On Tuesday, President Donald Trump signed an executive order to revive and expedite two multi-billion-dollar underground pipelines that would snake oil through US states to centers of the petroleum industry.

One is the contentious $3.8 billion Dakota Access pipeline, which would shuttle petroleum more than 1,100 miles, from North Dakota's Bakkan oil fields to holding tanks in Patoka, Illinois.

The other is the Keystone XL pipeline — a new segment of the existing Keystone Pipeline system, which begins in the Alberta, Canada oil sands, also called tar sands (use of either term is controversial), and ends in Patoka as well as points in Texas along the Gulf of Mexico. The XL segment, which could cost its builders as much as $10 billion, is partially built and would move larger volumes of oil in less time by shortening the route and burying larger-diameter pipes.

Proponents of the pipeline say it will lessen dependence on foreign oil while creating jobs and growing domestic industry. However, many Americans, and primarily Native Americans, are furious about Trump's latest executive order.

Barack Obama killed the Keystone XL pipeline in November 2015, stating it wouldn't have helped lower gas prices or create that many jobs. He also said the long-term contribution to climate change — possibly more than 22 billion metric tons of carbon pollution, according to Scientific American — wasn't worth the loss of America's global leadership on fighting emissions that exacerbate global warming.

"If we're going to prevent large parts of this Earth from becoming inhabitable, if not inhospitable [...] we have to keep some fossil fuels in the ground," Obama said.

Trump's televised revival of Keystone XL didn't mention its steep environmental costs, including the 54,000 square miles (140,000 square kilometers) of pristine Alberta wilderness that may be industrialized to feed it.

"We're not saying the project is good or bad. We're just saying the scale and severity of what's happening in Alberta will make your spine tingle," Robert Johnson, a former Business Insider correspondent, wrote after flying over the Canadian oil sands in May 2012.

Keep scrolling to see an updated version of Johnson's photo essay, which shows Canadian oil mining — a process in which tar-laden sand is dug from the ground and the oil is separated through a lengthy and messy process.

To get a look at the oil sand mines, we rented this Cessna 172, which the pilot was allowed to bring down to 1,000 feet. Through the open window we could see what really goes on in one of the most controversial places on the planet.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The Alberta oil sands are spread across more than 54,000 square miles but we're taking a look at just a small part of it. The red line is an approximate outline of the entire deposit — the green is where we'll be flying.

(Google Maps (Google Maps)

Thousands flock here to make real money in the oil sands, where creating synthetic crude begins in the strip mine.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

This is how the oil sands have been harvested since 1967.

(Robert Johnson - Business Insider)

Only two companies worked the sands in 1998. In May 2012 there were more than 10 times that number.

That's because in the late '90s oil prices rose, the Canadian government restructured its royalty system, and new technology caused a huge boom.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

From small companies to conglomerates like Shell, each outfit starts off the same way.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

First they cut down all the trees.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Then they scrape away the shallow layer of leafy, peaty topsoil called muskeg.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Trucks and shovels move in to scoop up the oil sand — this shovel is electric — and scoops up 90 tons in one load. It takes about 2.5 tons of sand to produce one barrel of oil.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The Cat 797 dump trucks are the largest in the world and can haul 1 million pounds in a single load — more weight than a fully loaded Boeing 747 airplane.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

They're so large people say they can drive over a Ford F-150 like it's a 'speed bump.' This shot of one inside a mechanic's shop shows what they mean.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

And the dump trucks are everywhere out here.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Carrying the chunks of compacted oil sand...

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

...Often across bridges like these, which are supposed to be the strongest in the world...

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

...To crushing plants like this, which break up the chunks into a fine mixture that can be transported along the conveyor belts below.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The conveyors take the sand to be conditioned — the first step in separating it from the oil.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Conditioning just mixes the oil sand with water to create a slurry, in which oil begins to part from the sand.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The slurry is then piped to containers where it separates into three parts: Oil froth on top; sand on the bottom; and oil, sand, clay, and water in the middle.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The sand and water mixture in the middle is pumped to open storage areas called tailings ponds.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The ponds are vast and some look more like lakes.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Most ponds are coated in a sheen of oil that can be deadly to waterfowl, like ducks and geese, that land on its surface.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Scarecrows like this are all over the ponds to help keep birds away.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The ponds are used to clarify the oil-water slurry. Solids slowly sink to the bottom, chemicals and oil float to the top.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The surface chemicals are skimmed off with floating lines like those used in oil spills.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

To give an idea of the size: That dump truck passing the pond is 50 feet long.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

This is what one pond looks like on the ground.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

And this is what the surface material looks like up-close.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

After the surface water is skimmed, it's relatively sediment- and chemical-free and is pumped from one pond to another.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

This clarified water is supposed to provide 90 percent of what the oil companies need to start all over again.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The solids left behind will be used to reclaim the land as the operation moves on.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

As the sand finally dries, it turns white. Sound cannons boom in these areas to scare birds away, especially after a 2010 incident where hundreds of ducks landed on a roadside pond and died.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Oil companies are required to return the land to its original condition and this reclaimed section, populated with Wood Bison, is not far from the pond.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

It looks a whole lot different on this side.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The petroleum industry is also working to limit surface mining and increase its share of "in situ" production of oil, which drills wells into hard-to-reach deposits, blasts them with steam, and pumps oil products to the surface.

