicyis_ riot ~ol1eehtrated ~t tlill'celi~r:;()'f 

rria:~·1lu.t aftiacts eacli p'attiet~ indepenaen.ily,~ · · ~-<>,, a:!,iY te:n.d~ncy. of the rot~ting liquid to x;ise. ftPoV~ $eJ~yel 

orf ·static equilibrium·~ would be :·balttnc~ against ·the 

weight of the particles-so displaced. · If the plane of 

rotation were' tilted, ·the centrifugal force would be 

direct¢. atah:~_rigle t6 th~. surface of st~tiC:equilipriuni~ 

The ve~tical components ~f the eentrifugal force ~ould 

be balanced a·gainstgravity, and the surface· would not 

tilt' to the same extent as the plane . of robitiorr: The 

horizo~tal compon,ents of' th~ centf}fugaJ'£orde :_-WOl;lld 

not be, opp.osed by g:r~v:ity but w.ould .. opel;'~te ·i'u",.the 

normal manner~' ·However, as the· '})'lane~ of :·rotation is 

tilted, the intensity ()f·the horizontaYcompone~tS w§~~d 

v~uy fro~ ~nity along the axis of tilt:'tq'the cq~~n_e 

of the angle-.oftilt.at :r:ightangles to that axis, and the 

horizontal outline 9f th,e e4dy .would become an ellipse, 

the horizontal projection of the tilted circle of rotation. 

<!A spinning flywheel has gyrostatic properties which, 

'though deduced empirically, are based· on the fundamental ~aws of motion, which apply to all kinds of 

matter, liquids as well as solids> So/by at~ributing 

gyrostat!c properties to Uqhids, it, may be· posSib~e to 

arrive at tentative conclusions as to: the. shape,'ih.i(I 

orientation ri£ ~n eddy eveJ:'tiiougli . silc:h' .. con~Iu~ions 

lack mathematical proof. 
CAROLINA BAYS AND THE SHAPES OF EDDIES _l97 

Because of its inherent inertia every particle of 

matter resists change in the direction of its motion. 

This resistance is manifested in the gyroscope, an 

adaptation of the flywheel. A spinning flywheel tends 

to keep the direction of its plane of rotation fixed in 

space. If one tries to tilt the wheel, it offers resistance 

and tilts (precesses) at right angles to the direction 

of the pressure (fig 22). If it is forced to yield, it 

sets itself perpendicular to the axis about which it is 

forced to tilt (fig. 23). An eddy presumably responds 

in the same manner, though gravity holds its surface 

nearly horizontal. 

The rotation of the earth on its axis is continuously 

turning the surface of an eddy out of its plane of rotation. The eddy, like a spinning flywheel, may react 

in either of two ways: the plane of the impulse to ro-\ 

tate may precess about the east-west diameter of the ' 

eddy or the plane may set itself perpendicular to the 

axis of the earth, about which it is forced to revolve. In 

a precessing eddy the plane will slope downward toward 

the equator at an angle equal to the latitude, cp, in which 

position the force causing it to precess is at its maximum; in a fixed eddy the plane slopes downward 

toward the nearer pole at the angle of the colatitude, 

90°-cp. 

The projection of a circle tilted at the angle cp is an 

ellipse whose proportions are such that the ratio of the 

"" ~ preces . o~\''~. · · ·-· · •. SJol} '·· ~ · .... 

·--~. 

FIGURE 22.---Axis and path of precession of a rotating disk. If pres· 

sure (li') tie ·applied at A, tending to tilt the disk about the axis 

P-P', th~ disk will tilt (precess) about A-A', and the fixed points 

P and P'. wlll fo1Iow"the dotted path of precession. 

r 1 

FIGURE 23.-Passive position of a rotating disk. If the rotating disk 

shown in figure 22 is compelled to turn about the axis P-P', it will 

twist through 90° into the position shown, in which position it offers 

no resistance to being turned about P-P'. 

shorter diameter (b) to the longer diameter (a) equals 

cosine cp. The projection of a circle tilted at the angle 

90°- cp is an ellipse whose proportions are b: a=sin cp 

(fig. 24). 

Because the plane of the impulse to rotate is tilted 

about the east-west diameter of the eddy, no matter 

whether the plane is fixed or precessing, one might 

suppose that an eddy would foreshorten along its northsouth diameter so that the longer diameter would extend due east and west, as would be true of the projection of a stationary body. This supposition is false. 

Let us first consider the fixed eddy, in which the 

plane of the impulse stands perpendicular to the axis 

of the earth. In this tilted position the rotation of the 

earth causes the eddy to describe a circle in space. Like 

the apparent motion of the sun and stars, this motion 

can be resolved into a vertical clockwise rotation from 

east to west as viewed from the north and a horizontal 

clockwise rotation as viewed from above in the Northern 

Hemisphere and counterclockwise in the Southern 

Hemisphere. These two rotations are one-quarter 

phase apart. Consequently, the .horizontal projections 

of points along the east-west diameter of the circle will 

shift hack and forth along a line extending N. 45 ° W. 

in the Northern Hemisphere or N. 45° E. in the South-
198 SHPRTER CONTRIBUTIONS TO GENERAL GEOLOGY 

Fxouam 24.-Ideal shapes of a precessing eddy at latitude 38° N. (left) and of a fixed eddy at latitude 35° N. (right). 

ern Hemisphere, and the longer diameter of the projection of the fixed eddy should extend in that direction. 

The orientation of a precessing eddy differs from that 

of a fixed eddy because the plane of impulse turns with 

the earth. There is no apparent rotation, for the plane 

remains tilted about the east-west axis, parallel to the 

axis of the earth. However, the plane is actually turning about the axis of the earth while it precesses at the 

same speed about an east-west axis. The resultant 

axis lies midway between the axis of the earth and an 

east-west horizontal line. The direction of the horizontal projection of this axis should be the direction of 

elongation of a precessing eddy. This direction can be 

determined graphically as follows: 

In a circle of unit radius (fig. 25) draw the north 

radius NO at a right angle to the diameter. Construct the angle N 0 P ( cp) , and project its cosine 0 B 

on the north radius. Then B represents the projection 

of the northernmost point on a tilted circle of radius 

0 P. Connect B with A and bisect AB at 0. 0 lies on 

the projection of the inclined axis, and 00 shows its 

direction. As the triangle OOB is isosceles by construction, angle BOO=angle OBO. The angle BOO 

(a) equals the bearing from the north of the projected 

axis, the direction of elongation of a precessing eddy. 

From the diagram (fig. 25) a general equation for the 

bearing (a) in terms of the latitude ( cp) can he derived 

as follows: 

OB: OP=cos cp 

OB: OA=cot a 

OP=OA=l 

. ·. cot a= cos cp 

So the ideal shape of a precessing eddy (fig. 24, 

left) should be an ellipse whose dimensions have the 

proportions· b: a= cos cp and whose longer axis deviates 

from the north by an angle a whose value is such that 

cot a= cos cp. 

The general direction of elongation of a pr€ cessing 

eddy is the same as that of a fixed eddy, west of north 

in theN orthern Hemisphere, east of ~orth in the SouthNORTH ~---- --.... .,.,.,..,.,.,.-- --"" ............... 

