Wednesday, December 14, 2011

On geology, oil, and mountains

Another geology question from David:  "Obviously oil and gas "pools" are quite deep under the surface of the earth.  Science tells us that the tectonic plates and their forces cause wrinkles or mountains.  These wrinkles go up.  What is the process for oil or decayed fossils to go down and then covered over with layers of rock?  The same forces apparently with the addition of sea bottom sediment and then a rise again?  There must be some intermediate process that causes the pool to stay together or are pools formed because the oil is trapped?"
Dear David,
Tectonic plates pushing mountains up is one kind of geologic process, and occurs due to the movement of the continental plates on the earth's crust.  Oil and natural gas formation is a different process, and generally much closer to the surface.  Oil, coal, and natural gas form when decaying plant or animal material gets covered and trapped by sedimentation, and eventually gets buried deeply by more sedimentation, or processes like landslides and volanic eruptions.  For oil and gas formation, trapping the material and providing pressure is key.  If left exposed, the material will decay into the soil instead of forming fossil fuels.  Fossil fuels are continuously forming right now, but at a much, much slower rate than we are using them.  The geologic processes that move continental plates (millions of years) are much slower then for fossil fuel formation (thousands of years) - the vast time scale of geology is something that we humans find very hard to grasp. 
Thanks for your question!

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