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This article is from the In-Depth Report The Titanic: 100 Years Later

From the Archive, 1912: What We Know About Icebergs

How they are formed; Their characteristics; How they drift; Precautions taken to protect shipping against them



Scientific American, April 27, 1912

Editor’s note: we are publishing this article on the occasion of the 100th anniversary of the sinking of the RMS Titanic on April 15, 1912

Scientific American
Vol. CVI, No. 17, April 27, 1912

An iceberg is a fragment of a glacier. Inch by inch the huge river of ice which we call a glacier creeps toward the sea, and here its projecting end is broken off by the action of the waves. "Calving" is the technical name which has been given to this process of breaking bergs from glaciers. It is a process that occurs all the year around, but more frequently in summer than in winter, a process, moreover, that sets adrift thousands of huge ice masses during the course of a year.


Icebergs were a known hazard in the North Atlantic. Here is a map from 1912 showing where they were likely to come from and where the Titanic sank on April 15, 1912. Credit: Scientific American, April 27, 1912

The icebergs that find their way into the paths of transatlantic liners come down from the coast of Greenland; for the interior of Greenland is a huge ice sheet fringed by mountains and promontories. Deer fiords reach far into the inland ice, terminated only by the sheer walls of giant glaciers. Sometimes, however, the ice slides down in broad expanses close to the margin of the sea.

In the vicinity of the great Bank of Newfoundland icebergs appear in greatest numbers- in other words, athwart the transatlantic oceanic steamer routes. According to data collected by the United States Hydrographic Office, to which we are indebted for most of the information that appears in this article, icebergs have been seen in April, May, and June as far south as the thirty-ninth degree of latitude and as far east as longitude 38 degrees 30 minutes west of Greenwich. Indeed, floating ice may be encountered anywhere in the North Atlantic Ocean north of the fortieth degree of latitude at any season of the year.

How Icebergs Drift Southward.
It is the Labrador current that carries an iceberg southward. But ere it reaches the high seas, the berg may be subjected to many mishaps. It may ground in the Arctic basin; it may be stranded on the shores of Labrador and break up; it may disintegrate entirely. The numerous islands, bays, headlands, shoals, and reefs that constitute the coast of Labrador mercifully obstruct the passage of many icebergs and prevent them from reaching the waters of the North Atlantic.

Bergs, when first liberated on the west Greenland shore, are out of the strongest sweep of the southerly current, and they may take some months to find their way out of Davis Strait, while again others may at once drift into the current and move unobstructed until demolished in the Gulf Stream.

Little is known of the Labrador current, beyond the fact that it skirts the coast of Baffin Land and Labrador; that its usual rate of motion is from 10 to 36 miles a day; that its breadth and depth are uncertain; and that it occasionally ceases altogether. The cause of the Labrador current's vagaries and the whole subject of ice movements is one that scarcely lends itself to prediction. It is simply known in a general way that on the Grand Bank of Newfoundland bergs often move southward or southeastward. Those that drift westward of Cape Race usually pass between Green and St. Pierre banks.

The iceberg that glints in the path of a steamer on the Grand Bank may not be of this year's "calving." Indeed, it may have been broken from its parent glacier years before. It has been figured by the Hydrographic Office that if bergs were liberated principally in July and August, they should reach the transatlantic routes in December and January. This, however, is rare. Evidently the irregular coast of Labrador must considerably arrest the flow, when it is considered that bergs are most numerous during the early summer off the Bank. Of two bergs set adrift on the dame day, one may reach the Grand Bank two years before the other.

The advancing limit of Arctic ice, having in its train an endless procession of masses drifting down from the North, reaches the northern average limit of the Gulf Stream in the month of April, and having spread itself along this line both East and West of the 50th meridian of longitude, the ice disintegrates and rapidly disappears. Still, after reaching this limit of southward movement, many bergs, on account of their deep immersion, find their way to the westward even within the current of the Gulf Stream.

The locality in which ice of all kinds is apt to be found during the months of April, May, and June lies between latitude 42 degrees 45 minutes and longitude 47 degrees 52 minutes west of Greenwich. Here the Gulf Stream and the Labrador current meet; here the movement of the ice is influenced sometimes by the one and sometimes by the other of these currents; and here in latitude 41 degrees 46 minutes and longitude 50 degrees

14 minutes the "Titanic" came to grief.


