Climbing for Science in Antarctica
Over the past several months I’ve talked a lot about Antarctica and what it’s like to be there, but I haven’t really said much about what I’ve actually done there and why. My research career has followed two paths, the unraveling of the history of the half-billion year old mountain belt that forms the foundation of the Transantarctic Mountains (TAM) (the Ross mountain belt of my last post), and the application of fission-track dating toward determining the uplift history of the present day TAM. The fission-track story is easier to explain, but even then…. Wikipedia has a good, succinct explanation of the technique if you want to delve into it. All dating techniques in geology rely on the rates of decay of radioactive isotopes. In order to determine a date, you need to quantify the abundances of radioactive parent and stable daughter isotopes in a sample, which usually means measuring them with a mass spectrometer. Different minerals have different “closure temperatures,” when parent and daughter atoms no longer leak in or out of the crystal. I like to say that this is when “the clock starts.” Fission-tracks are produced by the fission (splitting in half) of atoms of Uranium, rather than by radioactive decay (emission of sub-atomic particles), but the result is the same. In the mineral apatite, fission tracks anneal (heal themselves and disappear) at temperatures higher than ~110° C, and below that temperature they start to be recorded. That’s when the apatite-fission-track clock starts. In the 1980’s it was our coolest clock, barely hotter than boiling water, the kind of temperature that exists only a couple of miles down in the crust. Charting the passage of the 110° C isotherm (temperature horizon) through rock is a window into its history of uplift and erosion. The story starts in 1981-82 in northern Victoria Land, where I was working out of a large, helicopter camp collecting granite samples from throughout the region. Along for the early part of the season was Andy Gleadow, the Australian fission-tracker from the University of Melbourne. He sat in the fifth seat of the Huey as we flew around bashing off pieces of the mountains for chemical and isotopic analyses back home. Andy was a pioneer in what is known as “vertical profiling,” a sampling strategy wherein one collects samples over as much vertical relief in as limited a horizontal distance as possible. Samples at the top are always older, and samples at the bottom, younger, as they should be since rock cools from above. One morning we collected five samples from sea-level to the saddle between the two peaks at the summit of Mt. Murchison. The helo pilots did a superb job of finding quasi-level patches of rock or snow at places along the ridgeline. It was really slick. We covered 3,400 meters (11,000 feet) of relief in about two hours and the view was lofty. Andy took the samples back to Melbourne where they were analyzed by his Ph.D. student, Paul Fitzgerald, a New Zealander who was studying the art of fission-tracking. I met Paul in 1985-86 working out of another helicopter-supported camp, this one to the west of Beardmore Glacier. Paul was in the last year of his Ph.D., a very promising lad looking for his next step. I was starting to have kids and looking for a way to cut back on three-month field seasons I’d been putting in mapping up until then. We made a pact. If he would come to Arizona State, set up a fission-track lab, and teach me how to count, I would take him to the highest-relief granite peaks in the whole of the TAM. For the 1987-88 season, I was back in the dream world of Scott Glacier, along with Paul, brother Mugs (again), and a second climber, Lyle Dean. Our goal was to climb the biggest mountains that we could find and collect them at 100-meter spacing. Furthermore, in the name of Science, we needed to reach the summits where surveyed points allowed us to set our altimeters, essential for controlling the elevation of the sample set. Samples were 10-15 pounds each and we each typically had three or four samples in our packs at the end of the day. The first profile that we collected was from the top of the eastern buttress of Mt. Griffith, which we named Fission Wall. We climbed the smooth, hard snow slope to the right of the rock face with crampons, sidehilling back and forth, needing to frontpoint for only a short stretch in the middle when the slope reached about 50°. From the top of the buttress, we rappelled for about four pitches, collecting on the steep ground, and then were able to hike down face first from there. A couple of days later we completed the collection of Griffith with a climb to its summit along a similar steep snow slope. The high ridgeline offered a view over into the drainage of Amundsen Glacier and more than a hundred miles beyond. (The opening photo on the gallery on the homepage was shot from this ridge.) Our second climb and collection was to a summit that we named Heinous Peak. With 7,500 feet of relief, this was the most grueling climb of the season. Being from Arizona, I use a Grand Canyon depth measure when it comes to relief on a mountain. That was 1 1/2 Grand Canyons. From there we moved camp down to Mt. Borcik. The climb followed a chute that is out of sight in the photo. A fault ran through the cleft, and the rock was pretty rotten, but we managed to scramble up through this part. On the upper face we moved over mixed rock and ice to the summit. From there we traversed to the large snow chute and downclimbed. At the bottom of the chute was a cliff that was vertical for the length of our rope, save for about three feet that touched at the bottom. We rappelled down this face and then staggered back to camp so loaded with rocks we could hardly stand. The season ended with our crossing Scott Glacier to the Gothic Mountains where we collected a profile from Mt. Zanuck. Two years later Paul and I were back in Antarctica, this time in the the Sentinel Range of the Ellsworth Mountains, that grouping in West Antarctica, which claims the highest altitude on the continent, 4,897 meters (16,066 feet) at the Vinson Massif. Mugs was along again, and the second climber was New Zealander, Rob Hall. The normal route up the Vinson is a steep, scree-littered snow slope on the west side of the Sentinel Range up to a shoulder where you camp, and the following day begin a long, gradual ascent to the summit. From looking at air photos we thought we might be able to drive our snowmobiles down into the glacier that drains the front of the Vinson, and then to drive up to the climbers’ Camp 1. It worked, and from the shoulder we hiked up to about 13,000 feet where we put up a tent for the day we did the summit. Next we drove over to the low spurs in front of the Vinson and collected at scant outcrops on their crests. The day we summitted the Vinson we stopped at our high tent, rested some and drank a brew, then completed the ascent, sampled down to the snowmobiles, and drove back to basecamp, around 16 hours return. In total this profile was about 3,500 meters (10,000 feet) of relief, two Grand Canyons. The results warranted a paper in Science, and we even made the cover.