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> And then there’s all that plastic ... creating a layer that could persist for geological timescales. Won't the plastic eventually turn back into oil, on geol

> And then there’s all that plastic ... creating a layer that could persist for geological timescales. Won't the plastic eventually turn back into oil, on geologic timescales? Or are the conditions for that too specific to be relied on? Or am I completely mistaken, and oil->plastic is basically one-way?

hyperman1 8y ago
Ive heard there is too much oxygen in the air now for the original oil forming processes
- JumpCrisscross 8y ago
  > there is too much oxygen in the air now for the original oil forming processes This is addressed in the article: “...our work also opened up the speculative possibility that some planets might have fossil-fuel-driven cycles of civilization building and collapse. If a civilization uses fossil fuels, the climate change they trigger can lead to a large decrease in ocean oxygen levels. These low oxygen levels (called ocean anoxia) help trigger the conditions needed for making fossil fuels like oil and coal in the first place.”
_plastics 8y ago
The plastic that humans create will disintegrate and crumble into dust, but over very long time scales. When we pull crude petroleum from the earth, it's mostly fossilized plants from the carboniferous period. It's a deposit of stabilized mixtures, sealed in a natural chamber, air-tight and pressurized deep underground. Humans take the stable mixture out of its pressurized environment, bleed off volatile compounds, distill and crack with heat, separate groups of solvents from precipitates, and sort out chemicals according to classification. Plastics sourced from tar and oil are only a portion of the volume of crude resources mined from the ground. Also, synthetic plastics are created from chemical processes that result in plastic from reacting feedstock. So, no, it's one way. Fossil fuels are the fossils of plants from a period long before animal life was even a kingdom that emerged from the sea. It's not going back into the ground to become that stuff. And plastics are an incomplete fraction of what the crude mixture was. It's the solid components robbed of all the volatile solvents, and cured into hard or rubbery chunks. Ultraviolet sunlight, heat without pressure, and kinetic impact damage will degrade and reduce objects to dried out, brittle ash over thousands of years. But those thousands of years are nothing, next to the many millions of years of metamorphic, subterranian tectonic action needed to create them within a mixture of sister compounds.
osoba 8y ago
Also there are microorganisms that digest plastic. They could've thrived at some point and then diminished in numbers after much of the plastic from the previous industrial civilization was consumed.
microwavecamera 8y ago
Also it assumes our hypothetical prehistoric civilization took the same technological path we did and developed plastic or if it did used oil derived hydrocarbon monomers like we do.

hyperman1 8y ago

Ive heard there is too much oxygen in the air now for the original oil forming processes

JumpCrisscross 8y ago
> there is too much oxygen in the air now for the original oil forming processes This is addressed in the article: “...our work also opened up the speculative possibility that some planets might have fossil-fuel-driven cycles of civilization building and collapse. If a civilization uses fossil fuels, the climate change they trigger can lead to a large decrease in ocean oxygen levels. These low oxygen levels (called ocean anoxia) help trigger the conditions needed for making fossil fuels like oil and coal in the first place.”

_plastics 8y ago

The plastic that humans create will disintegrate and crumble into dust, but over very long time scales. When we pull crude petroleum from the earth, it's mostly fossilized plants from the carboniferous period. It's a deposit of stabilized mixtures, sealed in a natural chamber, air-tight and pressurized deep underground. Humans take the stable mixture out of its pressurized environment, bleed off volatile compounds, distill and crack with heat, separate groups of solvents from precipitates, and sort out chemicals according to classification. Plastics sourced from tar and oil are only a portion of the volume of crude resources mined from the ground. Also, synthetic plastics are created from chemical processes that result in plastic from reacting feedstock. So, no, it's one way. Fossil fuels are the fossils of plants from a period long before animal life was even a kingdom that emerged from the sea. It's not going back into the ground to become that stuff. And plastics are an incomplete fraction of what the crude mixture was. It's the solid components robbed of all the volatile solvents, and cured into hard or rubbery chunks. Ultraviolet sunlight, heat without pressure, and kinetic impact damage will degrade and reduce objects to dried out, brittle ash over thousands of years. But those thousands of years are nothing, next to the many millions of years of metamorphic, subterranian tectonic action needed to create them within a mixture of sister compounds.

osoba 8y ago

Also there are microorganisms that digest plastic. They could've thrived at some point and then diminished in numbers after much of the plastic from the previous industrial civilization was consumed.

microwavecamera 8y ago

Also it assumes our hypothetical prehistoric civilization took the same technological path we did and developed plastic or if it did used oil derived hydrocarbon monomers like we do.