1. ENGLISH - A Survey of Atlantis - from U.S. NAVAL INSTITUTE - August 1940

A Survey of Atlantis - from U.S. NAVAL INSTITUTE - August 1940

A Survey of Atlantis

By Captain Gilbert T. Rude, U. S. Coast and Geodetic Survey

August 1940

Proceedings

Vol. 66/8/450

Atlantis . . . the legendary continent of classical literature . . . the con­tinent of drowned valleys and sub­merged mountains . . . fires the imagination of dwellers on the real continents of today with the mystery of its vanished people. Through untold time the restless ocean has guarded its resting place; the storms of centuries have failed to disturb the eternal quiet of its hills and vales.

Legend would have this island empire possessed of fertile fields and populous villages, of fabulous mines and stupendous canals. Cities of vast palaces and colossal temples were peopled by a race of wealth and power, and ruled by mighty kings intent on the subjugation and enslavement of the races within the Pillars of Hercules. Magnificent harbors thrived with the how of merchant vessels and galleys of war.

This interesting legend conjures before the imagination a weird and fantastic picture. The once thriving Atlantean seaports are now cities of silence, their builders for­gotten. Where throbbed the pulse of a mighty civilization the denizens of the deep now lazily swim. Palaces, once the scene of youth and laughter, are but hollow tombs; temples no longer resound to honestly words of wisdom. The magnificence and wealth that was Atlantis perished in a single night in the final great catastrophe. The island continent was locked by earthquakes, volcanoes belched destruction, and seismic sea waves lent their pounding might. The land slowly settled beneath the seething waters to become the continent of mystery.

The story of Atlantis has come down to us through 23 centuries in the form of a dialogue by Plato, the Greek philosopher and historian. He represents the story as having been passed down to him in verse written by his ancestor, Solon of Athens, who antedated him by 200 years. Plato further states: “My great-grandfather, Dropidas, had the original writing, which is still in my possession, and was carefully studied by me when I was a child.” It is recorded that the legend was narrated to Solon by a very old Egyptian priest as an ancient tradition gleaned from sacred Egyptian records then 8,000 years old.

Plato tells us that during one of the visits Solon was wont to make to Egypt, to discuss philosophy and ancient history with the wise men of Sais, this learned priest of great age narrated to him a de­tailed description of Atlantis and of its destruction:

This power came forth out of the Atlantic Ocean, for in those days the Atlantic was navi­gable; and there was an island situated in front of the straits which you call the Columns of Her­cules. The island was larger than Libya and Asia Minor put together and was the way to other islands, and from the islands you might pass through the whole of the opposite continent which surrounded the true ocean; for the sea which is within the Straits of Hercules is only a harbor, having a narrow entrance, but that other is a real sea, and the surrounding land may be truly called a continent. Now in the island of Atlantis there was a great and wonderful empire which had rule over the whole island and several others, as well as over parts of the continent; and besides these, they subjected parts of Libya within the Columns of Hercules as far as Egypt, and of Europe as far as Tyrrhenia.

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But afterward there occurred violent earth­quakes and floods and in a single day and night of rains all your warlike men in a body sank into the earth, and the island of Atlantis in like manner disappeared and was sunk beneath the sea. And that is the reason why the sea in those parts is impossible and impenetrable because there is such a variety of shallow mud in the way; and this was caused by the subsidence of the island.

Modern writers who have had the te­merity to enter the controversy of the existence of Atlantis date its destruction some 11,500 years ago. They have at­tempted to show by circumstantial evi­dence, which seems far from complete and not wholly convincing, that the island continent did exist. To support a land bridge hypothesis they make use of biological evidence, of the scientists’ study of mollusca and insecta, and of the similarity of fossil remains of certain animals of Europe and America. Corroboration is offered from comparison of the fauna and flora of both hemispheres. They endeavor to show from the researches of the anthropologist that be American Indian, instead of coming from Asia by way of Bering Straits, came from Europe by way of Atlantis.

Archeologists who have surrendered to be lure of Atlantis also offer as circum­stantial evidence the once mighty and highly cultivated ancient Mayan civilization of Yucatan. They seek to show that Mayan civilization arrived in Central America fully developed, having originated in some locality other than the American continent. They postulate a similarity between the gods, the religion, the arts and be architecture of the Mayan civilization and those of the early civilizations of Europe, and attempt to establish an indirect contact of the Mayans through the Atlantean continent with the early people of both the old and the new world. The theory is also advanced that this highly cul­tured civilization did not spread from Europe to Yucatan by way of Atlantis, but that this lost continent was its birthplace, the center in which it originated, developed to maturity, and thence spread east­ward and westward to Europe and to Cen­tral America.

