Why do oil spills happen? Causes, examples and prevention


Although oil escapes naturally from fractures in the earth, most oil spills are destructive and man-made. They are the result of human error: equipment malfunctions or breakdowns, lack of control or regulation, deliberate acts of sabotage or illegal dumping.

Here, we break down all the main reasons oil spills have occurred throughout history, give examples, and explore ways to prevent spills.

Human error

Accidents resulting in oil spills are often the result of a combination of error, negligence, and a lack of sufficient regulation and oversight. The Exxon Valdez oil spill is one of the most infamous examples.

Exxon Valdez Oil Spill

Protective gear teams clean up Alaska’s blackened coast after the Exxon Valdez oil spill.

jean-Louis Atlan / Sygma via Getty Images

When the tanker Exxon Valdez ran aground on a reef in Prince William Sound in Alaska in 1989, Captain Joseph Hazelwood was initially blamed. It was reported that he had been drinking that day, Hazelwood left the bridge as he crossed the strait, leaving an unqualified third officer in charge. But the National Transportation Safety Board (NTSB) later concluded that several factors played a role, including a broken radar and tired, inexperienced crew members working under stressful conditions.

In addition, the NTSB found that the Exxon Shipping Company had failed to provide adequate supervision and adequate rest for the crew. There were also flaws in the US Coast Guard’s vessel traffic system and the escort system designed to ensure safe passage.

Equipment malfunctions

In some cases, oil spills have occurred due to a combination of equipment malfunctions and human error.

The Santa Barbara oil spill

On January 28, 1969, workers on an offshore platform owned and operated by Union Oil had just drilled a new well nearly 3,500 feet below the seabed. When they removed the casing from the pipe, a pressure differential caused an eruption that sent the oil and gas up to the surface. Workers tried to plug the well, but this only intensified the pressure. Natural faults cracked beneath the seabed, releasing oil and gas for weeks.

Although nominally caused by equipment malfunction, the root cause was the oil company‘s lack of preparedness and federal oversight. Union Oil did not have an emergency plan or adequate equipment and know-how to stop the spill. It later emerged that the federal government had granted Union Oil a waiver to bypass safety measures that could have prevented the spill.

BP’s oil spill

Pelicans recently cleaned up oil after the BP oil spill.

Spencer Platt / Getty Images

On April 20, 2010, the Deepwater Horizon oil rig, operated by BP, exploded in the Gulf of Mexico, killing 11 people. The explosion caused a leak in BP’s Macondo wellhead located nearly a mile below the water’s surface, releasing 134 million gallons of crude into Gulf of Mexico waters over a period of months .

An investigation by the Bureau of Ocean Energy Management and the US Coast Guard found that the main cause of the explosion was a faulty cement base from the 18,000-foot-deep well. The investigation concluded that BP and the owner of the platform, Transocean Ltd., had violated several regulations by cutting corners to cut costs.

Kolva River Spill

The 1983 Kolva River spill in Russia, when millions of gallons of oil seeped into fragile waterways and wetlands, highlighted the risks posed by poorly maintained pipelines. The problem persists. In the United States today, there are many aging pipelines vulnerable to leaks and spills.

Critics point to laxity, infrequent inspections and inconsistent safety regulations and protocols as factors that increase the risk of pipeline spills. Pipelines experience hundreds of leaks and ruptures every year.


There are several examples of tankers colliding with other ships, such as the Sea Star spill in 1972 when a South Korean supertanker sank after colliding with a Brazilian tanker off the coast of Oman, and the spill of the Nowruz oil field in 1983, when an oil tanker struck an oil rig. in the Persian Gulf.

Pipelines, too, can be breached by collisions. One example is the recent spill off the coast of Huntington Beach, California. As investigators continue to investigate its causes, they suspect the offshore pipeline was struck by a ship’s anchor.

Deliberate acts

Oil workers during the Gulf War plug a well during an eruption, Kuwait, 1991.

Allan Tannenbaum / Getty Images

The largest oil spill on record occurred during the Gulf War in 1991, when retreating Iraqis tried to deter US forces by dumping oil directly into the Persian Gulf. The 380-520 million gallon spill resulted in an oil slick 4 inches thick over 4,000 square miles.

Concerns are growing that oil platforms and infrastructure are becoming targets of terrorism or other deliberate sabotage. Many oil spill response organizations have little experience with terrorist incidents, which require special preparation and safety. Yet sabotage of pipelines and other infrastructure is common in some countries, including Colombia, where armed groups have regularly targeted them, resulting in environmental spills. Nigeria and Russia have seen similar rebel attacks on oil infrastructure. Often, resources are lacking to respond effectively to such attacks.

As large, dramatic spills grab the headlines, millions of gallons of oil are illegally dumped at sea and on land every year. According to Marine Defenders, most human-made oil spills in water come from intentional discharges from ships. The advocacy organization says more than 88 million gallons of oil are intentionally spilled into U.S. waters each year, nearly eight times more than the Exxon Valdez spill. The group works to change the attitudes and practices of seafarers regarding illegal dumping.

Prevent future spills

While extreme weather conditions and natural disasters result in accidents involving drilling and transportation systems, humans are ultimately responsible for the majority of oil spills.

There are many opportunities for improvement by adopting more stringent standards, protocols and regulations. But while these reforms have the potential to significantly reduce oil spills and their impacts, they will not prevent all oil spills.


About Keith Tatum

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