Earthshots: Satellite Images of Environmental Change

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» Athabasca Oil Sands, Alberta, Canada

One of the world’s largest reserves of oil sits under the boreal forest of northwestern Alberta, Canada. The deposit covers about 142,200 square kilometers (54,900 square miles), an area a little larger than the U.S. state of Wisconsin.

Known as the oil sands region, it accounts for the largest segment of Alberta’s economy. According to Alberta Energy, proven reserves in the oil sands in 2016 were 165.4 billion barrels.

This series of imagery focuses on the largest of the three oil sands areas in Alberta, the Athabasca region. Located just north of Fort McMurray along the Athabasca River, the mining of the Athabasca region has grown dramatically over the last three decades.

Map of the featured area.

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).


Getting oil from oil sands is fairly straight-forward. But that doesn’t mean it’s easy.

In the Athabasca region near Fort McMurray, the oil sands are less than 75 meters (246 feet) from the surface, close enough for surface mining.

Surface mining techniques require the forest to be cleared. The soil and rock above the oil sand (overburden in mining jargon) is then removed. This creates the maroon or gray irregularly shaped open pit mines seen in the Landsat images. The open pits are created in a series of benches, or steps, that are 12–15 meters (39–49 feet) high. Huge hydraulic power shovels dig the oil sand and drop it into trucks that have a capacity of up to 363 metric tons (400 tons). The trucks haul the oil sand to a facility that separates the oil and sand.

The oil sand mixes with hot water to form a slurry. In this slurry, the sand settles to the bottom, clay and water sit in the middle, and the bitumen floats on the top. The bitumen is skimmed off the surface and the rest gets pumped to tailings ponds, also visible as the large blue shapes in Landsat images, often outlined in tan.

The September 29, 2016, image is from the European Space Agency (ESA) Sentinel-2 satellite. The resolution of the bands used in this image is 20 meters, compared to Landsat’s 30 meters. Enlarge that image to see a little bit more detail of this surface mining area.

To extract oil that is too deep for surface mining operations, in situ mining, or “in place” mining, is used. Mining companies use steam and gravity to bring the sticky oil to the surface. This method is used where the oil sand layer is deeper than 75 meters (246 feet).

Two parallel L-shaped wells reach into the deep oil sand deposit. One injects steam through holes in the pipe. This warms the oil and lowers its viscosity. The oil then flows down to the well below where it’s pumped to the surface.

This method is not as visible in the Landsat images as the surface mining is. Each well needs a “well pad,” a small area of boreal forest cleared. A growing number of small dots appear in a grid pattern over the time series images. A vertical line appears near the top of the 2009 image. This airport was built to fly in workers close to the mining sites.

Again, a Sentinel-2 image from September 29, 2016, shows the area in slightly finer detail at 20-meter resolution. The dots that represent well sites appear a little sharper in this view.

The mining companies are required to restore the disturbed land to be at least as productive as it was before it was mined. Overburden that was removed for surface mining is replaced on top of the sand and sediment layer. Mining companies must ensure the overburden is not contaminated during the storage period.

Native species are then planted, such as white spruce, aspen, dogwood, and blueberry.

For example, a location called Wapisiw Lookout was a tailings pond from 1967 to 1997. The image series shows it later filled in by 2009, and then green by 2011.

In the Sentinel-2 image provided for this series, the 20-meter resolution allows the bench pattern in the open pits to be visible, especially in the pit in the upper left corner of the image. Click on that image and enlarge it to get the full effect.

Data from satellites such as Landsat and Sentinel-2 continue to monitor the mining and reclamation of the Athabasca region. The frequent repeat cycle of these satellites—8 days for Landsat and 10 days for Sentinel—ensures that the land can be observed as it changes.

You might have noticed that fire scars of varying size show up in some of these images. These fire scars show up as red or maroon against the green vegetation. Fires are a part of life in the boreal forest, but in 2016, an unusually intense forest fire, fueled by dry conditions and high winds, devastated the region.

The 80,000 residents of Fort McMurray were forced to evacuate, the largest evacuation on record in Canada. The fire destroyed 2,400 structures in and around Fort McMurray, and at least another 500 were damaged. Many structures still standing suffered smoke damage.

At its peak, the fire moved 30 to 40 meters (98 to 131 feet) per minute. It burned a total of 589,552 hectares (nearly 1.5 million acres), and part of that area is shown in the series of images. Using shortwave infrared (SWIR) and near-infrared (NIR) bands to help penetrate clouds and smoke and create false-color images, Landsat shows the burned area in dark red. It’s clear that Fort McMurray was quickly surrounded by the blaze.

Landsat’s infrared sensors are valuable for producing burn severity maps and other products quickly after images are acquired.


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