The Grid: Charting the World's Worst Oil Spills

(April 28) -- The crude that's pouring into the Gulf of Mexico from last week's rig explosion off Louisiana has the potential to cause widespread environmental damage, but it's a far cry from the world's worst oil spills.

These disasters are usually the result of accidents involving tankers or oil platforms. However, the biggest oil spill in history was deliberate. Iraqi troops sabotaged an offshore terminal and several tankers as they fled Kuwait in January 1991. An estimated 380 million to 520 million gallons of oil was released in the Persian Gulf (shown in red on the chart below).

The two worst accidents occurred within weeks of each other in 1979. On June 3, a well blowout in Mexico's Bay of Campeche caused a fire and platform collapse. By the time crews were finally able to cap the well nine months later, a total of 140 million gallons of crude had leaked into the water. The supertankers Atlantic Empress and Aegean Captain collided off Trinidad and Tobago on July 19 -- and 90 million gallons of oil ended up in the Caribbean.

The 1989 Exxon Valdez disaster remains the biggest in the United States, but it doesn't crack the top 30 on the list of worst oil spills worldwide. Experts estimate that, at the current rate, it would take months for the oil leaking from the damaged well off Louisiana to equal the 11 million gallons that spilled into Alaska's Prince William Sound 21 years ago.

Animals in Alaska are still being exposed to residual oil from the Exxon Valdez that's trapped in the sediment of beaches, according to research published this month in the journal Environmental Toxicology and Chemistry.

"The amount of oil that is there is a teeny fraction of what spilled," the study's lead author, Daniel Esler of Simon Fraser University in British Columbia, told Discovery News. "But a teeny fraction of 11 million gallons is still a lot of oil."

Each oil spill is unique, scientists say, and the size of the slick doesn't necessarily indicate the scope of the environmental fallout. Two years after the 1991 spill in Kuwait, international researchers found little long-term damage to the region's environment.

Sources: smithsonian.com, infoplease.com