/ ' // B ', // _________ :::,)'P 

/ ./ / ' ~~ //a / ', I / / \ I / / \ 

I // / \ 

I C, / \ 

I / \ 

I _,-" / \ 

I / // \ 

I // / \ 

I , / I 

1 ," a q,/ 1 

A~-------------- c)---------------J 

FIGURE 25.-Determinatlon of the direction of elongation of a precessing eddy at latitude f$. OB is the horizontal projection of the north 

radius of the eddy, which is parallel to the axis of the earth; OA 

is the west radius, which lies on the axis of precession. AB is bisected by 0, which therefore lies on the projection of the resultant 

axi~ which is the direction .of the elongation (a) of the eddy. 
CAROLINA BAYS AND THE SHAPES OF EDDIES 199 

ern Hemisphere; for fixed points on the eddy that are 

:moving eastward are simultaneously moving toward the 

equator regardless of the direction of the precession, and 

the projeeted diameters are rotated clockwise in the 

Northern Hemisphere and counterclockwise in the 

Southern. 

STRUCTURES BUILT BY EDDIES 

It has been shown that the ideal shape of an eddy 

should be either one of two ellipses having definite proportions and of different orientations. These shapes 

were deduced from the gyrostatic properties of matter, 

which are known for solids and inferred :for liquids. 

The actual shape of an eddy is evanescent and intanlgible; but if the eddy continues to rotate for a long time 

at the same location it may, under favorable conditions, become surrounded by a bar of sand or mud 

dropped where the current slackens. Such a bar should 

approximate the shape of the eddy beside which it accumulates. If such bars conform in shape and orientation to the hypothetical shape and orientation of an 

eddy as here inferred, they offer convincing evidence 

that the actual outline of an eddy may approximate the 

ideal. Moreover, one can infer that an elliptical bar 

whose proportions have the sine ratio and whose a 

axis extends N. 45 ° W. was built around a fixed eddy, 

whereas a bar having the cosine ratio and whose orientation satisfies the equation cot a=cos cp was built by 

a precessing eddy. 

Illustrations of both types of bar are presented in 

this paper. Sand bars that conform very closely to 

the ideal shape and orientation of a precessing eddy are 

of :fairly common occurrence on the Eastern Shore of 

Maryland and Virginia (pis. 41-45). One of them 

(pl. 41) still encloses a tidal eddy, but others are partly 

or completely filled with salt marsh or bog. Sand bars 

conforming to the shape and orientation of a fixed eddy 

surround some of the Carolina bays, which are out of 

the present reach of tides (pis. 46-53). Some other 

Carolina bays, of less symmetrical shape, may once 

have enclosed eddies that changed from fixed to precessing or vice versa. 

STATIONARY TIDAL EDDIES 

An eddy is formed between two currents flowing in 

different directions, between a current and quiet water, 

and where a current flows past an obstruction. Eddies 

may migrate with the current, or they may be stationary above or below an obstruction. Tidal currents are 

particularly productive of stationary eddies because 

they commonly flow through or into wide bodies of 

otherwise quiet water. 

In many estuaries tidal currents flow continually, 

with only brief pauses approximately every 6 hours, 

when the direction of the current reverses. If the main 

current is restricted to a rather ·definite channel, such 

a reversing current can give rise to a permanent lateral 

eddy whose flow is always in the same direction. The 

incoming tide has a definite direction, which determines 

whether the resulting eddy will flow clockwise or counterclockwise. Once set in motion, the eddy might 

have sufficient momentum to continue its rotation during the brief interval at high tide while the direction 

of flow in the main channel is reversing. At ebb tide 

the eddy has no directional impulse other than its momentum, and the eddy may continue to rotate in the 

same direction as during flood tide, just as water circulates in an emptying washbasin in whichever 

direction the circulation is started. 

EDDY-BUILT BARS OR NEPTUNE'S RACETRACKS 

If eddies have a definite shape and orientation, a 

stationary eddy, under suitable conditions, should be 

able to impress that shape and that orientation upon 

the container. Let us consider a stationary eddy in a 

tidal lagoon floored with loose sand or silt and rotating 

either continuously· in one direction or reversing its 

direction with each change of tide. Entering rapidly 

through the inlet, the incoming 'tide scours sand from 

its narrow channel and scatters it along its course, 

gradually building a bar into the lagoon, following the 

curvature of the current. Eventually the bar may 

almost encircle the eddy, leaving a gap at the inlet. 

Wind-driven waves may heap up the sand above tide 

level, converting the bar into a beach ridge, which may 

be capped by dunes. 

In the course of time water plants may take root 

in the shallower parts of the lagoon, and their continue(). 

growth will slow up and eventually stop the eddy. 

Further silting and growth of plants may change the 

lagoon into a tidal marsh partly encircled by an 

elliptical sand ring. Finally, if sea level falls the 

tidal marsh will be replaced by a fresh-water bog 

resembling in every respect the so-called Carolina bays. 

If the sea withdraws from a permanent eddy, there 

will remain a basin partly encircled by an elliptical 

ridge broken by one or more gaps where inlets had been. 

The proportions of the ellipse should be such that the 

ratio of the length of the shorter diameter to the length 

of the longer diameter would approximate either the 

sine or the cosine of the latitude. Moreover, the 

ellipse should bear a definite orientation. 

These specifications are met by Neptune's racetracks, 

the name applied to the definitely oriented, elliptical 
200 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

san9. rings (pl. :4:7} that surround some of the Carolina bays. This name was first used orally by the 

writer (Cooke, 193.3) in an address to the Geological 

Society of Washington on March 22, 1933. It first 

appeared in print 12 years later as the title of a fanciful 

article in the. Scientific Monthly (Cooke, 1945a) . N eptune's racetracks seems approp~iat~ not only 1

because 

the shape of the rings resembles a racetrack but because 

the tides and the waves ("Neptune's horses") played 

an essential role in their construction. The marine 

origin of the racetracks in the manner postulated was 

indicated by the recent discovery of similar features 

in the slutllow tidal waters of Chesapeake Bay. (See 

pis. 41-45.) 

OCCURRENCE OF EDDY-BUILT BARS 

RELATION TO THE CONTEMP~RARY SEA LEVEL 

filled l}jgher by fresh-water alluviation or by windblown ,s.and. In any event, the top of the ridges, when 

properly evaluated, should give an approximation to 

the height of the contemporary high-tide level. 

SILVER BLUFF (6-FOOT) SEA LEVEL 

The name Silver Bluff (Cooke, 1945b, p. 248) has 

been applied to a shoreline approximately 6 feet above 

the present sea level. The na1ne is derived from a bluff 

at Miami, Fla. (Parker and Cooke, 1944, p. 24), where 

a wave-cut cliff of Miami oolite is separated from the 

shore of Biscayne Bay by an alluvial plain. Similar 

evidences of a strand line about the same level have been 

recognized in the Hawaiian Islands by Stearns (19~8,. 

p. 627), who named it the l{apapa strand. Elliptical 

bars, probably referable to the 6,.foot stage, occur on 

the Eastern Shore of Mary land and Virginia in the 

~~e:ged_. elli~tic~~ bays and the surrounding Nep- vicinity of Pocomoke Sound, an arm of Chesapeake 

tune's racetracks are not confii1ed to any ·one level. Bay. 

