May 30th, 2016 15:00: A group consisting of 11 geology students, a T.A., and a professor, finally roll into the caldera of Santorini after an eight-hour ferry ride (let me mention, this ‘ferry’ was definitely the size of a small cruise ship). All passengers swarm to the left side of the ferry to get the best view of the place of their home, honeymoon, or in our case, our classroom. After it took me too long to find my glasses, I was immediately speechless by what I saw.
I heard people, with all of their various accents, talk about the beauty of the white houses and how nice they all looked on the cliffside. Yeah, I saw the houses, but my eyes shot down. I was looking at the rocks that allowed these houses to sit where they are.
Rocks in shades of red and brown are stacked on top of each other as if someone was layering sheets of cake. Thick rounded puffs of black rock protrude from the edges of the rim. A hefty layer of white rock blankets the outermost part of the island. “There are no words for what I’m seeing”, I thought, “How could I describe this to anyone?”
I felt two emotions at that moment: frustration and excitement. Why frustration? I knew at that moment, I would not be able to share this experience of mine with anyone. There was no way to capture the exquisite beauty of Santorini – not through any assortment of words pictures. Why was I excited? For the same reason. This experience would be unique to me. The memories and knowledge I will gain will be mine to cherish. From that first glance, Santorini began to speak to me, and I began to listen.
May 31th, 2016 11:00: This day, we walked down the path known as Karavolades – a 600 stair pathway from Fira down to the old port. I had remembered seeing this switch-backed walkway from the ferry the day before (and I was crossing my fingers hoping that I would not have to walk up it…little did I know…).
This walk was one for the books in many aspects. First off, the smell of fresh donkey feces is not to be forgotten. Second, and more relevant, was the view of the caldera cliff that we got in our journey down. Being in the ferry, I was able to see the caldera as a whole, kind of like a puzzle piece perfectly put together. Now, on this walk, that I was up close and personal with each specific layer and I was starting to see each bed of rock as a puzzle of its own.
Geologically speaking, they way in which I was viewing the rock from the ferry would be referred to as macro scale, meaning that I was taking a step back and seeing the caldera wall as a whole – noticing the colors, layers of deposition, fault lines, marker beds, etc. When I was making observations from the walk itself, I was looking from a meso scale, meaning that I could look at each individual layer and identify similarities and/or differences specific to that bedding i.e. size of grains, sorting of grains, presence of other rocks, etc.
From the macro scale I was using on the ferry, I was unable to see bedding within the layers of rock, simply because of the distance separating me. On the walk down to the old port, after I got past the smell of donkey feces, I was able to use a meso scale and actually see the rocks that compose these beautifully constructed layers.
All of the layers encompass their own beauty and uniqueness, but there was one section of rock that caught my attention immediately. From the top, on about the 8th switchback, as I was trying to catch my breath (exercise really isn’t my thing), I noticed something peculiar about a layer of rock. Imagine a tiger, except instead of mostly orange with black stripes, it is mostly black with orange stripes. Now take that image in your head and attach it to a rock. Incredible, huh?
My professor, Lisa Skinner, provided me with the photo seen on Figure A. This figure outlines the layer of rock that I had seen on the walk, except this is a view from the ferry. From this macro view, this rock layer blends in pretty well, as the orange stripes cannot be seen from this distance.
Ever since I was a kid, I was always the person to ask too many questions, so naturally, I bombarded Professor Skinner with a bunch of questions regarding this unique layer. “What is this layer? And why are there orange stripes here but nowhere else?”, were just a few questions that my very curious self asked.
Figure B, below, is a photograph I took on switchback 8 coming from the top of the walk. Here, you can see the black and orange band in relation to the surrounding layers and the orange stripes start to be clear to the naked eye.
The reason this layer stands out from the rest is because this layer formed from pumice fall that was SO HOT (around 535°C ) upon deposition, that it ‘welded’ together to form a solid rock. This welded layer is called a welded tuff (tuff meaning layer of ash and pumice). The orange layers within the bed reflect a change in deposition of the pumice.
These orange zones are pumice pieces that did not get as hot as the surrounding black rock, and thus, did not weld. Rather, these beds of pumice expanded and became deposited in the welded bed as pumice fall. The reason they look orange is because the rock oxidized- a chemical weathering process where iron essentially rusts .
The high temperatures required to weld the tuff also made the material plastic-like and malleable. This weakness in the rock allowed for bigger chunks of pumice to collapse under pressure and continue the welding process .
Figure C, shown below, is a photo taken from the book, Santorini – Volcano, Natural History, Mythology. In this photo, the uniqueness of the black and orange layers are clear.
Learning about the welded tuff gave me an insight into the power that this volcano has held in the past and sustains to this day. Not only did the volcano erupt meters of ash and pumice, but it did so so violently with such high temperatures, that a new rock layer was created almost instantaneously. That is impressive…and scary. 600 steps up the side of a caldera cliff sounds intimidating, and like the work out of a lifetime, but I absolutely recommend doing so. Santorini has a story to tell, and going on this walk was just the introduction.
 Friedrich W.L., 2009, Santorini – Volcano, Natural History, Mythology: Denmark, Narayana Press, 312
 The University of Auckland, 2005, Geology Rocks & Minerals: https://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/ignimbrite.html (accessed June 2016).
 San Diego State University, n.d., How Volcanoes Work: Pumice-Flow Deposits: http://www.geology.sdsu.edu/how_volcanoes_work/Thumblinks/ignimbrite_page.html (assessed June 2016).