Playing devils advocate here, but it does make you think....

So weve all heard about global warming and clean energy and x,y,z... but if you think about it, burning off the planets oil reserves the way we do could be a good thing. Picture it, 100 million years ago a dense forest (for what ever reason) trees and animals get cought in mud. and as time goes on this mud gets buried, into huge deposits under emense pressure and gases forming a huge pocket. over time this mud becomes oil. Fast forwarding to today Theres millions to billions of tons of oil in the earths crust. something has to happen to it. either it goes down to the earths magma, or it comes up in one huge burst. if it goes down the earths magma will become too thin and obviously highly combustable.... that would result in possibly lots of volcano's followed by the magma not churning properly and cooling off. the inevitability of a cooler core is the planet would become like mars. Since volcano's form from pockets in the earths crust, usually consisting of natural gas, its reasonable to say the oil deposits could make a super huge volcano... the difference would be millions of gallons of oil first setting on fire from the heat, then bursting all of the oil's toxicity in the atmosphere all at once. Considering we use millions of gallons per year with millions of gallons to left down there, and with that comparably small amount we've managed to heat the earth up just a little.... what would happen if a huge oil volcanic burst happened?

By slowly burning off the earths oil deposits were allowing the toxicity to be filtered by plants. essentially allowing it to be cleaned up at a rate that sustains life in the process. If one volcanic burst of this stuff happened, it would block out the sun and kill off every plant on earth before they would ever have the chance of filtering it.... Essentially were preventing probably the worst global catastrophe thousands or millions of years before it even happens.

Oil in the mantle won't do a thing, won't ignite, won't explode, doesn't thin it out. There's sea-water (trapped in rock) in the mantle too.

It's all part of the process.