The oil type mined in the Athabasca oil sands region is bitumen. This naturally occurring oil is so viscous that even at room temperature it acts like cold molasses.
The oil sand is quartz sand; each grain of sand is surrounded by a thin film of water, and then covered in the heavy oil. The bitumen is too thick to flow or to be pumped without first being heated.
Of the three oil sands areas in Alberta, only the Athabasca region has reserves shallow enough for surface mining. The Athabasca River, over tens of millions of years, eroded away the sediment that covered the bitumen, making it reachable. Surface mining causes a larger and more visible disturbance of the land surface than other types of mining. The surface mineable area there covers about 4,800 square kilometers (1,850 square miles).