Growing up as the oddball of the family, I found comfort in reading.. reading and learning about history. The things of the past and how they differentiate from how things are today. On the very first day we spent in Athens, we walked up the three thousand year old pathway to the Acropolis, the very same pathway that the Athenians of Classical Greece took. At first glance I saw this piece of history, from the marble columns to the Porch of Maidens and I was amazed that people of the past without the technology that we have today built these things with such precise and critical thinking.
The Acropolis was stated to have originally been a military base, on top of a high, flat, piece of rock that that is high enough where you could see any and all attacks. The name comes from the Greek word “Akro” which means high and “Polis” which is city, I slowly started to notice that looking down off of one of the edge, that there were two noticeably different rock layers. I later learned that the Acropolis was strategically placed on a layer of limestone and other metamorphic rock. Limestone is a sedimentary rock consisting mostly of calcium carbonate (CaCO3). Limestone is only the top layer of the base of the Acropolis. The second layer called the “Athenian Schist” is actually not even a true schist in the correct geological terms.
Instead, the rocks of the Athenian schist are very lightly metamorphosed sedimentary rocks. Metamorphic rocks are formed when pressure and high amounts of heat are added. That added heat and pressure cause the atoms in rocks to rearrange and create and new rock without melting.
Limestone, on the other hand, forms in shallow and calm marine water. Knowing this tells us that the area where the limestone is had to have been surrounded by the ocean for the limestone to form. . This leads me to question, why is there only limestone in this particular place in Athens? The rest of the modern city is built in a low lying valley.
Figure 1: This picture shows where the construction meets with the limestone underneath.
While sitting in the garden of our hostel in Athens, just down the road from this massive 3,000 year old ruin, I learned that the limestone under the acropolis wasn’t originally there in the beginning. The limestone itself was brought up by faulting. Faulting is the process in which tension and pressure between plates is so powerful that blocks of rock fracture or break. The particular fault that moved the limestone is called a thrust fault. Thrust faults are the result of compression between two plates, which or where the land is being pressed together.
Figure 2: Here you can see the clear separation of the limestone, the schist, and the constructed base of the acropolis.
The limestone under the Acropolis is older than the sandstone at the base of the hill (the “Schist”). It moved to its present position from an original position some distance away. It moved there along a break in the rock a “thrust fault.”
You can the Acropolis towering over the land from any location in Plaka. The Acropolis was placed on top of this complex layer of rocks. Sedimentary Limestone and the Athenian Schist. The limestone was moved from a distance away and shifted on top of the Athenian schist by thrust faulting. Thinking back at pictures taken of the acropolis, I no longer just see odd looking rocks. I see in my head a series of events from each rock movement to the next.
- Regueiro, M., Stamatakis M., Laskaridis K., The Geology of the Acropolis (Athens, Greece) European Geologist, November 2014