A 2008 United States Geological Survey estimates that areas north of the Arctic Circle have 90 billion barrels of undiscovered, technically recoverable oil (and 44 billion barrels of natural gas liquids ) in 25 geologically defined areas thought to have potential for petroleum. This represents 13% of the undiscovered oil in the world. Of the estimated totals, more than half of the undiscovered oil resources are estimated to occur in just three geologic provinces – Arctic Alaska, the Amerasian Basin, and the East Greenland Rift Basins.