John Roachfor National Geographic NewsJune 25, 2003Findings reported from the first ever detailed exploration of the Gakkel Ridge--the northernmost segment of the worldwide mid-ocean ridge system that snakes for 1,100 miles (1,800 kilometers) beneath the Arctic Ocean--underscore the waiting discoveries on the frontiers of Earth science.For decades scientists longingly eyed the Gakkel Ridge. But since it lies beneath a cover of sea ice, access to it has been limited. Apart from a single submarine study, much of what was known about the undersea region's geology was extrapolated from studies of other, more accessible, ocean ridges.Then in August 2001 an international team of scienti ...view middle of the document...
Discovery means to learn something not known before." Langmuir co-authored a related expedition research paper also published in Nature.Volcanoes and VentsMid-ocean ridges form where two tectonic plates pull apart and hot magma from deep within the Earth oozes up to fill the gap. The ridges circle the globe and the magma that solidifies between the plates forms the ocean floor.The Gakkel Ridge was known to be the slowest spreading ridge in the world, averaging just 0.4 inches (1 centimeter) per year. By contrast, other volcanically active mid-ocean ridges elsewhere in the world spread at rates as fast as 7.5 inches (19 centimeters) per year.But based on rock samples dredged from the ocean floor and detailed sonar mapping, researchers were surprised to discover that the Gakkel Ridge is actually a hotbed of volcanic activity and hydrothermal vents."We expected very few fresh volcanic lavas. Yet the first maps and samples revealed a highly active volcanic province," said Langmuir, noting that the abundant and recent volcanic activity was both surprising and remarkable.Researchers discovered that volcanic activity along the ridge did not correlate directly to its rate of spread."Instead of finding a linear relationship between the spreading rate and amount of volcanic activity, we found that the intermediate part of the ridge was really the least active," said Peter Michael, a geoscientist at the University of Tulsa in Oklahoma and an expedition co-leader. "It tells us that there are other factors in the mantle that are controlling the amount of volcanic activity we see," said Michael, co-author of a related expedition research paper also published in Nature.The expedition team found much more hydrothermal venting activity than expected. To get hydrothermal activity, water must percolate down through cracks in the ocean floor to where it interacts with a heat source such as magma. The heated water then reverses direction and, as it rises, leaches elements from the surrounding rock. When the element-rich hot water reaches the ocean floor, it spouts out."The hydrothermal signal was so omnipresent that we thought there must...
