On Jan. 23,1960, U.S. Navy Lt. Don Walsh and Swiss explorer Jacques Piccard made the only voyage to the bottom of the Challenger Deep in the bathyscaphe Trieste, shattering by four kilometers the depth record they had set just 15 days before. As Walsh tells the story, the U.S. Navy brass told him to keep advance publicity to a minimum-in case he and Piccard did not come back. They received a hero’s welcome in Washington, but the return expedition they had planned never got funding. The 60-foot vessel had to be towed to dive sites, and this was expensive. Its deep-diving passenger sphere was retired in 1961. “If all our early exploration was only a trip for the record book,” says Walsh, now a marine consultant in San Diego, “then we all missed the point.”
From the eastern edge of the Mariana Trench, the ocean’s abyssal plain stretches out at a depth of 4,000 to 6,000 meters, eventually covering one third of the earth’s surface. Strewn like gravel over this vast undersea prairie are manganese modules metal-rich nuggets between half a centimeter and 25 centimeters across. Named after their main ingredient, manganese, the nodules on the Pacific Ocean floor alone contain 359 times more cobalt, 83 times more nickel and 9 times more copper than land mines worldwide, according to Japanese estimates. A consortium of more than 20 Japanese companies-including Hitachi, Sumitomo and Mitsubishihas been working on robots and vacuums to collect the nodules, and expects to have a system in operation by 1996.
At the bottom of the Challenger Deep, the weight of the water exerts a pressure of 16,000 pounds per square inch, which was enough to compress the 5-inch-thick walls of the Trieste by a tenth of an inch, cracking the exterior paint. Later submersibles, like the U.S. Navy’s Alvin and Japan’s Shinkai 6500, switched to titanium, which is strong but heavy. The most advanced undersea vehicles-including the coming Exploreruse lightweight ceramics, which should resist the crushing pressure without so much as a chip.
A two tectonic plates collide, they buckle into the earth’s crust forming a trench. At the Japan Trench, the Pacific plate Is sliding under the Eurasian plate.
As the Pacific plate slides or “subducts 2 into the earth, it pulls the edge of the Eurasian plate down, creating friction at the point of contact (thrust zone).
Eventually the friction Is overcome 3 and the Eurasian plate springs free, shaking Japan and creating tidal waves that batter the Japanese Islands.
