More than four years after the Deepwater Horizon oil rig blew, killing 11 workers and causing the devastating Gulf oil spill—the worst in U.S. history—a federal judge has placed the blame squarely on BP.

On Thursday, a judge for the U.S. District Court of Eastern Louisiana issued a ruling that BP exhibited "gross negligence" and "willful misconduct" in the lead-up to the April 2010 explosion and spill.

The ruling holds that BP is subject to "enhanced civil penalties" under the Clean Water Act, which could add up to $18 billion more in fines to the $28 billion that BP has already spent on cleanup efforts and damage claims in the Gulf. The explosion spewed more than 200 million gallons (750 million liters) of oil into the Gulf of Mexico. (Related: "Gulf Oil Spill 'Not Over': Dolphins, Turtles Dying in Record Numbers.")

BP said that it "strongly disagrees" with the decision and that it will immediately file an appeal. (See National Geographic's in-depth series: "Gulf Oil Spill: One Year Later.")

National Geographic spoke with Robert Gramling, a sociologist at the University of Louisiana in Lafayette, and co-author of the book Blowout in the Gulf: The BP Oil Spill Disaster and the Future of Energy in America, to find out what the ruling means for BP and oil drilling in the future.

View Images Oil-saturated waves wash up on Orange Beach, Alabama, following the Gulf oil spill. Photograph by Tyrone Turner, National Geographic

Did this verdict surprise you?

It did surprise me a little—this is Louisiana [chuckles]. I'm just surprised that the judge came out as forcefully as he did. I think it was a correct decision. And I think that one thing you should keep in the back of the mind is that it took over two decades before there was a final deposition on the Exxon Valdez spill. (See "On 25th Exxon Valdez Anniversary, Oil Still Clings to Beaches.")

There was $5 billion instead of $18 billion in question, [but] I'm sure this will be appealed all the way to the Supreme Court. It'll go on for years, if not decades. The quote that one of my colleagues cited when he was investigating the Exxon Valdez spill was, "Someone who is yet unborn will be arguing this case." He was almost right.

Why is this such a milestone?

What you basically have is the largest oil spill in the U.S. and the biggest technical disaster that's ever happened in this country. It was very clear that BP cut corners, and did so in order to save time and money, and that is gross negligence.

View Images A rescue worker handles a severely oiled brown pelican on Queen Bess Island, Louisiana. Photograph by Joel Sartore, National Geographic

What will happen to BP?

They will come out with the PR and all of that and hope that over time it goes away. It's hard to predict. The spill has already receded in the background in most of the country.

Will it be able to appeal?

When you deal with the legal system, you can never predict the outcome. I'd be very reluctant to say, well, this will be held or be overturned. I don't think there's any doubt that BP will be found negligent. Were they just negligent or grossly negligent—that will be the arguing point. BP has already admitted they're responsible for the failure of the well. [The appeal] hinges on those two words, gross negligence.

To overturn it, they're going to have to find some error—they can't just say, "We don't agree." We shall see. I'm sure that the state of Louisiana is ecstatic about this because they've pretty much promised to put any funds that they get out of this into coastal restoration. (Quiz: How much do you know about the Gulf oil spill?)

How does this impact the oil industry as a whole?

Let's put it this way: After Exxon Valdez, Exxon really became the best player in the Gulf—the most careful company. When we start doing things like [drilling for oil] off the [U.S.] East Coast, where we're even more stretching the limits of our technology than we are in the Gulf, it's going to require people to really be careful.

View Images A boat cuts through surface oil near the Deepwater Horizon blowout. Photograph by Joel Sartore, National Geographic

So this ruling and the Gulf oil spill has pushed companies to be more careful?

Absolutely. After all, these are businesses, and BP has lost a lot of money. The Atlantic Ocean [where more drilling is planned] is a lot more dangerous than the Gulf of Mexico—it's deeper and gets bigger waves. The Arctic is even more dangerous than the Atlantic. Apparently there was some negligence in maintaining the blowout preventer, so I think that's something that companies will be very, very careful with—that's all that stands between you and another Deepwater Horizon. (Related: "What Happens When Oil Spills in the Arctic?")

What's the situation on the ground there in the Gulf?

If you live along the coast, anywhere from about Panama City, Florida, to [Louisiana's] Plaquemines Parish, every time we have a tropical storm we get more oil. It's still out there. Commercial shrimpers say there are areas that have not come back and areas where there's still oil in the marshes.

The real other lesson here that we learned with Exxon and with every big oil spill is that once you have the oil spilled in a marine environment, there's almost nothing you can do about it—the skimming and the burning and the booming off and all of that. All of the thousands of boats BP had out there in the Gulf, those were for the media—just about useless.

Virtually all of our efforts in terms of drilling for oil in the marine environment ought to go to prevention, because cleanup and recovery is virtually impossible.