A huge iceberg, in the shape of a ship’s sail, floats in the North Atlantic, in a photo published in 1912. Credit: Scientific American, April 27, 1912

The Menace of the Iceberg.
It is the huge mass of an iceberg that the mariner has most to fear. While it may vary in size, an ordinary iceberg will measure from 60 to 100 feet to the top of its walls, and it will have spires or pinnacles towering from 200 to 250 feet above a base that may be from 300 to 500 yards in length. Only one-eighth or one-ninth of the entire mass lies above water. Mass, let it be borne in mind, is a different quantity from height. Hence, the statement sometimes found in books that the depth of a berg under water may be from eight to nine times the height above water is incorrect. It is possible to have a berg as high out of water as it is deep below the surface; for if we imagine a large, solid lump of any regular shape, which has a very small sharp high pinnacle in the center, the height above water can easily equal the depth below. The Hydrographic Office has recorded the case of a berg, grounded in the Strait of Belle Isle in sixteen fathoms of water, that had a thin spire about 100 feet in height. Often the bergs are so nicely balanced that the slightest melting of their surfaces causes a shifting of the center of gravity and a consequent turning over of 'the mass into a new position.

Disintegration occurs very rapidly. On the coast of Labrador in July and August, when bergs are packed thickly together, the noise of rupture is often deafening. When they are frozen, the temperature is very low, so that on exposure to a thawing temperature the tension of the exterior differs from that of the interior. In other words, the berg becomes like a huge Prince Rupert's drop, which, as every one knows, is a drop formed by allowing molten glass to fall into cold water. It is said that the concussion of gun fire will sometimes break up a berg, so unequal is the tension within and without. During the day, water, the result of melting, finds its way into crevices. At night it freezes, expands, and splits the berg. The greater the splitting action the more rapid is disintegration, because new surface is exposed. Were it not for these circumstances, large bergs would remain intact years before they melted completely away.

The Queer Shapes of Icebergs.
Not only is the huge mass of an iceberg a source of danger, but its eccentric shape is as well. The weird pinnacles, spires, domes, minarets, and peaks, that remind one of castles fashioned by some genius for the pleasure of some whimsical fairy princess, find their counterpart in unseen, outlying spurs that project under water and that are fully as dangerous as any reef. The United States Hydrographic Office has called attention to the accident sustained by the British steamship "Nessmore," which ran into a berg and stove in her bows. When she was docked a long score was found extending from abreast her fore rigging all the way aft, just above the keel. Four frames were broken, and the plates were almost cut through. As there was clear water between the ship and the berg after the first collision, it was evident that the ship had struck a projecting spur after her helm had been put over.

Warning the Mariner.
Since the routes taken by most of the vessels that ply between Europe and the United States pass directly through that part of the Grand Bank which is most thickly sown with icebergs, it becomes interesting to ascertain what precautions are taken to warn mariners of their danger. By means of the wireless telegraph each master informs the vessels in his immediate radius of icebergs and field ice that he has sighted. His warning is either directly communicated by wireless to land or relayed from ship to ship until it eventually reaches the United States Hydrographic Office at Washington, D. C. Wrecks, derelicts, ice, and other obstructions to navigation are promptly reported. On the basis of these reports the United States Hydrographic Office prepares a daily memorandum which is sent to sixteen branch Hydrographic Offices along the Atlantic Coast, the Great Lakes, the Pacific Ocean, and the Gulf of Mexico. In these branches the masters of sailing vessels and steamers may note the probable location of obstructions that have been reported. The daily memorandum issued by the United States Hydrographic Office at New York on April 15th last, a memorandum now of tragic interest because of the "Titanic" disaster, reads as follows:

NORTH ATLANTIC OCEAN.

OBSTRUCTIONS OFF THE AMERICAN COAST.

     March 28th—Latitude 24 degrees 20 minutes, longitude 80 degrees 02 minutes, passed a broken spar projecting about 3 feet out of water, apparently attached to sunken wreckage.—“Evelyn” (steamship) Wright.

OBSTRUCTIONS ALONG THE OVER-SEA ROUTES.

     April 7th—Latitude 35 degrees 20 minutes, longitude 59 degrees 40 minutes, saw a lower mast covered with marine growth.—“Adriatic” (Italian steamship) Cevascu.

ICE REPORTS.