The story of Atlantis has an equally strong appeal to the geologist. The noted Frenchman, Pierre Termier, not only paints a weird word-picture of the last night of Atlantis, but also makes a definite statement from geological evidence:

Geologically speaking, the Platonian history of the Atlantic is highly probable. ... It is entirely reasonable to believe that, long after the opening of the Strait of Gibraltar, certain of these emerged islands still existed, and among them a marvelous island, separated from the African continent by a chain of other smaller islands. One thing alone remains to be proved—that a cataclysm which caused this island to disappear was subsequent to the appearance of man in Western Europe. The cataclysm is undoubted.

Now that the technique of modern hy­drography has made feasible the extension of accurate and correlated marine surveys farther and farther seaward, it is not be­yond the realm of possibility that the mod­ern hydrographer through such surveys may yet obtain evidence, beyond that of a circumstantial nature, that Atlantis was more than a figment of classic imagination. Today, beyond the Straits of Gibraltar, there exist traces of what conceivably could have been a continent of the not- distant geologic past when the waters of the oceans, as some geologists claim, were several thousand feet below their present level. The Atlantic Ridge (Fig. 1), bounded by the 2,000-fathom contour, ex­tends the entire length of the Atlantic. The Azores, the surviving peaks of Atlan­tis, rise above the surface of the sea, and throughout the ridge are large areas in­closed within the 1,000-fathom and the 1,500-fathom submarine contours.

An accurate, modern hydrographic sur­vey of this well-defined ridge would indi­cate the character of the topography, whether definitely submarine or of a possi­bly subaerial erosive nature similar to that which is now known to exist along the con­tinental slope of North America through surveys made during the past decade by the Coast and Geodetic Survey. If the topography of the ridge is shown by such a survey to be of a subaerial character, evidence would thus be furnished that during some geologic age the ridge was above the sea level of that period, evidence which would be more conclusive than any yet ad­vanced of the existence of Atlantis.

At any rate, the survey would undoubtedly yield a wealth of information to the geologist in his interpretation of physio­graphic features and to the seismologist in his seismic studies. And from a definitely practical standpoint, as deep water fath­ometers come into general use, the characteristic features represented in this sub­marine mountain range would, when charted, prove of inestimable value to the navigator in fixing his position in thick weather when celestial objects were not available.

Until recent years it had been necessary to limit detailed hydrographic surveys to a belt of comparatively shoal water immediately adjacent to the coast line and practically within sight of land. Instruments methods developed within the past few years, however, have made possible accurate detailed hydrographic surveys over areas well off our coasts. Since the advent echo sounding, and especially of sono-radio buoys for controlling sounding lines by means of radio acoustic methods, the rigidly controlled and co-ordinated mod­ern surveys which have been extended beyond the edges of the continental shelves both coasts of the United States have disclosed a wealth of dissected submarine regions, deeply indented submarine gorges, towering submerged mountains. These discoveries, and their accurate surveys, have aroused general interest in the topography of the sea bottom and have given impetus to the extension of similar hydrographic explorations to the main oceanic basins.

From data now becoming available, it appears that the ocean basins had a geologic history similar to that of the con­tinents now above the sea. A noted Ameri­can geologist, the late A. C. Veatch, was of the opinion that the topography of the Atlantic Continental Slope, which has been uncovered by these recent surveys, showed definite stream erosion forms. The following is quoted from one of his papers:

In the new surveys one is confined to the facts, and there are many hundreds of soundings in the area of this project alone. While it is, of course, possible that interpretations differing in minor respects may be made by experienced topog­raphers, the stream erosion character of the slope and the existence of major features on it, as well as the marine erosional character of the shelf, cannot be escaped.

If then we accept the theory that the topographic features on the Continental Slope are of a character that can be formed only by subaerial erosion, a comparison with the submarine topography discov­ered by a detailed survey of the Atlantic Ridge may indicate whether this subma­rine feature was subaerial during the same period as the Continental Slope.

Based on his studies of the North Amer­ican Continental Slope and that of the Congo, Dr. Veatch places the former sea level at approximately 12,000 feet below its present level, and from an interpretation of the silting of the Congo trench es­timates the time of the return of the ocean to its present level at about 10,000 years ago. It is to be noted that this time ap­proximates the legendary time of the de­struction of Atlantis—about 11,500 years ago!