They are most abundant at certain levels that corre- Accomac County, Va.-Plate 41 shows a photogr&ph 

spond very closely with the altitudes of the shorelines of an area adjacent to Pocmnoke SotJ:nd in the Parksley 

of. several marine terraces as· determined from other quadrangle, Accomac County, Va., at and near latitude 

criteria .. Because the tide level has ranged through the ; 37o49' N., longitude 75°44' W. The nearest settlement 

entire gamut from the present sea level to that of the ; is Hopkins, a fishing village just off the. southwest 

highest marine terrace, it would not be surprising. to : corner of the photograph; and Parksley lies three mil~s 

find shore features at intermediate levels, but all the farther east. Crisfield, Mel., lies 13 miles northwest. 

racetracks that have been considered in this study fall The curved spit, Halfmoon Island, is separatea frmn 

very close to altitudes of well-established marine shore- the marshes of Webb Island by a narrow sandy channel, 

lines. which is dry at low tide. Halfmoon. Island consists 

In previous papers (Cooke, 1925, 1930, 1931, 1936, primarily of a firm, sandy, curving beach fringed on the 

1945a, 1945b, 1952), the writer has called attention to west by tidal marshes of uneven width which reach a 

emerged shorelines about 270 feet, 215 feet, 1~70 feet, 145 maximum of 500 feet at the northern end. The entire 

feet, 100 feet, 70 feet, 42 feet, 25 feet, and 6 feet above · spit lies less than 5 feet above high ... tid~ .tJ.¥vel. The 

the present sea level. The occurrence of elliptical bays : present maximum tidal range appears. t9:, ~e about 2 

and Neptune's racetracks on several terraces at alti- feet. The curve of the beach is continuecf~~der water 

tudes very near that of their supposed contemporary : beyond Halfmoon Point by a slightly submerged bar. 

sea level is mutually corroborative evidence of the actu- . Halfmoon and Webb Islands shut off from Pocomoke 

ality of the shorelines and of the hypothesis that. the 1 Sound a body of water named The Thorofare, which 

racetracks were shaped by tidal currents. The presence ; is the widened extension of Hunting Creek, below 

of racetracks on the marine terrace yields one more 1 Hopkins. The middle part of The Thorofare is occriterion for the determination of the altitude· of the : cupied by a broad drowned channel at least 10 feet 

contemporary sea level. · deep as indicated by soundings recorded on the ch&rt 

If Neptune's racetracks were formed by tidal eddies, of the coast. On each side of this channel the water is 

one would expect to find the bars somewhat lower than so shallow th:itone can wade far out from shore. East 

the contemporary high-tide level through most of their of The Thorofare lie broad salt marshes th!-lt extend 

circuit, and they should be broken by gaps where the about 2 miles to the mainland. The outer curve of the 

tidal inlets had stood and where the bars were left un- marshes is almost a counterpart of Halfmoon Island, 

completed .. Locally they might stand above tide level although it is broken by an indentation at the mouth 

w}lere the eddy had touched the shore. The bays of a tidal inlet. Along this curve patches of sandy 

(bogs) within .the ridges would have originally .. been beach alternate with peaty deposits. 

lower than sea level, but they might have been silted Halfmoon Island and the opposite marshes were 

up to sea level as .tidal marshes .or they might have been visited by Harold I. Saunders and the writer by canoe 
fterm Hopkins on May 23, 1950;'~'·:An attempt waa·ffiade 

to determine the direction of the currents· in The Thorofare, but a strong wind bloi-·ing .from the southeast 

made observation difficult and .the results inconclusive. 

Observations were continued on Halfmoon Island from 

a~out two hours·before until about half an hour after 

low tide and thereafter for an hour or more on the 

opposite shore. Throughout this time there appeitrecl 

to be a : gentle clockwise drift on both sides of The 

Thorofare. This current was not strong enough 'then 

to ~roll ·sand grains along the bottom, though it might 

determine the direction of drift of sand· or silt dislodged by breaking waves. It is supposed that Halfmoon island) was built as· a slightly submerged bar 

when sea level stood about 6 feet higher and the tidal 

etldy was faster than now. The direction of the bar 

irl'dicates cthat- it was built by a clockwise current. 

If Half.moon Island and. the opposing marshes were 

shaped by ·a precessing eddy, the:f shoul<i':form an 

ellipse of such proportions that the r;atio 9£ its shorter 

d~!tmeter to its longer diameter shouJd equal Q.79, the 

~osine of latitude 37°49' N. The directi():fl of itr:;longer 

4iameter s~wuld ,be N. 51°41' W. as det~rmined from 

th~~quation cot a= cos.37°4;~~-. An ellipse having these 

pr.q:P,ortions. and trend has been drawn on the photograph., plate 41. The reader can judg~ how well it fits 

the; cc:mto11r of the shores. 

Somewhat similar features partly encircle Island 

Bay (pl. 42), a branch of Pocomoke Sound 3 to 4 miles 

west of Hopkins, at latitude 37°47'30" N., longitude 

75°46' W., on the Chesconessex quadrangle. This area 

:Was not visited, but the photograph indicates a low, 

narrow, broken elliptical ridge in the tidn1 marshes 

border:ing the bay. It seems evident.· that this ridge 

antedates the marshes that now separate it from the 

open . water of Island Bay. The contour of the ridge 

fits the theoretical shape of a .. precessing eddy at th.at 

latitude. The development of marshes. within the 

ellipse carries the process one step farther toward 

q,~~~ture comparable to the Carolina bays. The ridge 

~.e~ms to be_abar built by a counterclockwise eddy. 

·.r·!~t se_ems probable that the ridges around Island Bay, 

lilF:~ H~M~oOJl Island, date from late in the Pleistocene 

(hite Sangamon), when sea level stood abo~t 6 feet 

higher than the present. At that depth the ridges 

would have beeri submerged bars, and the present salt 

:rn~rshes would have been occupied by shallow open 

~~t~r. ' · .:fh,e greater depth would h:;we permitted the 

~urrent · t'o'' 'circulate more freely within the ba~s,' an~:l 

U1~, t~d~l currents passing .up and down Pocomoke 

$.9qn<l~q1;1lg have had greater. opportunity to keep th~ 

~ddy in motl~n. i ·vc ·;, 

201 

During the 8il~-er:·•Bluff stage, the ·tidal· range on the 

E:astern Shore of Chesapeake Bay and itr its tributaries 

inay more nearly have approached. that in the open 

ocean, which is now about twice as great as in the ba;y. 

This greater range of tide may have speeded up the 

currents in Pocomoke Seund and increased the velocity 

of.the lateral eddies. 

SomeTset O(xunty; :.Md.-At the fishing· village vf 

Rumbley, latitude 38°5'· N., longitude 75°52' W;; in the 

Marion quadrangle in Somerset County, Md., 12 miles 

southwest of Princess Anne and 7 miles north of Crisfield, houses are strung out ill. single file along a Vshaped ridge averaging 100 feet or less in width .and 

rising generally less than 5 feet above sea level (pL43).. 

This V -shaped ridge appears to include adjacent seg-:-

me11ts of bars built by two tangent elliptical eddies, the 

northeasterly one flowing plockw~se arid the othel'" 

counterclockwise. The soil_ consists of rat1:J.er coarse, 

well-rouxided:. sand grains. mbmd with . much §ner silt~ 

Salt· marshes occupy much of . the area within thE( 

ellipses, except the drowned ·chann~ls of Goose Cree~ 

and Teague Creek; and there are irregular areas of salt 

marsh outside the ellipses fronting Manokin River, an 

arm of Tangier·Sound .. 

The actual direction of elongation of the two ellipses 

approximates N. 51 °47' W. very closely, the hypothetiea1 bearing of the longer diameter of the trace . 9f a 

precessing eddy at latitude 38°5' N,; and the ratio of the 

diameters of the ellipses is very nearly 0.787, the ratio 

of the hypothetical eddy. 

A smaller ellipse, representing a slightly more advanced stage of approach to the Carolina-bay type, is 

shown in plate 44. This ellipse lies 3 miles east ~f 

Crisfield, Md., at latitude 37°59' N., in the Crisfield 

quadra'ngle. It is almost completely filled with salt 

1narshes, which are drained by Gunby Creek into Pocomoke Sound. The orientation and proportions of this 

ellipse are nearly those of the ideal precessing eddy at 

this hi.titude. The eddy appears to have flowed counterclockwise. 

