Field Trips Through Time: A Geographical History of Santorini

As I walk the streets of Fira, Santorini and swim through the waves of tourists I see that most of them look out towards the center of the caldera. To them this island has always looked this way. Many know that around 1613 BC there was a cataclysmic eruption that forms the present day caldera and was a leading factor to the end of the Minoan civilization. Although they understand this, they do not realize that three cataclysmic caldera forming eruptions preceded the Minoan eruption and that even in the thousands of years in between each eruption the geography was constantly changing and morphing through volcanism and erosion into new shapes. As our class hiked around Thera, I saw before my eyes the different parts of this complex past that make it the paradise that it is today.

May 30, 2017

We hiked up to the saddle between Mt. Profitis Ilias (565 m or 1854 ft), the highest point on the island, and Mesa Vouno, where Ancient Thera is and where the Spartans inhabited. We had driven up Mt. Profitis Ilias the day before and so today we hiked up to Ancient Thera to get a good look at the South Aegean and Mt. Profitis Ilias. As I looked out at the view breathing heavily and sweating in the heat of the Greek sun I felt relieved to look out at Aegean and up at the oldest rocks on the island.

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Me pointing to to the highest peak , Mt. Profitis Ilias, while a tourist points to the Aegean.

For a volcanic island these rocks are different. They aren’t basalt or ash or pumice like I’ve seen everywhere else. These rocks are limestone and marble and schists. They tell me a different story from the violent explosions I have come to expect from calderas. Instead I see an ancient sea with sand and fish and mud that was buried and metamorphosed using the extreme heat and pressure of the earth then thrust upward to create an island like that of the rest of the Cyclades. This sea, the Tethys Sea, left deposits that can now be seen and traced all the way from the Alps to the Himalayas and even as far as Indonesia. Santorini would have looked much different then; just an island pinnacle protruding from the Aegean.

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Figure 1: The red is what the island would have looked like from 23 ma (million years ago) until the first volcanism 650 ka (thousand years ago). The blue represents the modern geography.

 

 

May 31, 2017

 

The inside of this cinder cone is amazingly red and the layers remind me of a purple onion. Each different layer, whether it is .5 cm or a meter thick represents a different volcanic event and there are thousands of layers making up the what is now the exposed inside of the 650-550 thousand year old cinder cone.  Lisa, our instructor, articulately explained this eruption style as, “BOOM! Stop. BOOM! Stop. BOOM! Stop.” We spent two hours drawing and describing only 5 of these beds.

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Figure 2: Due to the oxidation (A process that turns rocks including iron red through either being exposed to extreme heat or rusting of iron in rocks) of the cinders (small, vesicular, volcanic rock produced in short, violent eruptions) the rocks turn various shades of red even though some have remained the original black.
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Figure 3: At this time Santorini would have consisted of two islands. The red on the left being built of cinder cones, like the one above, and domes (circular and mound-shaped volcano built from the slow extrusion of viscous lava) that appeared 650-550 ka.

June 1, 2017

Today we hikedon the northern part of Thera. The hike toke us up Megalo Vouno and eventually to the postcard of Greece, Oia (most postcards I have seen are views from Oia). After taking a serpintine, narrow, cliff side road that would scare even the cockiest drivers, we got out to look back on the hill that had provided the pitch for that terrifying drive.

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Figure 4: Even after 530-430 thousand years, there are still peices of the Peristeria composite cone left visible under the later flows and faulting. On the east side of the hill we can see a lava flow from an even later volcano, adding more topographic detail

That hill turns out to be a peice of the Peristeria composite cone volcano (a large, conical volcano built up of many layers of alternating types of lava) that helped build the northern part of the island, starting as a sea mount and eventually poking its way out of the blue Aegean to fulfill every sea mounts dream of being a real island.

 

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Figure 5: Joining the southern islands, the Peristeria composite cone makes up the third island to the North.

June 2, 2017

Today we hike through 23 million years of geologic history. The Cape Plaka hike takes you from the top of the caldera rim all the way down to the ocean bellow. This is where I saw the reminents of the first caldera 200 thousand years ago. Known as the Lower Pumice Caldera, this cataclysmic event drastically changed the geography of the island making it for the first time as large as the island as all the magma stored in the chamber bellow exploded releasing massive amounts of matirial and causing the chamber to collapse in on itself.

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Figure 6: The resulting island from the magma chamber from releasing all of its volume and then collapsing creates a donut shaped island.

