What Are The 2 Largest Oil Spills On Record? (And What Caused Them?)

Oceanic oil spills are one of the worst events humanity can inflict upon the natural world. Whether it's from an oil rig's mishap or deliberate wartime actions, oil being dumped into the ocean can cause horrible, lasting damage to life both under and above the water. Natural environments are fouled, animals are sickened and injured, and toxic compounds find their way into humanity's sources of food and water. It's a net negative for the entire planet, and it takes a lengthy, expensive effort to clean up.

Unfortunately, despite how catastrophic oil spills can be for everyone and everything, they happen with worrying frequency. For about as long as there has been a fossil-fuel industry transforming crude oil to gasoline, and especially as long as there's been off-shore drilling, oil spills have occurred both by accident and through deliberate, malicious action. There have been more than enough over the decades to fill a list, but if we were to narrow the scope, the two worst oil spills were the accidental Deepwater Horizon spill of 2010 and the deliberate spill in the Persian Gulf in 1991.

In late April, 2010, global oil company BP was operating the oil-drilling rig Deepwater Horizon in the Gulf of Mexico when a sudden surge of natural gases broke through a well cap, traveling up through the drilling rig. The gases ignited, resulting in a massive explosion that killed 11 workers. When the drilling platform capsized and sank into the Gulf two days later, its accumulated oil reserves began leaking out. It took almost five months to cap off the well, and in that time, roughly 134 million gallons of oil fouled 1,300 miles of the United States Gulf Coast.

Investigations showed that BP's design decisions made the platform vulnerable to gas surges. While most drilling platforms use a two-fold pipe-in-pipe design to ferry oil up through a well, protecting the oil from gas surges, BP used only a single unprotected pipeline. And while the well's outer wall was sealed with cement, BP ignored contractors' advice to extensively test the cement as well as perform gas-removal procedures. In subsequent lawsuits, BP was fined a cumulative $65 billion in reparations to the many individuals and businesses affected by the spill. The Deepwater Horizon is the worst accidental oil spill in human history.

The worst deliberate spill occurred in the Persian Gulf in 1991. The previous August, Iraqi dictator Saddam Hussein had ordered the invasion and occupation of nearby Kuwait in pursuit of, among other things, the country's oil reserves. This sparked the Gulf War, drawing in combatants from the United States, the United Kingdom, France, Egypt, Saudi Arabia, and Syria. The conflict saw fierce combat on all fronts, from the important Abrams tank on the ground to some of the most intense dogfights in aerial combat history. 

Near the beginning of 1991, Iraq was forced to retreat from Kuwait following sustained combat. In the wake of the retreat, large quantities of oil began to appear in the ocean, creating floating barriers meant to impede pursuit by U.S. troops. Iraqi forces claimed that the spill resulted from U.S. forces sinking oil tankers, but it was eventually discovered that it was a deliberate action on their part. In an effort to cover their retreat, the Iraqi forces had opened numerous valves across the Sea Island pipeline, as well as setting fire to hundreds of Kuwaiti oil wells. 

Iraq's actions resulted in approximately 380 to 520 million gallons of oil being dumped into the Persian Gulf. The resulting slick fouled thousands of miles of coastline, and combined with the months-long burning that followed the war, long stretches of that coastline were rendered completely uninhabitable. The effects of this are still being felt.