Greetings from Christchurch! For those that follow on twitter, you already know that I made it safe and sound to New Zealand and started taking care of the most important tasks. I have some pictures to show you of the trip thus far and our CDC experience, but that will have to wait until I’m at McMurdo. Instead, I threw together a short, ~3 minute video from last year.
Now why, 11 months after the field season ended, did I decide to spend some time to edit a video and post it on the internet? Well mostly because I just rediscovered that I took so much video last year. But also because I do realize that I did not give you much of an idea of what day-to-day work was like last year and this was what we did for more than half the season. I talked a little about our active seismic work, but as my 9th grade English teacher taught me, why tell when you can show.
Background: last year, we shot 50,000 meters (~31 miles) of active seismics. This method consists of laying down a line of some really sensitive microphones called geophones on the surface and detonating a small amount of explosives in the middle of the line. In a highly over-simplied, once sentence explanation: the energy from the explosion radiates out from the source and bounces off the bedrock beneath the ice. The geophones hear the energy that bounces back, which not only can tell you about how thick the ice is, but can also tell you a few of the properties of the rock underneath the ice.
It’s a very informative data source, but extremely work intensive. For the experiments last year, we placed geophones every 20 meters (~65 feet). Geophones are extremely sensitive to noise like wind and blowing snow, so they have to be buried about 12-18 inches beneath the snow surface. The geophones are linked to a computer via a long seismic cable. We had two computers, which can record 48 geophones at once, each housed in a conestoga wagon (yes, like Oregon Trail). For each “move” (one position of wagons, cables, geophones), we have 96 geophones at our disposal. Because you want geophones on either side of a single explosion, we would only do 4 individual explosions per move. After completing these shots, we would dig up the first 48 geophones and move them to the end of the line. We continually leap frogged like this this 960 meters at a time, for all 50,000 meters.
Enough explanation! Here’s what a single active seismic shot looks like in 3 minutes. I originally meant to put this to silly music, but I thought you might appreciate the sounds of Antarctica.
Some random notes on this:
- We aren’t collecting this type of data this year. This is only related to last season! Sorry for the delay.
- Assuming we dug 1 foot to bury each geophone, then dug another 1 foot to remove it, as a team we dug just under 1 vertical mile. That’s like standing on top of a tall mountain in New Hampshire and digging to sea level. Yikes.
- I definitely have to stop writing and pack. Transport is at 8 AM tomorrow to the CDC for our Ice Flight!
- Our thoughts are with our Ellsworth colleagues who made the tough decision (on Christmas nonetheless) to call it a season. Terrible news.