Eli5 Where does fossil fuel come from?



So basically dinosaurs die and the body decomposition makes oil? Someone please explain!

In: Earth Science

Trees or algae that died millions of years ago and was then buried under the ground before it could decay.

So Mose oil comes from microscopic sea life. They die and fall to the ocean floor. They get buried before they can decompose. They get cook under a ton of pressure for a very long time and poof. Oil. Like wise for trees turning to coal.

There are few dinosaurs specifically in fossil fuel. In order to become fossil fuel you need something that does not rot. There are a few things that could cause this. First plants were around before bacteria evolved to break them down, algae blooms saturates the oceans ability to break down algae and it falls down to the bottom of the ocean where there are no oxygen, when plants developed lignin that allowed them to for example make huge trees and strong grass there were no bacteria around to break down this lignin, lakes and bogs creates conditions with little oxygen for plants to fall down into, etc. In all these cases you get carbohydrates buried in layers of dirt and stone over a long time. The pressure and temperatures is able to do what the bacteria was not and will break the carbohydrates apart. But without additional oxygen they just reform into the simplest structures possible without oxygen which is hydrocarbons or coal.

It’s mostly algae and other plant matter, but yes; things that died a long time ago get buried and break down slowly into more basic hydrocarbons. Depending on the precise pressures and local geology involved, they turn into various hydrocarbon substances ranging from gases (e.g. methane and other natural gases), liquids (crude oil), and solids (i.e. coal).