Plate 45 shows elliptical clearings on a low sandy 

ridge in the IGngston quadrangle partly surrounding 

l1 swampy forest at the head of Annemessex dreek. 

This is crossed bjr"the road to Rumbley 2 miles west 

of Westover in Somerset County, Md., at latitude 38°7' 

N. The east~r11.point of the ridge is barely perceptible where it is entered by the road from Westover; 

but it :is much more conspicuous where the road leaves 

it at th~ west. · Here the ridge rises about 5 feet above 

the swamp. The dotted line on the photograph shows 

how w:ell the .natural feature fits the theoretical shape 

of.a precessing eddy atJhat latitude... : 
202 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

All the known elliptical ridges in Maryland and Virginia lie at or below 5 feet above sea level. All approx~ 

imate the orientation and proportions characteristic of 

a precessing eddy at the respective latitude. All are so 

situated that tidal currents passing up and down adjacent estuaries could have set the eddies in motion and 

kept them going. The conclusion seems justified that 

they were built by tidal eddies during the Silver Bluff 

stage, when sea level stood about 6 feet higher than now. 

TALBOT (42-FOOT) SEA LEVEL 

A shoreline at or a few feet higher than 42 feet above 

the present sea level has long been attributed to the 

Talbot terrace. This terrace is named from a county 

in Maryland, but it is well developed also in the Carolinas. The typical Carolina bays and Neptune's racetracks lie on the Talbot terrace. 

Marion Oounty, 8. 0.-A group of Neptune's racetracks named the Pee Dee Islands (pl. 46) , in Marion 

County, S. C., northeast of Ariel Cross Road, lies within 

the Centenary quadrangle at latitude 34°51 N. The 

group includes four well-shaped rings, of which two 

are tangent to each other. The four rings stand a 

little higher than 40 feet above sea level and reach 

50 feet in two areas. The altitudes of two of the enclosed bays are 39 feet and 41 feet. So all of these 

features lie near 42 feet, the approximate altitude of the 

Talbot strand. The area forms a part of a Talbot 

estuary, which is now partly occupied by Back Swamp 

and Little Pee Dee River. 

One of the elliptical Pee Dee Islands measures 0.52 

mile by 1.02 miles; its ratio is 0.51. Another measures 

0.58 by 1.08 miles, ratio 0.54. These ratios approximate 0.56, the sine of the latitude. The actual orientation of the Pee Dee Islands is very nearly N. 45° W., 

the orientation that theoretically should accompany 

the sine ratio. The assumption seems justified that 

the islands are bars deposited by fixed eddies. The two 

tangent bars seem to have been built by complementary 

eddies, the northeastern flowing clockwise, and the 

other counterclockwise. 

Horry O.ownty, S. 0.-Many of the elliptical bays in 

Horry County, S. C., appear to have been formed in 

tidal flats or lagoons connected with the Talbot sea. 

Cotton patch Bay (pl. 47), 7 miles north-northwest of 

Myrtle Beach, lies slightly below 42 feet, and a point on 

the rim stands exactly 42 feet above sea level according 

to a spot elevation on the field sheet of the Nixonville quadrangle. Nine miles north-northeast of Myrtle 

Beach, three bays (pl. 48) reach 50, 51, and 52 feet above 

sea level. This group was formed behind a small barrier 

island that now stands nearly 60 feet above sea level. 

Possibly the level of these bays may have been raised 

by wind-blown sand, or high tide may have been higher 

there than elsewhere. The orientation of these bays 

approximates N. 45° W. 

Brunswick Oownty, N. 0.-Many bays with faint, incomplete elliptical rims (pl. 49) are indicated on both 

sides of the 40-foot contour line on the map of the 

Southport, N. C., quadrangle. Spot elevations on 

nearby roads, which doubtless are higher than the bays, 

range from 44 to 52 feet above sea level. These bays, 

too, lie near the level of the strand of the Talbot terrace. 

During Talbot time, this region seems to have been a 

broad tidal flat fronting on the open ocean and crossed 

by low bars and swales, which directed the tidal currents laterally, causing eddies. The area shown in 

plate 49lies about 4 miles northwest of Southport, about 

latitude 33°58' N. ·The orientation is nearly N. 45° W. 

PENHOLOWAY (70-FOOT) SEA LEVEL 

The sea level corresponding to the Penholoway terrace stood about 70 feet higher than the present. 

Though the typical area is in Georgia, the terrace is 

well-developed in South Carolina, where the town of 

Summerville is built on a barrier island that rose above 

the Penholoway sea. A broad Penholoway lagoon, 

now partly occupied by Little Pee Dee River and its 

swamp, was bordered on the east by wide tidal flats 

in which eddies developed. 

!lorry Oounty, S. 0.-The map of the Nichols quadrangle shows Flat Bay at latitude 34°8' N., 7 miles south 

of Nichols, in Horry County. The bay lies mostly 

below 70 feet, but points on its rim reach 71, 72, and 73 

feet above sea level. It measures about 0.7 4 mile wide 

by about 1.33 miles long. These dimensions yield a 

ratio of 0.556, as compared with 0.561, the sine of the 

latitude. The direction of elongation coincides closely 

with N. 45° W., the hypothetical orientation of the 

trace of a fixed eddy. 

Doe Bay and Gray Bay are two smaller tangent bays 

in the Duford quadrangle 3 miles southwest of Duford, 

Horry County, S. C. Both are nearly 70 feet above sea 

level, and points on the rim are 73 and 76 feet. The 

shape and orientation of both agree well with the hypothetical fixed eddy. 

WICOMICO (100-FOOT) SEA LEVEL 

Topographic maps of several quadrangles in South 

Carolina show the presence of elliptical bays on the 

Wicomico terrace. All the bays lie near the 100-foot 

contour line, which is the altitude of the Wicomico 

strand. They were separated from the open ocean by 

a chain of very low barrier islands. 
CAROLINA BAYS AND THE SHAPES OF EDDIES 203 

Florence County, S. 0~-Mill Bay (pl. 50) in Florence 

County~ at latitude 33°58' N. in the Lake City qu~drangle 7 miles north of Lake City, lies less than 100 feet 

above sea level. The rim at the southeast end and on 

part of the northeast side barely rises above that altitude. This bay is less symmetrical than most of those 

described, but its overall proportions, ratio about 0.53, 

compare fairly well with those of a fixed eddy (ratio 

0.559 at that latitude) ; and its general trend is about 

N. 45° W. It is as symmetrical as can be expected of a 

lake more than 2 miles long. 

Marion Oounty, S. 0.-Grassy Bay, at latitude 34°13' 

N. in the Marion and Mullins quadrangles 3 miles 

north-northeast of Marion, S. C., lies nearly 100 feet 

above sea level. An elliptical rim somewhat higher 

than 100 feet encircles it everywhere except along the 

southeast side, where the bay expands beyond the elHpse. The elliptical part of the bay measures 0.7 

mile in width by 1.25 miles in length. The ratio of 

these is 0.56, and the sine of the latitude is 0.562. The 

trend of the longer diameter as shown on the map approximates the theoretical orientation of a fixed eddy, 

N. 45° W. 

Maidendown Bay, at nearly the same latitude, 5 

miles west of Mullins, is not quite symmetrical, being 

somewhat broader at the northwest end. The bay lies 

very nearly 100 feet above sea level. The highest part 

of the rim along the northern quadrant exceeds 110 

feet. A benchmLark at the northwest end is 105 feet 

above sea level. The rim is broken at the southeast 

end. The dimensions within the rim are approximately 

1 by 1.86 miles, giving a ratio of 0.54. The trend of 

the elongation agrees with the theoretical orientation 

of a fixed eddy, N. 45° W. 

