Image: WOODS HOLE OCEANOGRAPHIC INSTITUTION
From the surface there is nothing special about this restless interface between the cosmos and the abyss. Its perfectly normal ocean: our arrival is greeted by angry waves that toss the ship about as rain squalls spatter by. But the goal of the 23 scientists on board is what lies 2,500 meters beneath it-- a geologically active area known as the Juan de Fuca ridge, where new crust is forming as two great continental plates pull apart.
They have come equipped: Atlantis is the mother ship for Alvin, the deep diving submersible that won popular fame when it located the wreck of the Titanic. Between now and July 4, when Atlantis returns to port to pick up another compliment of scientists, Alvin is scheduled make nine dives to the seafloor.
The ridge, which runs parallel to the west coast of North America, is forming as two crustal plates pull apart and magna flows upward from the Earth's mantle. It is marked by undersea volcanoes and solidified lava lakes. Fields of hydrothermal vents spew out superheated water laden with dissolved minerals. And this hostile environment is literally teeming with life. These vents, where water temperatures can sometimes reach 400 degrees C, are home to an entire ecosystem of creatures, including tube worms, limpets, aquatic spiders and bacteria uniquely adapted to total darkness, high temperatures and sulfur-laden water.
Because of its relative nearness to shore and its wealth of geophysical, chemical and biological features, the Juan de Fuca ridge is among the most intensely studied pieces of undersea real-estate in the world. It has been mapped by sonar; cores have been drilled from the seabed by the international drillship, JOIDES Resolution; and it has been explored by both manned and unmanned submersibles.
Even so, there is much more to be learned from this subsea laboratory. Just two years ago, in fact, the Resolution deepened a hole that had been drilled into a major deposit of copper sulfide ore only to find a larger and even higher purity copper deposit beneath the seabed. In a paper published in Nature in March, Robert A. Zierenberg of the University of California at Davis, who was part of the Resolution team, pointed out that similar deep deposits may exist beneath copper deposits on land, which were once formed in the oceans.
In addition, the newly drilled hole began spouting heated seawater, making it the first manmade hydrothermal vent on the seafloor. On this expedition, Zierenberg is on board Atlantis to revisit that hole to observe the growth of mineral deposits around hydrothermal vents and determine how they are colonized by organisms. Cindy Van Dover, now at the University of Alaska, who discovered these islands of life while diving with Alvin in 1977, is also on this expedition to collect specimens.
Other holes drilled into the Juan de Fuca ridge haven't been equipped with devices known as CORKS--steel plugs that close the hole at the seafloor and dangle a long string of instruments for measuring temperature and pressure down the hole. Scientists, including Earl E. Davis of the Geological survey of Canada on this voyage, visit these sites periodically with submarines such as Alvin and extract the computerized data collected by the sensors. The Juan de Fuca ridge contains the largest concentration of these monitored boreholes in the world's oceans.
During this brief voyage, the scientists traveling to the seafloor in Alvin will take samples of water and mineral deposits, collect specimens of the unique creatures that live near hydrothermal vents, and try to solve one intriguing mystery: The water coming from high-temperature vents glows with light, and no one knows why. But Alan Chave, this expedition's chief scientist, is hoping that a specially designed camera, constructed by Anthony Tyhson of Bell Labs, will provide some clues. In any case, Alvin is almost certain to bob to the surface at the end of each dive with a fascinating story to tell.