Project FAMOUS (French-American Mid-Ocean Undersea Study) was the first-ever marine scientific exploration by manned submersibles of a diverging tectonic plate boundary on a mid-ocean ridge. It took place between 1971 and 1974, with a multi-national team of scientists concentrating numerous underwater surveys on an area of the Mid-Atlantic Ridge about west of the Azores. By deploying new methods and specialized equipment, scientists were able to look at the sea floor in far greater detail than ever before. The project succeeded in defining the main mechanisms of creation of the median rift valley on the Mid-Atlantic Ridge, and in locating and mapping the zone of oceanic crustal accretion.
Study area
The Project FAMOUS study area was located on a section of the Mid-Atlantic Ridge about west of the Azores (Sao Miguel) at 36° 50’ north latitude. It includes a -wide median valley or rift valley on the crest of the Mid-Atlantic Ridge that trends slightly east of north. Within the median valley lies the present boundary between the North American and African tectonic plates. The floor of the rift valley is deep and wide and the bounding rift mountains are at a depth of about , or about above the floor. The rift valley is long and it is offset to the eastward in the north at Fracture Zone A; in the south, it is offset westward at Fracture Zone B.
Methodology
A significant obstacle in marine surveys was the use of echo sounders with a wide transmit beam, which smeared-out details of the sea floor features. The crustal accretion or creation process was thought to take place over a few kilometers width of sea floor, which was below the resolution of ship echo sounders. Thus, near-bottom and on-bottom approaches were employed along with new sonar mapping tools. Investigations included airborne magnetics, advanced surface ship sonar, and geophysical measurements, seismology, deep-towed instruments, large format bottom photography, fixed on-bottom instruments, and on-bottom dives with research manned submersibles in the rift valley of the Mid-Atlantic Ridge. The Woods Hole Oceanographic Institution (WHOI) in Massachusetts provided surface ships and the submersible ALVIN; the French provided surface ships and the bathyscaph Archimède and submersible CYANA. The British conducted side scan sonar surveys and on-bottom seismic experiments. Lead institutions were WHOI and the French Centre Oceanologique de Bretagne, Brest, France. Project leaders were James Heirtzler, Claude Riffaud, and Xavier Le Pichon.
Operational challenges
In the 1960s, Canadian scientists had begun a detailed study of the Mid-Atlantic Ridge at a latitude of 45° N that included multiple expeditions by surface ships. With Project FAMOUS located on the ridge in more clement latitudes around 37° N, a coordinated multi-national, multi-ship series of more than twenty expeditions took place over four years, between 1971 and 1974. Bilateral briefing meetings were held as new expeditions were completed. The unique operational features of Project FAMOUS included the use of newly developed narrow-beam and multibeam echo sounders along with deeply-towed instruments and manned submersibles to achieve a new, higher level of resolution of a spreading center. Key to this approach was improved ship navigation with transit satellites to allow detailed mapping, in an era before GPS. This was augmented by use of acoustic on-bottom transponder navigation of ships, instruments, and submersibles. Besides the approach using instruments with increasing detailed resolution, the submersible divers were trained to recognize the volcanic terrain they could encounter through prior field exercises undertaken in Iceland and Hawaii. The pressure hull of the ALVIN submersible was also specially upgraded to allow it to reach the great depths of the rift valley. In total, forty-four dives with the three submersibles were completed over dive seasons in 1973 and 1974.
Main results
Project FAMOUS represented a new experimental approach to sea floor geology and was considered a major technical achievement at the time. The demonstration of the viability of sea floor observations by submersibles made possible the subsequent discoveries of hydrothermal vents at the Galapagos spreading center and on the East Pacific Rise at 21° N.