After leading an expedition to gather echograms of the ocean’s floor, Maurice Ewing discovered the existence of the Midoceanic Ridge and postulated, with Bruce C. Heezen, the existence of a midoceanic rift.

From the blind creatures of sea, land, and air to the development of sonar and from a war that encompassed the world to seafloor mapping, modern science received the research necessary to prove the theory of continental drift Continental drift and in the process to make great strides in filling in gaps and adding new information to the world of ideas. Alfred Wegener, the multifaceted scientist responsible for proposing the theory of continental drift, first began formulating his notion when he noticed that the coastlines of Africa and South America fit together as if they had once been parts of one huge continent. Preceded by at least five others, including Francis Bacon, in his observations on the jigsawlike quality of continents, Wegener was the first to investigate the possibility fully. His research spanned the sciences and culminated in the publication Die Entstehung der Kontinente und Ozeane
Origin of Continents and Oceans, The (Wegener) (1912; The Origin of Continents and Oceans, 1924). His hypothesis explained the mysteries of similar fossils found on opposite sides of the earth and the similarity of geographic detail in parts of the world. Unfortunately, his hypothesis neglected to explain how the continents could be in motion, constantly breaking and rejoining. Midoceanic Ridge
Exploration, underwater
[kw]Heezen and Ewing Discover the Midoceanic Ridge (1956)
[kw]Ewing Discover the Midoceanic Ridge, Heezen and (1956)
[kw]Midoceanic Ridge, Heezen and Ewing Discover the (1956)
Midoceanic Ridge
Exploration, underwater
[g]Atlantic;1956: Heezen and Ewing Discover the Midoceanic Ridge[05060]
[c]Earth science;1956: Heezen and Ewing Discover the Midoceanic Ridge[05060]
[c]Geology;1956: Heezen and Ewing Discover the Midoceanic Ridge[05060]
[c]Science and technology;1956: Heezen and Ewing Discover the Midoceanic Ridge[05060]
Ewing, Maurice
Heezen, Bruce
Fessenden, Reginald Aubrey
Hess, Harry Hammond
Wegener, Alfred

The explanation Wegener omitted was found several years later during World War II. In 1912, spurred by the Titanic disaster, Reginald Aubrey Fessenden completed an off-again, on-again project aimed at creating an echo-detection device for seagoing vessels to be alerted to the presence of icebergs. About 1914, the former assistant to Thomas Alva Edison produced his invention that created sound waves under water. By listening to the echoes picked up by the underwater microphone, Fessenden could detect objects by changes in the echo in the same way many ocean creatures, and even some land creatures, had used blind vision for millennia. Fessenden’s early device became known later as the sonar when Paul Langevin improved on his concept and introduced it to the seafaring public for general use.

Following the example of creatures known for their ability to navigate in the darkness, such as the bat and certain aquatic animals, sonar was created. Sonar Sonar is an abbreviation for “sound navigation ranging”; it was used by ships to seek, hunt, or guard against the new terror of the seas, the German submarines. Sonar operates by the emission of high-pitched signals, followed by the interpretation of the echoes to indicate the presence of submarines, sea life, or anything else noteworthy below the surface. During the war, the Navy used a device similar in working principles to sonar, called the Fathometer Fathometer , to map the ocean’s floor around Iwo Jima. Aboard the USS Cape Johnson
Cape Johnson (ship) was Harry Hammond Hess, a geologist from Princeton University. He realized that with the technology of echo sounding, the seafloor could be mapped at last. While Hess’s eventual contribution to the exploration of the seafloor was more along the lines of data interpretation rather than actual physical data gathering, the task he made possible was carried out by a colleague and friend from Columbia University, Maurice Ewing.

Leading a group of scientists from Columbia University’s Lamont Geological Observatory Lamont Geological Observatory in Palisades, New York, Ewing began his journey in 1956 with the intent to map a string of undersea mountains called the MidAtlantic Ridge Midatlantic Ridge . He found in the process, however, that simple mapping was next to impossible in the light of the discoveries made by his team. Sounding by echo with sonar and the Fathometer and utilizing data from oceanic earthquakes, they charted their progress, noting with interest that the underwater earthquakes reported by the seismologists Beno Gutenberg and Charles Richter occurred with increasing frequency along the ridge. Another exciting and inexplicable discovery was made during the process of dredging rock from the seafloor in the hope of finding ancient crustal rock from the formation of the earth. Instead of churning up chronological layers of rock with the newest at the top, the expedition found only relatively new rock formations; the oldest among the rocks found was approximately 150 million years old, and the others were even younger. Perhaps the greatest discovery of all—that of the Midoceanic Ridge—occurred after the actual data collection and during the interpretation of the echograms.

Columbia University graduate student Bruce Heezen, in collaboration with Marie Tharp Tharp, Marie , also from Columbia University, began mapping the ocean floor based on data from previous expeditions. Working in the Lamont Geological Observatory, they examined the echo-sounding passes, revealing more topography. Much of the topography was very rugged terrain pierced by land jutting upward in the form of cliffs, crags, and, more important, mountains. The increasing detail of their mapping soon revealed that the ridge was not a regular mountain range or system. The ridge was 1,829 to 3,048 meters high and 74,028 kilometers long, with a continuous V-shaped, groovelike valley, later known as a rift valley. Often compared to the laces of a baseball, the superlative mountain range crisscrossed the world.

