For the last week, I’ve been outside under the Santorini sun drawing and describing the post Minoan eruption stratigraphy of the island from different localities. I’ve been attempting to find answers to the history of the island’s geography through the rocks. And these rocks are so easily taken for granted, sitting while hundreds of tourists walk by unfazed by the stories they could tell. But that’s why I’m here. My purpose in coming to Santorini was to study the geology and write about what I learn. It’s my goal to share my knowledge and translate the more advanced topics of geology to layman’s terms so those reading can understand the work I’ve completed.
In order to understand the story of rocks, I had to take myself away from being a tourist. I had to sit for long hours staring at what initially looked to be the same rock. I had to draw and describe what I saw in precise detail. And in doing so, I opened a novel of a volcanic eruption that completely changed the landscape of Santorini as we know it overnight.
There are plenty of scientific and in depth ways to study rocks, but we got down to the basics; pen, paper, and good observation. The first locality we went to was Vlychada Beach, on the southern end of the Akrotiri peninsula. We spent two work days drawing stratigraphic columns (see Natalie’s blog, “Field Notes For the First Time” for a full explanation on how to draw stratigraphic columns). This location had an outcrop showing clearly four out of a total of five phases of the Minoan Eruption. It shows Phase 0 (the 2 cm warning layer) and a sharp contact with Phase 1 (a hot pumice fall deposit). Phase 2 (a cold, wet pyroclastic surge) lies on top of Phase 1. Phase 3 (a cold, wet pyroclastic flow) was missing at this locality, and there is an erosional contact between Phase 2 and Phase 4 (a final hot pyroclastic flow). The missing layer indicates that either Phase 3 was not present in this area at all or that if it was, it could have been eroded away. The key to understanding what was deposited, how it was all deposited, what [if anything] was missing, and fully understanding the story in the rocks came from careful observation. Before we were told about the phases and the details of deposition, we had to draw what we saw in a stratigraphic column and describe the rocks within each rock deposit.
The more detail I put into my sketches, the better I could interpret what was going on. It was tedious work in the moment but paid off when things started clicking in my head. The next locality we visited was Cape Plaka, a hiking path on the interior rim of Santorini, just south of Fira. This was where I was able to see my hard work pay off. After spending several hours drawing each detail in the outcrop, using Brunton compasses and meter sticks to measure the beds and calculating trigonometric angles, I was able to see the phases and compare them to what I had seen and drawn at Vlychada Beach. At Cape Plaka, the warning layer was missing, but Phase 1 and 2 showed clearly. What differed from the previous location was the presence of Phase 3 and the absence of Phase 4.
Here’s the turning point. Over the course of our studies, we’ve seen a double banded layer throughout the island which has acted as a trace layer to compare beds. I saw the double band at Vlychada clearly and drew it as separate layers. I unknowingly saw it at Cape Plaka and lumped the alternating bands into one bed. It wasn’t until later that evening that I reflected on my drawings and noticed that the double band was present at both localities. It goes to show that precise and detailed drawings can hold more information than expected!
We did an outcrop sketch at Cape Mavroptra, a locality on the northeast side of the island. This differs from a stratigraphic column because it is drawing exactly what you see, like a realism sketch of the outcrop. While it is helpful to draw, I did not feel like I noticed every distinct detail like I would have if I was drawing and describing with a strat column. Stratigraphic columns are my preferred method of rock interpretation. Another way to capture the outcrop is through photos. Pictures are less intricate for rock descriptions because information tends to get overlooked in a photo versus being at the locality looking at the actual rocks and lithic fragments with a hand lens and noticing bed changes or minute rock alterations.
All methods are helpful, some more than others. But the success of being able to compare, contrast, and eventually interpret lies in the details of the drawings and descriptions. If I had drawn anything with less careful observation, I could have missed important information that adds to the whole story of the eruption. Once our columns were drawn, we had a lecture on the Minoan eruption and its phases. It was satisfying to be able to look at my notebook and see everything that was being talked about in an accurate visual representation, displaying the details of the eruption and telling the full story of the rocks.
T.H. Druitt. 2014, New insights into the initiation and venting of the Bronze-Age
eruption of Santorini (Greece), from component analysis, page 10. Fig. 5. Generalized log of Minoan Deposits.
Field Notes for the First Time (https://nauingreece.wordpress.com/2017/06/08/field-notes-for-the-first-time/#more-4525)