The picture on the left is one of my favorite pictures I've taken of an ice core. The little sand like particles you see are actually tiny air bubbles - the exact air bubbles that scientists including myself extract and analyze! This image is magnified by about 10x, so to the naked eye, the air bubbles are incredibly tiny.
If you're looking closely now, you'll also see a shaded band with a dark area. This is a visible volcanic ash layer! You are actually looking at volcanic sediment that has been trapped inside an ice core! This volcanic event occurred around 3,000-3,500 years ago. I had an earlier blog about this ash layer when I was in the field back in January. This visible ash layer occurs at 306.5 meters depth in the SPICE Core and therefore has undergone many years (about 3,500 years!) of compaction. So just imagine what the ice sheet at the South Pole looked like when this sediment was laid down -- the whole ice sheet would have been covered in a few centimeters of dark brown, black ash material. It would have been snowing ash! Although my camera was unable to pick it up, we could actually see small black ash particles in the magnifying glass. This is the only visible ash layer we have observed so far in the SPICE Core. However, electrical conductivity measurements have picked up dozens of volcanic events. These events, along with annual layer counting, will aid in the construction of a time scale (i.e. for a given depth in the ice core what is the age of the ice).
Mindy Nicewonger is a PhD candidate in the Department of Earth System Science at the University of California, Irvine.
Banner photo: Mindy standing in front of the C-130 Hercules in McMurdo, Antarctica (Nov. 2014).