Scientists Excited by Arctic Ocean Ridge Finds
for National Geographic News
|November 29, 2001|
The floor of the Arctic Ocean is one of the last frontiers on Earth, and mapping it was thought to be an impossible tasktoo much ice, too remote, too difficult.
But on its inaugural research expedition, the U.S. Coast Guard Cutter Healy, a specially designed icebreaker equipped for science, has returned with highly detailed maps, exotic life forms, and new discoveries of volcanic activity below the ice cap.
"This was an epic journey in search of geological knowledge from a remote corner of the Earth," said Peter Michael, chief scientist for the Arctic Mid-Ocean Ridge Expedition (AMORE). The AMORE expedition was a joint project with Germany. The Healy and Germany's icebreaker Polarstern traveled to the Arctic from July 31 to October 3.
The co-chief scientist on the journey, Charles Langmuir of the Lamont-Doherty Earth Observatory at Columbia University, compared the Arctic expedition to the major discoveries of early U.S. explorers. The icebreakers' findings will provide fertile ground for new exploration over the next decade, he said.
"We have completely unexpected results," said Langmuir. "The ocean ridge below the Arctic is completely unique. We found 12 new volcanoes where we expected to find none, and we found unexpected and abundant hydrothermal activity."
The Gakkel Ridge
The Arctic expedition, funded by the National Science Foundation, focused on the northern end of the mid-ocean ridge. The ridge is a volcanically active mountain range, 52,000 miles (84,000 kilometers) long, that runs beneath the North and South Atlantic Oceans, the Arctic Ocean, the Indian Ocean, and the South Pacific.
"Ocean ridges are like great gashes in the Earth, where hot rock from the Earth's core is forced up," said Henry Dick, a marine geologist at Woods Hole Oceanographic Institution and also a co-chief scientist of the expedition.
The Gakkel Ridge is the deepest and most remote portion of the global mid-ocean ridge system. It extends 1,100 miles (1,800 kilometers) from north of Greenland to Siberia, lying about three miles (five kilometers) beneath the Arctic ice cap.
Scientists study the mid-ocean ridge to better understand how the Earth's mantle was formed. The theory is that volcanic eruptions beneath the ocean create new oceanic crust, which then moves away from the ridge. This process, known as seafloor spreading, is thought to underlie the movement of continents.
"Unlike volcanoes on land, which are tall and conical in shape, undersea volcanoes are long, linear, and oozing," said Langmuir. Volcanoes on land don't spread.
The Gakkel Ridge is the slowest spreading ridge in the world, spreading at a rate of one centimeter (less than half an inch) a year. Ridges in other parts of the mid-ocean range spread up to 18 centimeters (7 inches) a year. Because it is so slow-spreading, scientists expected there would be very little volcanic activity along the Gakkel Ridge.
"Most of what we know about mid-ocean ridges is from the mid-latitudes," said Langmuir. Many theories about seafloor spreading can be tested only on a slow-spreading ridge like the Gakkel.
Unexpectedly, the AMORE expedition found an abundance of both volcanism and hydrothermal activity.
"What we found on this expedition changes fundamentally the way we see the flow of the mantle and the generation of magmas beneath ocean ridges," said Dick.
Origins of Life
The researchers tentatively named the field of undersea hydrothermal vents they found the "Aurora." Hydrothermal vents, sometimes called "black smokers" or chimneys, eject plumes of superheated water that look almost like an underwater cloud of smoke. Exotic forms of life have been found at vents in other locations, and some scientists think that life on Earth may have originated in these plumes.
The energy that supports these organisms comes from chemical reactions rather than photosynthesis, as on the surface of the planet.
"The abundance and taxonomic breadth of the animals we found was quite a surprise," said Linda Kuhnz, a biologist from Moss Landing Marine Labs in California who participated in the expedition.
The isolation of the Arctic Ocean has long intrigued biologists. They hope that some of the samples recovered will help answer the question of whether the life forms and ecosystems in the Arctic resemble those from the Atlantic Ocean or Pacific Ocean, or whether they have evolved separately.
"We took samples of mud, water, rocks, and animalseverthing we could think of, and now we're getting ready to go into the lab and see what we've got," said Kuhnz.
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