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Planet EarthPlanet Earth

Our Longest-Lasting Changes to the Earth Are Hidden From View

We are modifying unseen parts of the Earth’s crust on a scale that far exceeds any other living creature.

ByAllison EckNOVA NextNOVA Next
This salt mine has contributed more permanently to global geologic change than any manmade constructions on our planet's surface.

Like many animals, humans burrow underground. But unlike other animals, we are modifying unseen parts of the Earth’s crust on a scale that far exceeds any other living creature. Whereas tree roots can plunge as far as 223 feet beneath the Earth’s surface, the world’s deepest borehole can stretch as far as 7.5 miles into the ground.

What we are doing is so different from what plants and animals normally do—a process known as bioturbation—that geologists are calling it “anthroturbation.” Jan Zalasiewicz of the University of Leicester in England is the lead author on a recent paper suggesting that the cumulative effect of our myriad mines and wells—even subway systems and sewers—is irreversibly changing the Earth more than alterations on the surface. In other words, most of the wear-and-tear on our planet is happening hidden from view.

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Here’s David Biello, writing for Scientific American:

Such mines and boreholes are also abundant: there are at least 1 million boreholes in the U.K. alone and at least that many wells currently active in the U.S. Mines leave voids in precise geometric patterns very different from anything seen in normal geology. Least subtle of all may be the subterranean scars from the development of nuclear weapons—not the uranium mines, although those will be there too, but masses of shattered rock atop the radioactive melt core of a bomb test, which can be hundreds of meters across. Just one such test in Alaska created as much melted rock as a medium-sized volcano.

The scientists in charge of the geologic timescale—known as stratigraphers—have used the appearance of animal burrows to define the beginning of the Cambrian period, more than 500 million years ago. In similar fashion, anthroturbation might herald the Anthropocene, a putative new geologic epoch marked by Homo sapiens’ extensive impacts on the planet.

Erosion won’t do away with these subterranean etchings, Zalasiewicz says. One hundred million years from now, if there’s still an Earth, extraterrestrial visitors to our planet will be able to see Homo sapiens ’ legacy not in our buildings or monuments, but in our labyrinthine tunnels.

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