About 20% of Alberta's oil sand deposits can be reached with surface mining. The other 80% is ripe for the in situ method, which has a less visible footprint compared to mining. The split in method of production today is about 50/50.

So far, only a small portion of Alberta's oil sands are developed. And Canada requires any mining operation to reclaim the area. But there are costs to expanding in situ production.

In situ extraction still impacts wildlife, such as caribou herds, and it takes more energy — and generates more greenhouse gases — to extract oil compared to mining. Critics also say restoring a piece of developed land to its native condition is not realistic.

With the mining method, once the crude oil is pulled from the sand, it's shuttled to an 'upgrader' like Suncor's here on the Athabasca River — one of the sites where the oil from the sands is converted into synthetic crude.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

This is done by heating the raw oil, called bitumen, in a process called coking. Smoke from the process hovers about the whole area and a smell that fills the cockpit of the plane.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Here are some small piles of coke.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

And here's one very immense pile of coke waiting to be used or sold as fuel for smelting iron.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

After it's coked, the oil is "cracked" to break the heavy parts down into lighter, more desirable petroleum products.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

What's left after cracking gets sent to towers like this. Inside it's hotter at the top than the bottom, forcing dense material down and lighter petroleum products up.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Then everything is exposed to hot, high-pressure gas that removes even more impurities like sulfur.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The sulfur would normally then be sold.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

But a glut in the sulfur market in May 2012 kept prices low, so mountains of it grew.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Once the oil is "upgraded" it goes to a storage tank, like this one currently under construction.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

This is Syncrude's Mildred Lake plant along Route 63.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Route 63 is a deadly stretch of road. A family of seven died the day I arrived in Alberta, and their memorial is right across from Syncrude by the side of the road. After taking this photo, Syncrude security arrived and told me to leave.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Just north of the memorial sit these two machines some companies used in mining up until 2006 — a dragline on the left, and a gray bucketwheel to the right.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Spectacularly immense, this bucketwheel is the largest crawling machine in existence.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

That fence post in front of the wheel is about six-feet-tall.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

These bucket teeth that dug into the sand were very effective, but when the bucketwheel broke down, mining stopped — so they were phased out in favor of the shovels and trucks.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Fleets of trucks work the sands. That way, if one breaks down another one simply takes its place — but at $5 to $6 million apiece they are not cheap.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

And they go through tires pretty quickly. The ones for the big dump trucks run about $45,000 apiece.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

At 13 feet wide and 12,000 pounds each, 797-tires are a burden to dispose of — so they're put to use wherever they can be. Here they make a security fence.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

To keep vehicles from getting bogged down in the mud, these wooden boards are often laid down.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

But they're not always practical, so a nearby gravel mine pumps out stone to layer the roads.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The gravel mine produces its own uniquely colored pools of water.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

But they don't compare to the deep orange of this oil sand pit we pass in the plane moments later.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The companies out here all have their own landfills.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Even though city officials are building a state-of-the-art incinerator as part of their modernization effort.

(Robert Johnson - Business Insider)

Most oil workers live in housing like this and are bused in to the compound from their homes and families in Fort McMurray.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

There are no public gas stations up by the camps. Even this store was closed at noon on a Sunday.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

Which may have been just as well because the bootie dispenser outside the door was empty.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The average dump truck driver makes about $55 an hour plus overtime working the mines and the average family income here is around $190,000 a year.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

That kind of money prompts many people to settle down and stay far longer than they planned. (This is where the pilot lives with his parents.)

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

But the locals I talked to all said they'd like to see more transparency and updates on what exactly is being found and what they should watch out for.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

And just as you would imagine, the people who live here are very concerned about pollution — this site was fined $275,000 for contaminating the Athabasca River in 2011.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The provincial government tests the area waters constantly.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

The oil sands, with its up to 2 trillion barrels of oil sitting in the ground, is a complex place.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

And despite how you may feel about the immense environmental impact the oil companies may have on the world...

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

...You can be sure they're not going anywhere while there is still oil left to collect — with or without a Keystone XL pipeline.

(Robert Johnson - Business Insider (Robert Johnson - Business Insider)

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