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. This story has been updated to include details about in situ extraction, which is different from the mining method and makes up about half of Canada oil sands production. 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.

Source: Canadian Association of Petroleum Producers 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.

Sources: Canadian Association of Petroleum Producers, Pembina Institute, Oil Sands Magazine 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.

Source: Natural Resources Canada 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.

Source: Pembina Institute, CBC News 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.

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