Several years ago Professor Richard M. Field, Chairman of the Commission on Continental and Oceanic Structure of the International Union of Geodesy and Geo­physics, suggested to the author the dedirability of a hydrographic survey of the Atlantic Ridge and inquired as to its feasibility. It is the purpose of this article to propose a modern hydrographic survey of the Ridge and to describe from the stand­point of a practical hydrographer tentative plans, including methods and technique, adequate for a survey as well controlled as those made in recent years over the con­tinental shelves off the North American coasts. These proposed methods will be de­scribed in some detail since they not only indicate the feasibility of the project, but may be of assist­ance whenever such a survey is undertaken. The author’s interest in such a survey is centered primarily on its practical value for charting the submarine features, but he cannot help being fasci­nated by it as a problem to tax the ingenuity of the mod­ern hydrographer. He will therefore confine himself to the “how,” to the practical methods adequate to the suc­cessful accomplishment of the project. He will leave to the geologist, to the seismolo­gist, and to other interested scientists, the “why.” He will leave to the future the value of the survey as evidence of the existence of Atlantis.

At the time this survey was suggested sono-radio buoys used in obtaining hori­zontal distances had not been fully de­veloped by the Coast and Geodetic Survey nor had they been used in deep water. They have now entirely replaced station ships on offshore surveys and are being successfully anchored and used in increas­ingly greater depths.

It may be well to describe some of the methods which have already provided adequate horizontal control in shoaler water and which it is now proposed to subject to a more rigorous test by extending them to areas from 1,000 to 2,000 fathoms in depth. Such a survey is definitely feasible under technique developed in recent years; in fact, little additional equipment would be required beyond that now in everyday use on the vessels of the Coast and Geo­detic Survey. Recently the author an­chored a sono-radio buoy without diffi­culty in 400 fathoms of water for the con­trol of sounding lines well offshore toward the middle of the Gulf of Mexico. Ordinary 3/8-inch wire cable was used. A modern sur­vey vessel could, with equal facility, an­chor sono-radio buoys on the Atlantic Ridge in from 1,000 to 2,000 fathoms. It would be necessary, of course, to provide at somewhat greater cost wire cable of smaller diameter, with about equal tensile strength. The buoys would remain in position except, of course, in the most severe storms and no greater risk of their loss or change in position would be occasioned than that attendant to the operation of the present system of control buoys in our offshore surveys.

Experiments, which appear to promise Recess, are now being carried on by the Coast and Geodetic Survey in anchoring sono-radio survey buoys in deep water, 1,000 to 2,000 fathoms. The anchors, from 50 to 1,000 pounds each, are made up of several old railroad car couplings at a cost of about two cents a pound. It is proposed to use a detaching apparatus so as to de­tach the anchor to facilitate retrieving the more expensive wire cable. The Chief of the Division of Instruments of the Coast and Geodetic Survey, at the author’s re­quest, has devised such an apparatus which, by means of a 30- to 50-pound messenger, will detach the anchor. The apparatus will be attached to the an­chor cable about 100 fathoms above the anchor to obviate either fouling with the anchor or tripping from contact with the bottom.

A wire anchor cable is being selected un­der the advice and specifications of a lead­ing wire rope manufacturer. The problem involves the use of a high strength wire cord suitable for anchoring rather sizable buoys, the cord being used in lengths of 7,500 feet. The standard wire cord being considered for this service is 3/16-inch aircraft stainless steel cord in 7x7 construction. The breaking strength of this cord in stain­less steel is 6,100 pounds.

Formerly the position of the survey ship, at sea beyond the range of visual “fixes” on shore objects, was subject to un­certainties which increased with the dis­tance beyond the limits of this shore con­trol. Various methods had been attempted for controlling hydrographic surveys out of sight of land, but none gave satisfactory accuracy until the development of radio acoustic ranging. Soundings made in the past by piano wire and sinker were suffi­ciently accurate when made under good conditions of sea and weather, but the un­certainty of the actual geographic posi­tions of the soundings made it impossible to carry on detailed co-ordinated offshore surveys, since the positions of the sound­ings could not be accurately correlated. In fact, until the introduction of radio acous­tic ranging the determination of the geo­graphic positions of offshore soundings had been based entirely on somewhat refined methods of navigation, such determination depending on celestial navigation, on dead reckoning, or on a combination of both. Even with all the refinements possible to these methods, the finally accepted posi­tions were quite approximate.

Modern science has now provided the means for revolutionary improvements both in technique and in instruments for the more accurate measurement of depth by indirect methods and for the determi­nation of the geographic positions. The scientist afloat is making the ocean bottom echo its whereabouts back to him, and ac­curate marine surveys based on the scien­tific principles involved are robbing the sea of its hidden mysteries.

