Cascadia's Fault - Jerry Thompson [50]
After waiting a few moments for the rig to stabilize, he gave the order to spool it down the rest of the way. The piston hit bottom at 14,400 feet (4,380 m). It punched a five-foot (1.5 m) hole in the mud at the mouth of the seafloor canyon closest to the Aceh rupture zone—where the earth had begun to rip apart in the monster quake of 2004.
It took another two hours to haul the rig back to the surface, so naturally, it arrived after a hazy, overcast sunrise, just in time for breakfast. One of the coring technicians grabbed an industrial-size pipe wrench to unscrew the nose cone from the shaft before the boatswain and a single deckhand slid out a plastic pipe concealed inside the slightly larger metal piston, like an arm inside a sleeve. The see-through plastic tube containing the core sample looked surprisingly light as the two men hoisted it onto a set of stanchions bolted to the deck. Light, because it was almost empty. After more than four hours from deployment to recovery, the ten-foot (3 m) section of pipe contained maybe eight inches (20 cm) of clay and silt—a disappointment, to say the least. They would have to start over.
Later the next day five members of the science team lifted another, larger piston core from the sea. The boatswain and the crane operator hoisted the steel pipe casing away, exposing a twenty-foot (6 m) core tube inside (this one looked like ordinary, white PVC drainpipe). This time they’d captured a good sample. In the main laboratory, they mounted the plastic tube in a set of clamps on a long workbench and ripped it in half lengthwise with an electric saw. Everyone in the lab was buzzing with energy, measuring, labeling, and entering data into logbooks and computers.
Chris Goldfinger watched as Russ Wynn from the National Oceanography Centre in Southampton, England, dragged a putty knife across the surface of the new sample, skimming off the top layer of runny mush to create a smooth, flat finish. Now it was easier to see the four or five horizontal stripes of darker, lumpier material that stood out against the bland, gray goo of deep-sea mud. These brownish smudges presumably were the killer’s fingerprints—the turbidite layers from undersea landslides triggered by the deadly Sumatra temblor of 2004 and perhaps from a subsequent rupture in 2005.
Chatting later with a few of the grad students in the ship’s lounge, Goldfinger began telling the tale of how this kind of research—this deep-ocean version of earthquake hunting, cross-bred with oilfield exploration techniques—got started at OSU. He described how his thesis advisor, geology professor LaVerne Kulm, “took cores in the late’60s along the Cascadia margin. And remember, in 1968 plate tectonics was only four years old at the time. So people were just kinda getting used to the whole idea.”
“They were taking cores out here,” said Goldfinger, pointing to a place on the map more than sixty miles (100 km) to sea, southwest of the Columbia River estuary, “and they noticed that there was an ash deposit out there called the Mazama ash.” This gave Kulm and his team a timeline, a starting point from which to gauge the age of the other deposits, those darkish lines of turbidite debris they had found in the vertical column of marine mud.
Thirteen clearly defined turbidite deposits had been found in core samples taken many miles apart along various riverlike canyons on the ocean bottom. “Here, here, here, and here,” pointed Goldfinger, all over the map. “All of these places had thirteen turbidites. So one afternoon, as Vern tells it over beers, he and his students were puzzling about why—why would all these cores have the same number of turbidites? These come from different river systems, different parts of the margin, different geology. They have absolutely nothing in common except, apparently, they had the same number of turbidites deposited in these cores.”
Goldfinger was warming to his subject. “And the way Vern tells it, one of the students goes: ‘Hey, maybe it could be earthquakes! And then they