Canada's Athabasca Oil Sands- 1984 to 2011 imagery
1994
2004
2011
Buried under Canadas boreal forest is one of the worlds largest reserves of oil. Bitumena very thick and heavy form of oil (also called asphalt)coats grains of sand and other minerals in a deposit that covers about 142,200 square kilometers (54,900 square miles) of northwest Alberta. According to a 2003 estimate, Alberta has the capacity to produce 174.5 billion barrels of oil.
Only 20 percent of the oil sands lie near the surface where they can easily be mined, and these deposits flank the Athabasca River. The rest of the oil sands are buried more than 75 meters below ground and are extracted by injecting hot water into a well that liquefies the oil for pumping. In 2010, surface mines produced 356.99 million barrels of crude oil, while in situ production (the hot water wells) yielded 189.41 million barrels of oil.
This series of images from the Landsat satellite shows the growth of surface mines over the Athabasca oil sands between 1984 and 2011. The Athabasca River runs through the center of the scene, separating two major operations. To extract the oil at these locations, oil producers remove the sand in big, open-pit mines, which are tan and irregularly shaped. The sand is rinsed with hot water to separate the oil, and then the sand and wastewater are stored in tailings ponds, which have smooth tan or green surfaces in satellite images.
more
http://earthobservatory.nasa.gov/Features/WorldOfChange/athabasca.php
also
http://blogs.scientificamerican.com/plugged-in/2011/12/28/growth-of-the-alberta-tar-sands-from-1984-to-2011/