Most of the oil enjoyed during the 20th century was pulled up from big underground pools. Drills went down, tapped into the pool, and the oil came bubbling up. With demand on the rise and traditional deposits like this already drilled, however, oil companies are digging into "unconventional" deposits. This is the crude mixed in with shale and sand that until now has been economically and physically out of reach. That's where the Alberta oil sands come in.
There are two ways to separate the Alberta oil from the sand it's glued to. The way it's been done since the '60s is to basically strip mine huge swathes of land, separate the crude, and dump the waste off to the side. It's as ugly as it is spectacular to behold, it turns out, but that's not what's causing this new boom.