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Natural Oil Underfoot
By Dr. E. Kirsten Peters
More than a couple of times in the long history of personally changing the oil in my 1987 pickup, I’ve misjudged how vigorously the dirty fluid will flow out of the oil pan.
I don’t have any good equipment for the task, just a small plastic pail and my father’s old wrench. Because the dirty oil gushes strongly out at first, but only dribbles out near the end, I’ve got to slide the pail around quickly to adjust as the process goes along. If you’ve done this kind of work yourself, you might not condemn me for creating oil spills on the ground from time to time.
My little slicks don’t last many days, but when they first occur they remind me of oil seeps that come naturally to the surface of the Earth.
Petroleum has always bubbled up to the surface of our planet under its own power. Just for example, according to the Bible story, when Moses was a baby his mother launched him afloat on the Nile River in a basket she waterproofed with material that’s translated in scripture variously as tar or bitumen – material we would call natural asphalt and heavy crude.
In the ancient world, people didn’t burn petroleum as we do now, but they did know about the material and its properties. Moses’ voyage in his basket was made possible by the same general kind of sticky and icky fluid, if you will, that gushes out of the oil pan of my old truck.
In the past both geologists and environmental scientists have tended to dismiss natural oil seeps as small potatoes. We figured what kept Moses afloat was trivial compared to major oil fields and supertanker oil spills. But Mother Nature, as usual, is more complex than she first appears, as a recent press release from the National Science Foundation shows.
Here’s a surprising example of a natural oil seep just reported by scientists. Some 20-25 tons of oil percolate upward into the sea each and every day in the Santa Barbara Channel. That’s a large figure when you multiply it by 365 days per year, but the oil doesn’t lead to the disastrous environmental impacts that oil spills coming from a man-made sources so often do.
Here’s the way I think about it. The steady natural seeps in California have established their own biological controls that help Mother Nature respond to the rather unusual – but fully natural – chemicals in crude oil. To put it simply, nature cleans up after herself, and we could learn some lessons from her.
The oil off Santa Barbara bubbles upward in the ocean because the oil is lighter than seawater. As the petroleum goes up in a fairly steady stream, microbes go to work “eating up” the crude oil.
That’s right, whole groups of micro-organisms make a living breaking down the complex molecules in crude oil and gaining energy from the process. In the Santa Barbara Channel, there are many such microbes because they’ve had a steady stream of food for thousands of years.
It’s cousins of those microbes that break down the little oil spills on my driveway, by the way, and generally do so quite quickly. They are naturally around in soil.
But back to Santa Barbara: As you know if you’ve strolled the beaches of southern California, they are not covered with globs of oil. That’s because most of the natural petroleum globs are “eaten up” and hollowed out by the microbes before they get to the surface. What remains of the blobs is actually heavier than water, a mere shell of what first seeps out of the seafloor. At that point, the empty shells sink and become part of the sediment on the seafloor.
Using microbes to help clean up oil spills or the soils around abandoned asphalt plants is all part of the general realm called bioremediation. Chemists and environmental scientists use Mother Nature everyday in this way to help clean up our messes – work that’s possible exactly because so many of our wastes, including leaks of gunky and stinky crude oil, are fully natural chemicals.
Dr. E. Kirsten Peters is a native of the rural Northwest, but was trained as a geologist at Princeton and Harvard. Questions about science or energy for future Rock Docs can be sent to email@example.com. This column is a service of the College of Sciences at Washington State University.