Big Sister Bay (pl. 51) at latitude 34°11' N. on the 

Mullins quadrangle, is tangent to Little Sister Bay 

on the east and JReedy Creek Bay at the southeast end. 

The rims around Big Sister and Little Sister are approximately 100 feet above sea level; that around 

Reedy Creek Bs~y is a trifle lower. Big Sister is the 

most symmetrical of the group and measures about 

0.97 by 1.76 mih~s, giving a ratio of 0.55 as compared 

with 0.56, the sine of the latitude. The orientation is 

approximately N. 45° W. 

The rims around Big Horsepen Bay (pl. 52) at latitude 34 °9' N. in the Mullins quadrangle barely exceed 

90 feet above sea level. The water in which they accumulated presumLably was deeper than that at other 

bays here described. The presence of multiple rims 

indicates that the center of the eddy shifted a little 

when they were being formed. 

OKEFENOKEE (145-FOOT) SEA LEVEL 

An ancient shoreline now standing between 140 and 

150 feet above sea level was first detected in central 

Florida, where it is bordered by low sand dunes. Later, 

topographic indications of a shoreline near 140 feet 

were noticed in the District of Columbia (Cooke, 1952, 

p. 43, 48, 50). When the old Dean tract at Connecticut and Florida Avenues in Washington was graded in 

February 1953, these indications were verified by the 

uncovering of large, rounded cobbles abutting against 

a hill of schistose bedrock at an altitude of approxi · 

mately 140 feet. 

The Okefenokee terrace was named by Otto Veatch 

(Veatch and Stephenson, 1911, p. 35), who regarded it 

as marine but did not determine the altitude of its shoreline. The present writer (Cooke, 1925, p. 26--27) included in the Okefenokee terrace some areas near Okefenokee Swamp that are as high as 160 feet above sea 

level. He later recognized these as equivalent to the 

Sunderland terrace of Maryland and proposed (Cooke, 

1930, p. 588) to suppress the name Okefenokee terrace 

in favor of Sunderland terrace, which latter name has 

priority (Cooke, 1931, p. 508). However, the typical 

part of the Okefenokee terrace is bounded by the recently discovered 145-foot shoreline, and the name 

Okefenokee terrace has been revived (MacNeil, 1950, 

p.101). 

Florence Oounty, S. 0.-Morris Bay in the Florence 

West quadrangle 4 miles east of Timmonsville, S. C., lies 

very near the Okefenokee shoreline. Its altitude is less 

than 140 feet above sea level, but its southeastern rim 

reaches at least 143 feet. The rim is lower than 140 

feet or is wanting at the southern end and along the 

southwestern side. Morris Bay is very similar in 

shape, size, and orientation to Jacks Bay, which is 

shown in plate 53. 

Sumter Oo11mty, S. 0.-Two small tangent bays in 

the Mayesville quadrangle 2.5 miles south of Mayesville, S. C., lie higher than 130 feet above sea level. 

The rim between them rises above 140 feet both north 

and south of the point of tangency. 

Cumberland O.ounty, N. 0.-A bay at latitude 35°4' 

N., in the Vander quadrangle 4 miles east-northeast of 

Fayetteville, N.C., is less than 130 feet above sea level, 

but its rim stands higher than 140 feet on the northeast 

side. This bay measures 0.34 by 0.61 mile, which gives 

a ratio 0.56 as compared with 0.57 the sine of the latitude. The longer diameter trends very nearly N. 45" 

W., which is the theoretical bearing of a fixed eddy. 

A bay at the eastern edge of the Vander quadrangle 

is crossed by the Atlantic Coast Line Railway at a point 
204 SHORT.~R CONWRIBUTIQNS· TO GENERAL GEOLOGY 

6 miles east of Fayetteville .. The bay is more than a 

mile wide, its altitude is less than 140 feet. 

SUNDERLAND (170-FOOT) SEA LEVEL 

Th~: Sunderland terrace is bordered by a shoreline 

approximately 170 feet above sea level. Some of the 

elliptical bays in Darlington County, S. C., described 

by Glenn ( 1895) , are on this terrace. 

Darlington Om.unty, S. 0.-,Jacks Bay, (pl. 53) 1.n 

Darlington County, is near the northwest cornerof the 

Florence West. quadrangle. .. It is ~rossed by the Atlantic Coast Line Railway 1 to 2 miles southwest of 

Syracuse. The bay lies approximately 165 feet above 

sea level, and its rim rises higher than 170 feet along 

the ent{re northeast . side of the. bay, touches 170 feet 

on part of the opposite side, hut is lower or open on ,the 

southwest quadrant, where the tidal currents evidentlyhad access to it. · 

·The proportions of Jacks Bay are almost identical 

with those of the ideal fixed eddy at latitude q4°13' 

N. Its dimensions, as scaled from the. map, are 1 .by 

1.82 miles, which gives it a ratio. of 0.556 as compared 

with 0.562, the sine of the latitude. Its orientation is 

very nearly N. 45° W. 

Orangeburg Oounty, S. 0.:-A conspicuous semicircular ridge borders the southeast and southwest sides 

of a bay in the Orangeburg quadrangle 1 mile east of 

St. George Church and 2 miles north of Rowesvil_le, 

S. C. The present altitude of the bay is somewhat 

higher than 170 feet above sea level, but the bay may 

have been filled above the original tide level by the 

intermittent stream that now flows through it. The 

rim stands above 180 feet. Though i:l1complete, the 

ridge conforms to the shape of an ideal fixed eddy. 

CO_HARIE (215-FOOT) SEA LEVEL 

A group of 7 %" topographi~ maps (U. S. Geol. 

Survey 1953a, 1953b, 1953c) of the vicinity of Laurinburg, N. C., by 10:..foot contour lines and green woodland overprint, show many elliptical bays similar in 

proportions and orientation to the Carolina hays already described but at higher levels. The bays fall into 

two groups near two different levels-one slightly lower 

than 215 feet, the other slightly lower than 270 feet 

above sea level. 

Scotland Oounty, N. 0.-The bays of the first group 

lie on the Coharie terrace, whose shoreline stands about 

215 feet above sea level (Cooke, 1930, p. 588). "-'.,. orthy 

of mention are two bays in the Laurinburg quadrangle 

1 to 2 miles southeast of Laurinburg. These are surrounded by the 210-foot contour line, and the swampy 

surface of one of them lies 208 feet above sea level. 

This bay measures 1.33 miles long by 0.8 mile wide, a 

ratio of 0.60, compared with 0.57,the sine of the latitude 

(34°47' N.). Dunelike mounds encircling the south- eas~ern edge of this bay reach 225 feet ~hove sea level, 

The southeastern half of the adjoining. Wakulla 

quadrangle includes many bf).ys of various si~ at ap· 

proximately the sal!l~ level. A bay south of the 

Laurinburg-~axton airport is bordered on the east by 

a bar reaching sligh~Jy higher .than 210 feet. 

HAZLEHURST (270-FOOT) SEA LEVEL 

The name Hazlehurst was proposed by Cooke ( 1925, 

p. 29) for a terrace typically exposed between H~zlehurst, in Jeff Davis County, and Baxley, in Appling 

County, Ga. The name was later rejected (Cooke, 

1931, p. 506} in favor of Brandywine (Clark, 1915), 

which had 10 years' priority. The Brandywine terrace was regarded by Clark as the original surface of 

his Brandywine formation, which he thought was probably Pleistocene. But the Brandywine has since been 

interpreted as an alluvial fan, a fluvial deposit, probably 

of Pliocene age (Campbell, 1931; O:>oke, 1952, p. 40). 

