Did a massive underwater volcanic explosion create the oil we're now sucking out of the crust of the planet at ruinous rates? Possibly: Researchers at the University of Alberta hypothesize that such an explosion 93 million years ago first created a massive bloom of life as the volcano belched nutrients into the water, and then, as this smorgasbord depleted, the massive ensuing die-off depleted the oxygen in the ocean, allowing the dead organic matter to settle rather than decompose normally, as it would in an oxygen-rich environment. And then there it was: the black sludge that is the tweaky crank goodness our civilization runs on.
The good news here is now we know how to replenish our oil reserves: crack the skin of the planet, let an entire food chain of creatures feast on the minerals and then catastrophically die off, and then just wait several million years. It's just that easy!