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[[File:Arctic Ocean bathymetric features.png|thumb|350px|Main bathymetric/topographic features of the Arctic Ocean]]
The '''Gakkel Ridge''' (formerly known as the '''Nansen Cordillera''' and '''Arctic Mid-Ocean Ridge''') is a [[mid-oceanic ridge]], a divergent [[tectonics|tectonic]] plate boundary between the [[North American Plate]] and the [[Eurasian Plate]]. It is located in the [[Arctic Ocean]] between [[Greenland]] and [[Siberia]], and has a length of about 1,800 kilometers. Geologically, it connects the northern end of the [[Mid-Atlantic Ridge]] with the [[Laptev Sea Rift]].
The existence and approximate location of the Gakkel Ridge were predicted by [[Soviet Union|Soviet]] polar explorer [[Yakov Yakovlevich Gakkel]], and confirmed on Soviet expeditions in the Arctic around 1950. The Ridge is named after him, and the name was recognized in April 1987 by [[SCUFN]] (under that body's old name, the Sub-Committee on Geographical Names and Nomenclature of Ocean Bottom Features).
The ridge is the slowest known spreading ridge on earth, with a rate of less than one centimeter per year. Until 1999, it was believed to be non-volcanic; that year, scientists operating from a nuclear submarine discovered active [[volcano]]s along it. In 2001 two research icebreakers, the German ''[[RV Polarstern|Polarstern]]'' and the American ''[[USCGC Healy|Healy]]'', with several groups of scientists, cruised to the Gakkel Ridge to explore it and collect petrological samples. Among other discoveries, this expedition found evidence of [[hydrothermal vent]]s. In 2007, [[Woods Hole Oceanographic Institution]] conducted the "Arctic Gakkel Vents Expedition" (AGAVE), which made some unanticipated discoveries, including the unconsolidated fragmented [[pyroclastic]] volcanic deposits that cover the axial valley of the ridge (whose area is greater than 10 km2). These suggest volatile substances in concentrations ten times those in the magmas of normal mid-ocean ridges. The AGAVE expedition also discovered on the Gakkel ridge, using "free-swimming" [[submersible#ROVs|robotic submersible]]s, what they called "bizarre 'mats' of microbial communities containing a half dozen or more new species".
* [http://polardiscovery.whoi.edu/expedition2/index.html Polar Discovery: Gakkel Ridge]