Just a couple months ago, I had no idea that the sea of Greece was home to a caldera much like the ones that I learned about in my introductory geology course the first semester of my time at Northern Arizona University. I have realized that many of the geological processes in the world have been left in the shadows and ignored. Traveling across the Atlantic ocean to Santorini, I have began to broaden my understanding of the forces of earth in this part of the world. As inspiration goes, I have been drawn further in my curiosity to wonder: Is Santorini, the floating volcano in the Aegean Sea, not alone?
Santorini and its volcanic history that has brought us overseas is very unique. Despite the educational potential of Santorini, our destination of study could have presented equal adventure elsewhere in the Aegean Sea. Santorini is only one of the volcanic giants that make up the South Aegean Active Volcanic Arc or ‘SAAVA’. A volcanic arc is created when a tectonic plate slides into the plastic like layer under the two layers of another tectonic plate. By doing so, the H2O from the subducting plate melts this layer ‘the asthenosphere’ into a liquid state at which it rises to the surface and creates volcanoes where the magma can get through.
The five main volcanic islands of the Aegean sea are Methana, Milos, Santorini, Nisyros and Kos which are all spaced out in a ‘U’ shape dipping down from the west and back up slightly to the east. The formation of islands create the SAAVA, a perfect travel path for a Greek island hopping vacation. The Aegean arc is much different from most arcs in a way that the volcanic islands decrease in age in a pattern from west to east. The ages of normal volcanoes of arcs, however, are all relative. The process for this anomaly is as rare as NAU students studying geology in Greece.
The first and oldest volcanic zone is located just south of Athens. The volcano is called Methana and the rock is around 4 million years old . The island is composed of many small domes of cooled lava that once oozed out of the Earth . No significant explosive eruptions have occurred throughout the creation of this island. The volcanoes are still active however the magma last reached the surface in the 1700 .
Milos is the second volcano and it is a composite cone. This volcano has been inactive for thousands of years and is estimated by carbon dating to be 3.5 Million years old . 350 thousand years ago the volcano was highly explosive .
Santorini is third youngest of the arc at an age of 1.55 Million years old . Tonight I will sleep on this not erupting, but active, caldera. The island has many major eruptions and the Minoan eruption in 1600 BC was the most significant because of its ash cloud that reached far into Turkey and Africa. Flows of lava have been forming a complex of cinder cones to make up the the Kameni shield volcanoes which sits in the sea surrounded by the ring shape of islands. The lava flows of the Kameni islands slowed to a stop in 1950 .
Between Nisyros and Kos lie numerous different types of volcanoes about 150 thousand years old . A stratovolcano makes up the island of Nisyros and is still active. The last eruption was in 1888 with steam shooting out of the vent. Once in 1996, the island experienced severe seismic activity catching the wary attention of volcanologists. The stratovolcano of Nisyros sits on the rim of a caldera that is submerged in the sea from Nisyros to Kos. This volcanic zone is the youngest of the South Aegean Active Volcanic Arc.
Now the SAAVA is much different than the Aleutian Volcanic Arc of Alaska because of two main characteristics. The first process has been called subduction roll back. This occurred when the African tectonic plate dove diagonally down under the Eurasian plate, however the plate dropped and sunk more than it dove into the mantle which pulled the Eurasian crust back as it fell downward into the heat of the earth. With this pulling apart, the plates faulted giving the magma an easy passage upwards to form the first volcanoes of Methana and Milos. The second factor that has led to the unique SAAVA was the North Anatolian fault that broke and twisted much of the crust in the Aegean sea causing smaller faults to appear in a southwest to north eastward trend. These faults created more passages for the magma that has now created the volcanoes of Santorini, Nisyros and Kos. This can be seen in Figure 1. The subduction roll back and the North Anatolian fault are two oddities that have been added to what could have been a normal volcanic arc like the Aleutian of Alaska or Northern Cascade arc in the north west United States
I now understand much more of the Aegean Sea and the volcanoes of Methana, Milos, Santorini, Nisyros and Kos. The volcanoes have been specifically placed due to the African plate roll back and the North Anatolian fault. My mind has faulted with new concepts of the earths potential and leads me to wonder if even the South Aegean Active Volcanic Arc, in the same sense as Santorini, is not alone.
 Kokkalas, S, Aydin, A, 2013, tectonics, Geol. Mag, 150, N2, p 193-224.
 Wikipedia, 2015, Methana Volcano; http://en.wikipedia.org/wiki/Methana_Volcano (June 2015)