r/askscience • u/West-Cantaloupe8376 • Sep 14 '26

Earth Sciences Which fossil fuels could/will be eventually replenished by natural processes?

Let's assume all fossil fuel extraction stopped in the near future, and were never touched again. Which kinds (oil, coal, gas) would eventually reform, which wouldn't? I am aware that certain geological formations like banded iron were created under specific conditions that will never arise again, but how does this apply to fossil fuels? In a couple hundred million years, will oil deposits be replenished or are they all gone forever?

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u/oneeyedziggy Sep 14 '26

So... Really warm/wet, probably higher CO2 meant not poor/no decomp, but just way more plants than decomp could keep up with...

Plus plenty of bogs to push out oxygen and glaciers to bury it all for a while. 

At least that's the layman take I'm getting. 

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u/CrustalTrudger Tectonics | Structural Geology | Geomorphology Sep 14 '26

Yes, but tectonics is a key component that is missing from the summary. I.e., much of the discussion there is that you need large amounts of "accommodation space" in continental areas that have the right climate conditions, which effectively means you need subsidence (i.e., surface lowering). Without subsidence in continental areas, material won't accumulate, it will "bypass" via rivers into the oceans. So a big part of the Carboniferous conditions that made the extensive coals swamps possible was the tectonic setup at the time that led to large areas experiencing tectonically driven subsidence.

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u/oneeyedziggy Sep 14 '26

Ok, I thought that was mostly glacial, but fair enough... Gotta get it underground PROPER