I never traveled outside of the United States before. Therefore, I was never thrown into another culture. When we arrived in Santorini, I remember asking myself why the buildings looked so different. I found out that those buildings were just in the process of being built! It intrigued me to find out more about the buildings here. Where I am from, you often see complex structures made of wood, then insulation and dry wall. Before you know it, the homes are built!
Since we arrived in Santorini, we have been discussing the different hazards and geologic history on the island. As we’ve been talking about the hazards associated with the geologic history, I realized that both locals and tourists do not realize the dramatic affects that a high-magnitude earthquake can have on the towns. I will be discussing why earthquakes are common and how it will affect the buildings on the island of Santorini.
What Causes Earthquakes on Santorini?
As we have learned in class, an earthquake can be caused by tectonics or volcanoes. Volcanic earthquakes are caused by magma moving up beneath the surface and tectonic earthquakes are caused by plate tectonics and fault lines. Santorini has two major fault lines: the Kameni line and the Kolumbo line. The Kolumbo line runs through the northern part of Thera while the Kameni line runs through the southern part of Thera.
The Kolumbo line is one of the most active lines, which means that earthquakes are very common. Both sides of the fault are moving in opposite directions causing friction; when they get stuck and suddenly move, it creates seismic energy. The energy is carried and creates an earthquake. These tectonic earthquakes are usually higher in magnitude than volcanic induced earthquakes.
How are Buildings Made on Santorini?
Driving in Santorini is stressful, but at least we get to see amazing views and different architecture! Seeing many unfinished buildings allowed me to see the process of the how the homes are built. Each house we saw was in a different stage of being finished. They are made primarily of concrete followed by volcanic rocks. People depend on these materials because they are inexpensive. The picture below shows how homes are built on the island using concrete.
How did the Minoan Eruption Effect Buildings on Santorini?
Our hike down Cape Plaka (located on the caldera rim) showed us the different caldera forming eruptions through the layers. The last caldera forming eruption was the Minoan Eruption (1613 BC), which deposited 60 meters, or 200 feet, of ash and pumice onto the surface of Santorini. Pumice is a vesicular, light weight volcanic rock that is light in color. Locals built homes in the pumice deposits of this eruption.
Figure 4 shows what the popular city of Oia is built on. Oia is known for their architecture and where “Mamma Mia!” was filmed. Figure 5 was taken from the balcony of our apartments in Karterados, a town just outside of Fira.
The material shown is extremely unstable and can collapse at any time. During an earthquake, the pumice can become unstable, collapsing on homes built in the pumice and built on top of the pumice.
Why are Earthquakes a Hazard to the Buildings on Santorini?
Earthquakes are a hazard to buildings on Santorini because of the material they are built of and the material they are built on. Concrete buildings are rigid and will not be able to survive a major earthquake. They will have what is called a lateral collapse.
A lateral collapse is when each floor of the structure folds and collapses. Lateral collapse happens when the building is not able to move with the waves because of rigidity and stiffness.
The buildings built inside of the pumice will fall and collapse. Since they have pumice on top and on the bottom, they will fall and be crushed.
We know that an earthquake will happen and cause significant damage due to the earthquake of 1956 that hit Oia. The city of Oia crumbled and was rebuilt afterwards. We could be looking at a repeat of history if another high magnitude earthquake were to hit the area. It will impact the buildings and homes all over the island. Buildings near both the Kameni and Kolumbo lines are at the most risk along with the buildings built in or on top of the volcanic pumice. I hope that Santorini can find a way to build stable buildings in stable locations.