Echo sounding, the use of which has be­come practically universal, is almost self­explanatory. Depths are determined in­directly by the measurement of the time interval required for a sound impulse to travel to the ocean bottom and to return as an echo to the vessel. The construction of the specially designed, time-measuring instrument is based on a precise knowledge of the transmission of sound in sea water. In the old days more than an hour was re­quired to obtain a deep sea sounding in 20,000 feet; an echo sounding can now be made in that depth in about eight seconds. Since echo soundings are made by a ship running at full speed, it is evident that the reckoning of the ship’s position is subject to less error from the uncertain effects of wind and current.

Knowledge of the velocity of sound in sea water is also employed in the determi­nation of the geographic positions of the soundings. By the method of position de­termination known as radio acoustic rang­ing, the position of the survey vessel is de­termined by its distance from hydrophones suspended in the water from sono-radio buoys which have been accurately located by a “sea-traverse” measured by “taut wire” apparatus. The taut wire was de­veloped by the British and adapted by the Coast and Geodetic Survey to its radio acoustic ranging buoy control. The au­thor learned of the device from a descrip­tion given by Admiral Edgell at the 1932 conference of the International Hydro­graphic Bureau. The apparatus is com­posed of a reel of fine piano wire (about 140 miles in length) which can be payed out under uniform tension over a registering sheave as the surveying vessel steams along, thus enabling the surveyors to measure distances accurately where the water is relatively shoal and the bottom comparatively uniform.

Having established a system of buoy control over an area, the indirect measure­ment of distances from two or three buoys to the survey ship is obtained by the de­termination of the time required for a sound wave produced by the explosion of a T.N.T. bomb to travel through the water from the survey vessel to the hydrophones suspended from the sono-radio buoys. When a new position is required a bomb is dropped overboard while under way and the time of the explosion recorded on a chronograph tape on the ship. The sound wave travels through the water in all di­rections and when the impulse reaches the hydrophones suspended from the sono-radio buoys, radio signals are sent out to the survey vessel by small automatic radio sets installed within the buoys. These signals recorded on the same chronograph tape as was the original explosion. The time interval thus measured, multiplied by the apparent velocity of sound in water as determined for the locality, gives the horizontal distance of the survey ship from the various buoy hydrophones. The bombs, instructed aboard as needed, are seldom imposed of more than a quart of T.N.T., the quantity depending upon the distance of the ship from the sono-radio buoys, and timed to sink about 50 feet before ex­ploding.

The methods and the equipment for the control of the sounding lines on the pro­posed survey of the waters of the Atlantic Ridge would be somewhat similar to those now being used on our offshore hydro­graphic surveys along the Atlantic and Gulf coasts, combined with radio acoustic triangulation methods similar to those used several years ago for controlling the Georges Bank survey. This radio acoustic triangulation for main control has been supplanted almost entirely in recent years by sea traverses measured by the taut- wire apparatus. Such an apparatus, how­ever, would not be entirely suitable for the deep water area on the Atlantic Ridge, but could be adapted, at slight extra expense, for measurement of the initial base line.

The sketch in Fig. 3 illustrates the corre­lation of the various methods used in mak­ing a survey over an extensive area along the coast. The small circles represent the positions of survey buoys which have been anchored and then located by the taut wire. They are used as radio acoustic con­trol stations by the surveying vessel as the sounding lines are being run. When the bouys have been anchored approximately in the desired positions, as determined by courses and log distances, the vessel starts at the inshore end of the row of buoys, for example, at the position inshore near Barnegat Lightship. After anchoring one end of the fine steel wire, the vessel’s initial position is determined by sextant angles measured between triangulation stations on shore and a run is made along the line of survey buoys, paying out the wire under constant tension. The distances between buoys are read from the counter on the sheave as each buoy is passed. (The wire is not recovered.) The direction between ad­jacent buoys is determined by measuring simultaneously a vertical angle between the horizon and the sun, and an inclined angle between the sun and the pair of buoys when the latter are on range. In the above case (Fig. 3) the traverse, extending southeast­ward 50 miles from Fire Island, thence south-westward 57 miles, thence west-northwest­ward to the vicinity of Barnegat Light­ship, had a closing error of only 2¼ feet per mile. The total length of the traverse was 155 miles. Supplemental traverses were run where necessary to provide control for the entire area.

