Here to return to
Sand Dunes and Salt Marshes
SAND dunes have a fascination all their own. In the multiplicity of their forms and colors, varying with the seasons and
years, they are a constant source of pleasure, while in their wealth of plant and animal life their interest is never-ending. The beauty of the sand dunes is revealed at every turn, their secrets are legion. The course of their formation from the time they emerge out of the sea as reefs washed by every tide, until they have reached perfection in their wave-like crests fifty feet high is an absorbing study. Their surface records a continually changing story, — ripple-marks of the varying winds, magic circles made by the grass, and myriad tracks of living creatures.
A day spent in the dunes
with the roar of the waves and the cries of the gulls in one’s ears, the breath of the marsh and of the ocean in one’s nostrils, the wild beauty and loneliness of the scene in one’s eyes, is indeed an inspiration, a memory worth treasuring.
The reefs along the beach are constantly changing. One of these I have watched and recorded since 1892. When first seen, it was already above high tide except at its northwest extremity, and connected with the beach off the Ipswich range-light. Like other reefs, its slope was gradual on the seaward, steep on the landward side, and so narrow that I used — in those barbaric days — to build my blind in the middle of the spit and shoot over decoys placed at the water’s edge on both sides.
THE BEACH AND THE SEA FROM THE DUNES
As the sea threw up more and more sand, and the wind seized it and blew it inland, the spit extended and broadened and cut off a lagoon of several acres in extent, so protected from the sea waves that a different marine life flourished there. It was a godsend to the old lighthouse-keeper, for he could dig at his door all the clams he needed without having to wend his way to the inland creeks. This was the only place on the outer side of the dunes where common clams were found, for on the unprotected beaches the massive sea-clam, an entirely different species, alone flourishes. The spit grew year by year, and in 1904 had become an elevated plain three hundred yards broad, which completely enclosed the shrunken lagoon, now brackish and stagnant. The clams had all died and another set of inhabitants flourished there, dominated by great masses of slimy algae. But the sands kept blowing, and in 1906 the pool was entirely effaced. Clumps of beach grass appeared in places, and the sand collected about them and formed the beginning of dunes.
Later, owing to some change in the currents along the shore, the waves demolished their own handiwork, and in 1908 veritable sub-fossils, the shells of the common clam, began to appear on the outside beach, standing in place with their empty valves pointing upward as in life.
While clumps of beach grass are often responsible for the birth of a dune as just described, any obstacle or irregularity, in whose lee the heavier grains of sand settle, may also start a dune on its progress. However started, their forms are many and various, yet, as they are all dependent on the winds, they are shaped by the strongest or dominant ones, and these are the winds which blow from the northwest, north and northeast, during the winter months. Certain secondary or transient modifications are due to other winds, particularly to the prevailing southwest breezes of summer, but a visit to the dunes in a snow-spitting northeaster of winter gives one an idea of aeolian power not often realized in the gentler summer season.
THE LIGHTHOUSE IN THE SEA OF DUNES
Smiling skies, gentle balmy breezes, flowers blooming and filling the air with their perfume, bird songs ringing from every clump of bushes and grove of trees, perfect gems of color in a setting of brilliant white sand, — all of these are seductively enchanting. But the full glory of the dunes, to my mind, is to be found in the winter storms, when the biting wind sweeps with resistless force over them, driving snow and sand into the face of the toiling dune traveller, when the gulls scream noisily overhead, and flocks of ducks, restless in the foaming seas, scud by before the blasts, while over all the roar of the waves, pounding relentlessly on the beach, sounds a grand sea dirge. As one pauses for breath in the lee of a dune and watches the clouds rush by over the tumultuous ocean of sand, one feels to the full the primeval grandeur of the dunes and sees them in their true colors and stormy activities.
Ripple-marks form on the surface of the sand whenever it is dry and the wind blows. These are parallel ridges athwart the wind, with steep sides to leeward, gradually sloping ones to windward. Similar ripple-marks are left by the receding waves on the beach, or by the sweep of the tides in the estuaries, or by the rush of the brook to the sea. In the estuary the steep side of the ripple-mark is up-stream on the flood and down-stream on the ebb tide. In the bed of both water and wind stream the grains of sand are pushed along in parallel ridges up a gradual slope until they drop over and come to rest on the steep sheltered side.