So the name Brandywine is not appropriate for a 

marine terrace of Pleistocene age~ , 

The upper limit of altitude originally assigned (without adequate control) to the Hazlehurst terrace: was 260 

feet above sea level. Later it was raised to 270 feet 

(Cooke, 1931, p. 506). 

Scotland Om11nty, N. 0.-Bays in the Laurinburg 

quadrangle 4 miles north of Laurinburg stand about 

250 feet above sea level, but the adjacent ridges (bars) 

exceed 260 feet. The maps of the Gibson and Wagram 

quadrangles show several small bays at the same altitude. A bay in the Ghio quadrangle is surrounded by 

the 260-foot contour line and bordered by ridges reaching 270 feet. This bay adjoins an upland reaching 320 

feet, and evidently it lies at the shoreline of the Hazlehurst terrace. 

SUMMARY 

Liquids as well as solids have gyrostatic properties 

because all matter is subject to the fundamental laws 

of moti()n. Consequently, the plane of rotation of an 

eddy, when turned in space by the rotation of the earth, 

behaves like a gyroscope in that it either precesses about 

an axis at right angles to the axis of the earth or it sets 

itself perpendicular to the axis of the earth and remains 

fixed in that position. 

In either instance the plane is tilted with respect 

to a horizontal surface : in the preceSsing eddy the 

plane of rotation lies parallel to the axis of the earth, 

tilted at the angle of the latitude, cp; in the fixed eddy 

the plane is tilted at the angle 90°~</J. . 
CAROLINA BAYs~· AND TilE SHAPES OF EDDIES . 205 

The centrifugal forces lie in the plane of rotation. 

The vertical components of the ·centrifv.g~ forces are 

opposed by gravity .. Consequently, the surface of 

the eddy is less steeply tilted than the plane of rotation. 

The horizontal components vary in· intensity from a 

maximum along the axis of tilting to a minirrium proportional to the cosine of the angle of tilting at right angles 

to that axis. . So the horizontal outline of the eddy 

becomes an ellipse, the projection of a tilted circle. 

The proportions of the ellipse projected from a precessing eddy are such that the ratio of the shorter 

diameter (b) to the longer diameter (a) equals the 

cosine of cj> • . The proportions of the ellipse corresponding to a fixed eddy are represented by the equation 

b: a= sin cj>. 

The precessing eddy has two simultaneous motions 

in space: it is revolving about the axis of the earth 

and it is precessing about its east-west diameter. The 

resultant motion is a turning about an inclined axis 

midway between the axis of the earth and an eastwest horizontal line. The direction of this resultant 

axis, which is the direction of elongation of the projected ellipse, was determined graphically to satisfy 

the equation cot a=cos cf>, where a represents the 

declination from the north. 

The fixed eddy has an apparent motion like that of 

the sun, from east to west and from north to south (in 

the Northern Hemisphere) , these rotations being onequarter phase apart. This difference in phase shifts 

the axis of tilting 45 ° clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere, 

so that the elongation of the ellipse extends N. 45° W. 

or N. 45° E. 

These conclusions are purely deductive and without 

experimental or mathematical verification. However, 

the validity of the deductions appears to be corroborated 

by the occurrence of elliptical sand bars, evidently built 

by circulating waters, that simulate very closely both 

the proportions and the orientation of the hypothetical 

eddies. One of these, though apparently built at a 

somewhat higher stage of sea level than the present, 

still encloses a tidal eddy. Others occupy marine terraces at higher levels. 

In Chesapeake Bay there is a tidal eddy partly surrounded by a curved spit (Halfmoon Island, pl. 41) 

having the hypothetical shape and orientation of a precessing eddy. Other neighboring sand bars are partly 

silted up within; they show all transitions toward 

features resembling the Carolina hays. All these bars 

in and near Chesapeake Bay seem to date from Silver 

Bluff time, when the water level stood about 6 feet 

higher than now. 

The most symmetrical of the Carolina bays have the 

shape and orientation of fixed eddies. The sand rings 

around them (Neptune's racetracks) are int~rpreted as 

bars, beach13s, and. dunes surrounding tidal eddies in 

former estuaries or on tidal flats. Most of the racetracks lie within the supposed tidal ranges corresponding to several marine Pleistocene terraces. The highest described forms part of the Hazlehurst terrace at an 

altitude of 270 feet. 

PRACTICAL APPLICATIONS 

The equations derived herein for the shapes and 

orientations of eddies may apply not only to closed currents (eddies) but also to open currents, as at river 

bends, in which the horizontal components of the centrifugal force should be identical with those .in the 

corresponding segment of an eddy. Con~equently, 

hydraulic engineers may be able to determine from the 

equations the stable shape of the shore line in rivers 

or beside headlands or jetties. 

The equations may apply also to gases. If so, they 

may aid in the plotting of the direction of the wind 

around the vortices of hurricanes or in wind tunnels. 

There appear to be no theoretical limitation as to the 

size or velocity of the circulating currents to which these 

equations apply. However, it seems probable that there 

is at least a lower limit to both of these factors beyond 

which the effects of the rotation of the earth would not 

be noticeable. All of the bays herein described are of 

considerable size, ranging from about half a mile to 

more than 2 miles in diameter. 

LITERATURE CITED 

Campbell, M. R., 1931, Alluvial fan of Potomac River: Geol. 

Soc. America Bull., v. 42, no. 3, p. 825-853, 3 figs. 

Clark, W. B., 1915, The Brandywine formation of the middle 

Atlantic Coastal Plain: Am. Jour. Sci., 4th ser., v. 40, p. 

499-506. 

Cooke, C. W ., 1925, Physical geography of Georgia ; the Coastal 

Plain: Ga. Geol. Survey Bull. 42, p. 19-56, fig. 2, pls. 4-17. 

-- 1930, Correlation of coastal terraces: Jour. Geology, 

v. 38, no. 7, p. 577-589. 

-- 1931, Seven coastal terraces in the Southeastern States: 

Washington Acad. Sci. Jour., v. 21, no. 21, p. 503-513. 

-- 1933, Origin of the so-called meteorite scars of South 

Carolina: Jour. Geology, v. 42, no. 1, p. 88-96, 6 figs.; Washington Acad. Sci. Jour., v. 23, no. 12, p. 569-570 [abs.]. 

-- 1936, Geology of the Coastal Plain of South Carolina : 

U. S. Geol. Survey Bull. 867, 196 p., 18 pls. 

-- 1940, Elliptical bays in South Carolina and the shape 

of eddies: Jour. Geology, v. 48, no. 2, p. 205-211, 3 figs. 

-- 1943, Elliptical bays: Jour. Geology, v. 51, no. 6, p. 419-

427, 1 fig. 
206 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

Cooke, C. W., 1945a, Neptune's racetracks [Carolina bays]: Sci. 

Monthly, v. 60, no. 4, p. 286-291, 3 figs. 

--- 1945b, Geology of Florida : Fla. Geol. Survey Bull. 29, 

339 p., 47 figs., 1 pl. 

--- 1950, Carolina bays, traces of tidal eddies: Geol. Soe. 

America Bull., v. 61, no. 12, pt. 2, p. 1452 [abs.]. 

--- 1952, Sedimentary deposits of Prince Georges County 

and the District of Columbia: Md. Dept. Geology, Mines and 

Water Res. Bull. 10, p. 1-53. 

Glenn, L. C., 1895, Some notes on Darlington, S. C., "bays" : 

Science, new ser., v. 2, p. 472-475. 

