If all of humanity went extinct, or completely left the earth, what would be left? Buildings and roads tend to be quickly overtaken by plants and nature, as any good post-apocalyptic movie will show. But according to a new paper, even if our towers and monuments won’t actually stand the test of time, the holes we dig just might, says Gizmodo.
As the authors of the paper, published in the journal Anthropocene, write: “[N]o other species has penetrated to such depths in the crust, or made such extensive deep subterranean changes.” As they point out, the burrows and tunnels left by animals reach only a few meters under the surface of the earth at the most. Plants can have more extensive root systems, spreading for tens of meters. But compared to our boreholes, tunnels, mines and storage facilities, other lifeforms are still playing in the minor leagues.
But even tiny animal burrows have staying power. Trace fossils of animal burrows pervade the fossil record, and the authors suggest that our more substantive marks on the Earth’s surface and beneath it will likewise persist over even longer spans of geologic time.
They speculate that truly deep holes, extending kilometers below the surface, will show up in the geologic record for tens of millions of years or longer, protected from the weathering and erosion that affects features on the surface of the Earth. Other uniquely human features, like the remnants of underground nuclear explosions, could also last for incredibly long periods of time.
Scientific American points out that the lead author of this Anthropocene paper is also the head of a working group tasked with figuring out if humanity has actually entered the Anthropocene, a new geologic era defined by human impacts on the Earth. (A decision is expected by 2016.) Some geologists have argued that there needs to be a clear-cut boundary for when the Anthropocene begins in the geologic record, before the term is made official. The disturbance of the earth’s crust by humans and machines might count as that boundary.