Tectonism in the Aegean

As I began the hike to Ancient Thera, I saw before me an immense mountain of metamorphic and sedimentary rocks. Due to the rocks being millions of years old, I felt as if every step I took was another leap back in time and a look into the origins of Santorini. The tectonic setting in the Aegean Sea is rare due to the several processes that are constantly in motion. A subduction zone, normal faults, and a transform plate boundary come together to make a unique geologic setting.

For me, learning tectonism for the first time was like learning how to ride a bike, in the sense of it took me several tries to fully grasp it.  Plate tectonics is the theory that the Earth’s crust is broken into several different plates, some larger than others. which move independently of one another. The movement of plates is driven by the circulation beneath the Earth’s crust. These plates can either converge, diverge or slide past one another which, in the case of the Aegean, can create an interesting geological area.

The figure below shows the convergent plate boundary between the African plate (South of the yellow line) and Aegean plate (North of the yellow line). These plates are converging or coming together which means one plate is falling underneath the other due to differences in density.

Map
(Figure 1) Picture of the different tectonic plates along with the transform boundary and trench

With the various movement along each of these geological settings, they are turning the Aegean plate at about a 23 degree rotation [1]. This happens due to several components, the first being the movement of the Northern Anatolian Fault which is moving the northern part of the plate to the West. Also the the extension that is occurring due to the normal faulting that is taking place slightly north of the subduction zone, is pulling apart or thinning the crust of the Earth. This thinning process is due to the extension of normal faulting as a result of the diving pulling back on the overriding plate.

Aegean
(Figure 2) Map of the tectonic processes occurring within the Aegean Sea.

Subduction rollback is a process that occurs when the diving plate gets stuck with the lower part of the overriding plate due to heating. As the lower end of the subducting plate moves further into the Earth, forces pull it back in the opposite direction of its original movement. This in turn pulls the bottom of the overriding plate as well which in turn creates extension on this plate and propels the movement of normal faults.

Sh
(Figure 3) Picture of the subducting plate and overriding plate. Subducting plate is pulling the overriding plate back due to fusing of the plates.

Faulting is an important concept to help grasp the concept of the Aegean and how some of the islands originated. Faulting is the process of having movement along a crack, in sections of rock, that move in independent directions of each other. There are three types of faults: the first one is reverse which is associated with compression,the second is a normal fault which is more of an extension and finally there are transform faults. The main fault types that are present in the Aegean are normal faults and transform faults. Through the process of extension, normal faults have a thinning effect on the Earth’s crust.

On either side of a normal fault there is a hanging wall and a foot wall. In a normal fault the foot wall will be the section that is rising relative to the hanging wall. The figure below shows the movement of this fault along with how the preexisting rock for Santorini rose to the surface. The movement of the pre-existing metamorphic rocks, mainly phyllite, from lower part of the Earth’s crust to the surface is associated with the hanging walls and foot walls.

The picture below is Mount Profitis Ilias which is an enormous foot wall that had risen out of the Earth millions of years ago. If you can imagine this huge metamorphic, which is 50 to 23 million years in age, rose relative to the hanging wall and made its ascent to the surface of the ocean. This foot wall is the oldest on Santorini and it helps geologists uncover the history behind the beauty of the island. This same process was used to create the other metamorphic islands in the Aegean Sea due to the propelling of the foot wall towards the sea surface.

Once the pre-existing rocks reach the surface, the extension of the seafloor allows for spurts of volcanism to take place. As this magma accumulates towards the surface, domes, shields, and cinder volcanoes begin to form around the ancient rocks. This slowly build up to create both volcanic and non-volcanic islands.

Untitled
(Figure 4) This picture shows the direction of the footwall that contains basement rocks which are millions of years old.

As the years go on, these geological processes will continue to further change the position of the Aegean. The rate of the subduction rollback along with the increase in rotation of the Aegean block may create a completely new geological area. Also movement along the normal faults could potentially propel more pre-existing rocks through the surface of the sea. The future of Santorini and the islands that follow now lies with mother Earth and her mysterious ways.

References

[1] Piper, D.J.W, and Perissoratis, C., 2003, Quaternary neotectonics of the South Aegean arc, Marine Geology, v.198, p 259-288.

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9 thoughts on “Tectonism in the Aegean”

  1. Micah – you chose to tackle quite a difficult geological concept of Aegean Tectonics for your first post and I commend that. In this next week, lets find a narrower topic so you can try to incorporate more of your experiences into your topic. Now that you have one down, I think you will find the second easier to write!

  2. I enjoy your summary here Micah. The tectonic processes in action in the Aegean Sea are truly complex and unique! I like how you mention that islands that will likely form in the future as extension continues in this area. Geology is often used to investigate the past history of the Earth, but even a little knowledge can lead to insights into what the future holds as well. Very cool!

  3. The Aegean Sea seams to be very complex as Mike was saying, I wonder where the next limestone/schist block will pop out of the ocean. Nice post Micah

  4. Hi Micah,

    What you are doing well is providing a solid scientific background for every observation you make. What I enjoyed most of this post was the first paragraph in which you gave a little sense of your own experience on the island and your observation of the interesting geological features there. You clearly know what you’re talking about and, but I think there might be an easier way to write it which would likely be more fun for you.

    The best part of blogs like these are the unique perspective each writer can offer because your voice is the culmination of your experiences and your perspective on those experiences. The scientific data you provide gives an excellent objective sense of the forces at work in the Aegan sea, but what would make all this data more fun to read is if it was presented in a way that also includes your thoughts and feelings. You can keep the data, but try presenting it in a way that suits the emotions your surroundings inspire in you. In your first sentence you begin to do exactly that by describing the immensity of the mountain before you, and an interesting continuation of that thought would be to hear how that immensity made you feel. Keep some of the science, because this blog is meant to be casually academic, but filter the data through your own impressions. You took on a pretty grand subject for this post, so it could be worthwhile to provide a sense of your own awe. The science is good, but as a reader I want to hear what you feel and see so I can experience it by reading it.

    Justin Kanzler

    1. Thank you Mr. Kanzler for taking the time to read my post. I appreciate the feedback you gave me as to adding my own personal feelings. I did struggle with that part of the blog post but hope to improve on it for the next one.

  5. Hello Micah.

    I learned a great deal concerning the complicated tectonic make up of the Aegean Sea. Your post provides much information that can be easily received by readers who are unfamiliar with geological jargon and processes. As a student of English, it was a delight to be able to understand such different and interesting processes as subduction and faulting.

    Although your post does well in identifying and defining the various geological occurrences of the Aegean, I must agree with Justin. In this blog post, your own distinguished voice seems to be missing and your writing feels like more of a summary. This is not a bad thing, but I believe Prof. Skinner would like you to exercise a more personalized approach to sharing your findings. Maybe tie in your own personal opinion and findings (as found in the opening paragraphs of your post) to the processes and variety of processes in the Aegean.
    Solid job making complicated geological processes a bit easier to understand, I look forward to reading more about your time in Greece.

    Jose Martinez

    1. Mr. Martinez, I am glad I was able to present the data in a way that was easy to understand! I hope to improve on the personal aspect of the blog posts and be able to add my own voice to the text. Thank you for taking the time to read through my post.

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