As we are just a couple of days out from our planned departure for Erebus, we are finishing off training and testing out some of our equipment to make sure it will work in the field.
On Saturday, we went out for crevasse rescue training, along with another team. They will be working on a glacier, so the training is a useful precaution – in our case, although the upper slopes of Erebus are crevasse-free, our work comes with a small risk of breaking through the top of an ice cave. We may also need to use ropes to access some of the caves.
In the classroom, we went through some knots, principles of crevasse rescue, and self-rescue using prusiks, which are friction hitches tied around a rope. These can attach you securely to the rope when your weight is hanging on them, but slide freely when they are not loaded (usually when your weight is being held by a second prusik). We then headed out to the simulator – an artificial crevasse – a short way by hagglund from McMurdo. Unfortunately, photos are a little scarce as I was busy trying to learn things! We practised self-arrest (to stop ourselves from sliding, or being pulled, into a crevasse) using ice axes, creating anchors to which a rope can be attached and used to rescue a crevasse-fall victim, then put all the elements from our training together to pull either ‘Mr Orange’ or a heavy bag out of the crevasse.
The first part, which was hard enough, was self-arresting with a bag about half my own weight falling down the crevasse attached to the rope behind me. It was then up to my supervisor to secure a second rope into the snow, set up a pulley system, and rescue the bag (which had, by then, hit the bottom). I am not yet confident that I could rescue anyone from a crevasse or ice cave (unless it were myself), so here’s hoping for a safe field season!
It has been snowing a lot this weekend, so I put off going for a walk (until after I finish this post!) and spent another day in the office today.
Our preparation for fieldwork included putting together the system that we would use for gas sampling. This starts with a soil probe, which will go into a vent. Flexible tubing connects it to a series of copper tubes that will be used to collect gas so that we can measure its composition, and analyse helium and other noble gases. A tiny pump draws air through this system so that the air already inside will slowly be flushed out, and the gas from the vent will fill the tubes. On the other side of the pump, some glass vials will collect the outflowing gas for carbon isotope analysis. All of these samples will need to come back to UNM for analyses.
We tried testing the system with the soil probe in a beaker of water. We wanted to find out how long it took for the air in the system to be flushed out, which in this case would be when it filled up with water. It’s much harder for the pump to draw up water than air, though, so while we found a few leaks to deal with, we didn’t manage to time the flushing. Instead, we found the volume of the sampling train by filling it with water. It’s about 120 mL so, at a pumping rate of 10 mL air/min, it would take (in theory) 12 minutes to flush the system. In practise, we think that flushing for a couple of hours should be enough to ensure that we are measuring gas from the vent and not the ambient air.
After dinner, I went back to pack things up…
…and finally, I can head out into the sunshine for a walk, before a busy day tomorrow – getting our cargo ready to fly, more snowmobile training, and packing up our personal gear.