In a gentle wind the ripple-marks advance so slowly that one is unconscious of any change, but in stronger blasts the changes are very manifest. On a blustering March day with a keen wind from the northwest I watched some ripple-marks that were four inches apart from crest to crest, and found that they were advancing at the rate of a foot in eight and a half minutes.
The most common form of dune at Ipswich is one whose longest axis runs from east to west across the prevailing winds, and these again may be divided into two classes. Both advance to the south like waves before the boreal blasts, but the commoner, unlike the water wave, presents its crest to the storm and retreats backward. The sharp, steep side of the dune is undercut and worn away by the wind, and streams out on the sweeping slope to leeward. Owing to the multitude of interlacing rootstocks and rootlets of the beach grass the crest sometimes overhangs like a breaking wave, and masses of roots and sand fall from time to time as the wind undercuts them. Indeed, this slope of the dune, the reverse of the normal one about to be described, is, I believe, due entirely to these beach grass roots — bricks made with straw.
A SMALL AMPHITHEATER IN THE DUNES
These reversed waves of sand reach their fullest development at the southern end of the Ipswich dunes, where they form a series of parallel ridges, with their steep sides facing the north. They have advanced southward in the middle more than at either end, so that they describe the arcs of circles, and resemble a series of gigantic amphitheatres. One wave that I measured in 1903 could easily be traced for some 1,350 paces, or three-quarters of a mile, and it stretched from the estuary on the inside to the sea on the outside. Its breadth varied from forty to two hundred yards, and its height from twenty to fifty feet. The distance between the waves varies from a hundred yards to a quarter or half a mile.
The highest points or peaks of the dunes often show long ridges of sand extending in the wind’s axis to leeward of them, and these longitudinal dunes are sometimes found by themselves, and constitute a distinct type, although not often developed to a great size at Ipswich. They are prone to form near the beach and appear to be indicative of unusually strong winds.
Every now and then in the amphitheatre waves there are cross valleys with steep windswept walls. In the cuttings and on the sharp northward faces the stratifications in the sand are often marked, and the firmly packed layers stand out prominently, while the loosely formed ones are cut away. The strata often dip gently towards the south, for the sand is left by the wind on the southern or leeward slope, but they vary greatly and are irregularly superimposed. The angle of the northern slope of these dunes varies from thirty to ninety degrees, while that of the southern slope is about twelve degrees.
The other kind of transverse dune — the normal desert one — although rare at Ipswich, appears to form only where the wind is unhampered by the binding grass, and is one that resembles more closely a wave of the sea, for its steep crest is borne in front, while the long, sweeping side is left behind or to windward. In these respects it is but the magnification of the ripple-marks on the surface.
DUNES SHOWING WIND STRATIFICATIONS AND STEEP WINDWARD FACES
There are at the present time two very striking examples of this form of dune at Ipswich, one of which, like a devastating tidal wave, is overwhelming the southernmost of the pitch-pine woods, while the other, nearer the mouth of the Essex River, is burying in its progress a grove of white birches. Both of these are unprotected on the north for a considerable distance either by bushes or by grass, and Boreas rushes over them unimpeded. The northerly slope is hard and firmly packed, and extends gently upward at an average angle of nine degrees, whereas on the south the sand, freed from the mighty power, settles softly at an angle of rest generally as steep as thirty-two degrees. Here it is so loosely compacted that one may easily sink half-way to the knees.
Both of these dunes have crests higher than their victims, the trees. The pine grove has been so far imbedded that the remains of the buried trees are beginning to reappear on the northern side of the dune. The exposed wood is decayed and soft, but masses of hard pitch can be found here and there on the bark, so thoroughly infiltrated with sand that they look like sandstone or pieces of coral.
The rate at which the dunes advance varies greatly, but it depends chiefly on the season of the year. One of the fastest dunes is undoubtedly the large one just mentioned that is breaking over the birch grove, for here at the southern end of the dunes the sand is exposed to the full sweep of the north winds, and the region is widely destitute of grass or bushes. By means of marked trees I have been able to obtain exact measurements of the progress of the dune from time to time, for the edge of the sand as it advances into the grove is sharply defined.
