Permafrost Tunnel

My folks recently came to visit, and during their time here in Two Rivers, we were treated to a Permafrost Tunnel tour with Roy from the Army Corp of Engineers!

I like to think of myself as a moderately educated person when it comes to permafrost; however, I quickly realized that my comprehension of permafrost was as shallow as black spruce roots (aka real shallow). Good thing I was able to go on this tour and get a better grasp of how COOL permafrost is!

A lot of what Roy described was a bit over my head, but I’ll share some of the facts that stuck with me. Permafrost is perennially frozen ground for two or more years. Since temperature is the only requirement, permafrost can be with or without ice, ranging from hard rock without ice to organic-rich soil with more than half ice by volume. (Also, side note, I’m copying a lot of this info directly from info signs on the tour.) This graphic below shows how the northern part of Alaska is continuous permafrost, meaning over 90% while the Fairbanks area has a discontinuous permafrost distribution, meaning 50-90% permafrost.

The graphic below shows the the permafrost distributions across the polar regions. Take note of Greenland and the lack of permafrost. This is due to the Greenland ice sheet that actually insulates the ground and prevents permafrost!

After laying a groundwork of permafrost facts, we opened up the refridgerator-like door and stepped into the permafrost tunnel. I was picturing a narrow, dark tunnel with spelunking vibes, when in fact the tunnel was enormous and well-lit. Originally created by the Army Corp of Engineers, the tunnel was designed to research permafrost as a possible defense against nuclear attacks during the Cold War. Since then, the permafrost tunnel has been a place for research.

Throughout the tunnel, we could spot ice wedges, like the one shown below. Ice wedges form in a polygonal pattern similar to patterns seen in dried mud flats, except a much larger scale. Each polygon is in the range of 30-50 feet across. The ground cracks, water along with silt, organics, and sometimes air bubbles infiltrate the crack and then freeze. Since the wedges are created with millimeter size cracks forming over and over and over, it can take as many as 3000 years to create an ice wedge like the one in the photo below! Ice wedges haven’t grown in the Fairbanks area since the end of the last Ice Age (about 10,000 years ago). The ice wedges in the tunnel start about 20 feet below the ground surface and reach a depth of 60 feet.

You might notice that alot of the ground isn’t just ice, but is dirt-like:

“Most of the frozen material in the tunnel was originally loess or wind-blownsilt picked up off the river floodplains and deposited in the hills. The silt is bonded by interstitial that fills the pore spaces between the silt particles. In the tunnel, this interstitial ice slowly sublimates (goes from solid to gas without a liquid phase), allowing the silt to fall to the floor as dust. Organic material frozen in silt, now exposed to the air, oxidizes and produces a peculiar odor.” In other words, it smelled strange in the tunnel and was very dusty. We had to walk carefully so as not to kick up clouds of silt.

Doug and an ice formation… I can’t remember which kind so I won’t pretend to know.

Mom, Dad, and Ryne

Kalyn, Sam, and Ryne

Many bones have been found throughout the tunnel. Most are single or pieces of bones, not full skeletons. Most of the bones are dated to about 14,000 years ago; however, here is a stick dated to about 43,000 years ago!

Jess showing off a mammoth bone.

As we approached the door at the end of the tour, I was still in awe at this little slice of ground that we would typically never get to see. I have a new appreciation for the struggles of the Alaska Department of Transportation (no wonder Alaska roads aren’t smooth), and a deeper fascination with the incredible Arctic landscape. A big thank you to Roy for giving us this incredible experience!