National Geographic : 1949 Nov
New Discoveries on the Mid-Atlantic Ridge BY MAURICE EWING Professor of Geology, Columbia University Leader, National Geographic Society-Woods Hole Oceanographic Institution-Columbia University Expeditions to the Mid-Atlantic Ridge Illustrations by National Geographic Photographer Robert F. Sisson " TAND by to lower away!" As this cry sounded, all hands crowded to the rail of our little re search ship Atlantis, rolling easily as she lay hove to on the gray midocean swells. It was a tense but eagerly awaited moment on our second voyage of exploration of the Mid-Atlantic Ridge, the world's longest moun tain range, which runs a full mile deep under almost the whole length of the Atlantic Ocean.* We were about to probe deeper down into the mud on the Atlantic's hidden bottom than we ever had been able to penetrate before. This meant that we would be reaching far back into the ancient history of the Atlantic Ocean, and even of the earth itself, a history preserved in the sediments that had been piling up on the sea bottom for many millions of years. Taking core samples of the ocean bottom was just one of the many scientific projects in our exploration of the Ridge under the sponsorship of the National Geographic So ciety, the Woods Hole (Massachusetts) Oceanographic Institution, and Columbia Uni versity, New York City. Exploring the Undersea World Swung out over the ship's starboard side was our new and improved coring apparatus, with which we would delve into the dark, silent undersea world. It was a 40-foot steel tube, two and a half inches in diameter, with a sharp cutting edge on the lower end and 1,000 pounds of lead weights on top to drive it down into the mud of the ocean floor. Double the length of tubes we had pre viously used, and now equipped with a piston to help pull up the mud inside, it would enable us to penetrate twice as far down into the bottom sediment as we had gone before. We were ready now to lower this tube on the end of two to three miles of steel wire, let it drive itself deep into the bottom mud, as a corer is pushed into an apple, then pull it out and haul it back to the surface with the core of mud inside for analysis. Mud from the Atlantic Ocean bottom is slimy, unglamorous-looking stuff, as is mud from anywhere (page 623). But in that mud we can read a chronological history of every thing that has happened in and around the Atlantic Basin far back into Ice Age times evolution of life, changes of climate, risings and sinkings of the ocean bed. We need to learn more about all these things. Our ship lay over the western "foothills," or terraces, of the Mid-Atlantic Ridge, almost two miles straight down beneath our keel. Thick fog hemmed us in, and our foghorn was sounding a nerve-shattering "bla-a -a" at frequent intervals. This was the first test of the improved, longer coring apparatus we had built since our last voyage. Would it work? If by mis take we hauled the corer in before it ac tually hit bottom, or if the trip device failed to let it fall freely the last 10 feet, it would not secure as good a sample as the old shorter tubes, and hours of work would be wasted. If the wire kinked or fouled, it might break, causing the loss of our tube and perhaps thousands of feet of valuable wire as well. No wonder then that we all felt a little tense as Capt. Adrian K. Lane, called out, "Cast off and stand clear!" As he pushed the control lever, a grinding roar came from the big winch down in the hold, the heavy steel wire rattling and slap ping as it unreeled into the sea. After about an hour, when we had paid out nearly three miles of wire, its tension suddenly slackened-the coring tube had hit bottom. At once the winch was reversed, the tension gauge showed the sudden strain as the tube was pulled out of the mud, and then began the long haul up. As soon as the tube was visible under water alongside, I sang out, "In sight!" Then, as it came up and broke water, "Surface!" This signaled the captain to slow down the winch, then stop, and the corer was hoisted aboard. A smear of mud on the outside showed that the tube had successfully pene trated 26 feet into the bottom. We found that this 26 feet of mud repre * See "Exploring the Mid-Atlantic Ridge," by Mau rice Ewing, NATIONAL GEOGRAPHIC MAGAZINE, Septem ber, 1948.