Tunnelling for dinosaurs in the High Arctic
Dr Thomas H Rich (Australia)
I have no idea what made me look up at that moment. But, when I did, I saw a flash of light reminiscent of the sun glinting off the wings of a flock of birds abruptly and simultaneously changing direction. However, the light was not from a flock of birds. Rather, it was from thousands of individual, fist-sized lumps of rock, together with lumps of half-frozen mud on the steep slope above me. They were glistening due to a film of meltwater covering them and they were simultaneously starting to roll because the tonnes of rock on which they lay had suddenly started to collapse and plummet down towards me on a journey that would end in the frigid waters just below my feet.
At that moment, I was digging into permafrost at the base of the steep slope forming the left bank of the Colville River that flows across the North Slope of Alaska and terminates in the Arctic Ocean about 40km further downstream. (The North Slope is the tundra covered coastal plain in northernmost Alaska bordered on the north by the Arctic Ocean and 250km to the south by the east-west Brooks Range.) Like my companions, my efforts were directed towards recovering ‘polar dinosaurs’, at a locality named the Liscomb Bonebed in honour of the geologist who found it in 1961. Fortunately, the tonnes of mud and claystone that cascaded down the bank missed me by about five metres. Another landslide at another site during the year following his discovery had killed Robert Liscomb.
My wife and fellow palaeontologist, Patricia Vickers-Rich, and I had arrived at this place as the guests of professional colleagues who were excavating fossil plants and dinosaurs there. Our reason for doing so was that, like them, we had an abiding interest in the polar biota that lived during the Cretaceous period. In the preceding decade, together with the numerous volunteers who assisted us, we had amassed a small collection of dinosaurs and other fossil vertebrates from a site called Dinosaur Cove in south-eastern Australia (see Hell and high water: The digs of Dinosaur Cove).
When the dinosaurs found there were alive, that corner of the continent was well within the Antarctic Circle of the day. Therefore, we were interested in comparing our high palaeolatitude fossil assemblages with those from Alaska that were only slightly younger – that is, ‘slightly’ as measured by a palaeontologist. The difference in age is actually about 40 million years with the Liscomb Bonebed being deposited about 70Ma. (Dinosaur Cove is dated at 106 million years before the present.)
During our initial visit to Alaska in the summer of 1989, about every two minutes, we heard the rumblings of tonnes of collapsing rock. This occurred because the banks were made up of permafrost (that is, ground that has a temperature lower than 0oC continuously for at least two years.) It was this ice cement that held the bank together. When the ice melted in the summer sun, what had been rock because of the ice binding it together was transformed into a mixture of mud and fragments of claystone.
My near miss was one of these numerous collapses and had concentrated my mind on our precarious situation. I asked myself, ‘What were we doing working in such a potentially dangerous place when, to me, there was an obvious and safe way to avoid this danger?’
What occurred to me in the immediate aftermath of the landslide was based on my experience excavating polar dinosaurs in south-eastern Australia over the previous five years. There, the only potential dinosaur site known in the early 1980s was at the base of a high, steep cliff face pounded by the waves of the Southern Ocean that exposed the fossil-bearing rock. To collect these fossils, numerous volunteers, assisting my wife and me, had cut tunnels to gain access to where specimens could be collected.
From that experience, I gained an appreciation of how to cut a tunnel together with an official mine manager’s certificate from the State of Victoria that legally enabled me to do it unsupervised.
To excavate those tunnels, I had found a few people with experience in tunnelling to help as volunteers. To carry out the bulk of the hard, physical labour that was required, I recruited numerous eager, but initially inexperienced volunteers, who relished the idea of participating in a dinosaur dig. For the latter, working underground was something that none of them had done before. But under the tutelage of the few old hands on the crew, the novice volunteers quickly learned.
As a consequence of their efforts, 600 tonnes of rock was removed from the tunnels at Dinosaur Cove over a decade. This was achieved, first by blasting out a tunnel well above the fossil layer with explosives and then shovelling out the debris by hand. Only when that was done, could the fossil layer (that averaged only 10cm in thickness), together with one metre of overburden, be excavated by more gentle means. To achieve this without using explosives, a combination of compressed air driven rock breakers (that is, jackhammers) and hand tools were used. Of that 600 tonnes, only 20 tonnes was fossil-bearing rock that was carefully examined to yield a few hundred isolated bones and teeth plus two partial skeletons (almost exclusively of small dinosaurs), together with turtles, lungfish, rare pterosaur remains and two mammal specimens. The other 580 tonnes was overburden that had to be removed.
