Maurice Ewing (1906 - 1974) was an American geophysicist, oceanographer, and a pioneer of ocean floor research. He was born in rural Texas to a large farm family. His expertise in mathematics led him to be offered a scholarship to Rice University at a young age, eventually earning a Ph.D. in physics. "Doc" Ewing taught physics at the University of Pittsburgh and Lehigh University before becoming a professor of geology at Columbia in 1947, where he worked until 1972. Also an intense researcher, he collected years worth of core data from the world's ocean floors, bringing the ocean basins into view for the first time. Results from his research laid groundwork for further discoveries that would shape plate tectonics in the Earth Sciences.
Specific contributions to plate tectonic theory
Maurice Ewing became familiar with techniques for analyzing subsurface geology while doing sidework for oil companies. Using dynamite to produce seismic waves that would reveal underground structures, he then took the idea to the ocean. In 1935, Dr. Ewing discovered the continental shelf off of the Atlantic coast of the United States was not a permanent feature of the continent, but a wedge of eroded sediments over 4,000m thick sitting on top of ocean bedrock.
In 1947, the National Geographic Society commissioned Ewing to explore the mysterious ridge which had been discovered in the middle of the Atlantic Ocean. His finding revealed only a thin layer of sediments, not several billion years old, but just 100-200 million years worth of sedimentation. In addition, the young and thin ocean crust was made of volcanic basalt and not sunken continental material. After two more sucessive expeditions to the ridge, Ewing founded the Columbia Lamont Geological Observatory (now known as the Lamont-Doherty Earth Observatory) in 1949 with the main mission of studying the ocean floor.
Dr. Ewing's near constant ocean research created a need for a map of the Atlantic sea-floor. He assigned the job to Bruce Heezen and Marie Tharp, who produced a stunning 3-D physiographic map of the North Atlantic Ocean in 1959. As his research expanded, eventually maps created from cores, sonar data, and earthquake data revealed that the mid-ocean ridge was a global system of volcanic mountains. (see Heezen & Tharp "World Ocean Map" below) Although hidden underwater, it was, indeed, the largest geological feature on the Earth. The discovery was considered one of the most important in the Earth Sciences during the 20th century.
The maps also created a need to reexamine traditional theories about the Earth's geologic processes. As a natural response to such a startling discovery, subsequent research would reveal that the newest crust is being created at the ridge system. Support for this came, in large part, from magnetic striping of ocean floor rocks showing rock ages increasing with distance away from the ridge's rift valley. Harry Hess, from Princeton, combined the ridge system with the findings of great plunging crustal trenches in the Pacific to lay out his theory that the seas were spreading open. With sea-floor speading now accepted, it did appear the Earth's continents were in motion afterall, and the plate tectonics revolution was on.
Other interesting scientific contributions
Maurice Ewing's obsessive need for data collection led him to be the chief scientist aboard the famed research vessel Glomar Challenger. This ship was the first dedicated drilling vessel for ocean floor research. The ship headed the Deep Sea Drilling Program and provided cores that would greatly aid the plate tectonics revolution.
The existence of the SOFAR (SOund Fixing And Ranging) channel was first predicted and then discovered by Dr. Ewing. The channel is around 1km deep on average, and centers around the area where the speed of sound is at minimum in the water column. This effect is due to how the speed of sound decreases with falling temperatures down from the surface but then increases again with the higher pressures of the deeper ocean. Sounds above and below tend to be bent away from the channel allowing it to be very quiet. Sounds created, especially low frequency sounds, can travel very efficiently through the channel, up to several thousand kilometers. Humpback whales seem to take advantage of the SOFAR channel for communication. Dr. Ewing proposed that the military should set up an array of acoustic microphones to monitor the channel. Downed military pilots in WWII could carry a metal sphere that implodes at the average depth of the channel, acting as a distress signal and providing triangulated coordinates of their locations. This idea was later implemented by the U.S. military as the LOFAR (LO Frequency Analysis and Ranging) program to monitor submarine activity. The SOFAR channel was extensively mentioned in Tom Clancy's novel "The Hunt for Red October." In addition, Dr. Ewing was credited for finding a similar sound channel in the atmosphere, leading to the government's "Project Mogul" in 1947/48 that had balloons listening for acoustical disturbances created by Soviet atomic bomb tests.
Ewing's also first described the phenomenon of turbidity currents in the ocean. These colossal events are most commonly triggered by earthquakes or slumping on sloped seafloor. In what begins essentially as a landslide, sediment-laden or "turbid" water moves downslope underneath clearer water, picking up more speed and more sediment as it travels. Turbidity currents have been measured to move through canyons at several hundred miles per hour. They can result in widespread erosion and then sedimentation as slope begins to flatten. These currents explain how underwater cables can suddenly be severed and how oil deposits can be formed by rapid burial of organic material. Their existence illustrates how dynamic the seafloor can be.
Other cool stuff you should know
"Doc" Ewing published over 340 scientific papers and trained over 200 graduate students in his lifetime. He served as the Higgins Professor of Geology at Columbia for many years. The American Geophysical Union gives out a yearly Maurice Ewing Medal for ocean research. A 1995 U.S. Government investigation report dismissed the 1947 Roswell, NM alien ship crash as debris from Project Mogul experiments.
Wicander R., & Monroe J. (1989). Historical Geology: Evolution of the Earth and Life Through Time. St. Paul, MN: West Publishing Company.
Lippsett L. (2001). Retrieved February 6th, 2009. Living Legacies. Great Moments and Leading Figures in the History of Columbia University. Maurice Ewing and the Lamont-Doherty Earth Observatory. Web site: http://www.columbia.edu/cu/alumni/Magazine/Winter2001/ewing.html
American Geophysical Union. (2002). Retrieved February 6th, 2009. Shackleton Receives the 2002 Maurice Ewing Medal. From: Honors at AGU. Web site: http://www.agu.org/inside/awards/bios/shackleton_nicholas.html
Robert A. Muller. Retrieved February 17th, 2009. Sound Channel, SOFAR, and SOSUS. Web site: http://muller.lbl.gov/teaching/Physics10/old%20physics%2010/pages/SoundC...
Wikipedia. Retrieved February 17th, 2009. Turbidity current. Web site: http://en.wikipedia.org/wiki/Turbidity_current