Harry Hammond Hess Biography

Harry Hammond Hess's work as a geologist and geophysicist led to a greater understanding of the origin of major features in the world' s oceans as well as the origin of ocean crust itself. In 1945 he performed the first sonar survey of the ocean's greatest depths, the 6.9 mile (11.0 km) deep Marianas Trench. During World War II Hess discovered the existence of guyots, flat-topped, extinct volcanoes of the deep ocean basins. He was also involved in the drilling expedition--Project Mohole--to probe the Earth's mantle. As accomplished as these tasks are, he is best remembered for his work on the spreading movement of the seafloor.

Hess graduated from Yale University in 1927, and for the next two years he worked as an exploration geologist in northern Rhodesia. In 1929 he returned to the United States and began his graduate studies at Princeton University, earning a doctoral degree in 1932. Just two years later he began teaching at Princeton as a faculty member of the geology department.

During this time he participated in many fascinating projects such as the United States Navy submarine gravity study in the Lesser Antilles.While on numerous World War II naval missions in the Pacific, he studied the numerous isolated seamounts (volcanoes) rising from the ocean floor. This eventually led him to the discovery of guyots in 1945. These volcanoes, common in the Pacific Ocean, are thought to have been wave-eroded islands that eventually subsided far below sealevel. He named them guyots in honor of the Swiss-American geographer Arnold Henry Guyot (1807-1884).

After sixteen years at Princeton he became head of the geology department, but his achievements branched out into many other fields.

During and immediately after World War II, United States Navy vessels surveyed thousands of miles of ocean bottom using sonar. Hess compiled and interpreted these sonic profiles and produced relatively detailed bathymetric maps, that is, maps showing the depth and morphology of the ocean bottom. Thanks to these maps, he recognized the scale and form of deep oceanic trenches, such as the 6.9 mi (11.0 km) deep Marianas Trench, and oceanic ridges, including the 10,000 mile (16,090 km) long submarine mountain chain called the Mid-Atlantic Ridge. This undersea range, which begins in the southern Atlantic south of Africa and snakes its way across the ocean floor to the north Atlantic above Iceland, is generally over 200 miles (320 km) in width and rises up to one mile (1.6 km) above the ocean floor.

In 1962 Hess presented a paper showing evidence that the Atlantic seabed was spreading. His theory of seafloor spreading built on the findings of Alfred Lothar Wegener's continental drift theory. The discovery of seabed movement was a critical step in the development of the related theory of plate tectonics. Hess' findings created a flurry of research focused on proving or disproving his hypothesis. Through studies at a variety of locations, geologists have since learned how the seafloor "spreads" and how continents "drift".