In the five winter months, from December 5, 1909, to May 15, 1910, the dune advanced 87 1/2 inches, or about 17 inches a month, while in a little over five summer months, from May 15 to October 23, 1910, it advanced only 61 inches, or about 12 inches a month. The next winter was a favorable one for dune movement, for in the four and a third months, from October 23, 1910, to March 5, 1911, the dune advanced 256 inches, or at the rate of about 60 inches a month. The pine-grove dune advanced only 3 inches in the summer of 1910 from May 15 to November 6, but in the stormy weeks between the latter date and March 5, 1911, it advanced 71 inches.
PITCH PINES AFTER THE DUNE HAS PASSED
PINES OVERWHELMED BY THE ADVANCING DUNE
On January 29, 1911, the signal stake placed by the Coast and Geodetic Survey on a high dune near the beach was 175 inches due south from the retreating northerly face of the dune. After four windy months, on May 28, the stake was only 132 inches from the edge,-43 inches had been cut away.
In a recent book on the Sahara, Hanns Vischer describes similar dunes, but on a much larger scale. He says: “Gradually these dunes are piled up and form ridge after ridge, some of them over four hundred feet high. These rise from the north in soft curves to fall off on the other side like a mighty wave. The ceaseless wind, mostly from the northeast, moves the sand along the surface, continually changing the position and formation of these banks.” His photographs show dunes entirely devoid of binding vegetation, with camels walking on the hard windward surface, but sinking deeply into the steep leeward sides. The “amphitheatre” dunes so common at Ipswich, with the steep side to windward do not occur there, owing to the absence of binding vegetation.
Where the winds are irregular, as under the brow of Castle Hill, the dunes are often circular and cut out on all sides. Some have flat tops and stand out like miniature buttes, showing sections of nearly horizontal strata on all sides, while others are peaked or pyramidal in shape, and the circular scour of the winds gradually reduces their height without changing their shape.
The sand dune on the edge of the beach shown here — the frontispiece of the “Birds of Essex County” — was photographed in 1900, but by 1907 it had been entirely effaced. I always called this Eagle Dune, as I had watched a bald eagle perched on its summit, but there is a tradition that it long bore the name of “the headless sailor,” for human remains of this description had been found washed up at its base many years before.
In places there are pits in the sand which are so continually scoured by the wind that they remain open, and while they fill up on the windward side, they are cleaned out on the leeward and slowly move down wind.
ON THE EDGE OF THE BEACH
In a strong wind the peaks and crests of all the dunes smoke like so many chimneys, and a cloud of sand streams off, building the dune up to leeward. As Vaughan Cornish has suggested, a great mountain may be laid low by the slow process of denudation, while a humble sand dune still remains, for the process which denudes it at the same time renews it.
The sand blown from the dunes on windy days cuts with stinging force, and one must guard the binoculars, for glass is quickly ground as by a sand blast. A clouded condition of the glass is shown on exposed windowpanes in the dune camps, or on bottles or any piece of glass lying on the sand. A large flint spear-head, I found in the dunes, has been so smoothed that the sharp angles of fracture are effaced. Pieces of wood are in the same way ground down by the sand blast and take on curious shapes determined by the position of the harder knots.
The grains of sand which compose the dunes vary very much in color according to their composition, but at Ipswich the color of the dry sand is brilliant gray or white, although it may appear purple in the shadows or pink or gold in the sunset light. The winds have a selective power, and streaks and windrows of purple and garnet or even of black sands are often to be found. Under the microscope the grains appear like gems, and are seen to be more or less rounded and worn by the constant action to which they are subjected by the wind, while on the beach the majority of the grains are still somewhat angular, as if recently broken up by the pounding waves. The difference is not great, but is generally discernible. In size the sand granules of the dunes are smaller as a rule than those of the beach.
In the early spring the cranberry bogs large and small among the dunes are generally pools of water, and here, where vegetation abounds, the water is stained a brown color. Occasionally a pool may be found free from vegetation higher up in the sand, and the water appears in its true color, a greenish blue, suggestive of an alpine lake, and the snow-white peaks of sand in the vicinity serve to increase the illusion.
