Oil doesn’t come from dinosaurs, it comes from plankton.

When people hear “fossil fuels” they sometimes think that oil (petroleum) came from dinosaur fossils. This isn’t out of left field. At the Chicago World’s Fair of 1933-34 Sinclair Oil sponsored an exhibit that taught people that oil was formed during the time of the dinosaurs. Reinforcing this idea there’s also the logo & mascot for Sinclair Oil, Dino the dinosaur. Sinclair again pushed this connection of dinosaurs & oil at the New York World’s Fair in 1964 even though the science had become pretty clear that oil wasn’t made from dinosaurs. So what makes oil? Plankton.

What are plankton?

Plankton are water dwelling life forms that (more or less) drift with the current. The name “plankton” actually comes from the Greek for “wanderer” or “drifter” which makes them sound like edgy antiheroes in a pulp novel. There are lots of different kinds and sizes of plankton, and they fill all sorts of ecological roles ranging from being food for larger organisms to producing 50% of the Earth’s oxygen. Bacterial plankton formed in the oceans 3 billion years ago and were basically the only form of life until 600 million years ago. That’s an enormous amount of time. So as plankton over that time died, most fell to the bottom of the sea floor and began the process of becoming oil.

Let’s make oil

Lots can happen during hundreds of millions of years. The plankton that fell to the bottom of the oceans continued to accumulate as well as other sediment. The plankton would decompose releasing most of their chemicals but the hydrogen & carbon would remain. This continuous process of plankton and other sediment falling to the ocean floor meant that the former material would be pushed further down and compacted under intense pressure over millions of years, generating heat. It was this pressure and heat that “cooked” all of those plankton into oil.

While it is certainly possible that some dinosaurs may have found themselves a part of this oil making process, it’s just very unlikely they made up much oil – they usually weren’t in the right places and there weren’t enough dinosaurs (not enough raw material to cook with). Instead of being made from some of the Earth’s largest creatures, oil was made from massive amounts of some of the smallest.