oil

Oil production is booming across North America, as new technologies make it possible to extract liquid crude oil from sources like the Bakken shale oil field in North Dakota and Montana, or Alberta's tar sands. The ever-increasing volume of crude oil mined in remote Great Plains locations often finds its way to refineries via "rolling pipelines" – freight trains that tow a million barrels of oil around the United States every day. Production of Bakken crude has tripled over the past three years, and 79 percent of it is shipped out by rail.