A PEAKED DUNE
SHOWING BOTH THE STEEP WINDWARD FACE BY CUTTING, AND THE GENTLE WIND-SWEPT SLOPE
Half buried in the dunes is the Ipswich lighthouse, even whiter than the sands. In 1809, James F. Lakeman sold to James Madison, the President of the United States, eighteen hundred square feet in these sandy wastes “for the purpose of erecting a beacon.” In 1837, Captain Lakeman sold four acres to the United States for the erection of a lighthouse. In the deed it is stated that the northern corner of this lot was “about five rods [82 1/2 ft.] from water mark and beach.” This same corner is now  about a thousand and ninety feet from high-water mark, while the light itself is eleven hundred and forty feet from the upper edge of the beach.
The old light-keeper, Captain Ellsworth, who died in 1902, told me that when he took charge in 1861, he used to be able to talk from the lighthouse to men in boats in the water. In the line between the main light, — which slowly revolves with a long and a short flash and a period of darkness, — and the mouth of the Ipswich River is the range-light, which consists of a powerful lantern in a small wooden house. As the mouth of the Ipswich River where it enters the sea between treacherous bars is a long way to the southeast of the apparent mouth of the river and constantly shifting, the site of the range-light has to be changed every five or six years.
In the summer of 1910 there emerged from the dunes within five hundred and forty feet of the lighthouse the timbers of an old vessel, which must have been wrecked many years before, when that spot was within the reach of the tides. Now it is six hundred feet from high-tide mark. One of the old inhabitants said he remembered the wreck, and treasured the year 1863 in his memory as the date when the catastrophe occurred. Be that as it may, the old wreck at this point serves to confirm the story of the lighthouse-keeper’s conversation in bygone days with men in boats on the water.
The speedy way in which the sands swallow up wrecks was well shown by the fate of an old schooner that went ashore in the Christmas storm of 1909. The skipper had sold his farm and invested his all in the vessel, and this was his first trip for a load of sand from the perpetual supply on Plum Island. The gale swept down from the northeast thick with snow, the anchors dragged, there was not sea room enough to manoeuvre away from the lee shore, and he was wrecked on the beach at high tide. The poor man begged for farming work again, for there was no probability of saving his schooner, which, with every pound of the surf, settled deeper and deeper in the sand. Less than a year later she was buried to the deck.
THE OLD LIGHTHOUSE KEEPER AND SOME OF HIS FRIENDS
WRECK UNCOVERED AFTER MANY YEARS FAR IN THE DUNES, SHOWING ALSO RIPPLE-MARKS
In the seventies I used occasionally to take the long walk from Magnolia to Coffin’s Beach, which lies the other side of the Essex River from Ipswich, to spend a solitary day among its strange dunes and on its long flat beach. As I lay in my blind there, intent on shooting the wandering shore birds, I often thought of the tale of Coffin’s farm. When the old farmer was on his death-bed he gathered his sons about him and gave them his farm, and at the same time bade them never to cut the woods that lay between the farm and the sea. Scarcely was the old man buried than his words were forgotten by the thoughtless sons, who, instead of going farther afield for their wood, took that nearest at hand. As a result of their disobedience the winds were no longer restrained, the sand blew in and overwhelmed the fair fields, and now the tops only of a few apple trees extending above the sand show what the place once was.1
The same catastrophe has occurred at Ipswich. In the middle of the dunes on the marsh side is a long hill about sixty feet high, so covered with sand that it is generally considered a great dune. In some places, however, one can scratch the sand and find earth and gravel below; occasionally a boulder projects, and here and there one comes on ancient stone walls, some of which have been uncovered by the blowing sand within a few years. In 1892 there was an orchard near the top and on the southwesterly slope, somewhat less than an acre in extent. Part of this orchard was still nearly unscathed by the advancing sand, which had merely dusted the ground, but the rest was buried to the tops of the main trunks, and all the horizontal and drooping limbs were covered, yet the topmost branches blossomed and bore fruit. But the sand encroached more and more, and one after another the strangled trees gave up the ghost, and the tops only of dead branches stretched above the sand. The struggle was a hard one, and for many years some of the braver tree-tops blossomed with cheerful promise in the waste of sand, but came to no fulfilment of fruit. In 1910 all I could find to mark the place were a few wind- and sand-beaten apple-branches. The orchard was entirely buried in the white sand!