Grant, Chapman, 1945. A biological explanation of the Carolina bays: Sci. Monthly, v. 61, no. 6, p. 443-450. 

Johnson, Douglas, 1942, The origin of the Carolina bays, 341 p., 

46 pls., Colombia Univ. Press, Now York. 

MacNeil, F. S., 1950, Pleistocene shore lines in Florida and 

Georgia: U. S. Geol. Survey Prof. Paper 221-F, p. 95-107, 

pls. 19-25. 

Melton, F. A., and Schriever, William, 1933, The Carol.na 

"bays"-are they meteorite scars?: Jour. Geology, v. 41, 

no. 1, p. 52-66, 7 figs. 

Parker, G. G., and Cooke, C. W., 1944, Late Cenozoic geology of 

southern Florida, with a discussion of the ground water : 

Fla. Geol. Survey Bull. 27, 119 p., 26 pls., 4 figs. 

Prouty, W. F., 1005, "Carolina bays" and elliptical lake basins: 

Jour. Geology, v. 43, no. 2, p. 2()()-207, 4 figs. 

--- 1952, Carolina bays and. their origin : Geol. Soc. America Bull., v. 63, no. 2, p. 167-224, 20 pis., 35 figs. 

Stearns, H. T., 1938, Ancient shore lines on the island of Lanai, 

Hawaii: Geol. Soc. America Bull., v. 49, no. 4, p. 615-628, 

3 pis., 1 fig. 

United States Geological Survey, 1953a, Ghio quadrangle, N. C., 

topographic map. 

--- 1953b, Laurinburg quadrangle, N. C., topographic map. 

--- 1953c, Wakulla quadrangle, N. C., topographic map. 

Veatch, Otto and Stephenson, L. W., 1911, Geology of the 

Coastal Plain of Georgia : Ga. Geol. Survey Bull. 26, 466 p. 

30 pls. 
PJ~ATES 41-53 

r:E:OLO<i!CAL SURVEY 

N ~ 

0 . 

· o 

E 

-

PROFESSIONAL PAPER 254 P LAT!' 41 

Halfmoon Pt 

,...,.,.,.. ------ ........ 

/ ....... 

/ / ' ....... 

/ ' / ' 1'- >, I ' · / ' ' I ' I ' I ' 

I ' I ' I ',A.. · '\ I :r.~ / '\ I ,v.;o / \ 

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0 

[ 

' A / ....... .... ,"' -...._ ""';f _.,., ----o 

. . .... 0 

-? .... ~ 

1 Mile 

I 

HALFMOON ISLAND AND VICINITY. ACCOMAC COUNTY. VA. 

A low spit partlY surround ing a tidal eddy. The ellipse shows the hypothetica l shape of an eddy at tat. 37 °,1.9' N. 
<:f-: Uf.OCH' I I. :<1 ' 1(\'EY PROFE~"IO'-"AL PAPER 254 I'L.\'l'F: 42 

/ 

/ 

I 

Isla n 

I 

/ 

/ 

I 

/ 

/ 

/ 

Bay 

lSL\l\ U B.\ Y A'\ D \ lf:I'\JTY. -\CC0.\1 AC COt-l\'TY, \A. 

Sand bar.-; probabl~ formed aroun d a. tid ~d ~dd~. now pard) ,.iJied up. TJ.~ e ll ipse ohow~ the hypot hetical ~Shape of an eddy. 

Mile 
GEOLOGICAL S URVEY I'ROFE SS IO~AL PAPF R 254 !'LATE 4:l 

ELLIPTICAL RIDGES AT RUMBLEY, SOMERSET COUNTY, MD. DartJ built Ly two complementary eddies. 
GEOLOGICAL SURVEY I'ROFr~SS IO:\AL P.-IPER 254 PLATE 44 

.S 0 U Nj; 

1 ,Mile 

ELLIPTICAL MARSHES 3 MTLF.S F.AST OF CRISFIELD, MD. 

The direc tion of the doued line was calculated frorn the equation cot a.= CO@ cf:> . 
C~F:OLOr:JC I [, St.: R\' EY PROFESS IO:->AL P.'\.PER 254 I'IA'I'E 45 

ELLIPTJCAL CLEARIJ\"GS 2 MILES WEST OF WESTO\"l:: H, .\1D. 
GEOLOGICAL SURVEY PROFESS!OXAL PAPER 254 PLA'l'E 46 

PEE DEE ISLANDS, MARION COUNTY, S. C. Traces of two cor:nplemeotary fixed eddies. 
GEOLOGICAL SURVEY 

·~ ~{, \": 

~·· 

COTTONPI\TCH BAY, HORRY COUNTY, S. C. The trace of a fixed eddy. 

PROFESSIONAL PAPER 254 PLATE 47 

~: ~' ·,; ., 

\ 

, ; .. , .

 
GEOLOGICAL SURVEY PROFESSlO~AL PAPER 254 PLATE 50 

MILL BAY, FLORENCE COUNTY, S. C. 
OEOLOG!CAL SU RV EY PROFESS !OX A L PAPE R 254 PLATE 51 

BIG SISTER. BAY, MARlON COUNTY, S. C. 



Page 

Abstract________________________________________ 195 

Accomac County, Va _________________________ 20Q--201 

Annemessex Creek, Md________________________ 201 

Applications, practicaL________________________ 205 

Artesian springs, origin of Carolina bays________ 195 

Back Swamp, S. c_____________________________ 202 

Bibliography _________________________________ 205-206 

Big Horsepen Bay, S. C., traces of eddies __ 203, pl. 52 

Big Sister Bay, S. C., traces of eddies ______ 203, pl. 51 

Brandywine terrace, inappropriate name_______ 204 

Brunswick County, N. C., traces of eddies_ 202, pl. 49 

Crisfield, Md.,,elliptical marshes _______________ pl. 44 

Coharie sea leveL._____________________________ 204 

Complementary fixed eddies, Pee Dee Islands, 

s. c _________________________________ 202, pl. 46 

Cottonpatch Bay, S. C., fixed eddy _______ 202, pl. 47 

Cumberland County, N. C ___________________ 203-204 

Currents, tidaL________________________________ 199 

Darlington County, S. C_______________________ 204 

District of Columbia___________________________ 203 

Doe Bay, S. C__________________________________ 202 

Earth, gyroscopic effect of rotation of. ___ 196,197,205 

Eddy-built bars, occurrence oL ______________ 20Q--204 

Eddy-built bars relation to contemporary sea leveL____________________________________ 200 

