National Geographic News
Two decades after the worst oil spill in U.S. history, huge quantities of oil still coat Alaska's shores with a toxic glaze, experts say.
More than 21,000 gallons of crude oil remain of the 11 million gallons of crude oil that bled from the stranded tanker Exxon Valdez on the night of March 23, 1989.
The oil—which has been detected as far as 450 miles (724 kilometers) away from the spill site in Prince William Sound—continues to harm wildlife and the livelihoods of local people, according to conservation groups. (See an Alaska map.)
Dennis Takahashi-Kelso, who was on the ground at the Exxon Valdez disaster as Alaska's commissioner of environmental conservation, remembers wading through knee-deep pools of bubbling, thick oil. The smell of the pure oil was intense and pungent, he said.
When he returned to the same beaches years later, he found "surprisingly fresh" oil just below the sand.
"The damage that [the spill] created is something beyond anyone's imagination," said Michel Boufadel, Temple University's Civil and Environmental Engineering chair, who has just completed research on why the oil persists.
An 11,000-person crew removed oil from the beaches until 1994, when government officials decided to end the clean up effort. At that time, what was left of the the oil was naturally disintegrating at a high rate, and experts predicted it would be gone within a few years. But they were wrong.
Oil naturally "disappears" through two processes: As the tide rises over an oil patch, the water sloughs off bits of oil, which then disperse into the ocean as tiny, less harmful droplets that can biodegrade easily.
Biodegradation occurs when bacteria or other microorganisms break down oil as part of their life cycle.
But Prince William Sound is what ecologists call a closed system—it's not exposed to big, pounding waves, so the oil has time to seep into the sand, according to Margaret Williams, who oversees conservation in the Bering Sea for the nonprofit World Wildlife Fund (WWF).
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