THE HALF-BURIED APPLE ORCHARD IN 1892
ALL THAT REMAINED OF THE ORCHARD IN 1910
The seaward side of this drumlin, for drumlin it is, on which the old Lakeman farm once flourished, is in places a precipitous gravel cliff more or less whitened with sand. This cliff shows as surely as if it had stated the fact in words, that at one time waves of water, not of sand as at present, beat against its foot. The distance from the foot of this ancient sea-cliff to the sea, now filled in by sand dunes, is about twenty-four hundred feet. We have just seen that a vessel that went ashore near the lighthouse is now, after the lapse of about fifty years, some six hundred feet from the upper edge of the beach, so we might calculate that the sea beat at the foot of this gravel cliff about two hundred years ago. This, however, is not a safe estimate, and may be wide of the truth, for the beach and dunes are continually changing with changing sets of tide and currents, and while one part is building out another part may be washing away.
Yet this estimate just given is confirmed by an ancient manuscript map, now in the possession of Mr. R. T. Crane, Jr., to whom I am indebted for a photographic reproduction given here. This is entitled “A Representation of Castle Hill & Castle Neck with ye adjacent Sea, Rivers Creeks Hills Islands and Marshes, Protracted from a scale of forty rods to an Inch. P. B. Dodge Ipswich April 3 1786.” The old Lakeman farm was then inhabited by grandfather Choate, and the hill we have just been considering is called “Wig-wom Hill.” The foot of the hill is distant from the sea, according to the map, some eighty rods, or thirteen hundred and twenty feet. As the sea is now twenty-four hundred feet off, the dunes have gained eleven hundred feet in one hundred and twenty-four years. This corresponds fairly closely with the approximation of six hundred feet in fifty years obtained from the old wreck.
The southeastern end of the dunes do not extend beyond Hog Island in this map, and the distance from the farmhouse of Wigwam Hill to the end is about a mile. At the present day the distance is fully two and a half miles. I do not feel sure, however, of the accuracy of the scale of this map, although I may do the author an injustice. There are some other points shown by the map which, however, do not depend on scale, and are interesting as showing the changes that have taken place. One of these is the indication of trees or woods at the inner end of the point of the dunes, where no woods exist now; another is the “New Channel” between the end of Plum Island and Ipswich “Barr,” which is now entirely obliterated; and the third is the extension seaward of Steep Hill, the northeastern peak of Castle Hill. This latter point is more clearly shown on the map of 1846 made by Aaron Cogswell. Here the contour line shows a gradual sloping of Steep Hill to the beach with a field labelled “pasture” between, in which is a “Bass Tree.” The distance from the highest point on the hill to tide mark is about five hundred and twenty feet. At the present time the pasture and the bass tree are obliterated, while the northerly slope of the hill has become a cliff whose crest is on a level with the top of the hill; the tides wash its base. Thus it were better to build one’s house on the shifting sand which grows and endures than on the rocky hills that sink into the sea.
MAP OF CASTLE HILL FARM, 1846
In winter among the dunes the snow and sand are drifted mingled together or separately, and one often finds a deep white snowbank beneath a skimming of sand, which, if the snow is melting, is darker than the surrounding dry sand. Other signs of buried snow are the deep fissures formed in the sand by the contracting snowbanks, and the crunching sound that issues when one walks over the concealed snow. One of the largest snowbanks, which became almost a glacier, I watched during the severe winter of 1903-4. This was an immense drift of snow and sand, separate and commingled, encroaching on the north side of the grove of pitch pines. A layer of sand from one to two feet in thickness, which reflected but did not so easily conduct the sun’s rays, so protected the snow that it became compact and crystalline. On May 15th, this crystalline snow had a thickness of thirty-eight inches at its exposed face, under which, extending back to a distance of three feet, was a “glacial” cavern. The sand on top was cracked and crevassed, and this, together with the bending of the trees, suggested the possibility of some motion down the slope. On May 30th, the face of the “glacier” was covered with sand, but marks made on a tree showed that the drift had sunk forty-two inches since May 8th. A week later, on June 6th, I dug for the glacier but could not find it.
