Cruise to Top of the World Reveals New Insights into Formation of Earth's Crust
Volcanoes on the floor of the Arctic ocean and fissures that reach directly to Earth's mantle are findings published in today's issue of Nature that present new ideas on the formation of Earth's crust.
Two articles in Nature discuss results from the nine-week summer 2001 Arctic Mid-Ocean Ridge Expedition (AMORE), including the unexpected finding that the ocean ridge three miles beneath the Artic ice cap is volcanically active. The scientists also report that the ridge spreads so slowly-- about one centimeter or a third of an inch per year--that large sections of the earth¹s mantle are deposited directly onto the seafloor, a process that does not happen on other parts of the mid-ocean ridge system which spread at rates up to 20 times faster.
Co-chief scientist Henry Dick of the Woods Hole Oceanographic Institution, one of the principal investigators on the cruise and a co-author of one of the Nature articles, said he expected to find hydrothermal vents and some large volcanoes along the ridge because its formation is controlled by plate tectonics, and with so little magma coming out of the ridge, it is essentially a big crack in the earth. The team found many large volcanos and hydrothermel vents, defying current models of crustal formation that indicate just the opposite should occur.
The 2001 expedition involved more than 30 scientists from US and German research institutions and was conducted from the US Coast Guard icebreaker HEALY and the German icebreaker POLARSTERN. The US team was funded by the National Science Foundation and the German team by Deutsche Forschungsgemeinschaft (DFG).
Scientists recovered samples of fresh volcanic rock by dredging the seafloor at 200 stations and were able to collect many more samples than planned despite the ice cover and hostile environment. They also made high-resolution maps of the entire Gakkel Ridge, part of which had never been mapped before, and took water samples to search for hydrothermal vent activity. The Gakkel Ridge stretches about 1800 kilometers (1100 miles) from north of Greenland to Siberia and is the slowest spreading end member of the global mid-ocean ridge system that circles the earth like the seams on a baseball.
WHOI is a private, independent marine research and engineering, and higher education organization located in Falmouth, MA. Its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment. Established in 1930 on a recommendation from the National Academy of Sciences, the Institution is organized into five departments, interdisciplinary institutes and a marine policy center, and conducts a joint graduate education program with the Massachusetts Institute of Technology.