Oil spills

What is oil?

Crude oil, the liquid remains of ancient plants and animals, is a fossil fuel that is used to make a wide range of fuels and products. Oil is found below ground or below the ocean floor in reservoirs, where oil droplets reside in “pores” or holes in the rock. After drilling down and pumping out the crude oil, oil companies transport it by pipes, ships, trucks, or trains to processing plants called refineries. There it is refined so it can be made into different petroleum products, including gasoline and other fuels as well as products like asphalt, plastics, soaps, and paints.

A still from an animation of the WebGNOME predictions from a recent oil spill response training in the Florida Keys (hypothetical spill), showing the movement of the oil and its relative concentration.
8 advances in oil spill science in the decade since Deepwater Horizon
In the decade since the largest oil spill in American history, scientists have advanced lessons learned during the Deepwater Horizon response and assessment to prepare for future oil spill disasters.

How do oil spills happen?

Oil spills are more common than you might think, and they happen in many different ways. Thousands of oil spills occur in U.S. waters each year. Most of these spills are small, for example when oil spills while refueling a ship. But these spills can still cause damage, especially if they happen in sensitive environments, like beaches, mangroves, and wetlands.

Large oil spills are major, dangerous disasters. These tend to happen when pipelines break, big oil tanker ships sink, or drilling operations go wrong. Consequences to ecosystems and economies can be felt for decades following a large oil spill.

Where do oil spills happen?

Oil spills can happen anywhere oil is drilled, transported, or used. When oil spills happen in the ocean, in the Great Lakes, on the shore, or in rivers that flow into these coastal waters, NOAA experts may get involved. The Office of Response and Restoration’s mission is to develop scientific solutions to keep the coasts clean from threats of oil, chemicals, and marine debris.

Largest oil spills affecting U.S. waters since 1969-2017.
Largest oil spills affecting U.S. waters since 1969-2017. (NOAA/Office of Response and Restoration)


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Fear not! There are ways to reduce your oil consumption without having to trek several miles on foot through blizzard conditions.

How do oil spills harm or kill ocean life? 

Where the oil is spilled, what kinds of plants, animals, and habitats are found there, and the amount and type of oil, among other things, can influence how much harm an oil spill causes. Generally, oil spills harm ocean life in two ways:

Fouling or oiling: Fouling or oiling occurs when oil physically harms a plant or animal. Oil can coat a bird’s wings and leave it unable to fly or strip away the insulating properties of a sea otter’s fur, putting it at risk of hypothermia. The degree of oiling often impacts the animal’s chances of survival.

Oil toxicity: Oil consists of many different toxic compounds. These toxic compounds can cause severe health problems like heart damage, stunted growth, immune system effects, and even death. Our understanding of oil toxicity has expanded by studying the effects of the 2010 Deepwater Horizon oil spill.

Wildlife recovery, cleaning, and rehabilitation is often an important part of oil spill response. However wildlife is difficult to find and catch, oil spills can happen over wide areas, and some animals (like whales) are too big to recover. Unfortunately, it’s unrealistic to rescue all wildlife impacted during oil spills.

Daily composite of the oil footprint following Deepwater Horizon spill using all available satellite images from May 22, 2010.
NOAA’s eyes in the sky: How satellite technology pioneered during Deepwater Horizon patrols America’s oceans for pollution
Ten years ago an experimental satellite-based Marine Pollution Surveillance Report program was thrust into the national spotlight during the Deepwater Horizon oil spill. Since then, this program has grown in scale and accuracy, becoming an indispensable tool for oil spills of all sizes.

Who cleans up an oil spill — and how?

The U.S Coast Guard is primarily responsible for cleaning up oil spills, while NOAA experts provide scientific support to make smart decisions that protect people and the environment. There are different equipment and tactics that trained experts can use to contain or remove oil from the environment when a spill occurs. Booms are floating physical barriers to oil, which help keep it contained and away from sensitive areas, like beaches, mangroves, and wetlands. Skimmers are used off of boats and can “skim” oil from the sea surface. In situ burning, or setting fire to an oil slick, can burn the oil away at sea, and chemical dispersants can break up oil slicks from the surface.

