Ocean Drilling Tech: Exploring Seabed History With 600,000 Pounds of Pipe
Filed under: Discovery,News & Resources,Scientific Ocean Drilling
The crane operator launches the ship's air gun into the sea. (Photograph by Bill Crawford, IODP)
Popular Mechanics
By Trevor Williams
PM’s far-flung geological correspondent, Trevor Williams, of Columbia University’s Lamont-Doherty Earth Observatory, reports from the JOIDES Resolution, where scientists in the Integrated Ocean Drilling Program are plumbing the seafloor to unlock its ancient secrets. Their goal: To learn how the Earth responded to climate change 50 million years ago-and how it may react to future warming. Here, Williams takes a closer look at the mechanical process of coring the depths.
On the rig floor of the JOIDES Resolution, Joe Attryde turns up the water pressure in the drill pipe to 2500 psi, enough to break the shear pins holding the core barrel three miles below the ship and plunge the barrel another 30 feet into the deep sea sediment. The barrel captures a 2.5-inch-wide cylinder of layered mud and, with a tug of the winch cable, it starts its long trip back to the surface inside the drill pipe, through the “moon pool” hole in the center of the ship and onto the deck. Here the sediment core is delivered to geologists, ready to probe the climate record it holds. Meanwhile, another core barrel is lowered inside the pipe. Each successive barrel drills steadily deeper into the seafloor, recovering older and older parts of the sediment sequence.
A 3-mile vertical pipe hanging from a ship can be hard to picture. Imagine holding a very long drinking straw from the top of the Empire State Building and using it to drill into the sidewalk below-that’s about the scale. Then imagine that straw weighs 600,000 pounds and requires a 2000-hp engine to lift it. Adding to the challenge for deep-ocean drillers is the movement of the vessel: The pipe has to be raised and lowered to counter the rise and fall of the ship in the ocean swells and keep the drill bit in the same vertical position under the seabed.
Each time we arrive at a new drill site (there are five for this expedition), Capt. Alex Simpson sends out the call: “Lower the thrusters!” and six sets of propeller thrusters are deployed under the ship. They constantly adjust to respond to the winds and currents, keeping the ship precisely above the drill site. This is crucial: If the ship were to drift too far when it is attached to the seafloor, there would be a dangerously spectacular twang when it breaks.
A chunk of basaltic rock from the ocean crust caught in the extended core barrell (XCB) while drilling at Site U1332. (Photograph by Bill Crawford, IODP)
Joe Attryde and his counterpart on the night shift, Phil Christie, run the coring and drilling operations smoothly and safely. And they are ready with the fix when King Neptune decides things won’t proceed as planned. The seabed can hold surprises, like hard, flinty layers that can bend the core barrel; foreseeing these allows more robust rotary coring to be switched in. Between the two they’ve worked for 40 years in deep-ocean drilling, a level of experience common among the crew. The geologists and oceanographers of the expedition are in good hands. It takes teamwork between the rig crew and the scientists to recover the most pristine cores and to unravel the stories the cores tell.
The JOIDES Resolution is named after Captain James Cook’s ship Resolution, which circled the globe twice in the 1770s. (JOIDES stands for Joint Oceanographic Institutions for Deep Earth Sampling.) The similarities go beyond the name. Both ships were built for about 115 people, and science played a part even in the 18th century, when naturalists traveled onboard to describe the life in the new lands. Cook’s Resolution was the first ship to cross below the Antarctic circle in search of the southern continent. The members of the expedition didn’t see it, but found penguins and freshwater icebergs, hinting that it was beyond the ice floes. Our ship has made four Antarctic expeditions, and much of what we know about the geological history of ice on Antarctica comes from them. Indeed much of what we know about the Earth’s climate since the dinosaurs died out 65 millions years ago comes from the deep-sea sediment cores collected by our ship.
The JOIDES differs from the older Resolution too. Our expeditions last two months; Cook’s lasted 2 years and more. The original Resolution was a quarter the length of the newer one, but its crew was still able to find room to provision 19 tons of beer and 20,000 pounds of sauerkraut and salted cabbage (for vitamin C to fend off scurvy). The JOIDES Resolution is a dry ship, but on the bright side, we only have to eat sauerkraut once in a while. Cook’s reception in Hawaii was mixed. At first welcomed as a god, he pushed his luck and met his end. When the modern-day Resolution returns to Honolulu in a few weeks time with our cargo of deep-sea sediment cores, we anticipate much less drama-and a cold beer.
Trevor Williams is a geologist at the Lamont-Doherty Earth Observatory of Columbia University in New York.
