BP, in a series of newspaper advertisements about the Deepwater Horizon disaster, says it is “working around the clock to contain and collect most of the leak” and it will “take full responsibility for cleaning up the spill.”

But if past catastrophes are guides, the cleanup by BP workers will capture only a fraction of the crude belched up by the broken well. Much of the oil will be taken care of by nature; the rest is likely to stay with us for decades.

In Alaskan coastal zones fouled by the Exxon Valdez in 1989, scientists discovered oil, scarcely changed, 16 years later. In some areas, its composition had not altered much from the toxic clumps and goo that had formed just weeks after the spill.

Contrary to early expectations, oil still oozes from Alaska’s beaches, toxins intact, and is expected to remain — perhaps even for centuries.