June 3, 2017

Our hike up the cinder slopes of Megalo Vouno are what remains of the Simandiri Shield Volcano that filled in our donut hole of a caldera around 76 thousand years ago.

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Figure 7: The Simandiri shield volcano fills in the caldera 76 ka and is represented in green.

June 4, 2017

Boom. After 124 thousand of years its ready again to violently erupt and form the second caldera known as the Skaros caldera.

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Figure 8: A second caldera forming eruption once again creates a donut like island 76 ka.

The resulting ash and pumice and flows are what I walk as I see the cape bellow filled with blue water and much calmer that the events that created my foot path.

June 5, 2017

The Skaros shield volcano is the next volcano that filled up the new donut hole left from the eruption. Seeing the visible 23-27 layer that not only build up most of the cliffs under the city of Imerovigli, but also seeing where they were stopped by the bowl that was the old caldera.

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Figure 9: The Skaros shield volcano filled up the old caldera layer by layer until it “overflowed” on the other side.

Like pouring layers of paint in a bath tub until it starts to flow over, the shield volcano spanned across where the present caldera is all the way over to Therasia. One of my favorite moments from this day was realizing the size of this volcano.

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Figure 10:  The Skaros shield volano in 67 ka fills in the caldera from the Skaros caldera while in the south a bay is formed through non-volcanic processes.

June 6, 2017

Lisa took us to an outcrop of rock that is made up mostly of the Minoan tuff but bellow us is the surface that the Minoan people would have walked on.

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Figure 11: While observing an outcrop of Minoan rocks we stand where the Minoans stood before us.

They  would have been living and building and eating on this surface. It was made for them by the third caldera forming eruption of the volcano known as the Cape Riva caldera 21 thousand years ago.  The geography of the island was once again rearranged into an almost familiar shape.

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Figure 12: After the Cape Rive caldera the shape looked closer to the present.

The Minoan eruption. The caldera forming eruption that the tourists learn about in their tours and the last caldera forming eruption of Santorini took place in 1613± 13 BC. This massive eruption filled the skies 25 miles high with 10 million tons of ash, gas, and rock. The ash is a recognizable bed that reaches eastward all the way into Turkey.

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Figure 13: After the Minoan eruption the geography is almost that of the present.

 

The geography formed from the Minoan eruption is not the end of the story. My first night on this island Lisa waited until we all went to dinner so that she could see our faces as we saw into the caldera for the first time. I’m pretty sure that my face didn’t show half of what I felt when I saw into the caldera. In the middle I saw Nea Kameni and Palea Kameni. These only showed up in 197 BC (Palea Kameni) and 1707 AD (Nea Kameni). There was even once a third Kameni island that apeared in 1570 AD and was later incorporated into the now present island Nea Kameni. The last eruption was in 1950, building up the island and changing the landscape once again. Although we don’t know when the next eruption may be, tomorrow or in another thousand years, we do know that one day it will erupt, altering once again a continuously changing geography.

 

Sources

Friedrich, Walter L. Santorini – Volcano, Natural History, Mythology. Denmark: Narayana, 2009. Print.

 

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4 thoughts on “Field Trips Through Time: A Geographical History of Santorini”

  1. I really enjoyed this post and the maps are excellent. Great organization and great use of figures to help the reader understand how the geography of the island has changed over time.

    A significant correction for June 5th: Skaros is made up of “layers” of basaltic andesite and that city is Imerovigli…not Fira.

  2. Emily! I love your style of writing. I just read your ‘Feline Profiles’ and thoroughly enjoyed that, it’s so you! I loved this post too, like Lisa said, the organization was on point. I saw two spelling errors in the June 1st entry…”hikedon” and “toke us up”. But other than that, seriously wonderful job. You shared the islands complex volcanic history well, and I’m positive that people reading this will appreciate that you made the content easy to follow and understand. I hope you are having a wonderful trip!

  3. Paleogeographic maps are a powerful way to show evolution. One consideration is to place geographic names on the figures for places (towns) that you reference. Helps reader orientation. I really like this post.

  4. Hi Emily,

    Making the information more understandable by referencing an onion peel to the layers in the cinder cone was very clever. Also adding the ‘Boom. Stop. Boom. Stop.’ explanation that your professor used was very helpful. I did however note a few minor errors here and there, try reading your entry out loud when you’re proofreading. That will help you detect those errors before posting it.

    All the maps and pictures you used while explaining how the island was changing allowed a useful visual aid to better comprehend how the island was changing. Also, restating that the island was and still is changing in your closing paragraph reinforces the information given throughout your entry. Well done, you are doing great.

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