In the debate over whether or not the current phase of the Earth should be called the Anthropocene due to humanity’s outsized influence on the planet, is an interesting observation about one of the truly long-term fundamental changes humans have made to the planet: we’ve dug a lot of holes.
And not just any holes–in fact, human-dug holes have penetrated deeper into the Earth than any other known life form.
“Because it’s not in our immediate living environment, it doesn’t seem as significant,” said Jan Zalasiewicz, a senior lecturer in palaeobiology at the University of Leicester, in the United Kingdom. But, as Zalasiewicz and two of his colleagues argue in a new study, human activity below the surface is permanently changing Earth, and a sprawling web of holes from mining and energy exploration provides more evidence the planet has entered the Anthropocene.
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At 7.6 miles (12.3 km) long, the Kola Superdeep Borehole in Russia is the deepest hole in the Earth’s surface made by humans. (It was drilled in northwestern Russia in the 1980s as part of a scientific investigation.) There are roughly 1 million boreholes in Great Britain alone, according to Zalasiewicz.
Underground nuclear tests have also left their mark, the researchers note. Test sites often contain broken-up and melted underground rocks and disturbed water tables. Huge underground caverns hold stored radioactive waste from the tests.
These human-made changes below the surface will stay there, protected from the natural erosion and weathering that happens above the surface. The web of mines and boreholes “arguably has the highest long-term preservation potential of anything made by humans,” Zalasiewicz and his team of researchers wrote. The scientists estimate it will take millions of years for weathering and erosion to uncover tunnels just a few miles below the surface.