Harry Hess Uncovers A Deepsea Mystery

Even though sonar had been available for more than 20 years, it was not really put to many scientific uses until World War II, when a naval officer named Harry Hess turned an antisubmarine weapon into an important research tool. In the process, he would not only unlock the mystery of what the seafloor looked like, but give the theory of continental drift a whole new look.

Harry Hammond Hess was born in New York City in 1906 and graduated from Yale University with a degree in geology in 1927. After working as an exploration geologist for several years, he entered Princeton University where he received his Ph.D. in 1932. In 1934, he joined the faculty of Princeton, but his teaching career was interrupted in 1941 when he was called into active duty in World War II. Hess was a lieutenant in the naval reserve and eventually he was put in command of a ship called the USS Cape Johnson.

Hess's main duties while in the navy centered on antisubmarine warfare and landing troops on beaches on various islands in the Pacific Ocean. He quickly became an expert in the use of sonar and used it to keep track of the water depth around the islands that he patrolled. He soon realized that sonar would also work in deep water. As Hess and his crew sailed around the Pacific Ocean, he recorded thousands of miles of depth readings, thereby giving scientists their first real look at the ocean floor.

Hess discovered that the ocean floor was not smooth and flat as most scientists had believed, but was full of submerged mountains, valleys, ridges, and unusual flat-topped hills, which he named "guy-ots" after Arnold Guyot, the founder of the Princeton Department of Geology. After the war, Hess returned to Princeton and continued to conduct research on the geography of the ocean floor.

While Hess was at Princeton, geologist Bruce C. Heezen and cartographer Marie Tharp at Columbia University's Lamont-Doherty Geological Laboratory started to create a picture of the ocean floor that would become much clearer. In 1947, they picked up on the work Hess had started. Heezen, sailing aboard the research vessel Vema, began making detailed depth readings in the North Atlantic

Marie Tharp: Pioneering Geologist and Mapmaker Extraordinaire

Marie Tharp was a true pioneer in the field of marine geology. After receiving her degree in English from Ohio University, she attended the University of Michigan where she received her degree in geology. This was a time when few women looked for careers in the Earth sciences, but Marie was a person who liked making new discoveries and was not afraid of working in a "man's job." She started working for an oil company in Oklahoma but then decided to give research a try.

Teaming up with Bruce Heezen at Columbia University gave her the opportunity to become a star in the new field of marine geology. Unfortunately, because she was a woman, she was not allowed to accompany any of the early research cruises that were conducted in the late 1940s and early 1950s. Instead, Heezen went on the cruises and collected the data while Tharp stayed back at Lamont and, from the information that Heezen sent to her, created the maps that would radically

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Figure 4.2 Bruce Heezen and Marie Tharp created this world ocean floor panorama.

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change our view of Earth. Finally, after 33 cruises, the rules were changed and Tharp was able to accompany Heezen out to sea. After Heezen died in 1973, Marie Tharp created her final map. This one showed the entire seafloor of the planet, including all the features that had been discovered. This map, along with the data supplied by several other geologists, would put the theory of plate tectonics on a solid foundation.

Ocean. He supplied the information to Tharp, who then drew the maps. Little by little, a whole new picture of the ocean floor began to emerge.

First, they discovered a mountain chain in the middle of the Atlantic Ocean that runs from near the North Pole, south past Greenland, and almost all the way to Antarctica. From there, this ridge continues east, past southern Africa, through the Indian and Southern Oceans, past Australia and across the Pacific Ocean, and ending near Southern California. In all, this mid-ocean ridge, as it has become known, travels over 45,000 miles (80,000 kilometers), making it the longest mountain chain on Earth.

In the center of the mid-ocean ridge is a valley or "rift" lined with active volcanoes. In some places, like Iceland, these volcanoes have risen above the sea. In most places, however, the volcanoes lie under the water, and as they erupt, they add new rock to the surface of the Earth.

In addition to the mid-ocean ridge, Heezen and Tharp's maps also showed deep valleys, many of which run along the edge of the continents. These valleys are known as submarine trenches. In many cases, these trenches, which make an almost complete ring around the Pacific Ocean, contain enormous piles of sediment. One other unusual feature on the maps is a series of fractures, or faults, that cut across both the ridge and the trenches. Many of these fracture zones would cause the ridge to be offset and split by several hundred kilometers. This led some scientists to wonder if Earth was expanding. It was Harry Hess who came up with another answer and, in the process, solved another great scientific mystery.

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