In learning the tunnelling trade in Australia, I became aware that Alaskan miners routinely tunnel into permafrost for gold as well as to create passageways for pipes and other civil engineering projects. Therefore, when my mind was focused on the idea of excavating a tunnel on the North Slope, I already knew that there was a community of expertise that could be called upon to cut a tunnel into permafrost to recover dinosaurs if the money could be found to do the job. (Strictly speaking, the excavation on the North Slope was not a tunnel at all. Rather, it should properly be referred to as an ‘adit’ because it had only a single entrance.) After 18 years, the money was eventually found and an experimental tunnel was cut to see if this was a sensible way to recover fossils on the North Slope.
At the entrance of a tunnel, it is quite common to construct a portico or entrance way of steel or wood. In Alaska, porticos (or ‘snowsheds’ as they are called there) have two doors in them if the tunnel is cut into permafrost.
These doors are both insulated and, as a result, the walls and ceiling of the tunnel do not melt and collapse in the summer. In addition, on the banks of the Colville River, the portico would serve another purpose. This was to make access safer in summer when collapses of the permafrost bank occur. If a collapse occurred above the portico, the debris would simply flow around the portico sticking out from the bank. Therefore, one could enter or leave the tunnel during these months without fear of being buried by a sudden collapse of the bank above. Once inside the tunnel and by keeping the doors closed most of the time, the temperature would remain below freezing even at the height of summer.
Unlike Dinosaur Cove where volunteers performed the work, we hired a professional miner, Robert Fithian, along with his staff of four to excavate the tunnel above the Liscomb Bonebed in early spring – the first of two phases of the project. In addition, Bobby provided the camping gear suitable for the frigid conditions that occur during early spring on the North Slope as well as the mining gear along with the majority of the surface vehicles.
This difference in approach was taken for the following reasons. When I started tunnelling at Dinosaur Cove, I had at least a vague idea of what would be involved. In contrast, on the North Slope, I knew I was getting into a situation where it would be folly to assume I knew anything about the realities of cutting a tunnel in the early spring when temperatures can be as low as -40oC before the wind chill effect is factored in. My own previous limited experience in working at such temperatures was gained during a brief stay in Antarctica. That did give me an appreciation of what it would be like to live in a remote area such as the North Slope in early spring. By contrast, during the summer, from several previous visits to the North Slope at that time of year, I knew the logistics of the operation would be much more familiar and working in an established tunnel to collect fossils was something that I had done for a number of years. Therefore, it would be unnecessary to hire professionals for the second phase. That would be when the fossils would be collected from the Liscomb Bonebed exposed on the tunnel floor.
A major problem at Dinosaur Cove was gaining access to the site.
Located at the bottom of a cove with steep slopes that were 90m high, it was possible to get no closer than within 600m of the site with motor vehicles. From that point, everything had to be either carried in on people’s backs or conveyed to the site using an aerial tramway (or, as Australians call it, a ‘flying fox’), conceived, designed and constructed by an enthusiastic volunteer with an inventive bent. In the case of water and compressed air, these had to be piped in. Rarely, the services of a helicopter were also available. By contrast, with the tundra and Colville River frozen in early spring, it was possible at that time of year to take advantage of the frigid conditions to drive labour saving mining equipment right to the proposed tunnel entrance. Therefore, instead of hand tools being used laboriously to clear debris out of the tunnel after each round of explosives was fired to advance the face, a single individual operating a loader was able to do the same job in much less time and without the back-breaking labour.
Once the tunnel above the fossil layer in Alaska was completed early in April 2007 and the portico constructed, it was closed in anticipation of a group of palaeontologists returning the following August to excavate the floor of the tunnel to expose the Liscomb Bonebed and recover dinosaur bones from it.
During the summer, access to the site was by fixed wing aircraft and helicopter because surface travel across the tundra was not possible once it had thawed out.
However, that disadvantage was more than countered by the more pleasant camping conditions for the field crew as well as the lesser cost of accommodating people on-site in summer. Together with the reduced need for heavy equipment, the trade-off in access only by air was well worthwhile.
In early June, the Colville River rose sufficiently to flood the tunnel. On returning in August, the portico was, not surprisingly, found to be partially buried in talus.
