First, it must be said that an enormous amount of oil is from natural seepage and emergence. It has been estimated that, off the coast of Santa Barbara, California, natural oil seepage has amounted to about 80 Exxon Valdez spills over hundreds of thousands of years! In parts of the gulf of Mexico, visible natural oil seepage occurs every few days.
In fact, about half of the volume of the oil that is introduced into the sea comes from degrading formations or actual “springs” where oil and gas seeps from the bottom of the ocean.
In terms of anthropogenic oil spills, of the ten largest oil spills in history, the Exxon Valdez does not even make the list! The Exxon Valdez is actually the 34th largest, but the ruination of the Alaskan fishing industry, plus the idea that other places in the world, such as Angola and Trinidad/Tobago do not matter as much, have placed the Exxon Valdez ahead of many other spills in history.
There is also a history of military and civilian ships spills or releases that in total, might line up with some of the worst of the commercial tanker oil spills.
The top ten spills ranged from the biggest, the 1991 Kuwait spill of 520 million gallons, to the 1988 Nova Scotia Odyssey spill of 42 million gallons.
The top ten are Kuwait 1991, 520 million. Mexico 1980, 100 million. Trinidad and Tobago 1979, 90 million. Russia 1994, 84 million. Persian Gulf 1983, 80 million. South Africa 1983, 79 million. France 1978, 69 million. Angola 1991, 51 million or more. Italy 1991 45 million. Nova Scotia 1988, 42 million.
Of the top ten oil spills, one was deliberate, when Iraqi forces opened up the Kuwaiti oil tankers to slow the US invasion. Several involved problems with single hulled tankers, including collision, fire/explosions, storms, and sinking or running aground. Some involved explosions at drilling rigs or unmonitored pipelines that leaked.
Of the hull breaches on tankers, many have now been outfitted with double hulls, where the interior hull is more protected and will retain the oil in the event of a grounding, explosion or collision. But there are still a lot of single hulled tankers operating on the seas.
Also, advanced GPS navigation is helping to prevent collisions, while advanced weather analysis might be helping with rough seas. But the issue of rig blowouts, leaks on remote and relatively unmonitored pipelines, and deliberate acts of sabotage are not well controlled.
The 2010 British Petroleum Gulf spill may go down as either the biggest oil spill or the biggest assisted seepage in the history of the world, depending on whether the mile deep oil well is ever capped and the flow of oil stopped. Ironically, one of the biggest and most long term natural seepages goes on regularly in the same gulf!
Live Science Staff, “Natural Oil ‘Spills’: Surprising Amount Seeps into the Sea”, LiveScience, May 2009
“Natural Sources Of Marine Oil Pollution”
Environwonk, “Top Ten Oil Spills”
