You have to be prepared to enter the permafrost tunnel!
We woke up this morning in Fairbanks under a sunny sky and projected high temperatures of 85 degrees! That is pretty warm weather for this area. We were to meet a summer class at the university who were going out for a tour of the permafrost tunnel. The tunnel is located in the town of Fox about 16 miles north of Fairbanks. The U.S. Army Corps of Engineers dug the tunnel originally to evaluate excavation techniques in permafrost. The Cold Regions Research and Engineering Laboratory or CRREL is now managing the tunnel. Excavation began during the winter of 1963 and continued for the next several winters. Today the main tunnel is 360 feet long. Why in the winter? Remember you are digging into frozen ground and you want it to remain frozen so that is can be studied. The winter is the only time of year when the daily temperatures are low enough to maintain the ice in the tunnel. The summers would be too hot and would begin to melt the ground inside the excavation.
The tunnel is 360 feet long and goes back in time almost 50,000 years!
I also didn't understand the overall importance of such a project until I realized that almost the entire state of Alaska is on some kind of permafrost. In some places the permafrost is very shallow, but in others it is quite deep. Around Fairbanks there are areas that reach down more than 100 feet. Up in the north of Alaska the permafrost can be nearly 2000 feet deep! Many people have built their homes on permafrost ground and many more large buildings are on the same ground. If you build on frozen ground and then over the years your structure begins to melt the ground you will have problems. The ground will shift and sink over time. That is one of the reasons that the Alaskan Pipeline has been constructed on stands that keep it way above the ground where the hot oil will not warm the ground.
This is a bison horn sticking out of the wall of the tunnel that was put here at a time when bison herds roamed this area.
This root is thousands of year old but doesn't look that way because of the constant cold temperatures.
The bone here is about 14,000 years old. What kind of animal do you think it belonged to?
The excavation not only provided information for engineers, it also has turned out to be a wonderful place for scientists to study permafrost and the history of the ground around the tunnel. The ground inside the tunnel begins at several thousands of year old and goes all the way back to about 50,000 years. Not only can geologists study the rocks and silts and sands found there but also the paleontologists have found remains of animals and plants that have been preserved by the cold. Beetles, flies and butterflies along with shells are frozen in time. Plant roots and structures can been seen. There are also bones from bison, mammoths, and horses.
An ice lens is a layer of water that pulled together as the ground was freezing and forms a layer.
It is a very interesting place to visit. Even on a hot day like today the temperatures inside the tunnel were well below freezing thanks to the refrigeration system that is working most of the year. During the winter months outside air is pumped into the tunnel. If you would like to learn more about the permafrost tunnel go to http://permafrosttunnel.crrel.usace.army.mil and check it out. There is even a virtual tour you can take! Bring your coat if you plan on staying long.