4 August, 2002

Seismics on ice........

Today, Dr. Baker, his graduate students, several REU students, and myself lugged all of the seismic gear up on the ice. The focus of todayıs work was to attempt to locate the depth to the bottom of the ice. The set up was more lengthy today for several reasons than when we ran seismics on soil. The gear had to be packed a considerable up the glacier, and trust me itıs not light. When seismic data is gathered on soil, the geophones simply push into the ground, but on ice a tap hole must be hammered into the ice and then the geophone coupled into the hole.

Once this data was collected, all the gear was packed back down off the ice, and Dr. Baker, Laura Gilcrist (an REU student from the University at Buffalo) and myself loaded up the GPR gear and headed back up onto the glacier to collect data at the two boreholes that I have been studying.

We also attempted to run another experiment where we collected GPR data as a weight was being lowered into a hole. Unfortunately, after setting the gear up and beginning to lower the weight we found that the hole was only 20m in depth. This hole was fairly close to the terminus of the glacier so the ice would be expected to be thinner than further up the glacier, but 20m seems a bit too thin even for this location. Dr. Baker speculated that what might be happening is that sediments carried by subglacial streams may be backing up and pushing up into the the bottom of this hole.

Tomorrow morning I am heading up to Fort Wainwright, a military station in Fairbanks with Dr. Baker to do some GPR work. We will be using the radar to look for depth to permafrost in much the same way I have described previously using it to look for depth to buried ice. It will be a quick trip as I will be back here at the glacier by Wednesday evening.

Life Is Good,

DT

The line of geophones set along a profile line on the glacier. The line along which the data was collected was 300m in length. This data will help reveal the depth to the bottom of the ice.