After eight nights of working the night shift, we hit bedrock at the shallow wet drill. The final depth was 327 meters - by far the deepest borehole drilled in the Allan Hills, but nowhere near the deepest drilled in Antarctica (that would be Vostok, at 3,769 meters!). On the night of December 23, the winds were about 40 knots and we were all dragging. We were well past 300 meters and starting to wonder when we would ever hit bedrock. The day shift came in for dinner having reached 324 meters, and one of our team members, Ivo (a postdoc at Oregon State University) was absolutely convinced that we would hit bedrock that night. “You are going to go in there, drill 3 meters, and hit bedrock!”
The two teams were very supportive of each other - though sometimes we got a bit competitive and left little notes on the whiteboard during the night.
His statement proved to be prophetic. It was slow going at first. The first core we drilled that night was a short one, as the drill was having some problems cutting. Our two night shift drillers, Andrew and Dusty, changed out the cutters and tried again, bringing up a very nice 1 meter core. However, cutting that core was also a big of a struggle, because we had cut through a fairly sizable rock!
A rock in our ice core! It was about 3 cm long, which is much larger than the pebbles we had been seeing for about 20 meters at this point.
The next core section was only 50 centimeters, but it was starting to look a little brown. My fellow night shift core handler, grad student An from University of Washington, and I started to get excited - most of the previous cores drilled here are discolored at the bottom, because they contain sediment from the bedrock. “How do you know when you hit bedrock?” we asked Andrew. Well, he said, you don’t know for sure, but the signs include material from the bedrock, inability to drill any further, and importantly, very dull edges on the cutters.
It was getting late, close to midnight. Andrew looked at us and said, “What do you think? Are you up for trying for one more core?” Although tired, we were all happy to keep going. The next core section was again only half a meter long - and it came up very brown, and the ice chips were full of brown sediment! An and I got very excited - had we hit bedrock? Dusty inspected the cutters: yes, they were very chewed up, despite being newly installed earlier that night. We sent the drill back down for one more run and confirmed that there was no more ice in the borehole.
ALHIC 2501-338 - the final section of this ice core!
At that point, few members of our team were sleeping with walkie-talkies in their tents each night, because they wanted us to let them know if we hit bedrock during the night. I got to do the honors around 1 am, and received back whoops of joy over the radio.
Watercolor painting of our Shallow Wet Drill tent by Haylee Jameson from McMurdo Science Cargo, who visited us briefly to pick up a shipment of ice cores