OCEAN-FLOOR PLATES collide, shift along giant faults, or crack and spread apart. Two narrow, water-filled splits on the flanks of continents—the Gulf of California and the Red Sea—are oceans of the future just beginning to open, marine geologists say. Their basins are widening; heat comes up from below their floors.
In Mexico’s Gulf of California great volumes of sediment carried down by the Colorado River mask the seabed rifting. Someday that rift may rip north, open a seaway through Nevada, and break away much of California as an island.
In the Red Sea, in several deep basins or holes, a different sort of mud exists. Not only is it hot—more than 60°C (140°F)—but it contains incredible amounts of minerals: silver, lead, zinc, copper, iron, and others. The top 30 feet of ooze in one of these basins, the Atlantis II Deep discovered by Woods Hole in the early 1960s, is potentially worth billions of dollars. Though commercial interest has been great, exploitation has been held back by legal and technical factors.
Ever since the first Challenger’s cruise a century ago, it has been known that potato-size lumps rich in manganese and iron cover wide areas of the ocean floor, almost as thick as cobblestones. The nodules also hold copper, nickel, and cobalt. All that is needed is to lower a dredge and scoop them up.
The twin mysteries of exactly how these nodules form, and what keeps most of them unburied by seafloor ooze, remain to be solved. But careful estimates, particularly in mid-Pacific, show that enough exist to supply the entire world’s needs for manganese, an important ingredient of steel, indefinitely; they are being formed on the ocean floor faster than they could be mined.
Giant firms have gone into international partnerships to plan and test methods for recovering this sea-bottom bonanza. Inability of the world’s nations to agree on a Law of the Sea treaty, however, has delayed the start of deep-sea mining for more than ten years. But it will surely come, for the stakes are huge.
When seafloor spreading and magma up-welling were first recognized in the 1960s, geologists soon speculated that other minerals—extracted from deep in the crust by hot-water circulation—might be deposited along the mid-ocean rifts.
In Project FAMOUS, the French found an inactive vent surrounded by mineral deposits. Elsewhere along the Mid-Atlantic Ridge to the south, ships of the National Oceanic and Atmospheric Administration (NOAA) had earlier photographed a hydro-thermal field. But it was not until 1979 that explorers of the eastern Pacific floor came face to face with minerals actually spewing from vents in the seabed.
Alvin, from its ungainly twin-hulled tender Lulu, had been diving north of the Galapagos Islands, on a rift where warm springs and strange colonies of life had been discovered two years before. Now the submersible had come north to a site on the East Pacific Rise near latitude 21° North.
“The first dives were unbelievable,” said Bob Ballard, who has traveled along more of the sea-bottom rifts than any other man on earth. “Here were these fountains of black or white material, like smoke, billowing from crevices and hollow rock pillars along the rifts. They made me think of Pittsburgh’s smokestacks a generation ago.
“We drove Alvin up to one of the black smokers. Our claw thrust a plastic heat probe into the vent. The temperature recorder in the sub went off scale. Then we saw the plastic rod itself begin to melt, to droop like taffy. It didn’t take long to realize Alvin’s portholes might not stand such temperature [later calculated to be above 350°C-650°F]. We backed off in a hurry!”