Drumlin Roll Please…
Hi everyone! My name is Marion McKenzie, I’m a rising junior pursuing a double major in Environmental Studies and Mathematics, and I’ve had the privilege of studying in Professor Sarah Principato’s lab for the last 8 weeks.
This summer has turned out to be an adventure of a lifetime for both my lab mate, Brittany Bondi ’19, and me. After spending the last 7 weeks analyzing our study areas with a bird’s eye view, we were finally able to observe the topography of our summer work in person by flying to Iceland.
Although streamlined landforms can be found in many valleys across Iceland due to its very active glacial history, the valley of Bárđardalur, my specialized research area, has a very large number of these landforms: 159 to be exact (or so I thought).
My project focuses specifically on drumlins, streamlined sediment deposits left behind by glaciers, and for me, that glacier is the one that covered all of Iceland during the Last Glacial Maximum. These landforms are extremely beneficial to study, not only because they indicate the orientation and velocity of ice flows, but because they also allow us to know where else the glacier has been based on the types of till found. The sediments are deposited while the glacier is still over the land, and as the ice moves, these sediments are elongated to create the shapes we study.
Using Google Earth, I found landforms like the ones to the left and traced them using the polygon tool (shown to the right).
I then imported these shapes into ArcGIS and added long axes and short axes. These parameters were then used to analyze elongation ratios, density, packing, orientation, and a parallel conformity within the drumlin field.
The Tuesday of our stay in Iceland, we travelled to Bárđardalur to ground truth my findings and gather outcrop samples from some of my larger drumlins (also called mega-scale glacial lineations, or MSGL). We also anticipated the possibility of measuring the height, length, and width of the landforms using tape measures and altimeters, as well as leaving GPS place marks and recording latitude and longitude coordinates.
On the way to the site, we saw some of the landforms I had included in my landform data set. Without even leaving the car, we determined that many of the ones north of the main drumlin field were actually composed of bedrock and not sediment as we had originally thought. This discovery allowed me to adjust my data to become more accurate once we returned to Gettysburg.
After precariously parking the car on the side of a desolate gravel road, we began the long 2km hike up to the top of the MSGL visible from the road. The terrain was rocky at first and quickly became heavily vegetated as we reached a small stream.
After finding a way to cross the stream and climb our way through some thick moss, we reached the start of the rocky MSGL formation. While looking for striated rocks and boulders along the way, we conquered the many false peaks and finally reached the flat top of the land formation to see the drumlin valley below us.
Spending countless hours imagining what the view was going to look like still hadn’t prepared me for the sheer vastness of it all. Although I could only see two or three drumlins and a glimmer of the lake I’d used as a reference point, it was such a surreal experience to feel so small next to something I had been analyzing from a distance for so long.
The rest of our week was filled with completing the ring road around Iceland and learning all about the geologic history of the beautiful landforms we saw. This trip was absolutely incredible, and I look forward to the next opportunity I will have to return to Iceland to answer even more questions we formulated about landforms present there.
Cirque and Ye Shall Find
Hello, my name is Brittany Bondi and this summer I had the pleasure of working with Dr. Sarah Principato on a project involving a type of glacial landform called cirques. I focused specifically on a peninsula in northern Iceland, Flateyjarskagi, known for its high mountains and intertwining valleys.
A 20-meter Digital Elevation Model (DEM) of Iceland with Flateyjarskagi highlighted in red.
Cirques are amphitheater or bowl-shaped depressions in the earth typically found in high-elevation areas. They are formed when glaciers occupy and erode small hollows, slowly making them deeper and more bowl-shaped. Glaciers are constantly moving through a process, called rotational flow, that is vital to cirque development. As snow accumulates on a glacier, the snow is pressed and becomes glacial ice. Because of its increased density, it slowly transitions to the bottom of the cirque. The ice in the glacier as a whole moves through this process.
Cirques are defined by three characteristics: their headwall, toewall, and cirque floor. The headwall is the steepest and typically highest point of the cirque, while the toewall is the steepest point at the end of the cirque. The cirque floor is the flattest area and is usually located in the middle of the cirque. Using these three characteristics, one of my main goals was to determine the paleo-ELAs of my cirques. The equilibrium line altitude (ELA) is the approximate place where ablation (area where the glacier is melting) meets accumulation (area where the glacier is growing). To define this, I used three methods: the cirque floor method, toewall-to-headwall altitude ratio (THAR), and minimum point technique.
A profile graph of a cirque, showing the headwall, cirque floor, and toewall.
For my project, I utilized a combination of Google Earth and ArcGIS to map and analyze glacier-free cirques. After using Google Earth to map the locations of cirques, I used the 20m Digital Elevation Model (DEM) for the analysis within ArcGIS. A digital elevation model is a type of map that allows one to extract elevation data of a given area. I had to ignore glacier-occupied cirques because ArcGIS is unable to look at the bedrock below the glacier. If I were to extract the elevation of the cirque-floor of a glacier-occupied cirque, for example, I would merely get the elevation of the glacier, not the cirque formation itself. After drawing three profile lines on each cirque, I identified their headwall, toewall, and cirque floor. For the cirque floor method, the paleo-ELA is assumed to be equal to the cirque floor. For the THAR method, I used the headwall and toewall to calculate an approximate paleo-ELA. Finally, I also drew polygons around each cirque, which allowed me to extract the “minimum point” in each cirque, a.k.a. the cirque floor/ paleo-ELA.
Three profile lines on a cirque. The red dot represents the headwall, blue the cirque floor, and red the toewall.
After looking at other factors, such as aspect (or direction), distance to coastline, and length and width, I will statistically analyze these factors to determine what may play a role in why the cirques formed where they did. It will be interesting to compare these results to previous studies about other cirque-regions in Iceland (including those done by Gettysburg alumni!) and throughout the world.
On July 1st, my lab partner, Marion, and I joined Dr. Principato in a week-long excursion to Iceland to ground truth some of our data. Although we could not visit any of my cirques due to their extreme elevations and steep topography, while on the boat to Grimsey, the island 40 km north of the mainland, we had magnificent views of my region. It was breathtaking to see the area I had been studying for the past 6 weeks! It was equally as inspiring to see the many other landforms/marks made by glaciers both past and present throughout the country that have yet to be studied.
On a boat to Grimsey, passing some of the cirques I studied!
The two of us with our professor, Sarah Principato! We’d like to give a big thank you to the Gettysburg X-SIG program for this opportunity, and to Sarah for all of her hard work and guidance this summer. Thanks for reading, everyone!