Searching for Tephra

I first joined the Science of the Human Past initiative at Harvard because of the “S” in “SoHP.” As an earth science major, I was drawn to the possibility of being able to use the skills and lessons that I learned in my classes in order to gain a better understanding of historical events. It seemed like a great way to truly fulfill the liberal arts education that I was receiving: using science to dissect and understand records from the past.

As such, I have been involved with SoHP in every capacity that I can fit into my schedule. I have acted as a scribe at conferences, I have worked as a translator of climate events for the Digital Atlas of Roman and Medieval Civilizations (DARMC), and most recently, I have worked as a research assistant with Dr. Andrei Kurbatov at the Climate Change Institute of the University of Maine Orono. Let me elaborate a little more upon this.

In early June I received an email from Professor Michael McCormick asking me to consider a weekend trip to Maine where I would work at the CCI with Dr. Kurbatov in a quest to look for volcanic tephra hidden in the layers of the Colle Gnifetti ice core drilled in 2013 in the Swiss Alps. The goal of the trip was simple: find volcanic glass that could be analyzed and tied to specific volcanic eruptions in order to provide possible means of absolute dating for the ice core. I jumped at this opportunity to finally help out SoHP in my capacity as a scientist, and I booked my bus ticket as soon as I could.

When I arrived in Maine, I was greeted by Professor Kurbatov and his two graduate students, Teye and Sarah. Together, they walked me through the lab work that I would be doing throughout the weekend and explained the big picture nature of the research. The Colle Gnifetti ice core, if dated accurately, could be the most accurate measure of Mediterranean climate that we have to date, potentially reaching as far back as two millennia. In order to provide as accurate a record as possible, we needed to find some way of finding out exactly what year each ice layer corresponded to. Volcanic tephra provides the perfect dating tool, as we can geochemically analyze the tephra to see the elemental composition and then tie it to a specific volcanic eruption with a known timing. The only issue was finding that tephra.

I spent a whirlwind three days working with a Scanning Electron Microscope (SEM) equipped with EDS detector, which shoots a beam of high-energy electrons at a solid object in order to make an image. Once we lock the SEM on the particle we are looking at, it spectroscopically determines the elemental make-up; for volcanic glass, we were looking for twelve major elements, specifically silica and aluminum content. We took ice chips that were made during drilling, melted them down, and filtered the liquid through a .4 micron polycarbonate membrane filter. The tephra that we were looking for would be about 5-10 microns and required a sharp eye to scan through the jam-packed filters. Much of my time was spent determining whether a small chip might be tephra. Often times, even pieces that had the characteristic glass-shard shape were just small flakes of feldspar dust blown to the glacier from nearby deserts. However, if we could find just one piece of tephra, we can be justified in taking the next step, which would be to use the laser to scan through the ice core and find tephra in situ.

Currently, I am analyzing the data collected during my weekend from back home in Cambridge. I have modified and written a script in R to scan through the data files we created from the SEM/EDS instrument, and then plot the particles on a mineralogical chart. I should know soon the extent and amount of tephra that we found on these filters. More to come in that regard!

I have really appreciated the opportunity to work with SoHP and be a research assistant. Not many students can claim the truly interdisciplinary nature of the work that I am doing, weaving together science and history in such a way to improve upon both fields. I find it a little funny that I got offered a position to do geochemistry from my history professor, but I think this is a perfect example of how academia is changing in the twenty-first century. We are truly entering a phase in research where historians can be informed by science, and scientists can be informed by history. The lines between disciplines are becoming much more fluid, and I count myself lucky to be in a research group that is at the forefront of this movement.

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