system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does oil end up in the same places?



I might have a crucial misunderstanding of how oil works but if oil is made from dead organisms wouldnt it be evenly spread out across the world? Like why is there a lot of oil on norwegian coasts for example when these places aren’t really known to have had that much wildlife? Why are there places with little to no oil to find?
gpt
Oil is made mostly of marine algae and phytoplankton, which as you point out, are pretty much everywhere. However, in order to be converted into oil, that algae and plankton have to be buried for thousands of years without rotting. Rotting is specifically when dead organisms are broken down by bacteria and fungi. The chemical reactions required to break down algae into oil won't happen if bacteria beat them to the punch, so to speak. So you need your algae and plankton to die in a place bacteria won't get to them, which in the case of oil is generally areas of the sea floor with extremely low oxygen levels. So even though the ingredients are abundant all over the world, oil can only form in places where a lot of specific environmental conditions are just right.

A similar thing is actually true of coal, too. You get coal by burying wood for thousands of years without rotting, but modern fungi are super good are decomposing wood. The reason almost all the coal we have was formed between 200-300 million years ago, is that's the window when large woody plants had evolved, but fungi hadn't yet evolved the ability to break down wood. As soon as fungi developed the enzymes to digest wood, coal immedately became much rarer.