Nothing in this world is forever, and that includes fossils fuels. Sooner or later, they will run out. The world relies heavily on petroleum products not only for powering machinery, but for using that same machinery to transport products from A to B, to pave roads, to making plastics, to creating certain materials, to help making nitrogen-based fertilizers, the list goes on. Bottom line, without petroleum, the world could very well go to hell. This trope explores that fact. Examples of Post-Peak Oil include: