Magazine article Oceanus

Chinese Cruise Brings Back Clues to Past Tsunamis near Sumatra

Magazine article Oceanus

Chinese Cruise Brings Back Clues to Past Tsunamis near Sumatra

Article excerpt

Exactly one year after the devastating 2004 Indian Ocean tsunami, Jian Lin found himself on a Chinese research vessel off Sumatra, floating above the epicenter of the seafloor earthquake that spawned the great wave.

He participated in a solemn ceremony to honor the estimated 280,000 people killed by the tsunami. Then he hauled up cores of ancient sediment from the ocean bottom--cores that could reveal the history of tsunamis, help predict their likelihood, and perhaps save lives in the future.

"You are looking at a book," said Lin, a geophysicist, pointing to a 1 1/2-meter-long column of mud in his office at Woods Hole Oceanographic Institution. "Now we must learn to read the pages and hope it contains chapters that will teach us how--and how frequently--earthquakes create tsunamis in this region."

The tantalizing sediment samples culminated two 40-day voyages for Lin as U.S. chief scientist aboard China's new research ship, Dayang 1. It was the first time an American scientist has been invited to co-lead a Chinese deep-ocean research cruise (see page 34).

During 2005, Dayang 1 sailed an ambitious 300-day series of expeditions to explore mineral and biological resources in the ocean, particularly at hydrothermal vents. To this unique collaboration, Lin brought seafloor maps from previous WHOI expeditions and a WHOI-built deep-tow magnetometer to detect mineral-rich ocean crust around vents. He also brought six Miniature Autonomous Plume Recorders (MAPRs), on loan from Edward Baker, Lin's colleague at the National Oceanic and Atmospheric Administration.

Lin described MAPRs as "sniffers." Lowered on wires into the depths, they detect hot, buoyant, particle-filled fluids emitted from seafloor vents. The fluids rise several hundred meters above the seafloor and spread sideways into mushroom-shaped plumes above the vent "stems." MAPRs measure temperature, as well as the scattering of light (by dissolved particles) through seawater.

With these and other tools at their disposal, the international team aboard Dayang 1 discovered new regions of strong hydrothermal plumes in the eastern Pacific Ocean and atop of the Southwest Indian Ridge (SWIR). They also recovered microorganisms that live under extreme conditions in the deep ocean and many samples of sulfide rocks from hydrothermal vents. These represented firsts for China. By flying the magnetometer on an underwater vehicle only tens of meters above the seafloor, Lin and colleagues measured Earth's magnetic field at very close range to determine the magnetic properties of unusual rocks found on the ultra-slow-spreading SWIR. …

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