Heezen expanded on Tharp’s suggestion that the groove-shaped valley recorded by the echograms was a rift when it was compared to the median rift and the similar earthquake pattern found there. Although the then-current echograms—records of echo soundings—did not reveal the presence of a rift along the crest of the ridge, Heezen remained certain of his theory. He and Ewing developed a hypothesis on the existence of the rift and later suggested where the research team of the International Geophysical Year might look. By 1958, the Heezen-Ewing theory that the ridge contained a rift was proven correct. The work of Ewing and Heezen, which officially proposed the existence of the rift, sparked interest in further study of midoceanic ridges.

Beginning in 1872, HMS Challenger
Challenger (ship) began an expedition of discovery across the oceans. The first large-scale attempt to learn more about the earth’s waters resulted in massive amounts of data collected; it led to the precedent of large team efforts, combining the knowledge of several sciences to work toward one end. For various reasons, further group expeditions to the sea were put on hold for roughly half a century until, facilitated by war and technology, another group set out to discover the secrets beneath the sea. What had been previously impossible for HMS Challenger became feasible for the newest seagoing scientists—the actual mapping of the seafloor. Whereas the expedition of 1872 used a human-operated dredge and specimen containers, the 1956 expedition led by Maurice Ewing used the latest in sonar and dredging equipment to complete a goal first visualized by Hess.

Leading a group of scientists from the Lamont Geological Observatory, Ewing began his journey with the intent of mapping a string of undersea mountains called the Mid-Atlantic Ridge. He found in the process, however, that simple mapping was next to impossible in view of the discoveries made by his team. Hess tackled the strange information they gathered in a piece he called “an essay in geopoetry,” so named because of the extraordinary lack of supporting data for his proposition. Using the same information from which Ewing and Heezen developed and eventually proved their theory of the existence and location of a midoceanic rift, Hess went a step further in his speculations.

Hess proposed that hot rock rose from the earth’s interior through the frequently recorded earthquakes surrounding the midoceanic ridges. The continuous upwelling of hot rock continually forces the rift to part and the seafloor to spread as the material from each eruption cools and is pushed away at a rapid pace of a few centimeters per year. When the spreading seafloor encounters an obstruction such as a continent base, it moves under the obstruction, or subducts. Dubbed “seafloor spreading” Seafloor spreading by Robert Dietz, Hess’s theory helped validate Wegener’s idea of continents in drift. In addition to validating a decades-old theory, the work of Heezen and Ewing opened a new venue of research to scientists as the world entered the 1957-1958 International Geophysical Year. Midoceanic Ridge
Exploration, underwater

• Cox, Allan, and Robert Brian Hart. Plate Tectonics: How It Works. Palo Alto, Calif.: Blackwell Scientific, 1986. While only partially related to the topic of the Midoceanic Ridge. Cox and Hart’s work is a good follow-up on the interweaving of sciences used to create the total picture of the ocean’s floor.
• Hill, M. N., ed. The Seas: Ideas and Observations on the Progress of Study of the Seas. Vol. 3. New York: Interscience, 1963. Written for the researcher; well illustrated. Discusses geophysical exploration, topography and structure, and sedimentation. Includes reference sources at the end of each chapter.
• Idyll, C. P. Exploring the Ocean World: A History of Oceanography. New York: Thomas Y. Crowell, 1969. Geared for high school and college students. Contains photographs, charts, and graphs. A chronology of oceanographic developments is included.
• Menard, H. W. The Ocean of Truth: A Personal History of Global Tectonics. Princeton, N.J.: Princeton University Press, 1986. For the nontechnical reader. Menard’s writing style is very informative and his presentation is entertaining. Includes personal recollections and excerpts from letters.
• Pickard, George L. Descriptive Physical Oceanography: An Introduction. 5th enlarged ed. Boston: Butterworth Heinemann, 1995. A nontechnical introduction for undergraduates in the sciences and advanced high school students.
• Sears, M., and D. Merriman, eds. Oceanography: The Past. New York: Springer-Verlag, 1980. Written for the researcher and graduate student of oceanography. Most chapters contain numerous notes and references. It is an excellent reference source, but with few illustrations.
• Thurman, Harold V., and Alan P. Trujillo. Introductory Oceanography. 10th ed. Upper Saddle River, N.J.: Pearson Prentice Hall, 2004. General survey for students; good introductory text. Includes a glossary and references after each chapter. Well illustrated.
• Weiner, Jonathan. Planet Earth. New York: Bantam Books, 1986. This is a companion volume to the PBS television series, which is an introductory-level discussion of earth sciences in general. In addition to basic information on the work of Heezen and Ewing, there is a general background of the history of sea exploration and the projects that resulted from their work.

Hess Identifies the Cause of Continental Drift

Navy Conducts Sealab Expeditions

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