Tar Sands in Alberta, Canada

FORT MCMURRAY, ALBERTA, CANADA - NOVEMBER 2008: Once the oil is extracted from the tar sand, the remains travel through a pipe to a tailing pond. The tailing ponds are highly criticised by enviromentalists because they contain many toxic products which are very dangerous. Pictured here is one of Syncrude Canada Ltd's tailing ponds. Tar sands, or oil sands, are very dense and contain a form of petroleum The world's largest reserves of tar sands in Canada and Venezuela. Tar sands could equate to approximately two thirds of the total global petroleum resource. Until recently it was financially not viable to extract the oil from the sands, but new technology and rising oil prices have now made it viable. (Photo by Veronqiue de Viguerie/Getty Images)