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	Scientists prepare to lower a heat-flow probe to the seafloor from the fantail of R/V Thomas Washington in 1972. The probe allows scientists to calculate heat flowing through seafloor sediments. (Courtesy of Scripps Institution of Oceanography)
	The Southtow Expedition, on board Scripps Institution of Oceanography's R/V Thomas Washington in 1972, found clues leading to the discovery of hydrothermal vents at the Galápagos Rift. (Courtesy of Scripps Institution of Oceanography)
	The Deep-Tow geophysical instrument package of Scripps’ Marine Physical Laboratory is equipped with precision sonar, cameras, and geophysical sensors that transmit data back to the ship via a cable. (Courtesy of Scripps Institution of Oceanography)
	The Southtow expedition found intriguing mineral-encrusted mounds sticking out of seafloor sediments. The mounds, like this one photographed on the 1977 Galápagos expedition, are formed by hydrothermal venting. (Photo by David L. Williams, USGS)
	Mike Legg, then a graduate student on theSouthtow expedition, throws a sonobuoy overboard to detect micro-earthquakes at the seafloor. (Courtesy of Ken Macdonald, UCSB)
	Scientists on Southtow analyzed dead bottom-dwelling fish that they found floating on the sea surface. The fish were found in an area where scientists had detected a swarm of seafloor micro-earthquakes. (Photo by Philip Hastings, Scripps Institution of Oceanography.)
	K.O. Emery of the Woods Hole Oceanographic Institution received a letter from French scientist Xavier Le Pichon proposing a joint U.S.-French expedition to explore the Mid-Atlantic Ridge. (Courtesy of WHOI Archives)
	The 200-ton French bathyscaphe Archimède was one of three submersibles that participated in Project FAMOUS. (Courtesy of WHOI Archives)
	The French submersible Cyana took part in Project FAMOUS. (ourtesy of IFREMER)
	Alvin is photographed from Cyana’s viewport on the Mid-Atlantic Ridge during Project FAMOUS. (Courtesy of WHOI Archives)
	Alvin is refitted with its new titanium sphere to double its diving range to 12,000 feet. (Courtesy of WHOI Archives)
	WHOI’s James R. Heirtzler was the U.S. leader of Project FAMOUS. (Courtesy of Scripps Institution of Oceanography)
	Project FAMOUS used the U.S. Navy’s LIBEC camera system, which suspended high-intensity electronic flash lamps well above the ocean bottom. (Courtesy of U.S. Naval Research Laboratory)
	The LIBEC system shot 120-foot-wide sections of the seafloor that were pieced together. (Courtesy of U.S. Naval Research Laboratory)
	LIBEC collected 5,250 seafloor photos, which were fitted together and laid across the floor of a Navy gymnasium in Washington, D.C. (Photo by Emory Kristof © National Geographic Society)
	Alvin and its former mother ship, Woods Hole Oceanographic Institution’s R/V Lulu. (Courtesy of WHOI Archives)
	The Alvin group prepares to lift the sub to R/V Knorr’s fantail for the trip to Project FAMOUS’s Mid-Atlantic Ridge dive sites. (Photo by Frank Medeiros)
	Alvin pilot Jack Donnelly (middle) is flanked by two divers. (Courtesy of WHOI archives)
	WHOI’s Bob Ballard nervously monitors pilot Jack Donnelly’s efforts to free Alvin, which became stuck in a seafloor fissure during Project FAMOUS. (Photo by Emory Kristof, © National Geographic Society.)
	The Pleiades expedition on board Scripps’ R/V Melville in 1976 added more clues to zero in on the Galápagos Rift vent site. (Courtesy of Scripps Institution of Oceanography)
	Deep-Tow’s camera photographed telltale clamshells on the seafloor. (Photo courtesy of Peter Lonsdale, Scripps Institution of Oceanography)
	The clamshells were intriguing, but they were not proof of hydrothermal vents. At first, some scientists thought the clamshells (especially with a discarded beer can nearby) might be garbage thrown off a ship. (Courtesy of Peter Lonsdale, Scripps Institution of Oceanography)
	Divers prepare Alvin between the pontoons of its mother ship, Woods Hole’s R/V Lulu. (Courtesy of WHOI Archives)
	ANGUS, Woods Hole’s deep-towed camera system, is deployed during the Galápagos Rift Expedition. (Courtesy of WHOI Archives)
	R/V Knorr, scientists and technicians stand vigil, tracking ANGUS as it is towed near the seafloor in 1977. (Photo by Emory Kristof © National Geographic Society)
	A series of seafloor photos taken by ANGUS shows the sudden appearance of a dense accumulation of live white clams. Within hours, the clams led scientists to find hydrothermal vents for the first time. (Photo courtesy of WHOI Archives)
	Alvin’s manipulator arm picks up a large clam from the Clambake 1 vent site. (Photo by Robert D. Ballard, WHOI)
	ANGUS captured this photo of a skate swimming above lava near the Galápagos Rift vent site. (Courtesy of WHOI Archives)
	A purple octopus scavenges in a clam-filled vent site (Photo by Robert D. Ballard, WHOI)
	ANGUS took this photo of dead clams at Clambake 2. The clams died because the vent was no longer active. (Courtesy of WHOI Archives)
	Tubeworms, white crabs, and a pink fish gather at a Galápagos Rift vent site (Photo by John M. Edmond, MIT)
	Scientists of the 1977 Galápagos Rift Expedition (left to right), Bob Ballard, Jack Corliss, and John Edmond, convene on the deck of R/V Knorr. (Photo by Ken Peal, WHOI.)
	Biologist Fred Grassle dives to the Galápagos Rift vents in 1979 in Alvin. (Photo by Al Giddings © National Geographic Society)
	WHOI’s submersible Alvin was extensively modified to accommodate new equipment for the biological dives to the vents. (Photo by Fred Grassle, WHOI)
	Alvin explores the Galápagos Rift vent sites in 1979. (Photo by Emory Kristof © National Geographic Society.)
	The curious creature first called a “dandelion” by geologists during the 1977 cruise turned out to be a siphonophore, a cousin of the Portuguese man-of-war (Photo by Al Giddings © National Geographic Society.)
	Alvin’s meter-long temperature probe extends toward a community of galatheid crabs perched atop pillow lava and a dense field of mussels. (Photo by Robert Hessler.)
	The flesh inside the giant clams is blood red because it contained hemoglobin—the same substance that transports oxygen inside human blood. (Photo by Emory Kristof © National Geographic Society.)
	Biologists on the 1979 Galápagos cruise use a respirometer to measure the amount of oxygen mussels take up from seawater. (Photo by Ken Smith, SIO)
	Spaghetti worms drape volcanic rocks on the seafloor near the vents. (Photo by James Childress, UCSB)
	WHOI microbiologist Holger Jannasch searches for vent bacteria on a mussel shell on the 1979 cruise. (Photo by Emory Kristof © National Geographic Society.)
	‘Stands of snow-white tubeworms crowned with feather-like blood-red plumes.’ (Photo by Emory Kristof © National Geographic Society.)
	The first black-smoker chimney ever seen by humans—photographed at 21°N in 1979. (Photo by Dudley Foster, WHOI)
	The chimney “smoke” really consists of superheated (350°C or 662°F) fluids that are filled with dark mineral particles. (Photo by Dudley Foster, WHOI)
	Black-smoker chimneys form when superheated fluids hit near-freezing seawater. Minerals in the fluids precipitate quickly to form tubes that can grow very tall. (Photo by Patrick Hickey, WHOI)