Magazine article Science News

Debate May Resume over Volcano-Climate Link

Magazine article Science News

Debate May Resume over Volcano-Climate Link

Article excerpt

As huge volcanic eruptions darkened the skies over the northern Pacific Ocean 2.6 million years ago, temperatures dropped precipitously and the northern hemisphere drifted ever deeper into an ice age. Are these events directly related or merely coincidental?

Scientists who study the natural history of oceans set aside their debate on this question in the 1970s for lack of conclusive evidence. Now, extensive core samples gathered on leg 145 of the Ocean Drilling Program may prompt oceanographers to reexamine the connection between Pacific volcanism and the northern hemisphere's deep freeze, says David K. Rea, a marine geologist at the University of Michigan in Ann Arbor and co-chief scientist on the two-month cruise.

These new cores provide "a very exact definition of all the great changes that occurred 2.6 million years ago, which is the time when northern hemisphere glaciation really kicked in," Rea says.

Ship and crew returned in late September with core samples of soft, porous sediment pulled from the floor of the northern Pacific Ocean. Rea describes these sediments as having the consistency of soft cookie dough.

Since ordinary rotary core drills would have turned these soft sediments into soup, the crew used a technique called hydraulic piston coring, which collects fragile sediments virtually intact. This produced relatively continuous core samples that show important details in the sedimentary strata.

These high-quality cores offer a more detailed record of how the northern Pacific responded to climatic change and allow scientists to more accurately date individual events, Rea explains. …

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