During the years 1930-32 the Coast and Geodetic Survey made a survey of Georges Bank controlled entirely by radio acoustic triangulation (Fig. 4). The vertices of the triangles were marked by temporary sur­vey buoys and the lengths of the sides of the triangles were determined by bombing. The scheme of marine triangulation was carried 140 miles from an offshore buoy, located by a series of star observations made with sextants, to connection with shore triangulation stations on Cape Cod and on Nantucket Island. The connection was made with an error in geographic posi­tion of only 400 meters, about 3 meters per mile.

The particular plateau of the Atlantic Ridge, selected for illustrating the feasibility of a similarly executed survey in much deeper water, lies 300 miles south-westward from the Azores (Fig. 1). It is covered by almost 1,000 fathoms of water. To start such a survey a base line about 8 miles long with a sono-radio buoy at each would be measured by means of taut­-wire apparatus near the middle of the plateau, as indicated by the heavy line (Fig. 2). As on the Georges Bank survey, the initial ge­ographic posi­tion of one of the buoys at end of the oa.se would he determined by a series of star observa­tions taken by sextant from the survey ship. The azi­muth of the base would he determined by measuring simultaneously the vertical angle be­tween the hori­zon and the sun and an in­clined angle between the sun and the pair of buoys when on range from the ship’s bridge (Fig. 5).

Taut-wire methods which heretofore nave been limited to measurement of dis­tances in shoal water, with the wire un­supported and sinking to the bottom, would require a slight change in technique in the greater depths on the Atlantic-Ridge. For the measurement of this base the vessel would anchor the end of the piano wire of the taut-wire apparatus about 3 miles from one end of the base line and then steam directly for the buoy which marks that end. When within about a mile of the buoy and at about every 20 to 30 seconds thereafter, a small float of balsa or other light wood would be snapped onto the piano wire, which leads directly astern, by means of harness snap-hooks fastened to the wooden floats. With this method, at a ship’s speed of 10 knots, the wire would be supported on the surface of the water by floats spaced at intervals of from 300 to 500 feet. Since the taut-wire apparatus applies a con­stant tension to the wire as it leads astern from the ship (about 30 pounds), an adequately ac­curate meas­urement of the distance be­tween the two buoys of the base can be determined, provided, of course, the measurement is made on a calm day when there is little current or at a time when any wind-produced currents set nearly parallel to the direction of the base line, thus elim­inating an excessive horizontal catenary. By this method the 8-mile base could be measured with an accuracy of at least 8 to 10 meters, almost one part in two thous­and, a degree of accuracy quite adequate for a project in this location and in this depth of water.

The buoys marking the base line, as well as those marking the triangle vertices, nat­urally would swing in the current with a radius dependent upon the scope of anchor cable, which need not be greater, however, than 5 to 4, that is, about 1,250 fathoms of cable to each 1,000 fathoms of depth. In the limited area of such a survey all buoys would tend to swing to the same current direction. Since such a survey would be made on a scale of about 1:250,000, this radius of swing of the buoys would, of course, be negligible.

With this measurement of the base line completed all data would now be available for starting a survey, the geographic posi­tion of one end of the base line determined by astronomic observations, the azimuth of the base determined by sextant angles between the sun and the base, and the length of base measured by means of the taut-wire apparatus.

Having the length, geographic position, and orientation of the base line, the survey can be readily expanded into a scheme of radio acoustic triangulation somewhat similar to the scheme used to control the Georges Bank survey previously referred to. The base line would be located near the western edge of the plateau so that the control could be expanded northward, eastward, and southward as indicated by broken lines (Fig. 2). This radio acoustic scheme of tri­angulation laid out over the area inclosed within the 1,000-fathom con­tour would furnish con­trol for a modern radio acoustic survey of the entire area represented by stippling in Fig. 1, roughly a circle 270 miles in diameter and 57,000 square miles in area. An adequate hydro­graphic survey of this area, which of course is but a small section of the whole of the Atlantic Ridge, could be made by one sur­veying vessel in about four months during the summer season. With the knowledge and training obtained on the initial project, similar surveys could be readily extended with only slight variation in technique to the somewhat deeper waters of the remaining areas of the ridge.

A survey of the vast area comprising the Atlantic Ridge well merits the co-oper­ation of leading maritime nations. Its cost would be comparatively small, less than that represented by a single day of a modern war, and the resulting data would be of inesti­mable value. The Inter­national Hydrographic Bureau at Monaco could well sponsor such an in­ternational project when the time becomes more propitious upon the ter­mination of the differ­ences which have arisen among nations. With the return of cordial inter­national relations the na­tions of the earth might well consider the desira­bility of employing their combined navies in a hy­drographic survey of this drowned continent of classic legend.

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