Excerpt from Becoming Earth by Ferris Jabr, plus links to reviews, author biography & more

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Intraterrestrials

Earth's skin is full of pores, and every pore is a portal to an inner world. Some are large enough only for an insect; others could easily accommodate an elephant. Some lead only to minor caves or shallow crevices, whereas others extend into the unexplored recesses of Earth's rocky interior. Any human attempting to journey toward the center of our planet requires a very particular type of passageway: one that is wide enough, yes, but also extremely deep, stable along its entire depth—and ideally equipped with an elevator. One such portal sits in the middle of North America. About half a mile wide, the furrowed pit spirals 1,250 feet into the ground, exposing a marbled mosaic of young and ancient rock: gray bands of basalt, milky veins of quartz, pale columns of rhyolite, and shimmering constellations of gold. Beneath the pit, some 370 miles of tunnels twist through solid rock, extending more than 1.5 miles below the surface. For 126 years, this site in Lead, South Dakota, housed the biggest, deepest, and most productive gold mine in North America. By the time it ceased operations in the early 2000s, the Homestake Mine had produced more than two million pounds of gold.

In 2006, the Barrick Gold Corporation donated the mine to the state of South Dakota, which ultimately converted it into the largest subterranean laboratory in the United States, the Sanford Underground Research Facility. After mining ceased, the tunnels began to flood. Although the lowest half of the facility remains waterlogged, it is still possible to descend nearly a mile underground. Most of the scientists who do so are physicists conducting highly sensitive experiments that must be shielded from interfering cosmic rays. While the physicists slip into bunny suits and seal themselves in polished laboratories equipped with dark matter detectors, biologists who venture into the underground labyrinth tend to seek out its dankest and dirtiest corners—places where obscure creatures extrude metal and transfigure rock.

On a bitingly cold December morning, I followed three young scientists and a group of Sanford employees into "The Cage"—the bare metal elevator that would take us 4,850 feet into Earth's crust. We wore neon vests, steel-toed boots, hard hats, and, strapped to our belts, personal respirators, which would protect us from carbon monoxide in the event of a fire or explosion. The Cage descended swiftly and surprisingly smoothly, its spare frame revealing glimpses of the mine's many levels. Our idle chatter and laughter were just audible over the din of unspooling cables and whooshing air. After a controlled plummet of about ten minutes, we reached the bottom of the facility.

Our two guides, both former miners, directed us into a pair of small linked rail cars and drove us through a series of narrow tunnels. The cars jostled forward with a sound like the rattling of heavy metal chains as the thin beams of our headlamps illuminated curving walls of dark stone threaded with quartz and specked with silver. Beneath us, I saw flashes of old railing, shallow stands of water, and rocky debris. Although I knew we were deep underground, the tunnels acted like blinders, restricting my perspective to a narrow chute of rock. Glancing at the tunnel's ceiling, I wondered what it would feel like to see the full extent of the planet's crust above us—a pile of rock more than three times as tall as the Empire State Building. Would our depth become palpable the way height does when you peer over the edge of a cliff? Sensing the onset of inverse vertigo, I quickly shifted my gaze straight ahead.

Within twenty minutes, we had traded the relatively cool and well-ventilated region near The Cage for an increasingly hot and muggy corridor. Whereas the surface world was snowy and well below freezing, a mile down—much closer to Earth's geothermal heart—it was about 90°F with nearly 100 percent humidity. Heat seemed to pulse through the rock surrounding us, the air became thick and cloying, and the smell of brimstone seeped into our nostrils. It felt as though we had entered hell's foyer.

Excerpted from Becoming Earth by Ferris Jabr. Copyright © 2024 by Ferris Jabr. Excerpted by permission of Random House. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.