Q: What, if anything, has occupied the space created when the oil is removed? If the answer is water, why have not the sea levels gone down, even though the ice caps are presumably melting? Since we burn the oil (converting it to energy and lots of gases), would not that decrease the density of the Earth? If the density is decreased, would that not alter the “tip” and speeds of rotation/revolution of the Earth? Could not the removal of so many trillions of tons of substance from the Earth result in faster shifts of the tectonic plates, thus causing more frequent earthquakes, volcanic eruptions, etc?
-- Dan Sasser, Atlanta
A: What is missing in this analysis is a sense of scale and a misconception on how oil occurs in the Earth, Michael Roden, a geology professor at the University of Georgia, told Q&A on the News. "Oil, gas and water commonly occupy the pores between sand grains in a reservoir rock like a sandstone," he wrote in an e-mail. "When the oil is withdrawn, the sand grains still support the rock, and so not much in the way of a void is created. However, significant land subsidence can occur where either oil or water is pumped out." Even though a lot of oil and gas has been removed, both of these fluids are low-density, and given the immense mass of the Earth, the amount of redistribution of mass due to oil/gas/water pumping is trivial, so there are no large-scale effects, he wrote. For example, although oil is burned, and that produces a decrease in density of the Earth, Roden said the change is trivial.
Lori Johnston wrote this column. Do you have a question about the news? We’ll try to get the answer. Call 404-222-2002 or e-mail q&a@ajc.com (include name, phone and city).
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