On a mild, damp day in September, Thomas Douglas, a research chemist, escorts visitors through the tunnel door. Douglas works for a project of the US Army Corps of Engineers called the Cold Regions Research and Engineering Laboratory (CRREL), which has its fingers in everything from snowmelt modeling and wetlands plant inventories to research on stealth aircraft. But his own work focuses on several aspects of permafrost, and he leads occasional tours here.Inside, the permafrost tunnel itself is even stranger than its exterior. A metal boardwalk crosses a floor thick with fine, loose, cocoa-colored dust. Fluorescent lights and electrical wires dangle above us. The walls are embedded with roots suspended in a masonry of ice and silt, with a significant content of old bacteria and never-rotted bits of plant and animal tissue. Because of this, the tunnel smells peculiar and fetid, like a malodorous cheese (think Stilton or Limburger) but with an earthy finish and notes of sweaty socks and horse manure.
A trim person in a light jacket, Douglas strolls down the boardwalk with an amiable half-grin on his face, narrating the surroundings with the glib enthusiasm of a museum docent or a mountain guide. “This part of the tunnel here is about 18,000 years old. We’ve had it carbon-14 dated. This is kind of a bone-rich area right here,” he says. He gestures to what look like gopher holes in the silt—the gaps left behind by cores drilled by science teams. The bone of a steppe bison, a large Arctic ungulate that went extinct about 10,000 years ago, at the end of the last ice age, rests in the hard peat. A little further along: a mammoth bone. We have stepped both underground and back in time.
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The earthen walls look like they could be soft, like mud, but he raps the end of a long metal flashlight against one of them, and it makes a clinking sound. “You can see this is hard as a rock,” he says.Permafrost is one of the weirder concoctions of the Earth’s ice ages. In the abstract, it sounds like a simple substance—any earth material that stays frozen for two or more years. In reality, it is a shape-shifting material that underlies about 24 percent of land in the northern hemisphere—from the Tibetan Plateau to Siberia and parts of Arctic and sub-Arctic North America. Now many such areas are becoming both volatile and fragile. Permafrost can be hard as bedrock, but when it thaws, if it’s rich in ice and silt, it can morph into something like glue or chocolate milk or wet cement. In its frozen state, it can hoard materials for thousands of years without allowing them to decay. It can suspend bacteria in a kind of cryo-sleep—still alive for millennia.