     April 7th—Latitude 45 degrees 10 minutes, longitude 56 degrees 40 minutes, ran into a strip of field ice about 3 or 4 miles wide extending north and south as far as could be seen. Some very heavy pans were seen. –“Rosalind” (British steamship) Williams.

     April l0th—Latitude 41 degrees 50 minutes, longitude 50 degrees 25 minutes, passed a large ice field a few hundred feet wide and 15 miles long extending in a N.NE. direction. –“Excelsior” (German steamship). (New York Herald).

     Collision with Iceberg—April 14th—Latitude 41 degrees 46 minutes, longitude 50 degrees 14 minutes, the British steamer "Titanic" collided with an iceberg seriously damaging her bow; extent not definitely known.

     April 14th—The German steamer "Amerika" reported by radio telegraph passing two large icebergs in latitude 41 degrees 27 minutes, longitude 50 degrees 08 minutes. –“Titanic” (British steamship).

     April 14th—Latitude 42 degrees 06 minutes, longitude 49 degrees 43 minutes, encountered extensive field ice and saw seven icebergs of considerable size—“Pisa” (German steamship).

J. J. KNAPP,

Captain, U. S. Navy, Hydrographer.

From this daily memorandum it will be seen that the "Titanic" had been informed by the "Amerika" of the proximity of two large icebergs. A few hours later she met her doom.

Day after day the United States Hydrographic Office keeps mariners informed of the dangers that lurk off the Grand Bank. Through the courtesy of Lieutenant John Grady in charge of the Branch Hydrographic Office at New York, the writer was permitted to examine reports that passed through the office recently. On April 10th at 8:20 A. M. the steamship "Excelsior," in latitude 41 degrees 50 minutes north, passed through field ice only a few hundred feet broad, but at least 15 miles in extent in a north northeasterly direction. On the 11th the "Carmania's" captain reported about thirty large icebergs in latitude 41 degrees 54 minutes and longitude 50 degrees 30 minutes west, as well as extensive field ice. "Some large bergs," to quote the "Carmania's" captain, were "about 400 feet long and from one-quarter to one-half a mile in width."

Signs of Icebergs.
How can a ship's commander know whether ice is near or not? On that point the United States Hydrographic Office gives the following information:

Before ice is seen from deck the ice blink will often indicate its presence. This is readily understood when it is known that it is caused by the reflection of the rays of light from the sun or moon.

On a clear day over the ice on the horizon the sky will be much paler or lighter in color and is easily distinguishable from that overhead, so that a sharp lookout should be kept and changes in the color of the sky noted.

On a clear day icebergs can be seen at a long distance, owing to their brightness, and at night to their effulgence. During foggy weather they can be seen through the fog by their apparent blackness, if such a term can be applied.

They can also be detected by the echo from the steam whistle or fog horn. This should be remembered, since by noting the time between the blast of a whistle and the reflected sound, the distance of the object in feet may be approximately found by multiplying by 550.

The presence of icebergs is often made known by the noise of their breaking up and falling to pieces. The cracking of the ice or the falling of pieces into the sea makes a noise like breakers or a distant discharge of guns, which may often be heard a short distance.

The absence of swell or wave motion in a fresh breeze is a sign that there is land or ice on the weather side.

The appearance of herds of seals or flocks of birds far from land is an indication of the proximity of ice.

The temperature of the air falls as ice is approached, especially on the leeward side; but generally only at an inconsiderable distance from it. The fall of the temperature of the sea water is sometimes a sign of the proximity of ice, although in regions where there is an intermixture of cold and warm currents going on, as at the junction of the Labrador Current and the Gulf Stream, the temperature of the sea has been known to rise as the ice is approached. If a berg be grounded, water flowing past it will be lowered in temperature and thus give an indication of its presence. Change of temperature may therefore serve as a warning, and frequent observations, both of the temperature of the air and the sea, should be taken and considered.

SIGNALS IN RELATION TO ICE.
Information as to wind, temperature, weather indications, and the state of the ice can be obtained by communicating with the marine signal stations of Newfoundland. St. Pierre, and Canada. These are situated at Cape Race, Cape Ray, Belle Isle, Chateau Bay, Amour Point, Galantry Head (St. Pierre), and St. Paul Island.

Wireless telegraph stations are operated for the Department of Marine and Fisheries of the Dominion of Canada by the Marconi Wireless Telegraph Company at most of these stations, and vessels fitted with Marconi apparatus can communicate with them.

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