The slopes above it had thawed in the summer sun and, because the ice cement no longer held the surface together, the inevitable and expected collapses had occurred. After the talus had been cleared away, we entered the tunnel and found that timber and other debris that had been left in it by the professional miners the previous spring was welded to the floor and walls by a mass of ice about 60cm thick in which there were irregular lenses of slush. Four days were required to remove this using air-powered rock breakers. Without them, it might have taken most of the month we were scheduled to be at the site to expose the Liscomb Bonebed.
Once the fossil layer was exposed, it was a straightforward matter of using hand tools to excavate fossils from it in much the same manner as had been employed outside at the same locality in previous years. Underground, it was a bit colder than outside when the air there happened to be still. On the other hand, bone-chilling wind did not blow, nor were there snow flurries or sleet to contend with.
The remaining three weeks were spent digging to see what the quality of fossils that had not thawed out since they were initially frozen was like. The point is that fossils collected previously at the site had, in the few years or perhaps few centuries before their excavation, been annually frozen and thawed as they were gradually brought closer to the surface as the banks collapsed and receded a bit each summer. Because the bones deep in the tunnel had not been through that destructive process, we hoped that by collecting specimens in a tunnel, the quality of preservation might be better.
From the outset, my purpose in carrying out an excavation on the North Slope was to determine the advantages or otherwise of tunnelling for dinosaurs there. While safety was the initial impetus for this idea, my primary reason for carrying out this engineering experiment was that the approach might prove to be a valuable additional ‘tool’ in the kit of techniques to be employed on the North Slope and elsewhere in the Arctic to collect fossil vertebrates. (Ironically, on no subsequent summertime visit that I made to the North Slope after 1989 did the banks collapse with the frequency they did during my initial time at the Liscomb Bonebed locality.) To determine that, it was necessary to try it out. If it did prove to be beneficial, the rate of progress and the quality of the polar dinosaurs from there to be studied by others in the future might be significantly improved. Whatever they might learn as a result will help in furthering understanding (through the comparative method) of polar dinosaurs and their associated biota in south-eastern Australia – the primary goal of my own research programme.
Now that the tunnel has been dug and the first collection of fossils made from it, staff from the Museum of the North at the University of Alaska will continue the work necessary to improve the techniques of tunnelling used there and, first and foremost, to decide whether tunnelling really is a useful procedure on the North Slope. In the meantime, I shall be cutting my third fossil tunnel, again in south-eastern Australia. Only, this time, instead of dinosaurs, the primary objective will be the insects that lived alongside them. But if a dinosaur or mammal should happen to turn up …
More than 144 people contributed in one way or another to the success of this project over the 18 years from its conception to execution.
I thank them all. But one in particular needs to be specifically thanked – Ruth Berry. Without her seeing the potential of this project for a documentary to be entitled Dinosaurs on Ice and then obtaining the bulk of the financial support to make this palaeontological engineering experiment happen, it would not have taken place. Support for this project was provided both in cash and in kind by Big Island Pictures, Springhill, Queensland, Australia; Australian Broadcasting Corporation Enterprises; Arte France; WGBH Nova; Museum Victoria, Melbourne, Australia; Monash University, Clayton, Victoria, Australia; Museum of the North, University of Alaska, Fairbanks; together with grants from the Australian Research Committee and Conoco-Phillips, Anchorage, Alaska.
About the author
Dr Thomas Rich works for Museum Victoria, Melbourne in Australia and can be contacted at Museum Victoria, PO Box 666 Melbourne, Victoria 3001, Australia.
Haines, T. 1999. Walking with Dinosaurs, Chapter 5, Spirits of the Silent Forest, BBC Worldwide Ltd., London.
Rich, T. H. & Vickers-Rich, P. 2000. The Dinosaurs of Darkness. University of Indiana Press, Bloomington. 222 pp. Allen & Unwin, Sydney (2001).
Vickers-Rich, P. & Rich, T.H. 2004. Dinosaurs of the Antarctic. Pp. 40-47 in Rennie, J. (ed.) Dinosaurs and other monsters. Scientific American Special volume 14, no. 2. Scientific American, New York.
Dinosaurs on Ice, NOVA, Australian Broadcasting Corporation, 2008.
Walking with Dinosaurs, Episode 5, Spirits of the Silent Forest, BBC, 1999.