MAP OF IPSWICH SAND DUNES, 1786
While these snowbanks in the dunes are suggestive of alpine glaciers, the ice formations on the beach and ocean are suggestive of the polar seas. Both are miniatures of the real thing. During severe frosts an ice cliff forms at the upper edge of the beach, and this presents to the advancing tide a sea-wall from two to eight feet high. Against this the waves beat, and the spray flung up on the top freezes and adds to the height. While the top is fairly smooth, except where it is eaten away by the waves that have broken through it, the sea façade is hollowed into caverns or built out in parapets and festooned here and there with icicles.
Although the beach itself, uncovered by the tide, is generally free from ice, it is occasionally glazed over and strewn with great cakes that in zero weather extend out over the water to form in places a solid shelf, — an “ice-foot.” But in most places, during weather like this the ocean is beset with floating cakes of ice, and with newly forming ice which in the heaving and churning of the sea appears like grains of sago, and later takes the form of small rounded or many-sided cakes with raised edges, the “slob-ice” of the Labrador coast, the “pancake ice” of Scorseby. Everywhere beyond the ice and in the open leads the sea seems to boil and great clouds of mist roll upward, for the warmer water of the sea actually steams in this arctic weather, and the distant view is obscured. Here are patches and lanes of black water, there, bands of solid floe brilliantly white in the sunlight. Icebergs, the most magnificent arctic phenomena, once seen, always to be treasured in the memory, do not appear on this coast. It is far too distant from the parent glaciers.
On one occasion, in February, when the thermometer was six degrees below zero, and the water was covered with pancake ice, I heard in the still air a sighing, whistling note, an aeolian-harp-like sound, which appeared to have its source in the heaving, churning ice-cakes.
“GLACIER DUNE” SHOWING THE CRACKED SAND AND THE UNDERLYING SNOW
DUNE OVERWHELMING BIRCH GROVE, SHOWING THE STEEP LEEWARD SIDE
Another interesting phenomenon of arctic weather is the geyser-like bubbling occasionally seen along the beach at high tide in two or three feet of water. For minutes at a time geysers a foot in diameter belch forth great streams of air which throw the water up in miniature fountains. The explanation of this seems rather obscure, but I have thought that a sudden severe frost at the time of the ebb had sealed the surface of the sand, and the water, escaping beneath, had left numerous interstices into which the air permeated, to escape when the warm water of the rising tide melted the ice seal and forced out the air. Possibly the presence of dead thatch grass, thrown up and buried in the sand, aided in the accumulation of air. This phenomenon is very different from the tiny air spouts that arise from the burrows of beach fleas.
As one walks along the edge of the dunes near the beach in summer or winter, his attention may be attracted by a number of balls which appear to be made up of broken pieces of straw or grass. Some of these are not larger than a tennis ball, others the size of a cocoanut; some are perfectly spherical and firmly matted, others are loosely formed and often elongated in shape. Similar grass balls were found by Thoreau on the shores of Flint’s Pond in Lincoln, and they appear to have puzzled him considerably. It is evident from a careful study of a series of these balls and by actually watching their formation, that they are gradually built up in shallow water near the shore by the rolling action of the waves on particles of broken thatch, sticks, seaweed and grass which have collected in hollows and ripple-marks. A nucleus once started, more and more material is added as the ball rolls about.
These balls are to be distinguished from the hair balls, also occasionally found on the beach, that are formed in the stomachs of cattle, as well as from the balls formed by the rolling about of pieces of submerged marsh sod, which often take on a rounded pebble shape.
1 In Babson’s History of Gloucester, published in 1860, it, is stated that Peter Coffin, after failing at law and business, “went onto the farm, where he lived as long as it would yield him a support by the sale of the wood upon it, and then came back to town, and died Aug. 4, 1821, aged seventy-two.”