I grew up in Anchorage, Alaska and have experienced my fair share of earthquakes. I remember when I was ten years old and I woke up to my bed moving back and forth. I thought my brother was playing a prank on me, but I quickly understood that this was not due to human hands. I was scared of course, but I was also curious about why the ground was moving so violently.
It wouldn’t be until years later that I found out it’s because of plate tectonics. Our planet is made up of giant plates floating like sheets of ice on water that are about 100 km thick and are in constant motion (1). This first 100 km or so is called the lithosphere which is a rigid solid, and then below that is the more plastic solid asthenosphere. When two plates converge, the denser one will essentially sink into the earth like a rock sinking into liquid soap which creates a deep trench or, in other words, a subduction zone. These subduction zones create powerful earthquakes much like the one I experienced as a child in Alaska.
Figure 1: This shows the movement of the Eurasian, African, Aegean, and Anatolian Plates. It also shows the movement of the north Anatolian Fault (NAF). The red lines in the middle are the normal faults that the magma followed to create the Southern Aegean Active Volcanic Arc (SAAVA).
People experience similar earthquakes in the Aegean Sea because of the convergence of the African Plate and the Eurasian Plate, and this clashing of giants has created the Southern Aegean Active Volcanic Arc (SAAVA) (1). The story of the volcanic arc gets a little bit more complex though when you add in subduction rollback, the Aegean Microplate, the Anatolian Microplate, the north Anatolian Fault (NAF). Let’s start with picturing subduction rollback like a suction cup effect. The African Plate, when it descends into the earth, is dragging the Aegean Microplate with it like a suction cup against a piece of glass.
Figure 2: A cross section of the regional tectonics of the Aegean Sea showing the subduction of the African Plate and the pulling effect it has on the Aegean Microplate. The two pieces of land sticking up are metamorphic rock.
This pulling motion, from the sinking of the African Plate, is causing thinning of the crust on the northern side of the subduction zone where it meets the Aegean Microplate. Thus normal faults (extension) are creating a path of least resistance for magma to follow. If you look at Figure 2 they’re also uplifting metamorphic rock from deep within the earth. Metamorphic rock has been specially deformed from high levels of pressure and heat that become more intense as you delve deeper into our planet.
These normal faults though are getting younger the farther east you go because of the NAF. It goes the same for the volcanoes, meaning they’re becoming younger and are more active than the ones to the west. The southwest movement of the NAF is causing the Anatolian Microplate to move in a counter clockwise rotation which is creating an arc of normal faults, the volcanic arc!
The Southern Aegean Active Volcanic Arc (SAAVA) though makes for some of the most fascinating geology in the world, and yet there is still so much we don’t know about it. The clashing of the African and Eurasian giants 170 km below the surface is groundbreaking (1). To venture out on a boat through the Aegean and see all of this history first hand makes me wish I could see it all for the first time again and again. It is exciting how our planet lives and breathes every day.
 Friedrich, Walter, 2009, Santorini: Denmark, Aarhus University Press, 312 pages