However, cleanup activities can never remove 100% of the oil spilled, and scientists have to be careful that their actions don’t cause additional harm. After the Exxon Valdez oil spill in 1989, scientists learned that high-pressure, hot-water hoses used to clean up beaches caused more damage than the oil alone. Sensitive habitats need extra consideration during oil spill cleanup.

Who pays for oil spill cleanup and restoration? 

The Oil Pollution Act of 1990 established (among other things) that those responsible for oil spills can be held responsible to pay for cleanup and restoration. This process of assessing the impacts of a spill and reaching a settlement to fund restoration projects is called Natural Resource Damage Assessment (NRDA). Federal, state, and tribal agencies work together with the party responsible for the oil spill throughout NRDA and select restoration projects with help from the public.

Working with partners from state, tribal, and federal agencies and industry, NOAA helps to recover funds from the parties responsible for the oil spill, usually through legal settlements. Over the last 30 years, NOAA has helped recover over $9 billion from those responsible for the oil spill to restore the ocean and Great Lakes.

The Canadian Coast Guard Ship Louis S. St-Laurent ties up to the Coast Guard Cutter Healy in the Arctic Ocean
Keystone species arctic cod extremely sensitive to oil exposure
Vessel traffic and oil development have increased in the Arctic in response to warming oceans and declining sea ice. Anywhere oil is collected, transported, or refined there is a risk of oil spills. As ship traffic and oil development increase in the Arctic, the risk of oil spills also increases.

How does NOAA help after an oil spill?

When a person gets sick, a doctor evaluates their symptoms, diagnoses a problem, and then prescribes a treatment to help them get better. That’s also what NOAA experts do after an oil spill: they evaluate what happened, assess the impacts, and then design restoration projects to help the ocean recover. Restoration isn’t the same as cleanup. It requires projects like building marshland or protecting bird nesting habitat to actively bolster the environment.

Restoration projects are important because they speed up the amount of time it takes for different species and habitats to recover. In addition to restoring habitats, the group responsible for the spill may also be held accountable for restoring access to natural spaces by constructing parks, boat ramps, and fishing piers.

What are the largest marine oil spills in American history?

There are three oil spills that stand out in American history, each of which was the largest oil spill into American waterways at the time. In 1969, a blowout on an offshore platform off the coast of Santa Barbara, California, spilled over four million gallons of oil. In 1989, the Exxon Valdez oil tanker ran aground in the Prince William Sound in Alaska, spilling over 11 million gallons of oil.

The largest marine oil spill in all of U.S. history was the Deepwater Horizon spill. On April 20, 2010, an explosion occurred on the Deepwater Horizon drilling platform in the Gulf of Mexico, killing 11 people. Before it was capped three months later, approximately 134 million gallons of oil had spilled into the ocean. That is equivalent to the volume of over 200 Olympic-sized swimming pools. An $8.8 billion settlement for restoration was reached in 2016, and restoration is still continuing today.

Much of the funding collected after the Deepwater Horizon spill will go to restore wide-ranging and migratory species at important points during their life cycles and geographic ranges, including inland, coastal, and offshore areas.
10 things a non-scientist has learned in the decade since Deepwater Horizon
An oil spill science communicator for the Mississippi-Alabama Sea Grant Consortium shares her experiences as a resident of the Gulf of Mexico during Deepwater Horizon, and what she’s learned since then.


Though we tend to be the most familiar with the massive incidents like Deepwater Horizon, did you know that thousands of smaller oil spills occur each year, some spilling less than a barrel of oil? Oil spills, in addition to nonpoint source pollution, threaten our ocean ecosystem. Learning about pollution, as well as our role in our ecosystem, can help protect ocean habitats by improving stewardship behaviors.

Updated August 2020