Elliptical clearings, Westover, Md ______________ pl. 45 

Elliptical marshes, Crisfield, Md ______________ pl. 44 

Elliptical ridges, Rumbley, Md _________________ pl. 43 

Elongation of precessing eddy, determination of 

direction oL ____________________________ fig. 25 

Equation of fixed eddy, proportions of ellipse 

corresponding to__________________________ 205 

Fish, spawning of as origin of Carolina bays____ 195 

Fixed eddy _______________________________ 197-199, 204 

Cottonpatch Bay, S. C _____________________ pl. 47 

proportions of ellipse corresponding to, 

equation of. ________ !._____________________ 205 

Flats, tidaL___________________________________ 202 

Flat Bay, S. C_________________________________ 202 

Florence County, S. C_________________________ 203 

Fresh water bog replacing tidal marsh__________ 199 

Gases, application of equations to_______________ 205 

Goose Creek, Md_______________________________ 201 

Grassy Bay, S. C_______________________________ 203 

Gray Bay, S. C________________________________ 202 

Gyrostatic properties of matter_________________ 20-t 

Halfmoon Island, Va __________________ 200,201, pl. 41 

Halfmoon Point, Va____________________________ 200 

fiazlehurst sea leveL.__________________________ 204 

High-tide level, contemporary__________________ 200 

Hopkins, Va _________________________________ 200,201 

Horry County, S. C., traces of eddies in tidal 

lagoon _______________________________ 202, pl. 48 

Ideal shapes of eddies .. _________________ 196--199, fig. 24 

Island Bay, Va ___________________________ 201, pl. 42 

Jacks Bay, S.C., tracesofeddies ________ 203,204, pl. 53 

Kapapa strand_________________________________ 260 

Lagoon, tidaL _______________________________ 199,202 

INDEX 

Page 

Lake basins, origin oL_________________________ 195 

Laws of motion_________________________________ 196 

Little Pee Dee River, S. C__ _____ ______________ 202 

Little Sister Bay, S. C__________________________ 203 

Maidendown Bay, S. C________________________ 203 

Manokin River, Md___________________________ 201 

Marion County, S. C __ ---------------------- 202,203 

Marsh, tidal, replaced by fresh water bog_______ 199 

Maryland, Annemessex Creek__________________ 201 

Goose Creek________________________________ 201 

Manokin River ___ ------------------------- 201 

Princess Anne______________________________ 201 

Rumbley___________________________________ 201 

Somerset County _________________________ 201-202 

Tangier Sound.____________________________ 201 

Teague Creek______________________________ 201 

Meteorites, origin of Carolina bays ___________ ._ 195 

Mill Bay, S.C., traces of eddies ___________ 203, pl. 50 

Motion, laws oL_______________________________ 196 

Myrtle Beach, S. C____________________________ 202 

Neptune's racetracks _____________________ . ____ 199,200 

North Carolina, Brunswick County____________ 202 

Cumberland County--------------------- 203-204 

Scotland County___________________________ 204 

Northern Hemisphere.----------------------- 197,205 

Okefenokee sea leveL ________________________ 203-204 

Orangeburg County, S. C______________________ 204 

Origin, hypotheses, of Carolina bays____________ 19.5 

Passive position of rotating disk ________________ fig. 23 

Pee Dee Islands, S. C., complementary fixed 

eddies _______________________________ 202, pl. 46 

Penholoway sea leveL_________________________ 202 

Pocomoke Sound, Va___________________________ 201 

Practical applications _______ . ___ . ________ . ____ ._ 205 

Precessingeddy ______________ 198, 199,201,204, fig. 25 

Precession of rotating disk, axis and path of. ___ fig. 22 

Princess Anne, Md_____________________________ 201 

Reedy Creek Bay, S. C________________________ 203 

Rotating disk, axis and path of precession oL. fig. 22 

passive position oL _______________________ fig. 23 

Rotation, plane of, centrifugalforces in__ _ _ _ _ _ _ _ 205 

Rotation of earth, gyroscopic effect oL ___ 196, 197,205 

Rumbley, Md., elliptical ridges ____________ 201, pl. 43 

Scotland County, N. C_________________________ 204 

Sea level, Brandywine__________________________ 204 

Coharie_________________________ __ _______ ___ 204 

contemporary, relation to eddy-built bars__ 200 

Hazlehurst. ____ .___________________________ 204 

Okefenokee .... ____ . _____ . ________________ 203--204 

Penholoway _____________________ . __ _ _ _ _ __ _ _ 202 

Silver Bluff------------------------------ 20Q--202 

Sunderland_________________________________ 204 

Talbot.------- ___ ---------_________________ 202 

Wicomico_. ________________________ .. ____ 202-203 

Shapes of eddies, ideaL _______________________ fig. 24 

Silver Bluff sea leveL------------------------ 20Q--202 

Somerset County, Md ________________________ 201-202 

South Carolina, Back Swamp__________________ 202 

Big Horsepen Bay__________________________ 203 

Big Sister Bay______________________________ 203 

Cottonpatch Bay___________________________ 202 

Darlington County.________________________ 204 

Doe Bay___________________________________ 202 

0 

Page 

South Carolina, Back Swamp-Continued 

Flat Bay___________________________________ 202 

Florence County __ ... _____________ .. _______ 203 

Glassy Bay ____ .. ______ .. _________ ...... ____ 203 

Gray Bay .. ____________ .------------------- 202 

Horry County ______ .. ______________________ 202 

Jacks Bay ________________________________ 203,204 

Little Pee Dee River.______________________ 202 

Little Sister Bay___________________________ 203 

Maidendown Bay__________________________ 203 

Marion County __ ------------------------ 202,203 

Mill Bay___________________________________ 203 

Myrtle Beach______________________________ 202 

Orangeburg County________________________ 204 

Pee Dee Islands____________________________ 202 

Reedy Creek Bay ____ -------------------___ 203 

Summerville.______________________________ 202 

Sumter County____________________________ 203 

Southern Hemisphere, rotation of eddy in_ .. _ 197, 205 

Spawning of fish, origin of Carolina bays ___ ._._ 195 

Springs, artesian, origin of Carolina bays_______ 195 

Stationary tidal eddies__________________________ 199 

Structures built by eddies______________________ 199 

Summary._ .. _____ .. ___ . ___ . _____ . _____ . _____ 204--205 

Summerville, S. C______________________________ 202 

Sumter County, S. C ____ -_______________________ 203 

Sunderland sea leveL .. __ .. ___ . ________ .. _--- 203, 204 

'l'albot sea leveL_______________________________ 202 

Tangier Sound, Md____________________________ 201 

Teague Creek, Md_____________________________ 201 

Terrace, Brandywine, inappropriate name______ 204 

Coharie, elliptical bays on__________________ 204 

Hazlehurst, revival of name________________ 204 

elliptical bays on_______________________ 204 

Okefenokee, elliptical bays on .. __________ 203-204 

Penholoway, elliptical bays on_____________ 202 

Silver Bluff, elliptical bays on ____________ 20Q--202 

Sunderland, elliptical bays on______________ 204 

Talbot, elliptical bays on___________________ 202 

Wicomico ____ . ________ . ______ . __ . ________ 202-203 

The Thorofare, Va. __________________________ 200-201 

Tidal currents ________ .. ______ ... ------------_ 199. 200 

Tidal flats _____ . ___________ ... _________ ._ .. _____ 202 

Tidal lagoons ____ ----------------·---- ______ 202, pl. 48 

Tides, as motive power of eddies________________ 196 

Traces of eddies, Big Horsepen Bay, S. C ______ pl. 52 

Big Sister Bay, S. C ________________________ pl. 51 

Brunswick County, N. C _________________ pl. 49 

Halfmoon Island, Va _______________________ pl. 41 

Island Bay, Va _____________________________ pl. 42 

Jacks Bay, S. C ____________________________ pl. 53 

Mill Bay, S. C _____________________________ pl. 50 

Trend of bays_--------------------- ___ --------- 196 

Virginia, Accomac County_ ...... ___ . _______ . 20Q--201 

Halfmoon Island._. ______________________ 200,201 

Halfmoon Point. ____________ .. _ .... ---.-._. 200 

Hopkins ___________________ . _____ . __ ------__ 201 

Island Bay. __________________ -------------- 201 

Pocomoke Sound ... _______ . _____ . __ ---.____ 201 

The Thorofare ____________________________ 20o--201 

Webb Island_______________________________ 200 

Water plants, stopping an eddy________________ 199 

Webb Island, Va_______________________________ 200 

Westover, M d., elliptical clearings ... _ .... - ___ . pl. 45 

Wicomico sea leveL------ __ ---------- ___ ----- 202-203 

207