The Birth of an Island

Thousands of people mill around on the beautiful volcanic island of Santorini every day having little knowledge of the amazing geologic history that passes under their feet. The island is ever changing and is constantly forged then reforged by the liquified rocks churning beneath the sea. There are still those that know about the volcanism that has created the island you see today but fewer know of the true volcanic origins for this paradise.

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Figure A: This map is of the current shape of the full island of Santorini the shape has been formed by four caldera forming eruptions.
The geologic importance of understanding how the island of Santorini came to be cannot be understated as it helps volcanologists and geologists understand the history of the island helping to predict the future eruptions of the volcano. We journeyed throughout the original volcanoes of the island. However it wasn’t the view of the ocean that interested me it was the view of the original flows of dome volcanoes and the towering exposed cinder cone volcanoes that peaked my interest.

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Figure B: The map above shows the path we took on our search to learn more about the original volcanism on Santorini. We visited two very distinct locations Akrotiri lighthouse, and Red Beach.
The volcanism of Santorini occured due to the thinning of the Aegean micro plate allowing magma to worm its way up from the mantle. I wont be going any further into the tectonics of the Aegean as I would turn this short blog into a paper so if you are interested in learning more about the Aegean tectonics I recommend reading the blog Staying Active… Tectonically Speaking.

The volcanoes on the Akrotiri Peninsula are the oldest found on the island. The fascinating part is that the volcanism on the peninsula simply burst up from the ocean. The magma created the small island adjacent to the original limestone island and than traveled to a different location ending the eruptions on the peninsula.

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Figure C: This map shows the location of the original limestone island as well as the volcanic island that became the Akrotiri Peninsula. The limestone basement was what originally protruded out of the sea and at the time was unconnected to the Akrotiri volcanoes.
Volcanism on the peninsula began as underwater or submarine volcanoes and pushed their way up out of the brimming Aegean sea, with the activity in Akrotiri peaking at the creation of cinder cone volcanoes than petering out to nothing. The reason for the disappearance of volcanism in that corner of the island happened because the magma began following pre existing fractures and faults to a new location.

The submarine volcanoes began to break the surface of the Aegean just over 600 thousand years ago. The evidence for this is found in an area on Cape Akrotiri where there is soil containing old marine fossils such as sponges with evidence of the volcanism found where the lava flow meets the soil. Oxidization of the iron rich rocks occurred when the burning hot magma made contact with the marine soils

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Figure D: The image can barely do this beautiful outcrop justice but taking in the intricate geology that caused the oxidization of the ancient marine soils that spent so much time covered by hundreds of meters of water was mind bending and did nothing but heighten my interest in the fascinating field of geology.
The small island would have been the result of multiple eruptions of domes building on top of each other raising the land until it would eventually breach the water and continue to build the island. The oldest types of volcanoes found around Akrotiri are fascinating. It seems during the eruption period of the peninsula there were volcanoes above and below the water. These began slowly building the small island until its erupting would wane out with the last estimated activity on this specific peninsula being around 344 thousand years old.

The type of volcanoes that created the small island are some of my personal favorites which made writing this that much more enlightenening. There are two main types of volcanoes that built the island domes and cinder cones. These two types of volcanoes are fairly different in both eruption style and lava types leaving behind some of the most amazing formations and beautiful views in the world.

The oldest type of volcano found on the peninsula are domes which consist of a felsic lava type. This means that the magma had more time to stew in the magma chamber incorporating more of the crust as the non silica based materials had time to crystallize.Basically domes are a more silicate based volcano. What all this means is that domes can produce one of the most amazing lava flows jutting out of the ground at near vertical angles. These flows attributed greatly to the uplifting of the sea floor bringing the volcanoes and the soon to be island closer to the surface.

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Figure E: The view of a lava flow formed from a dome inside the rocks you can see the vesicles or places where gas bubbles had formed being stretched and sheared by the movement of the flow.
The creation of domes also led to something much cooler in my opinion which is pyroclastic flows and material which will sometimes occur when domes collapse. This pyroclastic material would have also helped to build the island up from its watery birth place. The domes where the driving force in the creation of the peninsula building up from the ocean floor dome by dome. Looking closer into the rock formations and the outcrops geologists have been able to age the oldest of the domes to just about 645 thousand years old.

The second volcano type and one of my personal favorites that formed the island were cinder cone volcanoes. These volcanoes are built by the exploding of mafic magma or less silica based magma into popcorn like rocks that stack up to make giant cones. The volcanoes are absolutely fascinating for the reason that they sprout up build their cone in maybe a couple of months to a year and then their eruption is done.

The creation of these cinder cones would have built upon the domes with their towering cone like hills and lava flows that cover the land in soon to cool lava that will build the island up bit by bit. All of these eruptions would have helped to shape the small island helping it grow larger. The final cinder cone to build itself and grow toward the sky is dated to around 344 thousand years ago.

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Figure F: This image shows the beautiful exposed inside of a cinder cone on the red beach. Sadly the camera couldn’t capture just how deep red the rocks were but we were able to study the layering that shows how the cone was built with the deposition of the small scoria rocks exploding from the volcano.
As I look back onto my exploration of how the peninsula of Akrotiri came to be, one thing stood out to me the most. We can’t be one hundred percent sure exactly where the original volcanic island was located. We are able to see where part of it might have been located and estimate from the rest of the island however, there have been many eruptions on Santorini which have covered many of the older Akrotiri flows. This blog post allowed me to glimpse into one of the most fascinating things I have learned about while on this trip to paradise.

While looking through the oldest volcanoes on the island of Santorini I was able to learn more about the formation of volcanic islands and the volcanoes that build them. Viewing the soils that are found under lava flows and ancient volcanoes even shows us the conditions of the original deposited layers before the volcanoes burst up. Finding out more about the original island of Akrotiri and more over how the volcanism erupted for over a hundred thousand years there before traveling was just more of an eye opening experience.

 

1. Friedrich, Walter L. “Volcanic Rocks and Their Deposition.” Santorini. Denmark: Aarhus UP, 2009. 36-37. Print.

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5 thoughts on “The Birth of an Island”

  1. Good job in incorporating our edits. The maps really strengthen this post. I find it so interesting that most people don’t know that the island is actually built of many volcanoes over many hundreds of thousands of years. Hopefully some of the people we have met here will read and enlighten themselves.

    There are a few redundancies in this post. In the beginning it would be helpful to clarify that the peninsula is made up of both domes and cinder cones (you only mention cinder cones at first). The 344 K number is mentioned twice. Finally, there is a significant typo in the last paragraph.

    I really enjoyed this post!

  2. Hope everything is going well Joshua,

    Your story on the creation of volcanoes and the process of the birth of this island was most interesting. You had a great level of enthusiasm infused in your entry and I could register it whilst reading it. You also did a great what was discussed in your entry at the end on the last paragraph; how the formation of volcanic islands occur along with the volcanoes under the sea that created them. I also found it interesting that we can figure out how the ground was before the volcanoes erupted by studying the soil under the lava. You could continue to improve the entry by shortening or separating the last sentence in your second caption. Try adding a comma after “me,” it will slow down the reading of the sentence and make it seem not as long like a “run-on” sentence. Overall it was a great entry.

    1. Thank you very much it was quite interesting to learn about the first volcanism found in the island. I also appreciate the pointers I feel as if I rushed this post so it does not flow in the way I had hoped.

  3. Nice take on the evolution of Santorini by describing the oldest volcanic rocks. I really liked this post. Worming magma, stewing magma, popcorn magma … very visual and fun to read.

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