Pockets of oil lurking under boulders look as if they had just spilled 11 days ago.

It may be a quarter-century since the Exxon Valdez disaster, yet blobs of oil along Alaska's coastline look as fresh as if they'd been spilled less than two weeks ago.

This remaining petroleum might not be obvious to the casual observer. But it's there, lurking under boulders and between rocks, a lingering legacy of the nearly 11 million gallons of crude that escaped from the 1989 tanker wreck. Look, here's a hidden pocket:

And this petroleum-sheathed rock did not just fall out of a time machine from the '80s:

The foul tenacity of the second-biggest single oil spill in U.S. waters, behind the 2010 Deepwater Horizon/BP catastrophe, was a topic at this week's 2014 Ocean Sciences Meeting in Hawaii. Researchers from the U.S. Geological Survey, NOAA, and elsewhere explained that they were able to chemically fingerprint Exxon Valdez oil as far as hundreds of kilometers from the site of the accident. And it remains some fresh-looking goop, the USGS' Gail Irvine said: "The oil itself has hardly weathered and is similar to 11-day-old oil."

Petroleum that's left in an open environment is vulnerable to environmental stresses that help break it down, like sunlight, evaporation, and microbes. But what scientists have learned is that oil that seeps below the ground and under stones can remain intact for extremely long periods. That's what appears to be happening in Alaska: Boulders and cobbles are forming a kind of "armor" that's helping extend the slimy crude's lifespan toward immortality.

Still, the knowledge that healthy oil can hole up on beaches has a couple "silver linings" for handling future spills, according to Christopher Reddy at the Woods Hole Oceanographic Institution:

"One lesson is that if you are responsible for cleaning up a spill, you want to be proactive about cleanup behind the boulders," said Reddy. Another is that response efforts should try to prevent oil from stranding in these areas where oil may persist for years or decades.

Recent photos of Exxon Valdez oil at top by Gail Irvine, USGS. Bottom photo of the stricken Exxon Valdez tanker on April 9, 1989 by John Gaps III / Associated Press.

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